Black''''s veterinary dictionary 21st edition - T ppsx

T T-Cells from the thymus gland concerned with cell-mediated immunity (See IMMUNE RESPONSE.) LYMPHOCYTES T2 Toxin This fungal toxin may poison cattle or poultry eating stored corn containing the fungus Fusarium tricinctum In cattle, the toxin may cause multiple haemorrhages and sometimes death; in poultry, there may be mouth lesions Tachycardia Tachycardia is a disturbance of the heart’s action which produces great acceleration of the pulse Tachypnoea An increase in the rate of breathing due to some pathological condition (See BREATHLESSNESS; PARAQUAT POISONING.) Taenia (see TAPEWORMS) Tail, Amputation of Amputation of the tail (docking) is, or has been, undertaken for a variety of reasons In the UK the Royal College of Veterinary Surgeons has ruled that docking a puppy’s tail is an unethical procedure except when it is done for prophylactic or therapeutic reasons Docking by lay persons is illegal In cattle, amputation of the tail is illegal except following injury and must, except in an emergency, be undertaken by a veterinary surgeon Pigs’ tails are often docked to prevent tail-biting Lambs tails are docked to prevent faecal soiling and fly strike (see under DOCKING; LAW; WELFARE CODES) Tail-Biting In pigs this ‘vice’ can be of great economic importance There are various reasons why it occurs: boredom, absence of bedding, and overcrowding (floor space of less than 1.5 m2 (5 square feet) per pig), are regarded as conducive to tail-biting High temperature and humidity are possible causes Bitten tails require amputation or dressing if pyaemia is to be prevented Tail sores in pigs These may follow tail-biting by or pigs out of a large batch, and if untreated can lead to pyaemia In months, out of 135 pig carcases condemned in an Oslo abattoir, 56 were affected with pyaemia – and of these, 43 had tail sores Talfan Disease (Teschen Disease; Porcine Viral Encephalomyelitis) This disease of pigs was first recognised in the Czech Republic and occurs throughout Europe In the UK, it was made a NOTIFIABLE DISEASE in 1974 Its cause is an enterovirus Experimentally, the incubation period is stated to be 12 days Piglets weeks old and upwards are affected; adult pigs may be infected but show no clinical signs By no means all piglets in a litter or on a farm become ill, and the mortality is usually low The main symptom is weakness or paralysis of the hind-legs There is little or no fever or loss of appetite Recovery occurs in a proportion of animals which are hand-fed The disease is present in Britain to a small extent, and apparently may be associated with abortion Tampan A soft tick of the family Argasidae (See TICKS.) Tamponade, Cardiac A rapid accumulation of blood or other fluid in the pericardial sac, compressing the heart and sometimes suddenly arresting its function Tannin (Tannic Acid) Tannin (tannic acid) is a non-crystallisable white or pale-yellowish powder, which is soluble in water and glycerine It is prepared from oak-galls, and is found in strong tea or coffee When brought into contact with a mucous surface, tannin causes constriction of the blood vessels When brought into contact with many poisonous alkaloids it renders them temporarily inert by forming the insoluble tannate, and so is a valuable antidote Uses Tannic acid has been used in diarrhoea and dysentery in young animals, usually as catechu or kino – vegetable drugs which contain a large amount of tannin It is often administered, in the form of strong tea, as the first step in the antidotal treatment of poisoning by ALKALOIDS Tannic-acid jelly is a valuable burn dressing It lessens the absorption of breakdown products from the burned area and hence diminishes the Tapeworms 687 Taenia Head, mature and gravid segments A typical tapeworm Each segment is called a proglottis (From H T B Hall, Diseases and Parasites of Livestock in the Tropics, Longman.) secondary effects of a serious burn It is not suitable for extensive areas owing to the danger of liver damage if large quantities are absorbed Tapetum (see EYE) Tapeworms An intestinal parasite commonly found in vertebrates Their life-cycle requires hosts, sometimes The presence of the adult worm may give rise to few if any symptoms or, on the other hand, to anaemia, indigestion, and nervous symptoms – or even to blockage of the intestine The cystic stage of tapeworms may involve the brain Tapeworms are of considerable public-health importance A typical tapeworm has a head or scolex, provided with suckers and, in some species, with hooks also Behind the scolex follows a neck, and behind that are the segments, each being called a proglottis The segments nearest to the head are the smallest, and are immature Next follow mature segments, and lastly the gravid segments containing eggs These older segments fall off and are passed out of the host’s body in the faeces Taenia This is the common genus of worms found in dogs and cats, and includes: T pisiformis (T serrata) is one of the commonest Its cystic stage, Cysticercus pisiformis, is found in rabbits and hares T hydatigena (T marginata) is the largest form, with mature segments wider than long It may reach a length of over metres (16 feet) Its cystic stage, C tenuicollis, occurs in the viscera of various animals, especially sheep, cattle and pigs T ovis is frequently mistaken for the last form, from which it can be distinguished only by microscopical examination Its cysticercus, C ovis, is found in the muscles and organs of sheep and goats It is a small form, easily overlooked T multiceps (T coernurus) is a more delicate form than the others, semi-translucent The intermediate stage is a coenurus, found in the nervous system of sheep and other ruminants and man T serialis is a more robust form, its coenurus being found in rabbits and hares Only species is common in the cat, T taeniaeformis (T crassicollis) The cystic stage C fasciolaris is found in the liver of rats and mice T 688 Tapeworms T saginata is a tapeworm of man which produces cysticercosis infection in the muscles of cattle; this is C bovis, known as measly beef T solum is another tapeworm of man, the intermediate stage of which (metacestode) is found in the skeletal and heart muscles of pigs, producing measly pork Diphyllobothrium D latum is the broad tapeworm of man, the dog, and the cat It is rare in Britain, but has a wide distribution Several species are found, but this is the commonest The life-history is interesting The ciliated larva liberated from the egg is swallowed by a crustacean, Cyclops strenuus or Diaptonius spp., in which it becomes an elongated form with a terminal sphere containing three pairs of hooklets, called a ‘procercoid larva’ The crustaceans are swallowed by a fish, when the larva, migrating to the muscles, becomes an elongated infective larva called a ‘plerocercoid’ The fish is eaten by a suitable host, and the adults develop In man, the tapeworm may attain a length of 18 metres (60 feet), and it may cause a grave form of anaemia (bothriocephalus anaemia) associated with gastric and nervous symptoms D mansoni is also widely distributed and has a similar life-history, but the infective stage is found in many hosts, including man, pig, and carnivores It is common in frogs in Japan The adult worm is found in carnivores Treatment of dogs infested with tapeworms is very important, because some of the species in their intermediate stages are dangerous to food animals Farm dogs should never be allowed to harbour tapeworms Routine use of anthelmintics is essential: a wide range is available, many based on praziquantel or dichlorophen All material passed should be destroyed Dipylidium caninum infests cats also; and may be transmitted by swallowing a flea In pigs, cattle, and sheep cysts of the tapeworm Taenia hydatigena (which infests the dog and may occasionally attain a length of metres (16 ft)) may be so numerous in the liver that the latter ruptures, causing death Tapeworms in horses Three species occur in horses, all belonging to the genus Anoplocephala A perfoliata and A mammillana are not uncommon in Britain, while A magna is also sometimes encountered A perfoliata, a stoutish worm with large head and no hooks, is a cause not only of unthriftiness but occasionally also of ileal and caecal obstruction, and/or intussusception, where numerous A perfoliata are present The infection may therefore be more serious than is generally supposed The intermediate host is a mite Tapeworms in ruminants All the tapeworms of ruminants have suckers and no hooks In Moniezia the intermediate host is a free-living mite The segments of Moniezia worms are much broader than they are long The worms may attain a length of several metres/yards, with a minute head little larger than a pin-head More than 1000 worms have been recorded from a single host Numerous species have been recorded H giardi is found in Europe, Australia, and Africa and is from to metres (3 to ft) long A closely related form, Thysanosoma actinoides, is found in North America It is about 30 cm (1 ft) long, and is found in the liver The sheep show general symptoms of malnutrition Bovine cystercercosis in Denmark Studies were conducted on 14 farms with a history of this disease On of the farms the source of infection was sludge from septic tanks applied to pasture or crops In herds the cattle grazed pasture near a sewage plant; while on farms people defecating on pasture was a possible source T Diphyllobothrium Head and segment Tapeworms in poultry A number of tapeworms have been found in poultry, of which the commonest are Davainea proglottina, which has a larval stage in slugs and snails and is widely distributed, and several species of Raillietina, with the larvae in house-flies, dung beetles and ants The following are also common in many countries: Amoebotoenia, Tapeworms with larvae in earthworms; and Hymenolepis of various species, some of which may be very numerous in individual birds ‘Measles’ in beef due to the presence of the cyst stage (Cysticercus bovis) of the tapeworm Taenia saginata, which is a parasite of man Cattle swallow the eggs of the adult tapeworm, and these hatch in the intestines, liberating young embryos, which burrow until they settle in muscle fibre or connective tissues Here they appear as small oval cysts, containing fluid, and each possessing the head of a potential tapeworm ‘Measles’ in pork is due to the presence of the cyst stage (Cysticercus cellulosae) of the tapeworm of man, Taenia solium It is extremely common among pigs in eastern lands, which have access to garbage and human faeces, from whence they pick up the eggs passed through the human intestines The eggs undergo a development similar to those of the beef-measles tapeworm Man may also himself harbour the cystic stage Cysticercosis in man Very high sporadic infection rates have been found in Africa with Taenia saginata and T solium, the tapeworms of major importance in man Where T solium is present, serious human infections with the cysticercus stage may be observed, as well as mild infections with the adult tapeworm When it occurs in beef cattle, the cysticercus of T saginata is a major economic problem and a serious obstacle to the export of meat A single human carrier of T saginata led to an outbreak of cysticercosis among cattle on a large farm in the USA Coenuriasis (gid or sturdy) in sheep This disease is caused by the pressure of cysts of the tapeworm Taenia multicepts on cells of the brain (or spinal cord) Sheep become infested by swallowing the unhatched eggs, excreted in a dog’s faeces, while grazing In the digestive tract the eggs hatch, and pass via the bloodstream to various parts of the body; only those reaching the central nervous system develop Here they form small cysts, each containing tapeworm head: this larval stage is known as Coenurus cerebralis Over a period of months, each cyst increases in size, and more heads are budded from the lining membrane of the translucent cyst wall Eventually a single coenurus may contain 50 or 100 or more tapeworm heads (scolices) projecting inwards 689 The life-cycle is completed if a dog eats the head of an infested sheep Signs These include impairment of vision, a staggering or high-stepping gait, circling, and standing with head lowered, raised, or pressed against an object Backward somersaults have been recorded Recumbency and opisthotonus may occur A softening of the bone of the skull, due to internal pressure of the cysts, is found in a proportion of cases Diagnosis Where there is no softening of the skull, a guide to the location of the cyst may be given by interpretation of the neurological signs as indicated by the sheep’s behaviour An intradermal test has been used: 0.1 ml of cyst fluid is injected into a shaved area of skin Thickening of the skin within 24 hours indicates the presence of a cyst in the animal Treatment Physical removal of the cyst may be attempted The sheep is anaesthetised and, in the absence of any skull softening, a trephine used to remove a disc of bone 1.5 cm (0.6 in) in diameter Draining the fluid from the cyst before its removal obviates the need to enlarge the hole The cyst is then removed completely (If this is not done, the remaining cyst wall is apparently capable of replacing the fluid.) Hydatid disease is caused by the cystic larval stage of the tapeworm Echinococcus granulosus, of which the dog and fox are the usual hosts Eggs released from tapeworm segments passed in the faeces by these animals are later swallowed by grazing cattle, sheep and horses, which may become infested also through drinking water contaminated by wind-blown eggs People become infested through swallowing eggs attached to inadequately washed vegetables, and possibly eggs may be inhaled in dust or carried by flies to uncovered food The handling of infested dogs is an important source In Beirut, the risk is put at 21 times greater for dog-owners than others, by the World Health Organisation, which states also that in California nomadic sheep-rearers are 1000 times more likely to have hydatid disease than other inhabitants of the state (WHO Technical Report 637) There have been successful campaigns to control human hydatid disease in both Cyprus and Iceland, by compulsory treatment and/or banning of dogs Swallowed eggs hatch in the intestines and are carried via the portal vein to the liver Some T 690 Tapping remain there, developing into hydatid cysts; others may form cysts in the lungs or occasionally elsewhere, e.g spleen, kidney, bone-marrow cavity, or brain Inside the cysts, brood capsules, containing the infective stage of the tapeworm, develop, and after or months can infest dog or fox In Wales, where the incidence of hydatid disease is relatively high, farm dogs and foxhounds are important in its spread Only some people are known to die from this disease in England and Wales each year – a figure which would probably be higher were diagnosis less difficult Condemnation of sheep and cattle offal from this cause runs into hundreds of thousands of pounds annually Routine worming of dogs is essential for control E granulosus is far from being a typical tapeworm, as it has only or segments and a total length of a mere to mm (0.12 to 0.35 in), so that the dog-owner will not notice the voided segments A problem of diagnosis also arises, in that this worm’s eggs are indistinguishable from those of Taenia tapeworms Examination of a dog’s faeces following dosing with arecoline would reveal the intact tapeworm However, this drug has now been replaced by more modern drugs which destroy the tapeworm but leave it unrecognisable Dichlorophen, praziquantel, nitroscanate, and benzimidazoles are used for treatment Tapping (see ASPIRATION) Tar Recently applied tar, in the form of asphalt on roads and pavements, often causes irritation between a dog’s toes, causing the animal to lick or bite the part The tar must be removed with a bland fat or oil Crude tar should never be used on an animal’s skin (See also PITCH POISONING.) Tarantulas These include the Chilean rose spider (Grammostola spatulatus) If found lying on its back, this creature should not be assumed to be dead, but merely moulting In the UK, tarantulas are being kept as pets; in Australia wild tarantulas (‘red-back’ spiders) bite a few hundred people each year An antivenin is available (See also PET ANIMALS ACT 1971; PETS.) Tarsorraphy An operation for producing union of upper and lower eyelids It is performed as a permanent measure after enucleation of an eyeball; and sometimes as a temporary expedient to give protection to an ulcerated or perforated cornea (but see LENSES, CONTACT) Tarsus The hock (See under BONES.) Equine hydatidosis in Britain is caused by T a strain of Echinococcus granulosus which has become specifically adapted to the horse as its intermediate host, and is often referred to now as E granulosus equinus This apparently is of low pathenogenicity for man In a survey covering 1388 horses and ponies examined at abattoirs in the north of England, 8.7 per cent were infected Prevalence of infection was closely related to age, rising from zero in animals up to years old to over 20 per cent of those over years old Sixty-six per cent of the infected animals had viable cysts Treatment of human patients Hydatid disease is one of the rare parasitic conditions that can be treated by surgery However, the result is often incomplete, with frequent local recurrences or accidents of secondary dissemination Repeated interventions are often mutilating and not guarantee a definite cure Mebendazole is reported to have been used successfully in patients Tartar Tartar is the concretion that often forms upon the crowns and upon the necks of the teeth, as well as upon exposed portions of the roots The material is of a brownish, yellowish, or greyish colour, and consists chiefly of phosphate of lime which has been deposited from the saliva, with which are mixed numerous food particles and bacteria of a harmful nature Tartar is most often seen in the mouths of dogs and cats, although the herbivorous animals may also be affected It is important that accumulated tartar be removed from time to time, for if it is allowed to collect for an indefinite period the gums shrink before the advancing deposit, the root becomes exposed and ultimately affected, and the tooth loosens and falls out In addition to this, there are generally signs of systemic disturbance, such as a bad smell from the breath, indigestion from inability to feed properly, and in bad cases, great irritability and loss of condition (See TEETH, DISEASES OF.) Teeth 691 Tasmanian Grey Tears An Australian breed of beef cattle, similar to the Murray Grey but developed from Aberdeen Angus and White Shorthorns (see EYE; for ‘soapy’ tears, see ALGAE POISONING; see also NAPHTHALENE POISONING) Taste (see under MOLYBDENUM) This special sense is dependent upon the taste buds, located in the crevices of the papillae The taste buds have minute projections – the endings of nerve fibres It is necessary for the purpose of taste that the substance should be dissolved in a fluid, and it seems that this is one of the functions of the saliva The sense of taste is closely associated with the sense of smell (See TONGUE; SMELL; JACOBSON’S ORGAN.) Tattooing Identifying marks or numbers may be applied to animals by tattooing On black skins, tattooing is not an effective method, and the use of nose prints has been tried for cattle The tattooing of dogs is widely practised in France (where it is compulsory for the Kennel Club’s register of pedigree dogs), and in Canada and the USA Tattooing, usually in the ear, is used to identify cattle, pigs, sheep and goats It is not entirely free from the risk of introducing infection, e.g blackquarter, tetanus FREEZEBRANDING and MICROCHIPPING are alternative methods (See also DANGEROUS DOGS ACT 1991.) ‘Teart’ Pastures, Soils Teaser (see under VASECTOMISED) Teat Canal One of the most important defences against bovine mastitis, as almost all infection enters the cow’s udder by this route The constant production and shedding of cells lining the canal helps to remove pathogenic bacteria (See also MASTITIS IN THE COW; ORIFICES, IMMUNITY AT.) Teat Dipping First practised by a veterinary surgeon in 1916, this has proved a useful measure for the control of mastitis in cattle Teats are dipped usually after milking, to help prevent streptococcal and staphylococcal infection However, pre-milking teat dipping has been advocated as a means of reducing coliform mastitis Results in the UK are reported as variable The liquid chiefly used for the purpose is an iodophor, but good results can be obtained with hypochlorite teat dips containing per cent available chlorine (See under MASTITIS IN COWS.) Taurine Teat Necrosis An amino acid essential to maintain the health of cats, and which must be provided in the food In the USA, feeding of cats on canned dog foods is reported to have led to a taurine deficiency, resulting in degeneration of the cat’s retina However, a level of taurine in the cat’s diet sufficient to prevent degeneration of the retina may be insufficient to prevent the heart disease, dilated cardiomyopathy (DCM) Most modern proprietary cat diets contain adequate amounts of taurine This is seen in piglets under intensive conditions of rearing, and is sometimes accompanied by skin necrosis affecting the limbs Inadequate bedding and abrasive concrete may be contributory factors Taxis Taxis is the method of pushing back into the abdominal cavity a loop of bowel which has passed through the wall as the result of a rupture or hernia Tear-Staining Tear-staining of the face in the dog may be due to atopic disease or to blockage of a lacrimal duct Teats, Cow’s (see under MAMMARY GLAND; also VIRAL INFECTIONS OF COWS’ TEATS; MASTITIS) Teats, Diseases of (see BOVINE HERPES MAMMILLITIS; TEAT NECROSIS, VIRAL INFECTIONS OF COWS’ TEATS) Teeth Teeth are developed in connection with the mucous membrane of the mouth, being actually calcified papillae They are implanted in sockets or ‘alveoli’ in the upper and lower jaws, being only separated from actual contact with the bone by a layer of ‘alveolar periosteum’ The incisors are implanted in the incisive bones of the upper jaw, and in the anterior part T 692 Teeth, Diseases of of the mandible; they are situated in the front of the mouth, and used for grasping and cutting They are absent from the upper jaw of cattle, sheep, and goats, as well as other ruminating animals The canines are situated behind the incisors, and are used mainly for fighting purposes, being most developed in carnivores and omnivores They are useless to the domesticated herbivorous animals, and in them are usually of small size They are not present in the upper jaws of ruminants, and in the lower jaws have the shape and function of incisors The molars are the remaining teeth, situated further back in the mouth They are used mainly for chewing, and are specially adapted for this purpose by having broad strong irregular tables or grinding surfaces The term ‘cheek teeth’ is often applied to these teeth, since, strictly speaking, they are composed of ‘pre-molars’, which are represented in the milk dentition, and ‘molars’, which are not so represented (See DENTITION.) Each tooth has a portion covered with enamel, the ‘crown’; a portion covered with cement, the ‘root’; and a line of union between these parts known as the ‘neck’ A constriction occurs at the neck in the temporary incisors of the horse, in the incisors of the ruminants, and in incisors and molars of the dog and cat; in the remaining teeth there is no such constriction Structure Teeth consist of tissues In the middle of the tooth is the ‘pulp’, occupying the ‘pulp cavity’ It is soft and gelatinous, well supplied with blood vessels and nerves, and is large in the young tooth It nourishes the remaining tissues, and forms dentine for as long as the pulp cavity is open In later life it is small T Tooth structure (From de Coursey, The Human Organism, McGraw-Hill.) or absent, the pulp cavity having filled with dentine formed from the pulp The ‘dentine’ forms the greater part of the tooth It is hard, yellowish, or yellowish-white in colour, and is surrounded in the crown by enamel, and in the root by cement The ‘enamel’ consists of a comparatively thin layer of a brilliant white colour and extremely dense and brittle, which forms a cap to the dentine, or is arranged in layers through it The ‘cement’ is always the outermost layer of a tooth, being formed on the outside of the dentine in the root, and filling up the irregular spaces and hollows of the crown The implanted part of a tooth is fixed into the socket by a layer of vascular fibrous tissue, which serves as the periosteum both of the tooth root and of the lining of the alveolus It is known as the ‘alveolar periosteum’ Enamel is the hardest tissue in the body, and consists mainly of phosphate of lime It is composed of prisms placed side by side, with one end resting on the dentine and the other end towards the free surface in a simple tooth, such as the canine of a dog Cement is practically of the same structure as bone, without possessing Haversian canals Arrangement and form For times of cutting of the various teeth, see DENTITION Teeth, Diseases of Most diseases or disorders affecting the teeth are associated with pain or discomfort, which results in absence of appetite, capriciousness in feeding, or other disturbances Irregularities In certain cases, the incisor or molar teeth develop out of their normal positions in the jaw, with the result that perfect apposition between the upper and lower teeth is not possible, and the rate of toothwear is not uniform In other instances, extra or ‘supernumerary’ teeth are formed; in the incisor region these are usually placed behind the arch of normal teeth, while extra molars may be found as projections from the gums on the inside or the outside of the line of normal teeth When the temporary teeth are shed, it sometimes happens that the permanent teeth erupt irregularly to one side or behind the temporaries, and are distorted accordingly This frequently happens in puppies, and to a lesser extent in the herbivora In the former, trouble is likely to be experienced between 31⁄2 and or months, and in young horses at 21⁄2 and 31⁄2 years of age In such cases it is necessary to extract any temporaries which persist, so that Teeth, Diseases of the permanent teeth can arrive in their proper places in the mouth In dogs frequently, in sheep sometimes, and in other animals less commonly, there may be a discrepancy in length between the upper and lower jaws When the upper jaw is too long, the condition is known as an ‘overshot jaw’, and when the lower jaw projects too far forward, it is popularly spoken of as an ‘undershot jaw’ In bulldogs, pugs, and other breeds of dogs with very short upper jaws the undershot condition is practically normal, while in certain breeds with extremely long upper jaws, such as the greyhound and show collie, overshot jaws are very common Abnormal wear, which is due to malformations of the jaws, to excessive softness of the teeth, or to the direction of the teeth, is another mechanical cause of tooth disorder (See SOIL-CONTAMINATED HERBAGE with reference to sheep.) Abnormal wear varies in different cases, and is productive of some well-known conditions, as follows: (1) shear mouth, in which the molar teeth of the upper and lower jaws wear so that in time they appear like the blades of a pair of sheep-shears, the upper row being worn away on its inner border, and the lower one along its outer border; (2) step mouth, where the cheek teeth, instead of being all at the same level, are arranged with some higher than others, somewhat like steps – a high tooth in the lower jaw being opposite a short one in the corresponding upper jaw; (3) overhanging upper jaw, which is where the first upper cheek tooth on either side is placed too far forward in the mouth, and does not come into accurate apposition with the tooth immediately below it, causing the formation of a hook – at the same time the last lower cheek tooth is situated too far back and also forms a hook; and (4) curved tables, where the line of cheek teeth in the upper jaw shows a convexity in its centre, and a corresponding concavity exists in the lower row Signs In most of these instances the animal affected (almost always a member of the horse tribe), instead of chewing its food and swallowing it in the usual way, rolls it round and round in the mouth until it collects into a sodden mass, often about the size of a couple of fingers, and puts it out of the mouth instead of swallowing it (See QUIDDING.) Pain may be shown when the hand is passed along the outside of the cheek, especially when pressure is put upon the line of teeth 693 Treatment Rasping the teeth by means of a special tooth-rasp will reduce smaller irregularities, and bring the teeth back into their proper function Caries is not synonymous with tooth decay, although the term – borrowed from human dentistry – is often used in veterinary practice to include all tooth decay Caries is the destruction of the tooth enamel and invasion of the dentine by bacteria, resulting in the formation of a cavity True caries has been confirmed in dogs but is comparatively rare in farm animals Neck lesions in cats’ teeth A painful condition affecting middle-aged to elderly cats, characterised by cavitation of the necks of teeth This makes extraction difficult because of the risk of breakage of crowns Inflammations of the periosteum lining the root cavity of a tooth are common They may be due to small particles of food getting forced down into the socket of the tooth, to fractures or fissures of the teeth, to caries, tumour formation, depositions of tartar, and to certain specific diseases, such as actinomycosis, etc Signs These vary from a slight redness of the gum around the root of the tooth, which is painful when pressed by the finger, to a large suppurating tract running alongside the root of the tooth down into its socket, and perhaps through the skin to the outside or into one or other of the sinuses Abscess formation in the tooth socket may take place, and the abscess may burst into the mouth, to the outside through the skin, or up into a sinus In many cases there is a distinct bulge of the surface above the diseased tooth, which may give to the face a one-sided appearance Treatment The affected tooth or teeth must be extracted, and the areas of suppuration cleansed and curetted if necessary The cavity usually has to be packed with antiseptic gauze afterwards for a few days until it begins to fill by healthy granulation tissue Periodontal disease is a name for chronic infection of the periodontal membrane It is one form of inflammation of the periosteum, or alveolar periostitis It causes loosening and shedding of the teeth, pain, failure to masticate, and loss of weight T 694 Teeth, Ewes’, ‘Trimming’ Odontomata are tumours formed in connection with the root of one tooth, or they may be found in the jaw, sinuses, or even involving part of the nasal passage, and be composite or compound, when multitudes of small rudimentary teeth are present They cause swelling and bulging of the surface of the face, and can only be treated surgically Porphyria gives rise to a pink or brown discoloration of teeth (See under BONE, taken An aerosol of mouth flora can remain airborne for up to 30 minutes following scaling It is recommended that: (1) the working area should be well ventilated – preferably with forced air extraction; (2) masks should be worn at all times by anyone in the working area; and (3) a 0.2 per cent chlorhexidine solution should be used as the coolant supplied to the scaling equipment Telogen DISEASES OF.) The resting phase in the cycle of hair growth Toothache is most spectacular in the dog, TEM which rubs its mouth along the ground, paws at its nose or mouth, works its jaws, salivates, and may whine or moan A veterinary surgeon will offer a diagnosis and initiate the necessary treatment Triethylenemelemine, a gametocide which, in America, has been used in field trials for the control of birds The chemical is mixed with corn, and has the effect of making the male bird infertile The birds continue to defend their territories and nest, but not produce any young ‘Broken mouth’ is important in hill sheep (See under main dictionary heading.) Fractures of the canine teeth in dogs are not uncommon If the pulp is exposed, subsequent infection can lead to a painful abscess Extraction of the remainder of the tooth obviates this but, for show dogs or guard dogs, is undesirable Metal crowns have been applied to dogs’ teeth, but are liable to be dislodged Tooth transplantation has been used in veterinary practice but the results are seldom lasting, due to root resorption and bone replacement Fracture of the transplanted tooth is likely after a couple of years or so Teeth, Ewes’, ‘Trimming’ T It has been estimated that between 60 and 70 per cent of culling of ewes is on account of their teeth A small percentage will involve loss of molars or incisor wear, but the vast majority will be incisor loss Ewes have been treated for ‘bite correction’ by means of an electric grinder, a practice that originated in Australia The procedure has been strongly condemned on welfare grounds (See also ‘BROKEN MOUTH’.) Teeth Scaling The use of ultrasonic dental scalers is widely accepted in veterinary dentistry During the scaling, an aerosol of water droplets is formed, with a variable amount of periodontal debris spattered from the patient’s mouth In the debris there are likely to be viruses and/or bacteria – a danger for operator, assistant, or subsequent patient unless precautions are Temperament, Change in This may follow a brain tumour or infection, as occurs in BOVINE SPONGIFORM ENCEPHALOPATHY and RABIES, for example A horse may become bad-tempered as the result of EQUINE VERMINOUS ARTERITIS Poisoning may cause frenzy or aggressiveness, e.g BENZOIC ACID poisoning in the cat (See also BRAIN DISEASES; STRESS; FUCOSIDOSIS.) Temperature, Air (see under HOUSING OF EXHAUSTION; TROPICS) ANIMALS; HEAT Temperature, Body Body temperature is controlled by the heat-regulating centre in the brain – the hypothalamus, which also influences blood circulation, secretion of urine, and appetite – all of which have a bearing on body temperature Heat is produced by the muscles and by the digestive organs, and during very cold weather or exercise, heat from the former increases, while that from the liver and other digestive organs decreases The animal may also absorb heat from the sun’s rays Heat is lost by evaporation of water, and by sensible heat loss (see under HEAT LOSS) Water loss is achieved via the lungs and the skin, e.g by panting and sweating (The dog is, for all practical purposes, a non-sweating animal apart from the pads of its feet, and has to rely mainly on panting.) Diurnal variations in body temperature are normal; in the early hours of the morning it is Tendon usually at its lowest, and at its highest in the late afternoon For ordinary practical purposes the usual average temperatures of animals are given as follows: Horses 38.0°C (100.5°F) Cattle 38.9°C (102.0°F) Sheep, goats 40.0°C (104.0°F) Pigs 39.7°C (103.5°F) Dogs 38.3°C (101.0°F) Cats 38.6°C (102.0°F) Rabbits 38.2°C (100.8°F) Fowls 41.6°C (106.9°F) Small birds 42.5°C (108.6°F) Elephants 36.4°C (97.6°F) Camels 37.5°C (99.5°F) Temperature-taking The most satisfactory place is within the rectum In females the thermometer may also be inserted into the external part of the genital canal; as a rule, the vaginal temperature is about half a degree higher than the rectal temperature, so that when a series of temperatures is to be taken, one site or the other should be selected With dogs and cats, one person should hold the animal, preferably on a table, while another inserts and holds the thermometer In each animal, after the bulb of the thermometer has been lubricated with a little soap or Vaseline, etc., the tail is raised vertically by the left hand, and the thermometer is inserted through the anal ring and into the rectum, by a screwing movement if any resistance is encountered It is held in position for 30 seconds, or minute, according to the make of the thermometer, and then withdrawn With a piece of cotton-wool any adherent faeces are wiped away, and the temperature is read off Subsequently, the thermometer should be washed in cold water, and a cold solution of disinfectant used to disinfect it For purposes of temperature stress research, American scientists use a special ear thermometer in cattle As in similar medical research, this tympanic thermometer is more reliable than the rectal thermometer, and can sense changes as small as 0.05°C (1⁄50°F) Temperature in disease A high temperature is one of the classic symptoms of fever, and in greater or less measure accompanies practically all acute cases of disease A comparatively steady rise in temperature is as a rule succeeded by a correspondingly steady fall, and is to be looked upon as a more favourable sign of the natural course of a disease than when the temperature rises and falls with greater suddenness The reduction of temperature in simple fevers is 695 in almost all cases much slower than the rise A wavering temperature, which shows little tendency to come down to normal, generally indicates that there is some active focus of disease, such as an abscess, which the body cannot overcome Sudden rise in temperature in an animal which has shown a steady fall previously is an indication of a relapse or recurrence of the disease (See also FEVER; HYPERTHERMIA; HEAT-STROKE; TROPICS.) Fall of temperature may be occasioned by great loss of blood, starvation, collapse, or coma; it is characteristic of certain forms of kidney disease Certain chronic diseases in which emaciation is marked are also associated with a subnormal temperature (See also HYPOTHERMIA.) Temperature, near calving time A healthy cow – even though showing the familiar signs – is unlikely to calve during the next 12 hours if her temperature is 39°C (102°F) This is a useful guide to herdsmen (See also under FEVER; HOUSING OF ANIMALS, etc.) Temperature Control in Animal Housing (see CONTROLLED-ENVIRONMENT HOUSING) Temperature-Sensitive (TS) Viruses (see VACCINE) Tenderness Tenderness is pain that is felt only when a diseased or injured part is handled Tendon Tendon is the dense, fibrous, slightly elastic cord that attaches the end of a muscle to the bone or other structure upon which the muscle acts when it contracts Tendons are composed of bundles of fibrous tissue, white in colour, and arranged in a very dense manner, so as to be capable of withstanding great strains Some are rounded; some are flattened into ribbons; others are arranged in the form of sheets; while those of a 4th variety are very short, the muscle fibres being attached almost directly on to the bone or cartilage which they actuate Most tendons are surrounded by sheaths lined with membrane similar to that found in joint cavities, i.e synovial membrane In this sheath the tendon glides smoothly over surrounding parts The fibres of a tendon pass into the fibres of the periosteum covering a bone, and blend with them One of the largest tendons in the animal body is the Achilles tendon, which runs T 718 Transmissible Mink Encephalopathy accommodation; cross-suckling affected piglets onto recovered sows; using antibiotics to control secondary infection Control TGE is spread by direct or indirect contact with infected faeces; strict attention to disinfection and hygiene is essential Sows due to farrow, and sucking piglets under days old should be isolated Exposure of uninfected pigs to recently infected stock may help to develop herd immunity Transmissible Mink Encephalopathy A spongiform encephalopathy which has been reported in mink in the USA The affected mink were fed bovine offal Transplants (see EMBRYO TRANSFER and SKIN GRAFTING TRANSPLANTATION) Transponder An electronic device which stores information that can be read by a suitable scanner In miniaturised form, transponders are the basis of identity MICROCHIPS Transport Stress T Stress caused by transportation can adversely affect the welfare and health of farm animals and the meat quality of the carcase A method has been developed for measuring the adverse nature of the noise and vibration components of transport, using operant conditioning The equipment is a modification of a machine originally developed for testing tractors, and consists of a pen which is tilted up and down in all directions, generating a noise of 80 decibels It was found that pigs soon learn to press a panel with their snouts in order to obtain a 30-seconds respite from vibration and keep the machine immobile for 70 to 80 per cent of the time The animals switch the machine off more frequently when the speed of vibration is increased and also when they have eaten a large meal just before the test During an hour-long session the frequency with which the machine was switched off tended to increase, showing that aversion to the conditions does not diminish with time Pigs which have experienced the machine will press the switch when exposed to a recording of the noise even when there is no movement In contrast, naive animals not learn to operate the switch when exposed to the noise alone The advantage of this technique is that specifications for improved methods of transport can be based on the animal’s own preferences (AFRC.) Traumatic Pericarditis (see HEART DISEASES) Travel Sickness Travel sickness is observed in dogs and cats – some individuals being particularly susceptible – and may be relieved by the administration of a suitable tranquilliser prior to the journey Fitting a chain to a car so as to act as an earth has been recommended, but may be less effective than periodic stops and adequate ventilation It may also occur in horses on long sea voyages (See also TRANSIT TETANY.) Treads Treads are injuries inflicted at the coronet of the horse’s foot, either by the shoe of the opposite foot, or, when horses are worked in pairs, by the adjacent horse When situated in the posterior half of the foot, the upper free edge of the lateral cartilage may be damaged and a QUITTOR result Trefoil Consumption of the plant is a cause of in Australia LIGHT SENSITISATION Trematode An unsegmented flat worm or fluke (See LIVER-FLUKES; LUNG-FLUKES; RUMEN-FLUKES; SCHISTOSOMIASIS.) Trembling in Dogs (see under SHIVERING) Tremors Very fine jerky contractions of a muscle or of some of the fibres of a muscle They are often seen in nervous animals when frightened, and they are one of the signs of viciousness in a horse when seen on the quarters, especially when the horse is watching out of the corner of its eye Tremors are, however, encountered in certain nervous disorders, such as shivering in horses and chorea in dogs (See also ‘CRAZY CHICK’ DISEASE.) HYPOMAGNESAEMIA in cattle, and RABIES in many species, also give rise to tremors (For tremors in pigs, see SWINE FEVER.) Trephining Trephining is an operation in which a small disc of bone is removed from the cranium to permit the elevation of a depressed portion, or to allow access into the brain cavity In certain purulent conditions of the air sinuses of the horse’s head, trephining may be required to give drainage for the pus Trichostrongylosis Treponema A genus of spiral organisms of the family Treponemaceae, which includes also Borrelia and Leptospira (See also SWINE DYSENTERY.) Triatomid Bugs Triatomid bugs are the most important vectors of human trypanosomiasis in South and Central America Trichiasis Ingrowing eyelashes (see EYE, DISEASES OF) Trichinosis Trichinosis is an infestation of the muscles of the pig, man, dog, etc., with the larvae of Trichinella spiralis, a small roundworm Pigs become infected by eating infected rats, or raw swill or garbage containing pieces of infected pork Trichinosis constitutes a serious problem among sledge-dogs in the Arctic and may follow the eating of walrus, bear, seal, or foxmeat A temperature of –15°C for 20 days is needed to kill the larvae Infection in man occurs through the eating of raw or undercooked meat Human symptoms include pain in muscles; myocarditis, meningitis, encephalitis, and rarely death have occurred An outbreak of trichinosis in Paris, involving 300 proven cases, followed the eating of horsemeat either raw or served rare All this meat had come from shops, and originated from a single horse imported from the USA The main symptoms in this outbreak were fever, muscle pain, swollen face and eyelids, a rash, and digestive system upsets The disease has not been seen in the UK for some years, but outbreaks have occurred (See ROUNDWORMS.) Trichocephalus (Whip-Worm) Trichocephalus (whip-worm) is the name of a worm that infests the caeca of various animals (See ROUNDWORMS.) Species of this genus very commonly occur in the intestinal canal of many different species of mammals and birds Trichomoniasis Trichomonas fetus causes abortions, pyometra, and sometimes sterility in cattle The cow becomes infected by the bull at coitus, or vice versa Signs A transient vaginitis, which is often overlooked If conception has not occurred, a chronic form of endometritis follows If the cow is pregnant, the fetus dies and is either aborted to months later or retained in the uterus, where it becomes macerated and a pyometra develops Control of the disease includes the disposal of infected bulls, withholding all breeding operations on infected cows for at least months, and the serving of non-infected cows and virgin heifers by a ‘clean’ bull Freezing bull semen to –79°C, in the presence of 10 per cent glycerol, kills T fetus but allows the spermatozoa to survive This method of deep-freeze, commonly practised at AI centres, is one way of getting rid of the infection from semen Avian trichomoniasis, caused by T gallinae, affects the oesophagus of budgerigars, pigeons, etc, causing necrotic lesions with retching and vomiting Also known as canker or roup In pigeons, which feed their young on ‘crop milk’, squabs are easily infected which led to the belief among pidgeon-fanciers that the disease was inherited It can be treated with dimetridazole or nifursol Trichophyton (see RINGWORM) Trichostrongylosis Parasitic disease caused by infection with Trychostrongylus worms It can affect most Trichodinella and Trichodinia Trichodinella and trichodinia are skin parasites of fish Their sharp, rasping teeth damage the skin Trichoglyphs (see WHORLS) Trichomonas The flagellates of the genus Trichomonas are usually pear-shaped, with to anterior flagella, an undulating membrane and, in some species, free flagellum directed backwards 719 Trichomonas fetus T 720 Trichostrongylus mammals, causing poor growth, lack of condition and diarrhoea Trichostrongylus A large group of parasitic worms which infest both people and their domestic animals, and which cause persistent diarrhoea Trichothecenes Trichothecenes are fungal metabolites which contaminate animal feeds and human foods Examples are deoxynivalenol and nivalenol The most potent toxin is T2 TOXIN Throat irritation and digestive disorders are caused in people Baking does not destroy the toxin Tricuspid Valve The tricuspid valve is the valve lying in the heart between the right atrium and the right ventricle, which possesses cusps or flaps (See HEART.) Trigeminal Nerve Trigeminal Nerve is the 5th of the cranial nerves (See NERVES.) Trimethoprim A drug which inhibits the growth of many bacteria and some protozoa through reducing their synthesis of folinic acid (necessary for synthesis of nucleic acids) Effective against many Gram-positive and Gram-negative bacteria One part of trimethoprim is combined with parts of sulfadiazine, with which it is synergistic, in co-trimazine Several other preparations of trimethoprim with one or other of the sulfa drugs also exist Triorchidism T A condition in which testicles are present This was found in a cock – all being functional, and structurally independent A case in which there was duplication of the right testicle was seen in a calf (In man, triorchidism is not extremely rare, and even testes in a scrotum have been recorded.) Triplet Calves In the UK in 1985 a Friesian cow had triplets After initial breathing difficulties, all survived and were described as ‘fine, strong calves’ Quintuplets have been recorded Triploid An animal having one and a half times as many chromosomes in its cells as a normal (i.e diploid) animal (See COLCHICINE.) Triploidy accounts for up to 13 per cent of embryonic loss in animals, and for 20 per cent of all chromosomally-caused spontaneous human abortion (ARC) (See CHROMOSOMES; CYTOGENETICS.) Trismus The locking of the jaws, which is characteristic of TETANUS Trisomy The presence in triplicate of a particular chromosome In the cow, such a condition would be denoted as 61,XXX X-trisomy is associated with nymphomania and infertility in cows Trixacarus Caviae The mange mite which is a parasite of guineapigs Trixylphosphate A substance used in the manufacture of plastics Poisoning of cattle has occurred through contamination of molasses with this substance Symptoms included diarrhoea, coughing, unsteady gait, partial paralysis Trocar A sharp-pointed, rod-like instrument used with a cannula to puncture the wall of a body cavity It is often used to release gas in cases of bloat in ruminants Trochanter One of the protuberances on the femur which serve as attachment sites for hindquarter muscles Trochlear Nerve The 4th cranial nerve (see NERVES), also known as the pathetic nerve It controls the superior oblique muscle of the eye Trombiculosis Infestation with Trombicula autumnalis, the harvest mite Trophic Relating to nutrition; neurotrophic means the influence that nerves exert upon the tissues to which they are distributed, for health and nourishment Trophins Gland-regulating hormones Tropics, Livestock Production in the Trophoblast The outer layer of BLASTOCYSTS which make contact with the wall of the uterus, and through which nutrients and waste products are exchanged between fetal and maternal circulations (See also SYNCYTIUM.) Tropics, Livestock Production in the Livestock farming in the tropics, and even in some subtropical developing countries, is beset with difficulties not experienced to anything like the same degree in developed countries having a temperate climate In developing countries there is often the additional problem of limited financial resources Money may not be available for measures to counter or ameliorate adverse conditions for animals; to provide adequate supplies of safe drinking water, good-quality feeds, vaccines, prophylactic drugs; or to support disease eradication programmes on a large scale Veterinarians are usually few in number in relation to the large areas in which they are needed (see VETERINARY PROFESSION), and faced with great distances to cover and an absence of local laboratory services Heat Animals can survive in temperatures of up to 60°C (140°F) Temperatures above that are lethal Cattle in Death Valley, California, and in Queensland, Australia, for example, exist at temperatures of 52° to 58°C (125° to 136°F) Such heat, however, is far above the comfort zone – estimated as air temperature at between 21° and 26°C (70° to 79°F); or 13° to 18°C (55° to 64°) for adult cattle High temperatures impose stress upon the animal’s physiological processes and productive capacity Records for more than 12,000 inseminations over a 2-year period in a Florida herd indicated a sharp decline in conception rates of cows when a maximum air temperature the day after artificial insemination exceeded 30°C (86°F) (35°C (95°F) for heifers) Besides air temperature, radiation, air movement, and humidity all influence the animal’s immediate environment Body temperature is controlled by the heat-regulating mechanism (see HYPOTHALAMUS), and affected not only by environmental heat but also by the heat generated in the tissues (see METABOLISM) The more the animal eats, the more heat its body will produce Water intake also plays a part in the physiological reactions; as does sweating, but in this respect cattle are less efficient than people In great environmental heat, the point may be reached where normal body 721 temperature cannot be maintained, and it rises – a state of HYPERTHERMIA Death may result Even at non-lethal levels, tropical heat is a limiting factor so far as fertility and yields of milk, meat and eggs are concerned Poor feed, and water deprivation, can further depress growth rates, fertility, and yields Humidity can increase heat stress Signs Heat stress may cause the body temperature to rise to 42° to 43°C (110°F) in cattle The earlier symptom of rapid breathing progresses to panting The mouth may be kept open, tongue lolling out, and frothy saliva may be in evidence Appetite is lost Cattle may remain standing, huddling together Preventive Measures If heat stress is to be avoided or minimised, livestock must have shade (from trees or shelters) to protect them from the sun’s rays Cooled drinking water is beneficial to all livestock in tropical heat Pigs need to be able to wallow – their normal, instinctive method of cooling themselves Cool water sprays can help dairy cattle to withstand high temperatures Grazing should take place at night rather than during the day Zero-grazing may be practicable in some places, and beneficial too Poultry in the tropics grow larger combs and wattles than similar birds in temperate climates, as a physiological means of body cooling At very high temperatures they dip combs and wattles into water, for an extra cooling effect It has been suggested that the design of drinkers in intensive poultry units should be such as to make possible this beneficial practice Antibiotics and poultry In developing countries in the tropics, the widespread use of antibiotics – especially the tetracyclines – in modern battery poultry units has been blamed for encouraging the proliferation of drug-resistant bacteria Where indiscriminate use is coupled with poor sanitation and low personal hygiene, the situation may constitute a danger to public health In a study in Nigeria of E coli, 1248 strains isolated from battery hens at the University of Ibadan, and 2196 strains from a commercial poultry farm, were resistant to tetracycline, streptomycin, and also sulfonamides By contrast, all strains isolated from free-range town and village poultry were sensitive to these drugs Altitude In some regions, altitude mitigates the effect of heat The uplands of Jordan are T 722 Tropics, Livestock Production in the regarded as suitable for intensive poultry production; and Iran’s uplands, with their dry climate, make dairy farming practicable despite very high summer temperatures of 43°C (109°F) upwards, and very cold ones in winter When temperature falls during night-time hours, cattle may withstand a higher day-time temperature than they otherwise could Very high altitudes, e.g in the mountains of Peru, can themselves be an obstacle to livestock production (See ALTITUDE; MOUNTAIN SICKNESS.) Stock improvement When high-yield stock are imported into tropical regions from countries having a temperate climate, disappointment often follows At first, yields – whether of beef, milk, pork, or eggs – are better than those of the indigenous stock, as expected; but before long, in many instances, the initial gains are offset by a high mortality rate The exotic animals may not be able to tolerate the heat, may not produce so well when fed on local feeds of lower quality, and will have no resistance to many local diseases and parasites, especially ticks (For cattle resistant to heat and ticks, see DROUGHTMASTER; ZEBU; SANTA GERTRUDI; AFRICANDER.) In many situations it is often preferable to improve indigenous stock first, before introducing new blood from overseas, by selective breeding and better management; ensuring that they are better fed and not deprived of adequate quantities of drinking water After improvement has been obtained by these means (but not before), cross-breeding with exotic highperformance stock may be begun, preferably on a small-scale trial basis to start with Use may be made of AI Animal power In India it is estimated that work animals provide as much energy as the T entire electrical system of the country The num- ber of work animals is estimated to be 70 million bullocks, million buffaloes, million horses and million camels Throughout the Far East animal power remains the major factor in agriculture Small farms, difficult terrain, lack of roads and the structure of the rural economy in many countries mean that situation is unlikely to change in the foreseeable future (See WATER BUFFALOES.) Animal feeds In poorer countries the cost of importing cereal grains or high-quality protein feeds may be prohibitive, and local stock will then be dependent on feeds which may restrict their yields – though obviously this is not always the case Imported feeds sometimes deteriorate to some extent during long sea voyages and subsequent storage in a hot and often humid climate There may, for example, be a serious loss of vitamin E, so that a supplement is required if ENCEPHALOMALACIA is to be avoided (See also VITAMINS.) Local crops such as groundnuts, cotton seed, sorghum and sunflower seed may be contaminated by AFLATOXINS, so that precautions are needed Groundnuts may be affected in this way through being left too long in the ground before harvesting, or during subsequent storage Minerals In many parts of the tropics, milling and processing facilities are lacking – at any rate in the more remote areas; this fact makes feed supplementation more difficult Mineral and trace element supplements are necessary for avoidance of deficiencies In South Africa many years ago, Sir Arnold Theiler showed that the need of cattle for phosphorus drove them to eat the bones of dead animals, and many cattle became infected with botulism in that way and died (See LAMZIEKTE.) In several parts of the world a deficiency of copper in the herbage has impeded livestock production, and appropriate dressings of the land have brought great benefit (See TRACE ELEMENTS.) Some tropical crops Apart from the crops mentioned above, many others – or their byproducts – are used For example, cattle may have the leaves of shade trees, or sugar-cane; pigs may be given dried leaf meal, banana waste, coca pod husks, or sweet potatoes; poultry may receive millet (if any can be spared from human food requirements) or sago (See GOSSYPOL – Gossypol poisoning; CASTOR SEED POISONING; COCOA POISONING.) Tropical diseases In some tropical regions the presence of animal parasites and their vectors makes livestock production difficult, costly, or even impracticable This is true of the African tsetse-fly belt, extending roughly from latitude 15°N to 30°S Here control of trypanosomiasis (see TRYPANOSOMES) is dependent on drugs for prevention, drugs for treatment, and use of insecticides against flies Aerial spraying, bush clearance, and attempts to eradicate reservoirs of infection among wild animals will, if undertaken, obviously add to the cost, which in some territories may be beyond local resources For many years control of tsetse flies Trypanosomes had been successfully achieved by aerial spraying with insecticides, but the ever-rising cost of these, and of aviation fuel, has led to the abandonment of many such government schemes Fly traps have had to be used instead The Manitoba trap designed specially for tabanids is reported to be very successful; another widely used trap is the Laveissire In other territories long-term, government-controlled campaigns have proved successful in maintaining and extending production Humpless cattle, such as the N’Dama, in West Africa had long been regarded as historic relics, and their reduced susceptibility to trypanosomiasis as a biological oddity It has been shown, however, that despite their relatively small size, N’Dama cattle could survive and be productive in endemic trypanosomiasis areas where Zebu cattle died Comparative studies on types of large East African zebu (Bos indicus) Boran cattle, on a beef ranch in Kenya, indicated that a Boran type bred by the Orma tribe has a superior response to tsetse fly challenge The Orma Boran when compared with an improved Boran was found to have lower trypanosome infection rates and, when untreated, better control of anaemia as well as decreased mortality In areas where trypanosomiasis is endemic in susceptible cattle, sequential use of such drugs as diminazine and suramin has been effective in controlling the disease without causing drug resistance to develop Trypanosomes cause disease also in Asia and Central and South America Ticks are of great importance in the tropics, transmitting numerous protozoal parasites, viruses, and rickettsias (See under TICKS.) Among the major diseases caused by viruses are cattle plague (rinderpest), African swine fever, foot-and-mouth disease, and various types of encephalitis Bacterial diseases include anthrax, botulism, haemorrhagic septicaemia (pasteurellosis), and salmonellosis A notable mycoplasmal disease is contagious bovine pleuropneumonia; another is contagious agalactia of sheep and goats Vaccine storage/transport One of the problems of veterinary medicine in the tropics is the storage of vaccines at a sufficiently low temperature (below 8°C (46°F)) With the high cost and scarcity of kerosene or liquid propane gas in many rural areas, and the fact that electricity supply is often unreliable or nonexistent, there is scope for solar refrigerators Under a WHO scheme these have been tried in 13 countries Photo-voltaic panels exposed to 723 the sun supply electricity direct to an ordinary commercial refrigerator Sterilisation In the tropics the sun’s rays can be used for sterilisation purposes Research at the American University of Beirut showed that oral rehydration solution, for treating dehydration, can be sterilised in plastic bags or transparent plastic or glass vessels by exposure to sunlight In an experiment such a solution, contaminated with fresh sewage, proved to have a zero coliform count after hour It appears that the sterilising effect is not heat, since the temperature of the solution rises by less than 5°C (41°F) after hours, but is rather solar radiation in the near ultra-violet range Another application is the Solomon solar steriliser which uses only solar energy to boil water and sterilise needles and syringes The prototype consisted of a metal-lined plywood box topped with a truncated pyramid of glass The steriliser, in use in the Solomon Islands, is easily constructed, has no moving parts, and requires no fuel; but it does need orienting to the sun every half-hour (World Health Organisation.) Carcase disposal, following post-mortem examinations, may present problems in undeveloped areas An Australian veterinarian working at an Indian sheep project found the answer If unsuitable for boiling as dog food, and yet not likely to spread infection, the carcase is dragged out into the open He timed events on one occasion ‘At 2.46 p.m., postmortem examination completed; no vultures to be seen in a clear sky At 2.50 the first arrived; at 2.53 there were approximately 40 vultures around the carcase; at 2.58 carcase stripped to bones and sinew – vultures leaving.’ Trypanocide A drug which will kill the host’s body TRYPANOSOMES within Trypanosomes Trypanosomes are small single-celled parasites found in the bloodstream in certain diseases that are classed together as the trypanosomiases The trypanosome is of an elongated shape with a single flagellum and an undulating membrane There are nuclei – a large nucleus (macronucleus or trophonucleus) near the centre of the body; and a small kinetoplast (micronucleus) at the posterior end remote from the flagellum In some forms there is no free flagellum T 724 Trypanosomes Transmission is generally by the bite of an insect (except in the case of dourine) The transmission may be mechanical, i.e carried directly from an infected animal to an uninfected one by the bite of a blood-sucking fly; or cyclical, when the insect host is not infective for a definite time after ingestion of the parasite In this case the parasite passes a definite part of its life-cycle in the fly In many cases transmission may be both mechanical and cyclical Thus the tsetse fly may have two infective periods, one immediately after biting a sick animal and the second some time later (about 20 days) after the trypanosome has progressed to its infective stage along normal lines Life histories of trypanosomes In the blood of the mammalian host, the trypanosomes reproduce by splitting lengthwise (longitudinal fission) A quantity of blood is T Some typical trypanosomes (drawn to the same scale and magnified 2000 times): (a) Trypanosoma brucei; (b) T montgomery; (c) T congolense; (d) T vivax; (e) T simiae; (f) T equinum; (g) T equiperdum; (h) T evanis; (i) and (j) T theileri Tsetse Fly sucked up by the tsetse fly, a species of Glossina, and in that host the flagellates undergo a developmental cycle The location chosen by the parasite for its development varies with the species Thus some will develop only in the salivary glands, others in the gut, and still others in the proboscis After some time they assume the infective form, and are ready to be passed with the salivary fluids into the bloodstream of a suitable vertebrate host African trypanosomiasis Tsetse-borne trypanosomiasis renders approximately 10 million square km of prime African land unsuitable for cattle production It has been estimated that if this disease could be controlled, the infested area would increase its cattle holding capacity from 20 million head to 140 million head The disease is of greatest importance in cattle, which are hosts of the following trypanosomes: Trypanosoma congolense, T vivax, T uniforme, and T evansi Usually a chronic disease, acute cases also occur, and the mortality may be high (See also PREMUNITION; and, for resistant breeds, TROPICS.) Signs These include intermittent fever, anaemia, anorexia or pica, a progressive loss of condition, and increasing weakness (See under CHANCRE for the hard swelling which is often the first pointer to trypanosomiasis.) Lymph nodes are enlarged in many cases, the coat harsh, and abortion may occur Some cattle recover, but in others apparent recovery is followed later by a relapse and death In acute cases, death may occur within a fortnight Horses Additional signs include oedema of the limbs and abdomen, and corneal opacity Species of trypanosome infecting horses are T brucei, T vivax, and T evansi (See also DOURINE, caused by T equiperdum, transmitted at coitus, and occurring also in Asia.) Dogs The eyes may be affected, as in horses Canine trypanosomiasis is caused by T brucei, T congolense, and T evansi Pigs often suffer from acute and fatal trypanosomiasis caused by either T simiae or T evansi Control This is difficult, on account of trypanosomiasis existing in wild animals in the vicinity of cattle herds, and the fact that vaccination has not been practicable 725 In well-managed herds in areas where tsetsefly numbers are relatively low, drugs are used for preventive purposes against the trypanosomes; but as the latter develop drug resistance, it is usually necessary to change drugs In other areas, reliance is placed on drugs for treatment rather than prophylaxis; these can achieve survival of cattle where untreated animals die (See also under TSETSE FLY for another aid to control of the disease, and under TROPICS for breeds resistant to trypanosomiasis, and for drugs in current use.) Diseases caused by trypanosomes are separately described under NAGANA, DOURINE, SURRA and (for human trypanosomiasis) SLEEPING SICKNESS and CHAGAS DISEASE The latter also affects domestic animals and is described immediately below American trypanosomiasis (Chagas disease) Caused by Trypanosoma cruzi, this occurs in South and Central America, and also in the southern states of the USA WHO estimates that at least million people are infected with T cruzi The infection can be carried from both wild and domestic animals to people by bloodsucking triatomid bugs; and the latter also cause people-to-people infections Blood transfusions, and infection of the human fetus in utero, have also to be borne in mind Dogs, cats, and guinea-pigs are among domestic animals which are hosts; pigs and rabbits also have the disease Rats, mice, foxes, ferrets, and vampire bats are other vectors Signs Fever, anaemia, emaciation, ascites, with death from heart failure following myocarditis in children Trypsin Trypsin is a proteolytic enzyme of the pancreatic secretion It changes proteins into peptones It is said to be helpful in cases of non-specific diarrhoea in dogs Tryptophan One of the essential AMINO ACIDS Excessively high levels of tryptophan can result in fog fever (atypical interstitial pneumonia) Tsetse Fly Tsetse fly is the insect vector which is of such importance in the transmission of African TRYPANOSOMES (See also FLIES – Glossina; TROPICS.) Destruction of tsetse flies in the fly-belts – tracts of bush country in which only cattle T 726 Tubercle which have acquired some degree of immunity to trypanosomiasis can survive – has proved an almost insuperable problem One method is the sterilisation of tsetse flies by the chemicals tepa or metepa, or by gamma radiation, and the release of sterile males This can be complementary to the use of insecticides A difficulty at present is the rearing of tsetse flies in sufficient quantities Wide use is also made of fly traps, to which tsetse flies may be attracted by means of PHEROMONES or other chemical compounds such as CO2, acetone, or octenol Tubercle Tubercle is a term used in quite distinct senses As a descriptive term in anatomy, a tubercle means a small elevation or roughness upon the surface of a bone, such as the tubercles of the ribs In a pathological sense a tubercle is a small mass, barely visible to the naked eye, formed in some organ as the starting-point of the disease which has been called after the tubercle, viz tuberculosis Tuberculin Test T The tuberculin test, in its original form, came into use in 1890 It was developed by Koch, who grew his tubercle bacilli on broth Today, Purified Protein Derivatives (PPD) extracted from bovine and from avian tubercle bacilli are used These greatly improve the reliability of the test, although false positives still occur Tuberculin (PPD) is prepared from killed bacteria by adding trichloracetic acid; the precipitated tuberculo-protein is allowed to sediment, collected by centrifugation and adjusted to a standard strength Tuberculin has in the past been used by instillation beneath the lower eyelid of one eye (the ophthalmic test); or by subcutaneous injection (the subcutaneous tuberculin test) Today, in the UK, the test used is the double intradermal comparative test Skin is clipped free from hair over an area the size of a 50p piece in places on the neck A fold of the clipped skin is gathered up and measured with special callipers Using a standard tuberculin syringe, 0.1 ml of tuberculin is injected into the skin (not subcutaneously) Avian tuberculin is used for one injection, bovine for the other – the avian tuberculin being given above the bovine After 72 hours, the test is read by again measuring the thickness of the skin and the nature of the swelling produced by the injection A reaction to the avian tuberculin can mean exposure to Mycobacterium avium (especially if cattle are close to woods – pigeons are often infected), the presence of non-specific mycobacterial infection, of Johne’s disease or so-called skin tuberculosis The swelling caused by the avian tuberculin is compared to that caused by the bovine, using the same callipers If reaction to the bovine is mm or more than the avian, that is considered a positive reaction; a swelling of mm indicates an inconclusive reaction Reactors are normally slaughtered at a licensed abattoir and certain organs removed for examination, even if there are no visible lesions Inconclusive reactors are usually retested 75 days after the first test If a herd being tested has previously been vaccinated against Johne’s disease, the State Veterinary Service will normally carry out the test as this vaccination produces a severe reaction to tuberculin Testing other animals Tuberculin testing of deer requires special training, as a swelling of as little as 0.5 mm difference, can be considered significant Poultry can be tuberculin-tested using only the avian tuberculin injected intradermally into the left wattle Any resulting swelling of that wattle is regarded as significant Sheep, goats and pigs can be subjected to the double intradermal comparative test, with the avian tuberculin being given on the left side of the neck and the bovine on the right As pigs are not clipped, a ring made by indelible marker is drawn round the site of the injection Primates in zoos or research facilities may be tested; only mammalin tuberculin is used and the test carried out under sedation, using the left eyelid Any swelling is regarded as significant Tuberculosis (TB) A contagious disease of man, all the domesticated animals, many wild animals in captivity, birds, fishes, and reptiles It is caused by Mycobacterium tuberculosis (bovine, human, or avian strains) It is a NOTIFIABLE DISEASE in cattle and deer The disease is usually a chronic one, though the miliary form is acute It is characterised by the formation of nodules or tubercles in almost any or all of the organs or tissues of the body (See also ‘SKIN TUBERCULOSIS’.) Occurrence The prevalence of tuberculosis in animals bears a direct ratio to the intensity of the methods of agriculture in an area Cattle closely confined, and housed to a great extent in buildings, are much more often affected than are those living a free open-air life The cattle in the prairies of North America, on the tablelands Tuberculosis (TB) 727 of Central Africa, and in the steppes of Eastern Europe, are almost entirely free from its ravages, while it is unknown in many islands (Iceland, Sicily, etc.) Bovine tuberculosis eradication campaigns have succeeded in several countries Superficial, as well as deep, lymph nodes may become enlarged A subclinical infection may occur, and result in overt illness only when stress, under-feeding, exposure or some other infection lowers the animal’s resistance Animals affected Among the ordinary Cattle As a rule a considerable period of time domesticated animals, cattle and pigs are more commonly affected than are other species Dogs are rarely infected but have been known to contract TB Horses and sheep appear to be more resistant, though cases of progressive avian TB have been recorded in both species Donkeys and mules are only very seldom attacked elapses between infection and the appearance of the first symptoms Tuberculosis of the lungs – the commonest type – gives rise to a hard, dry, short cough in the early stages Later, coughing becomes more frequent and DYSPNOEA is evident Appetite is variable Sometimes a difficulty in swallowing is noticed Loss of condition follows, with pale mucous membranes, and a staring coat There may be diarrhoea Superficial lymph nodes may become enlarged Those at the back of the throat or at the corner of the lower jaw, or the glands of the neck, shoulder, or stifle, may be swollen Tuberculosis of the udder – which is allimportant from the milk standpoint – begins insidiously The gland slowly becomes diffusely thickened, and more solid to the touch than normally After milking, it does not feel quite so elastic as it should, and in some cases distinct hard nodules can be felt (Tuberculoid mastitis Over 700 cases of this, due to rapidly growing acid-fast organisms other than Mycobacterium tuberculosis, occur in the UK annually – mainly due to not cleaning the teats before introducing antibiotics.) Tuberculosis sometimes involves the brain or spinal cord, giving rise to symptoms described under MENINGITIS Tuberculosis of the bones and joints is not uncommon In the skin there occasionally develop hard tumours, about the size of a hazelnut (see also ‘SKIN TUBERCULOSIS’), which, if they are opened, are found to contain cheesy or mortar-like masses in their centres Later, ulcers may develop with the formation of multiple small abscesses in any or all of the organs The abscesses are millet-seed sized (hence ‘miliary’) This form of tuberculosis is rapidly fatal Methods of infection Cattle are infected in chief ways: (1) by the respiratory system; and (2) by the digestive tract They are susceptible to infection from humans suffering from bovine tuberculosis, and serious breakdowns in attested herds have been traced to farm workers suffering from the disease Cattle are also susceptible, to a lesser degree, to infection of the human type (See also under TUBERCULIN TEST re avian tuberculosis.) Badgers have been implicated in the spread of bovine TB and longrunning tests are taking place in the UK to establish whether this is the case (see below, Tuberculosis in wildlife) Sometimes tuberculosis may be contracted through a wound (e.g after dehorning) or by direct introduction into the tissues of a penetrating instrument, and an infection of the udder may easily occur through the teat canal An aerosol infection commonly results from coughing cows, and infected sputum may contaminate feed or be swallowed, thereby spreading infection to the intestines Within the body, infection may spread via the lymphatic system or the bloodstream Tuberculosis of the vagina occurs in cows, and the disease may be spread from them to healthy cows through the medium of the bull Infected dung can be a source of infection Nature of the lesions A typical lesion is a tubercle – a small nodular swelling whose centre contains either pus or dry yellowish cheesy material The peritoneum, liver, lymph nodes, lungs, etc., may be affected Sometimes the disease remains localised to the area of its first infection and does not spread In other cases the defensive forces of the body overcome and destroy the focus of infection Tuberculosis may affect bones and one or more joints, causing arthritis Sheep and goats A distressing painful cough, always present, but most noticeable upon exertion; and a gradual, but quite definite, loss of condition, with progressing weakness, are the main symptoms observed in these animals Sheep are very rarely affected, but milking goats kept in the vicinity of infected cattle not uncommonly develop tuberculosis There is nearly always a marked anaemia, pneumonia, T 728 Tuberculosis (TB) sometimes diarrhoea, and occasionally an infection of the udder corresponding to that found in cattle Horses Tuberculosis in the horse is not very common, but there are certain symptoms which should always lead one to suspect its presence: a gradual emaciation in spite of good food and without any other established possible cause; a slight fluctuating increase in the temperature, an occasional moist weak cough; a tucked-up appearance of the abdomen, or in some cases (where ascites exists) a heavy pendulous condition, ‘pot-bellied’ Cases in which the abdominal organs are affected sometimes terminate by lung complications – i.e miliary tuberculosis sets in – the animal becomes feverish, distressed in its breathing, refuses all food, and generally dies within a few days Tuberculosis may also become localised in the skin, lymph nodes, brain, or udder, but these are not common It is comparatively often found that sooner or later some part of the skeleton (the bones of the neck being a very usual situation) becomes infected Occasionally, tuberculosis in the horse may be caused by the human or avian type of the tubercle bacillus Pigs Tubercular poultry, or wild birds such as wood-pigeons, are a not uncommon source of infection A diagnosis may be established by means of the tuberculin test Symptoms are as in the horse Scouring and emaciation may occur Anaemia is common As in horses, the bones are especially vulnerable to attack Lesions, which, to the naked eye, appear identical with tuberculosis, may be caused by infection with Corynebacterium equi Even the use of a microscope sometimes fails to differentiate between the infections T Deer Disease caused by bovine or avian tuber- cle bacilli can be found The clinical signs, which may not be noticeable until the disease is advanced, include respiratory signs Caseous lesions are rarely seen as tuberculous lesions are usually filled with pus Dogs and cats Where tuberculosis is common in the human population, these domestic animals are liable to become infected – either as the result of receiving tubercle-containing milk, or as the result of infection from sputum or discharges from a human case Not only may dogs and cats contract the disease from man, but they may occasionally be sources of infection to healthy human beings, and especially to children As in other animals, the symptoms are somewhat vague until the disease is well established The first signs may be no more than a capricious appetite, slight loss of condition, general weakness, and exhaustion when at exercise Pulmonary tuberculosis usually begins with a short dry cough It is less common in these animals than the abdominal form (but see PLEURISY) Tuberculosis of the abdominal organs is indicated by impaired nutrition and anaemia, attacks of diarrhoea and constipation alternating with each other There may be vomiting, also ascites Body temperature is very variable Joints and sinuses may be sites of infection in the cat Occasionally skin tuberculosis is seen in dogs and cats, and may take the form of raised plaques with a tendency to ulcerate Treatment The treatment of tuberculosis in the domesticated animals is not attempted, for reasons: (1) because of the nature of the disease; (2) because of the ever-increasing danger to human beings who have to attend affected animals; (3) for economic reasons; and (4) for humanitarian ones However, in zoological gardens, animals are sometimes treated (See PAS.) Prevention Good hygiene, good feeding and good ventilation all help Animals brought in from areas known to be infected should be quarantined on the premises and a tuberculin test carried out by the veterinarian befoe they are allowed to mix with other stock History of control in Britain It was not until 1928 that measures to control bovine tuberculosis were introduced by the government In that year, the Tuberculosis Order, enacted in 1915, came into force, and the attempt to control the disease by the detection and elimination of ‘open’ cases began In 1935 the Attested Herds Scheme carried control measures a stage further Area Eradication, which began in 1950, and meant, at first, an extension of the Attested Herds Scheme on a voluntary basis, and then the compulsory slaughter of reactors within the prescribed areas, followed In October 1960, the whole of the UK was declared one Attested Area – bovine tuberculosis being virtually eradicated from all herds of cattle In 1962, the incidence of bovine tuberculosis in herds in England and Wales was Tularaemia 0.14 per cent The number of reactors slaughtered was 8846 During 1968, 5,854,915 cattle were tested in 108,452 herds and as a result 2170 reactors (including ‘affected’ animals) and 202 contacts in 1040 herds were slaughtered The Tuberculosis Orders 1964 provide for the notification and slaughter of cattle found to be affected with certain forms of tuberculosis – i.e tuberculosis of the udder; giving tuberculous milk; tuberculous emaciation; chronic cough accompanied by clinical signs of tuberculosis; or found to be excreting or discharging tuberculous material Since 1990, TB outbreaks in cattle have been increasing by 20 per cent a year in certain parts of the UK, including the West Country and Staffordshire The search is on for a vaccine, which, unlike BCG, does not interfere with the diagnostic skin test Trials of a promising DNA-based vaccine took, place in 2004 Tuberculosis in wildlife In many countries, complete eradication of TB has been elusive because of reservoirs of infection in wildlife In Britain, BADGERS (Meles meles) can become infected and die from TB The form of the disease in badgers is variable but is often respiratory; it can be spread between badgers by aerosol (in the breath) or by the shedding of bacilli in the urine The State Veterinary Service has carried out a long-term policy of eradicating badger populations in the vicinity of cattle herds This has not resulted in an overall improvement of the situation as the disease has spread from the original infected area In 1999, following a report by Professor Krebs, a longterm study to evaluate how TB may be spread between cattle, badgers and other wildlife was begun but was interrupted by the 2001 footand-mouth disease outbreak The aims are to establish definitively what proportion of TB outbreaks in cattle is caused by badgers; and whether culling badgers is an effective way of controlling the disease The trial is in parts: (a) badgers are culled on and around farms following TB outbreaks; (b) those where all badgers are killed; and (c) those where no badgers are culled Part (a) of the trial was discontinued in late 2003 as interim results showed an increasde of 27 per cent in TB breakdowns in that area compared with the other two DEFRA emphasises that the trial will not endanger the viability of the UK badger population of over 300,000; it is estimated that no more than 12,500 badgers will be culled More than that number are believed to be killed annually in road accidents 729 Tuberculosis has been found in other wild animals including deer, foxes and weasels, as well as pigeons and their predators The relationship of tuberculosis in animals and man; bovine tuberculosis This is not a pedantic way of saying ‘tuberculosis in cattle’, but indicates that one is referring to disease set up by the bovine strain of tubercle bacillus as opposed to the human strain or the avian strain Man may become infected by any one of the strains The bovine strain of the tubercle bacillus is particularly pathogenic for children under 16 In considering statistics dealing with incidence of bovine tuberculosis in humans, it must be borne in mind that bovine tuberculosis can be spread from one person to another, just as it can be from animal to man Human infection with tuberculosis may also arise from eating infected meat, but this risk, is, in civilised countries, not great owing to meat inspection services, and cooking of the meat The protection of the human population from TB involves the tuberculin test, meat inspection and pasteurisation of milk Tuberculosis (Amendment) Order 1973 The Tuberculosis (Amendment) Order 1973, made under the Diseases of Animals Act 1950, requires anyone who suspects a carcase to be affected with tuberculosis to notify a veterinary inspector and to retain the carcase (or parts of it) for examination The purpose of the Order is to enable the herd of origin to be traced Isolation of suspected tubercular cattle is also empowered Tuberculosis, Avian (see AVIAN TUBERCULOSIS) Tularaemia Tularaemia is a disease of HARES, ground squirrels, rabbits, and rats, caused by the Pasteurella (Francisella) tularensis, and spread mechanically either by flies or ticks, or by direct inoculation – for example, into the hands of a person engaged in skinning rabbits In man, the disease takes the form of a slow fever, lasting several weeks, with much malaise and depression, followed by considerable emaciation It was first described in the district of Tulare in California, but is found widely spread in North America, also in parts of Europe and Japan Sheep and pigs are attacked and many die Streptomycin may prove effective in treatment Dogs are susceptible, too T 730 Tumbu Fly Tumbu Fly A ram (see under SHEEP) Tumour T Tup (see under SCREW-WORM FLIES) Turbinate Bones Malignant tumours are those which tend to grow and spread rapidly, destroying neighbouring tissues and infiltrating the healthy structures near by They are liable to ulcerate through the skin when superficial, are nonencapsulated, and may spread to distant parts of the body by the blood- or lymph-stream, giving rise to secondary tumours there (Further information upon malignant tumours appears under CANCER.) Benign tumours grow slowly at one place, press neighbouring parts aside, but neither invade nor destroy them, only seldom ulcerate through the skin or mucous membrane, have usually a capsule of fibrous tissue surrounding them, and when once completely removed by surgical excision or other means, not recur While this classification serves in a measure to differentiate typical varieties into classes, it is by no means absolutely satisfactory There are certain kinds of normally benign tumours which may remain comparatively small and circumscribed for a number of years, and then suddenly become malignant Benign or simple tumours include ANGIOMA, CHONDROMA, fibroma GLIOMA, LIPOMA, MYOMA, MYXOMA, NEUROMA, ODONTOMA, and PAPILLOMA The last-named may be benign in the beginning but become malignant later; also MELANOMA and ADENOMA (See also CYSTS; WARTS; CANCER.) While normally all tumours tend to increase in size – either slowly or rapidly – some grow to a certain size, remain stationary, then decrease in size, and a few may even disappear completely Two of the most common tumours of the dog are mammary carcinoma and anal adenoma (usually benign) (See also EOSINOPHILIC GRANULOMA.) (see under NOSE and RHINITIS) Tumour Angiogenesis Factor (TAF) This has been isolated from human and animal tumours It stimulates mitosis in endothelial cells and rapid formation of new capillaries for tumour nourishment (Unlike a skin-graft, which sends out capillary shoots to join the capillaries of the recipient tissue, a tumour has to rely entirely on the host, and makes use of TAF for this purpose.) Tungiasis Infestation with Tunga penetrans, the jigger flea (See under FLEAS.) Turkey Coryza A disease of the upper respiratory tract, with sneezing and nasal discharge, whose probable cause is Bordetella avium It occurs in turkey poults, usually in conditions where ventilation is poor and the birds are stressed Turkey Viral Hepatitis This occurs in Europe, the USA, and Canada; and in 1982 isolation of a picorna-like virus causing hepatitis and disease of the pancreas was isolated from an outbreak in Scotland The infection, which is highly contagious, is often, if not usually, subclinical, but may take an acute form, and prove fatal Turkeys Diseases include Arizona disease, blackhead, coccidiosis, erysipelas, fowl pest, hexamitiasis, haemorrhagic enteritis, moniliasis, Oregon disease, ornithosis, mycoplasmosis, pullorum disease, reticuloendotheliosis, rupture of the aorta, sinusitis, synovitis (see also GROUNDNUT MEAL MANIOC) Turkey meningoencephalitis occurs in Israel Influenza viruses cause disease in North American domestic turkeys Turkey rhinotracheitis has been seen in several countries, and appeared in the UK in 1985, causing severe financial losses due to deaths, carcase rejections, and lowered egg production The first sign is sneezing Turnips Like kale, these contain a goitre-producing factor, and if fed in large amounts to pregnant ewes are liable to cause abortion – unless iodine licks are provided (See VAGINA, RUPTURE OF.) Turpentine, Medicinal Oil of Turpentine is the oleo-resin which exudes from various members of the pine family, especially the Pinus australis, P taeda, and P sylvestris The oil distilled from this oleo-resin is known as oil of turpentine The natural turpentine is not used in medicine, as it is highly irritating and when the word ‘turpentine’ is employed, the oil of turpentine is indicated In collections of gas in the abdominal organs, medicinal turpentine has been used (e.g tympany in horses and cattle) Large doses are liable to irritate the stomach and kidneys Twitch Turpentine should never be given when an animal is suffering from nephritis, inflammations of the bladder, stomach, or bowels, as its active irritant action only increases the already existing inflammation (See under SMELL.) Externally, oil of turpentine is used as a constituent of liniments Turtles (see AMERICAN BOX TORTOISES; TORTOISES) Threat to public health from pet turtles Serious infection can be transmitted to owners by turtles, including aquatic turtles (terrapins) Six of 28 lots of embryonated eggs of the red-eared turtle (Pseudemys scripta elegans) imported into Canada from Louisiana were found to harbour salmonellae Salmonella poona and S arizonae were isolated from the eggs and the packaging moss, and the turtles hatched from the contaminated eggs continued to shed salmonellae into the tank water for up to 11 months Of the 37 strains of salmonellae isolated, 30 were resistant to gentamicin, probably because of the widespread use of the antibiotic to try to produce salmonella-free eggs for export Such high levels of antibiotic-resistant salmonellae in turtle eggs could pose a serious risk to human health ‘Twin Lamb’ Disease A colloquial name for PREGNANCY TOXAEMIA Twinning, Artificial In the interests of increased beef production, techniques have been developed to encourage the production of twin calves A suitable dose of pregnant mare’s serum (PMS), injected subcutaneously at a suitable time, e.g days before oestrus, will on average give twins; but there will be some triplets and singles The FOLLICLESTIMULATING HORMONE contained in the serum causes an extra follicle to mature and shed an extra egg with resultant twinning Over-dosage, however, leads to undesired quadruplets, etc.; or to numerous eggs which pass quickly down the Fallopian tubes without being fertilised; result – no calf at all There is a risk of stillbirths and of strain on the dam Twins (Calves) Twins tend to run in families For example, a cow had pairs of twins, her daughter pairs, and a grand-daughter pairs That might be called twinning at its best Of course, there is sometimes trouble Perhaps the condition of the dam is pulled down; or perhaps the ‘cleansing’ is retained, becomes infected, and infertility follows 731 Predicting twins The presence of twins can sometimes be detected by manual examination, but ultrasound scanning is more reliable and allows earlier detection The concentration of oestrone sulphate, a hormone produced by a cow carrying a viable fetus and present in blood plasma or milk, can be used to confirm pregnancy The concentration is higher in cows carrying twins, but the difference does not become significant until about the 220th day of gestation However, even at this late stage, the prediction of twins could be used as a guide to increase the feed allowance of cows carrying more than fetus In strains not noted for twins, twinning may occur on farms where there is a herd infertility problem Identical twins – always of the same sex – result from the division of the fertilised egg into 2; whereas ordinary twins are produced as the result of the fertilisation of eggs These eggs may come from the same ovary, when the fetuses may develop in the same horn of the uterus Sometimes they result in a FREEMARTIN There is apparently, with cattle, a close affinity between identical twins – as there undoubtedly is with human beings In a Swedish study, pairs of twins were split at birth and reared separately for 15 months At this age they were all put into a field together Within a few days each twin had found and paired off with its sister (See ERYTHROCYTE MOSAICISM; also GENETICS; SUPERFETATION; TWINNING, ARTIFICIAL; TRIPLET CALVES.) Twins (Foals) In the mare, the presence of twins in the uterus is a common cause of abortion About per cent of pregnant mares conceive twin fetuses, but the birth of healthy twins is exceedingly rare – about 0.01 per cent Twins, Monozygous Identical twins, from the same ovum Twitch This consists of a loop of soft rope threaded through a hole near the end of a stout piece of wood The twitch is applied to the horse’s upper lip, where it compresses the sensitive nerves It used to be thought that the twitch merely diverted the horse’s attention away from other parts of the body, but this view is now disputed It is thought that pain perception or awareness are diminished through the activation of ENDORPHINS Twitching significantly increases T 732 ‘Tying-Up Syndrome’ plasma levels of beta-endorphin, which returns to normal 30 minutes or so after the twitch is removed Twitching could therefore be said to be analogous to ACUPUNCTURE ‘Tying-Up Syndrome’ Also known as set-fast, this condition in racehorses appears to be identical with azoturia Symptoms include stiffness, a rolling gait, blowing and sweating and, if exercise continues, the adoption of a crouching attitude Pain is evident The animal may lie down and be unable to rise (See azoturia, under BOVINE MYOGLOBINURIA.) Tylan The proprietary name of a preparation of tylosin Tylosin A macrolide antibiotic effective against Grampositive organisms; it concentrates in acidic conditions, as in the udder and the lung It is used as a growth promoter in pigs (See ADDITIVES.) Tympanites The drum-like condition of the abdomen, which results from distension of the stomach or bowels with gas, as the result of fermentation, constipation, or of simple obstruction (See under STOMACH, DISEASES OF; INTESTINES, DISEASES OF; BLOAT; TYMPANY; TYMPANITIC.) Tympanitic Resonance in Cattle T Right-side tympanitic resonance (ping) caused by gas distention of intra-abdominal structures was diagnosed in 366 adult cattle, in a USA study The source of the ping was identified as the abomasum in 137 animals, various segments of the intestinal tract in 157 and peritoneal gas in two The source of the noise was not identified in 70 The principal final diagnoses were: left displacement of the abomasum (116), right displacement of the abomasum (77), abomasal (and omasal) volvulus (60), other gastro-intestinal conditions (73) and non-gastrointestinal conditions (40) Tympany Tympany is distension of a hollow organ with gas (See TYMPANITES; BLOAT.) Typhilitis Inflammation of the caecum or 1st part of the large intestine, into which the termination of the small intestine opens Typhus of Rats and Mice Typhus of rats and mice, caused by Rickettsia mooseri, may kill about per cent of people infected by it Tyzzer’s Disease This was first described in mice in 1917, and has since been reported in horses, cats, and laboratory animals including rats, rabbits, gerbils, and rhesus monkeys Cause The spore-forming, Gram-negative, motile Bacillus piliformis Signs The disease is characterised as a rule by severe diarrhoea, debility, and death; though sudden death in foals without preliminary symptoms has been reported in the USA Jaundice, slight or marked, was a post-mortem finding, together with some liver necrosis and enteritis In the cat, the infection gives rise to symptoms of loss of appetite, depression, diarrhoea, collapse and death Necrosis of the ileum and hepatitis are among post-mortem findings Tzaneen Disease This is a tick-borne infection with Theileria mutans in cattle, the African buffalo, and the Indian water buffalo, and often occurs simultaneously with other infections There may be only a mild fever or, less commonly, serious illness, and death Anti-malarial drugs are of use ... fox, T cati, and T vitulorum of cattle (the last-named not present in the UK) Infection with these worms is known as toxocariasis This is important not only from the veterinary aspect but also... must have enough to eat and be supplied with fresh water regularly The tether must not be able to cause injury, e.g by being too tight or too short Tetracyclines Tetracyclines are bacteriostatic... protection It is not uncommon for the tibia to become fractured, but the parts remain held together by the very dense periosteum that covers the bone In the smaller animals, the setting of the