Black''''s veterinary dictionary 21st edition - V pot

V Vaccination A method of producing active immunity against a specific infection by means of inoculation with a vaccine, i.e a preparation of the necessary antigen(s) (See IMMUNITY; IMMUNISATION; IMMUNE RESPONSE; VACCINE.) Vaccination in mammals is normally carried out by inoculating individual animals The method of administration depends on the type of vaccine Most inactivated vaccines are injected intramuscularly or subcutaneously; temperature-sensitive live vaccines may be administered as drops into the nasal passages; vaccines against husk are given orally Mass vaccination of poultry against Newcastle disease may be achieved by dispersing aerosols of vaccine over the heads of the birds with fine spray pumps or adding vaccine to the drinking water Some fish are vaccinated by dipping the fish in a solution of the vaccine Fox populations in Europe have been vaccinated against rabies by impregnating chicken heads or other baits and spreading them in known fox runs Multiplecomponent vaccines containing antigens against a number of diseases are available For example, sheep can be simultaneously immunised against pulpy kidney disease, lamb dysentery, braxy, blackleg, black disease, struck, Clostridium oedematiens infection and tetanus by a single 8-in-1 vaccine (In connection with foot-and-mouth disease, see also RING VACCINATION.) Vaccine When an animal is inoculated with a vaccine as protection against a specific disease, e.g blackleg, this is carried out with the object of stimulating production of antibodies in its system, which will confer active immunity against blackleg organisms Vaccines may be prepared from live microorganisms; from inactivated (killed) microorganisms; from genetically engineered subunits of the pathogenic fraction of the organism; or from toxoids – heat- or chemically-treated micro-organisms that have lost their virulence but retain their antigenicity, i.e ability to create resistance to disease Live vaccines are vaccines prepared from bacteria or viruses whose virulence is reduced by heat, chemicals or passage through an animal other than the normal host species For example, cattle plague vaccine may be prepared from the virus passaged through (i.e grown in) chick embryos Occasionally the live viruses used are related but non-pathogenic strains, useful because they will stimulate antibody production but will not produce the disease Viruses may be inactivated by phenol or ultra-violet rays, for example; or they may be modified in some way, such as by artificially induced mutation, to produce a temperaturesensitive virus which will replicate in the nose but not in the lungs Such a virus vaccine can be administered by nasal spray Tissue culture vaccines – live vaccines grown on cell cultures – are used in the prevention of canine distemper, rabies, etc., and in treatment of benign skin papillomata (warts) of cattle Vaccines are sometimes used for treatment as well as for prevention of a particular disease X-irradiated worm larvae vaccine is used in the prevention of PARASITIC BRONCHITIS It is important that, in the commercial production of live vaccines involving the use of chicken embryos (or of tissue cultures derived from them), contaminant viruses are eliminated For example, the avian leukosis virus has contaminated distemper vaccine and would represent a risk to vaccinated poultry if contaminating vaccines for them Scrapie was accidentally spread by an early louping-ill virus contaminated by the scrapie agent It is essential that vaccines are stored under suitable conditions of temperature, etc.; that they are not used after the expiry date shown on the package; that where doses are stated to be necessary, both are given – and at the correct interval Failure to observe these rules can mean that the vaccinated animal does not become an immunised animal; it has led to dogs presumed properly vaccinated against rabies becoming rabid after exposure to a natural infection (See also INJECTIONS; GENETIC ENGINEERING.) Inactivated vaccines are prepared from killed micro-organisms that retain sufficient antigenic activity to promote immunity They are not as potent as live vaccines, and doses at specified intervals are usually necessary to produce effective immunity Inactivated vaccines often contain an adjuvant, usually an aluminium salt such as aluminium hydroxide, which enhances the immune reaction Some are water-based, others formulated in an oily medium Oilbased vaccines can cause serious reactions if accidentally self-injected into the operator Leptospirosis vaccine is an example Subunit vaccines are genetically engineered so that only the antigenic fraction of a pathogen is 748 Vaccinia Virus utilised The vaccine does not cause infection but does stimulate immunity Feline leukaemia vaccine is an example; another is Aujeszky’s disease vaccine The virus component of the subunit vaccine has difficulty in penetrating the cells of the vaccinated animal; it does not multiply well within the cells and the animal does not shed the virus By testing for the fraction missing from the vaccinial strain of virus, a vaccinated animal can be determined from one carrying the infection Toxoid vaccines are produced by treating toxins from micro-organisms so that their harmful effects are removed but the antigenic properties remain Tetanus vaccine is an example Vaccinia Virus This term may refer to the virus of naturally occurring cow-pox, or to a strain which has undergone mutation and was used for vaccination against smallpox (See POX.) Vacuole ovariohysterectomy or a caesarean operation, and leads to urinary incontinence It has been suggested that the fistula may occur following accidental ligation of the ureter during surgery, or because the ureter becomes involved in an inflammatory adhesion originating in the vaginal stump Intermittent haemorrhage occasionally occurs in mares having very prominent varicose veins at the dorsal aspect of the vulva-vaginal area; it does not appear to affect health or fertility Persistent vulval haemorrhage from varicose veins of the dorsal wall of the vagina has also been described It yields to local haemostatic treatment Vaginitis Inflammation of the vagina (See under INFERTILITY – Diseases of the genital organs in female; also ‘WHITES’; EPIDIDYMITIS – Epivag; VULVOVAGINITIS, GRANULAR; PROLAPSE.) A cavity within a cell Vagotomy Vacuum-Dipping of Eggs Severing of the vagus nerve (See HYPERTROPHIC OSTEOPATHY.) A technique used in assisting the eradication of Mycoplasma spp in poultry Fertile eggs are dipped in a concentrated solutions of antibiotic (usually tylosin) and subjected to a negative pressure Some of the air in the egg’s air pocket is thus extracted and about 0.5 ml of antibiotic drawn through the shell into the egg and absorbed This process is more effective in helping to eliminate M gallisepticum than other mycoplasmas Vagina The vagina extends from the cervix of the uterus to the vulva Vaginal mucus is altered in character during pregnancy, a fact which can be made use of in pregnancy diagnosis (For inflammation of the vagina, see VAGINITIS.) An artificial vagina is used at AI centres for the collection of semen V Vaginal prolapse in ewes This may precede lambing by up to 55 days, but most cases occur within the last 21 days of pregnancy Rupture of the vagina, with protrusion of the intestine and rapid death, occurs not uncommonly in ewes of a large breed, of mature age, carrying a twin – a week or two before lambing is due Bulky foods – swedes, turnips, kale – are often involved Vaginoureteral fistula This has been recorded in dogs and cats, as a complication of Vagus (Pneumogastric Nerve) The vagus (pneumogastric nerve) is the 10th cranial nerve This nerve is remarkable for its great length, and for the attachments which it forms with other nerves and with the sympathetic trunks It arises from the side of the medulla, passes out of the skull, and runs down to the jugular furrow of the neck, where, along with the sympathetic, it accompanies the carotid artery to the entrance to the chest From this point the right and left vagi differ from each other in their course They both pass through the chest cavity, giving branches to the pharynx (which run up the neck again), to the heart, bronchi, oesophagus, etc Each nerve then splits into parts and the upper branches fuse with each other to form the dorsal trunk, the lower branches behaving similarly to form the ventral trunk These branches now pass through the diaphragm, with the oesophagus, into the abdominal cavity, and end by giving branches to the stomach, duodenum, liver, and various ganglia nearby (See Parasympathetic system under CENTRAL NERVOUS SYSTEM – Autonomic; also BRAIN.) (See GUTTURAL POUCH DISEASE.) Valgus A bone growth-plate defect (See DISEASES OF.) Valine One of the essential amino acids under BONE, Vasectomised 749 Variocele Variocele is a condition in which the veins of one or both testicles are greatly distended Variola (Pox) Variola (pox) is the inclusive term for fevers of animals and man, in which a skin eruption takes the form of a ‘pock’, caused by a POX virus Varroasis One-month-old foal with bilateral carpal valgus (With acknowledgements to Professor L C Vaughan and the Royal Veterinary College.) Valves Valves are found in the heart, veins, lymph vessels, etc., and serve the purpose of ensuring that the fluids will only circulate in one direction (See HEART; VEINS; ILEOCAECAL.) Valvular Disease (see HEART DISEASES) Vampire Bats Vampire bats are important transmitters of rabies in parts of South and Central America, the West Indies, etc The bat laps blood from the wounds inflicted with its upper incisor teeth on cattle, horses, etc In Mexico infected vampires have made necessary the preventive inoculation of 800,000 cattle a year Trypanosomiasis can also be transmitted by vampire bats Vampire bats imported into the UK remain in quarantine for the rest of their life Varroasis is a parasitic disease of honey bees, Apis melifera, caused by the mite Varroa jacobsoni The mite feeds on the developing larvae and on the adult bees The result is weak bees and sometimes the death of the queen Whole hives can be wiped out, causing great economic loss not only to the apiculturalist but also to fruit and arable farmers; beekeepers often supply hives to fruit growers and to fields of rape and linseed Varroasis is prevalent in the UK and is a NOTIFIABLE DISEASE As both parasite and host are arthropods, products used for control of the disease must have a fine division between toxicity to the mite and toxicity to the bee Suspending strips impregnated with flumethrin or fluvalinate in the hive can be effective Other treatments include tobacco smoke or a vapourising block containing thymol and aromatic oils Eradication, however, is difficult The disease came from Asia, where it does less harm because Asiatic bees groom each other, thus removing the mites Long term, it has been suggested that European and Asian bees may be cross-bred to try to introduce the grooming habit into the European bee population A leaflet available from DEFRA gives more details of the disease and its control Vas Deferens (see under TESTICLE) Vascular Consisting of, or containing a high proportion of, blood vessels Vanadium Vasculitis Inflammation of a blood vessel A trace element essential in minute quantities for the growth of chicks; as little as 10 mg/kg of diet is an overdose that will suppress growth It works with insulin to increase the amount of glucose and aminoacids taken up by muscle Vasectomised Varicose Veins (see under VEINS) Varied Diet, Need for (see DIET AND DIETETICS; AMINO ACIDS; CAT FOODS; DOGS’ DIET) A male animal in which the vas deferens has been cut Such an animal is sterile though it retains its libido and may be used for the detection of oestrus (e.g in cattle) In breeding catteries one or two toms are sometimes vasectomised for the sake of peace, quiet and contentment of queens not being bred from until a later oestrus Sterility does not immediately follow vasectomy (or castration), as some sperms will be in the seminal vesicles and can lead to conception V 750 Vasodilator after mating It may be weeks or more before the animal is sterile Vasodilator Anything which causes dilation of blood vessels A drug used for this purpose is isoxuprine hydrochloride (See NAVICULAR DISEASE.) Vasomotor Nerves Vasomotor nerves are the small nerve fibres that lie in or upon the walls of the blood vessels and connect the muscle fibres of the middle coat with the nervous system By the continuous action of the nerves the muscular walls of the vessels are maintained in a moderate state of contraction Any continuous and generalised increase in this action results in a raising of the blood pressure of the body, while a diminution produces a lowering of the pressure Such vasomotor nerves are called vaso-constrictors, but there are vaso-dilators as well The latter are able to dilate the vessels, and cause either a general or a local fall in the blood pressure, along with an increased supply of blood to the part Vasopressin A hormone secreted by the posterior lobe of the pituitary gland.It is also called ANTIDIURETIC HORMONE (ADH) (See PITUITARY.) Vector The carrier which transmits a disease from one animal to another For example, the mosquito transmits malaria to man and a variety of diseases to animals Veins V With one or two exceptions, the veins lie alongside or near to the corresponding arteries – thus the renal vein brings back blood that has been carried to the kidney by the renal artery and lies alongside it The veins are, however, more numerous and more irregular in their courses than are the arteries, especially on the surface of the body In regions, such as the cheeks, brain meninges, and in the abdomen and thorax, there are veins arranged quite irrespective of the distribution of the arteries Structure A vein is a thin-walled tube which possesses a structure similar to that of an artery, and consists of coats, viz an outer fibrous, a middle composed of muscular and elastic fibres, and an inner coat composed of an elastic membrane and flattened epithelial cells If an ordinary vein is split open along its length, there are seen to be a number of flap-like valves attached to its inner surface These are like little Valves of a vein showing pumping action of adjacent muscles (Grollman, The Human Body, Macmillan Co., as used in R D Frandson, Anatomy and Physiology of Farm Animals, Baillière, Tindall.) pockets, and are so arranged that they offer no resistance to the blood when it is flowing in the right direction, but prevent any back-flow These valves are most numerous in the veins of the limbs, where gravity would naturally tend to produce a back-flow, and least numerous in the veins of the internal organs Chief veins The arrangement and relations of the veins are very different in animals of varying species, and even in different individuals, so that only a general description can be given here Pulmonary veins – as many as or in the horse and fewer in other animals – return the oxygenated blood from the lungs to the left auricle of the heart They possess no valves Opening into the right auricle are veins: (1) coronary sinus; (2) anterior vena cava; (3) posterior vena cava; and (4) azygos vein The coronary sinus is a short thick trunk that discharges the blood used by the heart walls back into the general circulation The anterior vena cava drains the blood from the head, neck, fore-limbs, and much of the chest wall It is formed by the confluence of the jugulars and the brachial veins, Venereal Tumours (Infective Granulomata) and receives other branches from the neck, vertebral region, and the chest wall The posterior vena cava drains all the remainder of the body except the region of the diaphragm, the posterior intercostal areas, the oesophagus, and the bronchial tubes, the blood from these parts being collected into the azygos vein which joins the right auricle separately in most animals The posterior vena cava is formed under the lumbar region by the union of the right and left common iliac veins, which drain the blood from the pelvis and hind legs, and which are distributed in a more or less similar manner to the corresponding arteries of these parts From here it passes forwards below the lumbar muscles in company with the abdominal aorta, until at the level of the last thoracic vertebra it passes downwards and forwards, past the pancreas, and reaches the liver Its further course is partly embedded in the liver substance until it arrives at a special opening in the diaphragm, called the foramen venae cavae, by which it gains the thoracic cavity From here it passes along in a groove in the right lung to reach the right auricle Its main tributaries are as follows: (1) lumbar veins, which empty blood from the lumbar muscles, etc.; (2) internal spermatics in the male, and utero-ovarian veins in the female, from the generative organs in either sex; (3) renal veins, one from each kidney, satellites of the corresponding arteries; (4) several large hepatic veins, which return not only blood carried to the liver by the hepatic arteries, but also that which comes from the digestive organs by the portal vein to undergo a second capillary circulation in the liver (see PORTAL VEIN); and (5) phrenic veins returning blood from the diaphragm In the venous system, even more so than in the arterial system, there is an intricate arrangement of anastomoses by which, when one vein becomes damaged or diseased, lateral branches from it may enlarge and carry away the excess blood into other veins so that no great hindrance to the return flow of the blood to the heart may be occasioned If this were not so, the circulation might be from impaired minor causes Veins, Diseases of Those lying near to the surface are frequently injured along with other tissues when contusions or lacerations have been sustained, but so extensive is their communication with neighbouring veins that it is usually possible for these latter to enlarge and undertake the functions of the damaged vessels, and thereby prevent serious 751 consequences The deeper veins are protected from all but the most severe, and usually fatal, injuries Inflammation of a vein, or phlebitis, may follow the collection of blood samples when unclean instruments have been used, or when the resulting skin wound has not received attention In other cases it follows THROMBOSIS and infection Varicose veins are those which have become stretched or dilated to an extent not justified by the blood flow (See VARIOCELE and under VAGINA.) Veld Sickness (see HEARTWATER) Vena Cava Each of the large veins that open direct into the right auricle of the heart (For further details, see under VEINS.) Thrombosis of the posterior vena cava, which may follow abscess formation in the liver or elsewhere, is in cattle not infrequently followed by the presence of clots in the pulmonary vessels, abscess formation and sometimes erosion of the pulmonary artery wall – giving rise to a fatal haemorrhage Symptoms may include dullness, rapid breathing, a cough, chest pain, the presence of blood in material coughed up, anaemia, and widespread rhonchi (See RECUMBENCY.) Venereal Diseases Animals, with the exception of the monkey, are not subject to infection by the great human venereal diseases of syphilis and gonorrhoea, but there are several important contagious diseases that can be transmitted from animal to animal by coitus These include brucellosis, trichomoniasis, Campylobacter fetus infection, and infectious vaginitis of cattle, venereal granulomata or venereal tumours of dogs, and dourine or mal du coit of horses (See PROTOZOA; EPIDIDYMITIS; VULVOVAGINITIS, GRANULAR; CONTAGIOUS EQUINE METRITIS.) Venereal Tumours (Infective Granulomata) Venereal tumours (infective granulomata) characterise a contagious disease of dogs Signs In the female the original tumour is a warty excrescence which soon grows and becomes cauliflower-like In advanced stages there is a large mass of pinkish or greyish-red tissue, which easily bleeds when touched, occupying the greater part of the vaginal passage and V 752 Venezuelan Equine Encephalomyelitis often causing a bulging and swelling of the perineal region A dirty sticky blood-stained discharge accompanies the condition, and the animal’s general health suffers In the male the watery growths usually have a distinct stalk, and are attached to the skin or mucous membrane of the prepuce, or to the penis (See also under WARTS.) Venezuelan Equine Encephalomyelitis A strain recognised in the 1930s A severe outbreak occurred in Venezuela and Colombia in 1962–4, when thousands of horses died and about 30,000 people were infected A later outbreak spread to Mexico in 1970 where 6000 or more horses died, and then to Texas, USA (See also EQUINE ENCEPHALITIS.) Venom (see SNAKES; TOADS; BUFOTALIN; SPIDERS; SCORPIONS) Vent Gleet This condition in poultry is an inflammation of the cloaca, with which is associated a thin yellowish watery discharge which has a characteristic and particularly unpleasant odour The cloaca and adjacent skin appear swollen and congested, and the bird exhibits signs of irritation Other birds attracted by the reddening of the region may peck at vent; this leads on to cannibalism Egg production drops, and in some cases eggbinding and impaction of the oviduct result Culling is advisable There is a similar condition in ducks but the material round the vent is more solid This must be removed and the affected area treated with antibiotic cream Cases of severe infection of the eyes of poultry-keepers treating this condition are not uncommon Ventilation V Ventilation may be summed up as ‘the measures necessary to rectify the pollution of the air in a building – without the production of a draught’ Whenever animals are enclosed in a confined building they gradually use up the oxygen and discharge into the air quantities of carbon dioxide and water vapour, until, if no fresh air is supplied, the percentage of oxygen decreases below the amount required One of the problems in livestock buildings is condensation, which can lead to bronchitis and pneumonia For buildings used for cattle and sheep, provision of Yorkshire boarding is one of the best and least expensive methods of avoiding or curing condensation Necessary air space m3 ft3 Cow, horse (Byre or stable) 5.6 200 (Loose box or yard) 16.8–33.6 600–1200 Bacon pig 1.7 60 Poultry (layers on slats) 0.17 (layers on deep litter) 0.34 12 The required amount of air for each animal must be continuously brought in from the outside, and an exit must be provided for an equal amount This is arranged for by the provision of inlet and outlet ventilators Inlets These include windows, direct inlet pipes, perforated bricks and gratings, Yorkshire boarding, and electric fans Windows, of which the Sheringham Valve type is the most common and useful, serve the dual purpose of lighting and ventilation Those on the lee side of a building serve as outlets when the wind is strong In the Sheringham Valve windows, the incoming air is deflected upwards by the hopper-like flap that falls inwards, so that it is spread over a greater area than is the case with other openings Inlet pipes are used, often in conjunction with windows, to ensure a supply of fresh air in the region of the animals’ heads Ventilation rates – (maximum) Changes of air m3 ft3 per hour per hour per hour Bacon pig 20 5.7–34 200–1200 Broiler chicken 40 6.8 240 Laying birds 30 10 360 Outlets These include an open ridge, louvreboard ventilators, outlet shafts, open eaves, exhaust fans, and other devices The most satisfactory outlet is undoubtedly an open ridge along the whole length of the building The heated impure air rises and is drawn through the open space by the suction of the wind The disadvantages of this system are that the open space will allow entrance to a certain amount of rain or snow in bad weather; the system is also inapplicable to buildings possessing lofts Extraction area (Necessary with natural ventilation) Outlet per animal: cm2 Cowhouse 930 Farrowing house 95 Fattening house 65 Calf house 65 Poultry (adult) house 13 sq ins 144 15 10 10 Verminous Bronchitis Ventilation methods for cattle houses: Top, Chimney; Bottom, Continuous ridge outlet (With acknowledgements to The UFAW Handbook on Care and Management of Farm Animals, Churchill Livingstone.) Mechanical ventilators may be either of the plenum or in-forcing type, or of the vacuum, exhaust, or outforcing variety In the former a larger power-driven fan is enclosed in a chamber with communication to the outside of the building, and is connected by ducts or shafts with all parts that are to be ventilated In the exhaust variety one or more electric fans are enclosed in turrets placed along the ridge of the roof Ventilation tunnel These have a fan to draw air into the building and force it out through vents over the stock The temperature in a livestock building is a result of the heat released from the stock (for example, a dairy cow gives off heat equivalent to 0.5 kW; and with a heavy milker the figure may be kW) and the varying quantity of ventilating air drawn from outside ‘Because heating and refrigeration are only economic for young stock, the properties of the air entering the building are those of the outside air and vary considerably, depending on the weather In hot weather a large amount of air is used, but in cold weather only a small amount is required and in many traditional systems this gives rise 753 to different patterns of internal air flow By studying the relevance of airflow patterns to the conditions near the stock and to the response of the ventilation system the Environment Department, NIAE, has designed a ventilation system which provides near uniform internal conditions as the outside temperature changes The system ensures a desired airflow pattern by automatically adjusting the inlet gap to maintain an air speed of about m/s Calculations and experiments have shown that this system will maintain the required airflow pattern for outside temperatures down to 0°C (32°F) ‘Another shortcoming of traditional systems is the influence of wind on ventilation rates, particularly in cold weather when fans are running slowly For this reason the NIAE have discarded the method of varying fan speed to control rate of ventilation and recommends switching the fans on or off When fans are off they are covered by simple backdraught shutters and when on they are at full speed and so are least affected by wind The fans are switched on or off in predetermined steps and the inlet gap is adjusted automatically to match the steps in ventilation rate ‘The diagram [above] shows the essence of the system which has proved effective in fattening piggeries, broiler houses and turkey buildings and is fully described in the NIAE Report No 28.’ (See also HOUSING OF ANIMALS; CARBON MONOXIDE) Fan failure (For this and the resulting mortality, see under CONTROLLED-ENVIRONMENT HOUSING.) Ventral Ventral in anatomy indicates that a particular organ or structure is situated towards the abdominal surface of the body, as distinct from the spinal or dorsal aspect Ventricle A chamber of the heart, or a small cavity in the brain (see HEART; BRAIN) Ventriculus (see GIZZARD and diagram for PROVENTRICULUS) ‘Verminous Aneurysm’ ‘Verminous aneurysm’ is a misnomer for EQUINE VERMINOUS ARTERITIS Verminous Bronchitis (see PARASITIC BRONCHITIS and GAPES) V 754 Verminous Dermatitis (With acknowledgements to the Scottish Farm Buildings Investigation Unit.) Verminous Dermatitis (see STEPHANOFILARIASIS; SUMMER SORES) Verminous Ophthalmia V (see under EYE, DISEASES OF) Vero Cells A continuous heteroploid cell line derived from African green monkey (Cercopithecus aethiops) kidney tissue These cells are approved as a substrate for the production of virus vaccines, including rabies They are much easier to grow than human diploid cells, and provide a better yield; so that manufacturers are keen to use them for vaccine production Latent virus in these cells is a potential danger Verotoxin A total of 1012 milk filters were collected from 498 diary farms in south-west Ontario The supernatants of 20 (2 per cent) of the milk filter cultures had verocytotoxic activity Seven verotoxin-producing E coli strains were isolated, of which had been previously associated with disease in humans Verruca (see PAPILLOMA) Vesicular Stomatitis 755 The NIAE ventilation system Verrucose Covered with warts or vegetative growths In pigs a verrucose endocarditis is recognised, the growth being found on the heart valves The condition may be associated with swine erysipelas or be caused by staphylococci or streptococci made, and it was then discovered that each had a hard, painful swelling of one of their seminal vesicles Inflammation was found to be due to infection with Actinobacillus actinoides Other organisms sometimes involved include tubercle bacilli, Brucella abortus, streptococci, and Corynebactrerium pyogenes Version (Turning) Version (turning) means the changing of a presentation at parturition so that some other part of the fetus than that which was presented originally comes through the pelvic opening first Vertebra (see SPINAL COLUMN) Vesicle (Small Blister) A vesicle (small blister) is a collection of fluid in the surface layers of the skin or of a mucous membrane Vesicles are present in a number of diseases, and according to their location, some assistance is afforded for diagnostic purposes For example, in foot-and-mouth disease the vesicles are present in the mouth and on the feet, while in cow-pox they are found on the teats, udder, and other parts Vesicles, Seminal These secondary sex glands, like the prostate, have openings into the urethra and are situated close to the neck of the urinary bladder (See also under SEMEN.) Infected seminal vesicles can (rarely) cause problems At a bull-rearing unit, yearlings appeared fit and well Their appetite was good and they showed no signs of pain or discomfort When, however, samples of their semen were taken, clots of pus were noticed This finding led to a careful examination of the bulls being Vesicular Disease of Pigs Vesicular disease of pigs is described under SWINE VESICULAR DISEASE (See also VESICULAR STOMATITIS.) Vesicular Exanthema A viral disease of pigs (and rarely of horses but not of cattle) which has to be distinguished from foot-and-mouth disease It was eradicated from the USA in 1959 and has never been recorded elsewhere It is thought that the vesicular exanthema virus may have been a ‘land variant’ of the San Miguel sea-lion virus, isolated from sea-lions off the coast of California Vesicular Stomatitis Vesicular stomatitis is caused by a rhabdovirus transmitted by mosquitoes and biting flies, and may affect horses, cattle, pigs and, occasionally, sheep The blisters seen on the tongue have occasionally caused confusion with foot-andmouth disease, and vice versa – with serious consequences Lesions can also occur on the udder or around the coronets It is a disease of the summer, and mainly of the western hemisphere, especially in the Caribbean area In man the disease is influenza-like, with fever, sore throat, and several days’ malaise Two strains of the virus are recognised – the New Jersey and the Indiana Experimentally, V 756 Vesicular Vaginitis numerous mammalian species can be infected – likewise ducks Vesicular Vaginitis (see VULVOVAGINITIS, GRANULAR) Vesiculitis (see VESICLES, SEMINAL) Veterinary Degrees Veterinary degrees are conferred on graduates from the veterinary faculties of Bristol, Cambridge, Edinburgh, Glasgow, Liverpool and London universities They lead to membership of the Royal College of Veterinary Surgeons (MRCVS) which allows the graduate to practise in the UK as a veterinary surgeon Higher degrees (PhD, MSc, etc.) are available after postgraduate study, as well as certificates and diplomas in specialist areas of veterinary medicine and surgery Graduates of veterinary schools in other EU countries may also become MRCVS University degrees in veterinary nursing are also available Veterinary Facilities on the Farm V Every breeding cow and heifer in Britain has, during its lifetime, to be caught, ear-tag read, restrained and a blood sample taken from neck or tail vein This will take place at least or times, quite apart from any herd or individual handlings necessary for clinical reasons or breeding management Taking a blood sample can take as little as 30 to 45 seconds given efficient holding facilities; 200 cattle could be sampled in a morning’s work On most farms there is a lack of cattle-handling facilities of the right type, so that the catching of a single animal can and does take all the farm staff about 20 minutes with the very real possibility of broken gates and fences and varying degrees of personal injury, even before blood-sampling is attempted Experience in the design and erection of cattle handling units for dairy and beef cattle has shown the main points to be as follows: Collecting pens should be large enough to hold all stock to be handled, or all the stock in units as they are housed, e.g 50s or 100s A post-and-rail pen × 18 m (30 × 60 ft) or 12 × 13.5 m (40 × 45 ft) will hold 100 cows with calves at foot A pen of × 12 m (30 × 40 ft) will hold 60 adult cattle or 80 young cattle The forcing pen leads from the collecting pen to the race or chute, and should be funnelshaped It should hold no fewer than 12 cows plus calves, or 15 adult cattle – enough to provide a group for handling without having repetitive stops while 2s or 3s are run into the cow-race The optimum dimensions are as shown in the diagram, and should not be made larger for large units The dimensions are those within which cattle cannot evade pressure to go into the race by adopting a whirlpool movement Race An 18 m (60 ft) long race, 680 mm (2 ft in) wide internally and 1.680 m (5 ft in) to the top rail, will hold 10 to 12 cattle It should be made up of verticals (sleepers) m (6 ft in) between centres sunk 900 mm (3 ft) into the ground, the bottom concreted with a brushed surface There should be horizontal rails Height above ground of the 2nd and 3rd rails is specific in that it accommodates the large, fat or pregnant animal Catwalk and working space Catwalks should be provided on both sides of the cow race, 760 mm (2 ft in) above ground level and not less than 300 mm (12 in) wide, in wood Space should always be provided for catwalks, even when building in close proximity to an existing wall – i.e the face should be stood off from the wall, however tempting it may be to use an existing wall for one side Cattle can then be run in either direction for procedures on either flank (vaccinations, branding, testing, etc.) Crush and veterinary gates The crush should be stood off 1.079 m (3 ft in) from the end of the cow race with the same internal width of 680 mm (2 ft in), and suitable gates to hold animal No firmly, stop animal No from backing out of crush before being held and prevent animal No from pushing up The materials and sizes are the same as for the race Yoke or headstock A device for restraining cattle by the neck, strongly made from wood or metal and designed so that the head cannot jerk about While securing the animal firmly, it incorporates a quick-release frame to free it in an emergency Three-way cattle shedder If fat cattle are weighed, cows examined for breeding function Veterinary Products Committee (VPC) or large stores sexed, then this at once dictates grouping by weight, pregnancy or other findings A 3-way shedder immediately after the crush renders this separation an easy task Dispersal and recirculation Having dispersed any large group of cattle to their appropriate categories of in-calf, empty, etc., there should be a series of gates in the far end of all holding pens, allowing cattle to be recirculated, retained or individually extracted Suckler cows and calves Suckler cows are usually handled for clinical reasons (vaccinations, treatment, blood-sampling) or to find out breeding status at that time (in-calf, ovulating, empty) This usually means that calves are at foot To simplify handling, calves can go with their dams right into the forcing pen without any attempted separation If a calf race is then sited to run from near the mouth of the cow race, with a shedder gate, then calves of to months can be run off separately This allows vaccination, castration, dehorning or weighing to be done very quickly with no time and energy dissipated on catching each calf individually Critical dimensions for the calf race are 410 mm (1 ft in) internal width and 1.040 m (3 ft in) to top rail The shedder gate should be close-boarded to prevent visual contact between calves and cows in cow race Calves will run into the calf race quickly if the shedder is operated from an overhead platform, but they tend to flinch at an operator working through the rails at head or shoulder level In addition to the cattle-handling facilities described above, it is useful to have a footbath suitable for cattle (see FOOT-BATHS), and looseboxes for calving or isolation purposes With a very large herd of, say, 500 cows, 15 loose-boxes would not be too many Veterinary Investigation Centres (VICS) Together with the Central Veterinary Laboratory, Weybridge, the VICs form the Veterinary Laboratories Agency They provide laboratory facilities and a consultative service for veterinary surgeons in private practice, assisting with the diagnosis of disease and herd problems Their work includes autopsies, serological tests, biochemistry and parasitology VIC staff carry out research into disease problems of local importance, and also provide a surveillance function for DEFRA in warning of local disease which might become important nationally In Scotland similar VICs operate but are affiliated to the Scottish agricultural colleges 757 Veterinary Medicines Directorate (VMD) The government agency with responsibility for overseeing the evaluation and licensing of animal medicines, protecting the consumer from unacceptable or hazardous residues, and advising the Veterinary Products Committee Address: Veterinary Medicines Directorate, Woodham Lane, New Haw, Addlestone, Surrey KT15 3NB Veterinary Nurses A title restricted to those who have completed the course of instruction and passed the examinations authorised by the Royal College of Veterinary Surgeons People wishing to train as veterinary nurses must first find employment for not less than 35 hours per week in a veterinary practice or other veterinary centre approved by the RCVS The greater part of the training is given while working; VN training is now part of the NVQ scheme The practical training is supplemented by formal tuition to provide the necessary background knowledge Residential courses are available All pre-enrolment queries about training are dealt with by the British Veterinary Nursing Association, Level 15, Terminus House, Terminus Street, Harlow, Essex CM20 1XA There are more than 80 training centres, approved by the RCVS, where student nurses can study for the qualifying examinations A Diploma in Advanced Veterinary Nursing, and a university degree in veterinary nursing, can also be obtained Veterinary Poisons Information Service Addresses are National Poisons Information Service, National Poisons Unit, Avonley Road, London SE14 5ER; and Leeds Poisons Information Service, The General Infirmary, Great George Street, Leeds LS1 3EX Veterinary Practitioner Someone on the Supplementary Veterinary Register; not an MRCVS The SVR was closed to new entrants in 1967 Veterinary Products Committee (VPC) This, under the Medicines Act 1968, advises the Medicines Commission, and ultimately, the Licensing Authority, on the marketing of medicines for animals Its approval is needed before an animal medicine may be licensed for sale It has to consider the safety, quality and efficacy of V 758 Veterinary Profession any veterinary medicine in relation to the treated animal, the safety of consumers of produce derived from treated animals, and the safety of farmer, pet-owner, and the environment (See also SUSPECTED ADVERSE REACTION SURVEILLANCE SCHEME.) Veterinary Profession This comprises those engaged in private practice, in the Animal Health Division of the Ministry of Agriculture, the Royal Army Veterinary Corps, the overseas veterinary services, in research and teaching at the universities, and also at AFRC research establishments, and those of the Department of Environment, Food and Rural Affairs etc., in food inspection and other municipal services, in AI centres, in research and advisory appointments with, e.g FAO, and in commercial undertakings There are about 12,500 veterinary surgeons working in the UK and about 2,800 veterinary practices Over the next few years the traditionally male-dominated profession will become about two-thirds female, as the majority of veterinary students are women Veterinary Surgeons Act 1966 This relates to veterinary education, the management of the profession, and the registration and professional conduct of veterinary surgeons and practitioners The practice of veterinary surgery continues to be limited to veterinary surgeons and practitioners whose names appear on the registers maintained by the Royal College of Veterinary Surgeons Unregistered persons may carry out only the very limited treatments, tests, or operations specified in section 19 of the Act, any exemption orders made thereunder, or schedule The Amendment Order to the Act permits a veterinary nurse to carry out any medical treatment or any minor surgery to a companion animal, provided that the latter is under the care of a registered veterinary surgeon who has authorised the treatment Veterinary Surgery (Epidural V Anaesthesia) Order 1992 (see under LAW) Vial (see AMPOULE; GLASS EMBOLISM) Vibices Vibices are long tapering markings that sometimes occur on visible mucous membranes during certain diseases, such as purpura haemorrhagica and pernicious anaemia of horses Vibrio Vibrio is a bacterium shaped like a boomerang In stained smears they are often seen in pairs either in the form of an ‘S’ or of a flying seagull Vibrio fetus (see CAMPYLOBACTER INFEC- TIONS, FETUS) ‘Vibrionic scours’ in pigs (see SWINE DYSENTERY) Vibriosis Vibriosis caused by infection with Vibrio anguillilarum is a serious disease in marine fish farms Affected fish suddenly lose appetite and turn dark in colour Post-mortem examination reveals haemorrhagic internal organs; the kidney may be liquefied Surviving fish may have ulcers that erode the back muscles and the base of the fins Prompt treatment with antibiotics in the feed may save those still eating The infection has also been found in eels transported live in inadequate conditions Vibrissae The thick, stiff hairs or whiskers which project from the faces of cats, dogs, and other animals They are minor sense organs (See SKIN.) ‘Vices’ and Viciousness A definition comprehensive enough to include bad habits (See TAIL-BITING (in pigs), SUCKING (in calves); and FEATHER-PICKING, CANNIBALISM (in poultry).) The following concern the horse Bad habits, mild vices, or whims Horses which are shut in stables without exercise or work frequently learn vices and tricks which not only may be harmful to the animals themselves, but may be dangerous to persons who attend them Perhaps the most objectionable is the habit of kicking when being approached (See below, under ‘Kicking’.) Eating the bedding may be merely an endeavour on the part of the horse to acquire a sufficiency of coarse bulky food when the ration is too concentrated, or it may be a bad habit It can be prevented by supplying sawdust instead of straw, or peat moss litter Refusing to lie is often due to fear, nervousness, or physical inability, such as ankylosis of the spinal column Horses may lie when housed in a loose-box instead of a stall; a stout rope from one heel post across to the other may allow the horse to obtain some amount of rest (See SLEEP, etc.) Gnawing the walls is usually a sign of the presence of worms, bots, a mineral or other deficiency, or indigestion, and appropriate Viral Hepatitis in Dogs 759 measures should be taken to determine which condition is present, and to treat it accordingly Pawing in the stable may be a sign of impatience or loneliness; then it is not important, but sometimes it develops into a vice of such persistency that it entails great wear of the shoes, and may result in the production of holes in the stable floor It should be remembered that pawing is sometimes a sign of abdominal pain (colic) In addition to these there are ‘cow kickers’, which project one hind-limb forwards, outwards, and backwards, so that they may reach a person standing as far forward as the shoulder These are especially dangerous More serious vices (see CRIB-BITING AND WIND-SUCKING; WEAVING) Shying In many cases where horses suddenly Aggressiveness may be due to pain (see HORSES, BACK TROUBLES); and, in countries where the disease is present, to RABIES (See also BRAIN DISEASES.) When an animal shows an ungovernable temper under the pressure of sexual disturbances, it is unfair to consider it vicious Cruel treatment in the past may also be an underlying factor (and see also the effect of EQUINE VERMINOUS ARTERITIS) Kicking (a) Rearing and striking with the fore-feet is a dangerous vice that is more common among the light horses than among the heavy draught Sometimes the animal merely rears from a desire to get started with his work; sometimes he will not allow himself to be held by the head when in harness, but rears and strikes out at anyone approaching him; at other times he may strike out without rearing A saddle horse, when rearing, may with his head strike the face or chest of his rider and unseat him, and may so lose his balance that he falls over backwards and perhaps crush the rider (b) Kicking with the hind-feet ‘With a kicking horse, pass in front’ is a proverb that it is well to remember when dealing with the horse that uses his hind-feet for kicking The hindfeet can be used to strike an object within a radius of from 1.2 to 1.8 metres (4 to ft) all around them It is a well-known fact that a mule can deliver a kick with his hind-feet to a person standing at its shoulder, and there are many horses able to likewise Two methods of kicking with the hind-limbs are commonly employed: in the first, which is the horse’s natural method of defence and offence, the head is lowered, the body is lifted from the withers backwards, and both the hind-limbs are suddenly extended as far backwards as possible with tremendous force; in the second, the horse lifts one hind-foot and deals a short vicious backward or sideways kick without always fully extending the limb Biting is commonest among stallions It is well to take precautionary measures, such as muzzling while grooming, tying up short, using double head ropes, one to either side of the stall, etc stop, plunge to one side, snort, tremble, attempt to turn in the opposite direction and run away, when confronted by some unusual sight, sound, or smell, the same causes as occasion bolting are operative The horse does not trust his eyesight, is unable to interpret an unusual sound or smell, and consequently takes fright Among the many objects at which horses are liable to shy may be mentioned the following: pools of water shining in the sun-light, fluttering pieces of paper, clothes out to dry, dogs, cats, fowls, and other small animals darting into the roadway The odour of wild beasts, and the smell of blood and offal, that an animal perceives when passing a menagerie or a knackery or abattoir, are also likely to frighten it and cause it to shy Aversion to special objects Occasionally a horse is encountered which has an absolute horror of some special, usually quite harmless, common object, e.g pieces of white or coloured paper or rag, cock turkeys, pigs, goats, donkeys, small white inanimate objects of any nature, etc Grey horses have been known to attack bay horses, and a brown-bay horse, light grey horses Villus Villus is the name given to one of the millions of minute processes which are present on the inner surface of the small intestine These are structures concerned in the taking up of fat (See DIGESTION; INTESTINE.) Viraemia The presence of large amounts of infecting virus in the blood Viral Relating to viruses Viral Haemorrhagic Disease of Rabbits (see RABBIT HAEMORRHAGIC DISEASE) Viral Hepatitis in Dogs (see CANINE VIRAL HEPATITIS) V 760 Viral Hepatitis of Ducklings Viral Hepatitis of Ducklings Viral hepatitis of ducklings is a disease which attacks ducklings under weeks of age There are usually no clinical signs before death except general malaise On post-mortem examination, the liver shows enlargement and haemorrhaging It can be prevented by vaccination at day old Viral Infections of Cows’ Teats V These include cowpox Nowadays, true cowpox is (in the UK) considered to be a rare disease Another infection common to man and cattle is pseudo-cowpox or milkers’ nodules The skin disease in herdsmen is indistinguishable from that in shepherds who have been handling sheep suffering from orf It is now thought that the milkers’ nodules virus very closely resembles the orf virus, but that they are distinct entities Two doctors in Dorset who had patients with milkers’ nodules found, with the aid of a veterinary colleague, that the dairy herds in which the men worked all had some cows with pseudo-cowpox (or milkers’ nodules) lesions on the teats There are types of this infection: one is described as benign or chronic – this lasts for months, it is painless throughout, and starts with a mild redness of the teats, followed by the formation of many scabs which get rubbed off at milking The second, or acute, form involves pain before scabbing begins, but not afterwards First there is reddening, then blisters which burst, then very large scabs form So-called proud flesh is formed beneath the scabs When these drop off, a characteristic horseshoeshaped ring of minute scabs at the circumference is left All this takes to 10 days What looks like a wart remains for several months This pseudo-cowpox differs from true cowpox in that the latter infection is associated with more pain, fewer scabs, quicker development of them and recovery within weeks The virus which causes pseudo-cowpox or milkers’ nodules may be identical with, or closely related to, that of bovine papular stomatitis (BPS) Raised, roughened, brownish plaques are seen on the muzzle, and lesions on the lips and inside the mouth An ulcerative infection of the teats of dairy cows has been described in Scotland, and given the name bovine ulcerative mammillitis It is caused by a herpesvirus The disease has been seen only in early winter, and lasts for up to 15 weeks In severe cases it is of sudden onset, often appearing between milkings; the whole teat being swollen and painful Blue discoloration is common The resultant ulcer covers most, if not all, the teat In a less severe form vivid red discoloration was noted On account of the impossibility of milking cows with badly ulcerated teats, and because mastitis often follows, several animals may have to be slaughtered The same disease has been seen in south-west England where the onset appeared to follow a prolonged period of wet weather If the virus is of the herpes type, it may be that it is endemic in the cattle population and produces lesions only under conditions which result in devitalising of the tissues Another possibility is that biting flies transmit the infection (See also under FOOT-AND-MOUTH DISEASE.) Viral Pneumonia of Cattle (see infections listed under CALF PNEUMONIA) Virginiamycin An antibiotic used as a growth promoter which may be included in livestock rations Virino A low-molecular-weight nucleic acid and a host-derived protein (See SCRAPIE for a possible example.) Virion A mature virus; the ultimate phase in viral development Virology The study of viruses Virus Diarrhoea of Cattle (see BOVINE VIRAL DIARRHOEA) Viruses These are minute entities which carry their genetic information in one type of nucleic acid They use the energy system of the host cell for their own biosynthetic needs, and can be differentiated from bacteria by their size and by their inability to multiply except in living cells Most viruses produce disease in man, animals and plants They can be transmitted from one animal to another and stimulate the production of antibodies in infected animals Viruses are mostly invisible under the light microscope, although some of the larger examples (e.g the pox viruses) can be seen readily under the light microscope Most viruses can only be visualised in the electron microscope There is considerable variation in size Footand-mouth disease virus is about 25 nm in diameter, whereas African swine fever virus is about 10 times that size (See NANOMETRE.) Vision Many pathogenic viruses are capable of altering their antigenic structure, or their pathogenicity, or both, in response to pressures put upon them by, for example, vaccination The classical example is provided by influenza viruses, which are able to change from harmless to extremely virulent forms very quickly within the same species The nomenclature and classification of viruses has in recent years undergone many changes, and further changes are likely as new viruses are discovered and new information on the properties of viruses accrues (See table, page 762.) Anti-viral agents Since viral infections are not controllable by antibiotics, there has been a long search for other compounds which might achieve anti-viral activity Much hope was pinned on INTERFERON, but at present its use is very limited, and research has switched to attempts to stimulate natural production of interferon, or to find drugs effective against viruses Aciclovir may be used for ophthalmic infections by herpesviruses Zidurodine alleviates clinical signs in cases of feline immunodeficiency virus (FIV) However, anti-viral drugs have to be used with great care as the margin between an effective dose and the toxic one (the therapeutic index) is narrow Vaccines are available against a number of viral infections, e.g equine herpesvirus, canine distemper, and feline leukaemia (See also ROTAVIRUS; ASTROVIRUS; ONCOGENIC; DNA; RIBONUCLEIC ACID; CANCER.) Viruses, Plant Some of these can, by means of DNA technology, be adapted to produce ‘potentially safe and inexpensive vaccines for use against disease in animals’ AFRC research workers have, for example, produced a harmless plant virus carrying a fragment of foot-and-mouth disease virus Viscera Viscera is the name given to the larger organs lying within the chest and abdominal cavities The term ‘viscus’ is applied to each of these individually ‘Visceral Gout’ A disease characterised by the deposit of urates over the internal organs; it is found in birds and reptiles Visceral Larva Migrans A syndrome produced in man by the larvae of Toxocara canis Occasionally it is the cause of death (See TOXOCARA.) 761 Vision (see also EYE) Rays of light pass, in the first place, through the cornea, then through the aqueous humour that fills the anterior chamber of the eye The light then enters the hinder part of the eye, through the pupil – a round, slit-like, or elliptical hole in the iris, which can be automatically narrowed according to the strength of the light rays that are passing through it Immediately behind the iris lies the crystalline lens, a clear structure arranged in layers somewhat like an onion, which also by automatic alterations in its curves, brings the rays to a focus upon the retina after they pass through a second clear jelly-like humour – the vitreous humour The retina is the innermost of the coats of the eyeball, and consists of the specialised terminations of the fibres of the optic nerve Monocular and binocular vision In animals whose eyes are laterally placed in the head it is impossible for both eyes to look at an object directly in front of them One eye can be focused upon an object at any one time, while the other eye sees a completely different picture This is called ‘monocular vision’ When the eyes are placed towards the front of the head so that they can both be concentrated upon an object, as in man, horse, and dog, each eye sees a slightly different picture, but the ranges of vision overlap This is called ‘binocular vision’ It is partly owing to the fact that in binocular vision each eye sees slightly ‘round the corner’ of the object, that a sense of depth and distance is conveyed to the higher brain centres The pictures are not quite superimposed, and the previous experience of the animal enables it to judge distance by this difference in superimposition This is technically known as ‘stereoscopic vision’ A striking point in connection with the eyesight of animals is that, although many of them have their visual powers obviously very highly developed, they seldom trust their eyes in matters of emergency The visual images alone not convey to the mind the reality of the external world It becomes necessary for the animal to verify its visual impression by tactile or olfactory impressions In practically every case the fear of a harmless object may be immediately or shortly dispelled by allowing the animal to smell and examine it by touching it with the nose In birds, the central part of the lens has a magnifying power of up to 8x As a result (stereoscopic) vision is very accurate, enabling birds to locate food easily Birds, reptiles, amphibia and insects can ‘see’ ultraviolet light V 762 Vision Some viruses of veterinary importance Group Adenoviruses Alphaviruses Aphthoviruses Arboviruses Arenaviruses Bunyaviruses Caliciviruses Circoviruses Coronaviruses Enteroviruses Flaviviruses Herpesviruses Iridoviruses Lentiviruses Morbilliviruses Oncoviruses Orbiviruses Orthomyxoviruses Orthopoxviruses Papillomaviruses Paramyxoviruses Parapoxviruses V Pestiviruses Picornaviruses Poxviruses Reoviruses Retroviruses Rhabdoviruses Togaviruses Diseases caused Canine viral hepatitis Fox encephalitis (See also KENNEL COUGH.) Equine encephalitis Foot-and-mouth disease (See Togaviruses below.) Lymphocytic choriomeningitis (See also LASSA FEVER.) Rift Valley fever Animals affected Dogs Foxes Horses, birds, man Cattle, sheep, goats, pigs, deer, hedgehogs; (very rarely) man Mice, hamsters, man (Man) Sheep, cattle, goats, buffaloes, camels, man Sheep, goats Poultry Cats Pigs; (rarely) horses Chickens Pigs Nairobi sheep disease Gumboro disease Feline calicivirus disease Vesicular exanthema Anaemia Dermatitis and nephrosis syndrome Post-weaning multisystemic wasting syndrome Pigs Transmissible gastroenteritis Pigs Feline infectious peritonitis Cats Infectious bronchitis Chickens Enteritis Calves, foals, dogs, cats Swine vesicular disease Pigs; (rarely) man Teschen/Talfan disease Pigs Duck virus hepatitis Ducklings Avian encephalomyelitis Chickens Louping-ill Sheep, cattle, deer, dog, man Wesselbron disease Sheep, man Japanese B encephalitis Horses, man, pigs, birds Tick-borne encephalitis Rodents, goats, cattle, man Kyasanur forest disease Monkeys, rodents, man Omsk haemorrhagic fever Rodents, man Murray Valley encephalitis Wild birds, children St Louis encephalitis Wild birds, bats, horses, man Horses, cattle, pigs, dogs, cats, man (See table under HERPESVIRUSES.) African swine fever Pigs, African warthog Maedi/visna Sheep Caprine arthritis-encephalitis Goats Canine distemper Dogs, ferrets, mink Cattle plague (rinderpest) Cattle, sheep, goats Leukaemia, leukosis, cancer Mammals, birds Bluetongue Cattle, sheep African horse sickness Horses (but not donkeys) Influenza Horses, pigs, birds Cowpox Cattle, man Warts/papillomas/cancer/sarcoids Cattle, horses, dogs, man Newcastle disease Poultry, pigeons Parainfluenza Cattle, dogs (see KENNEL COUGH) Pseudo-cowpox Cattle, man Orf Sheep, cattle, goats, dogs Bovine papular stomatitis Calves Bovine virus diarrhoea Cattle Border disease Sheep Swine fever Pigs Equine viral arteritis Horses (This group includes Aphthoviruses and Enteroviruses (see above) and Rhinoviruses.) (See Orthopoxviruses and Parapoxviruses, above.) Respiratory disease, enteritis Calves, pigs, dogs, cats, rabbits, man (See Lentiviruses and Oncoviruses above.) Rabies (see LYSSA; DUVENHAGE; MOKOLA VIRUS; LAGOS BAT.) Vesicular stomatitis Horses (See Alphaviruses, Flaviviruses and Pestiviruses above.) Vitamins Visna A meningoencephalitis of sheep caused by a lentivirus (See MAEDI/VISNA.) Vitamins Vitamins are substances present in natural foods, essential for health, and which exercise an influence in nutrition out of all proportion to the amounts consumed Several vitamins are synthesised in the animal body, some being thus available independent of the diet, but it is important to note that a vitamin synthesised in the lower part of the alimentary canal may be available to an animal only if it eats its own droppings (Nocturnal coprophagy is a regular practice in rabbits.) Vitamin supplements now form an essential part of farm livestock feeding Animals, when feeding under natural conditions, with a free choice from a wide range of food-stuffs, consume, as a rule, all the vitamins they require But under the influence of domestication, and especially of intensive rearing, animals often have no choice in the matter and suffer from vitamin deficiencies, either because their artificial diet is too restricted, or because vitamins naturally present have been destroyed in the preparation of the food Vitamin A is formed from yellow carotene found in carrots, green vegetables, egg-yolk, fish roe, liver, cod-liver oil, kidney and milk This vitamin is necessary for the growth and general well-being of the young animal in particular Vitamin A is also necessary for healthy skin and teeth Cats are unable to synthesise vitamin A and obtain it from fish and liver Too little or too much vitamin A can be harmful In excess, it can adversely affect growth and bone development Vitamin B complex, water-soluble, includes riboflavin, nicotinic acid, pantothenic acid, choline, biotin, and thiamin (See also CHOLINE; FOLIC ACID.) Most of these are present in yeast and liver (For nicotinic acid, see NIACIN.) Vitamin B1 (thiamin, aneurine) is present in the husks of cereal grains, yolk of egg, yeast, and liver A deficiency can be caused by overheating the food of pet animals, or by the enzyme present in some fish Horse and cattle which eat bracken are affected by the thiaminase in that plant (See BRACKEN POISONING.) Vitamin B2 (riboflavin) is present in milk (and is not destroyed by pasteurisation), as well as in foods mentioned under B1 Riboflavin is a constituent of the flavoproteins – hydrogen-transporting enzymes concerned with the animal’s energy metabolism 763 Biotin, formerly known as vitamin H, is another of the B group of vitamins It is necessary for the health of skin and hoof It is referred to below under ‘Vitamin deficiencies’ Vitamin B3 (pantothenic acid) Necessary for skin health, and growth Vitamin B6 (pyridoxine), present in liver, yeast and cereals, is important for growth and protein metabolism Vitamin Bl2 is the anti-pernicious anaemia factor of importance in human medicine, and contains cobalt It is also known as cobalamin Vitamin C This is ascorbic acid; it is found in the juices of most fruits and vegetables Most animals can produce sufficient vitamin C for their own requirements, with the exception of primates, guinea pigs and the bulbul famly of birds In hot weather and other stressful situations, additional vitamin C may be needed for all animals Vitamin D, or calciferol, is the anti-rachitic principle found in cod-liver oil, meat juice, cow’s milk, and egg-yolk The absence of this vitamin causes rickets There is an intimate association between the presence of this vitamin, the action of sunlight or the artificial irradiation by ultraviolet rays, and the mineral balance in the body With its help, salts of calcium and phosphorus, instead of being eliminated from the intestinal canal, are absorbed into the system and made use of in the calcification of bone (See COD-LIVER OIL.) Too much vitamin D is harmful (See RODENTS – Rodenticides.) Vitamin E (tocopherol) (fat-soluble) This vitamin is found in red meat, oil of seeds, milk, and egg-yolk It is necessary for fertility, and its absence from a diet has been shown to cause sterility in rats by inducing firstly the death, and later the absorption, of the embryos Vitamin K complex – mostly fat-soluble vitamins concerned with the formation of PROTHROMBIN, and hence regarded as ‘the anti- internal-haemorrhage factor’ Present in alfalfa Synthetic preparations are available for therapy Vitamin excess (hypervitaminosis) may result in serious disease (For an example, chronic hypervitaminosis A occurs in cats fed almost exclusively on liver.) An excess of yeast, fed to pigs as a vitamin B supplement, has resulted in severe rickets Vitamin deficiencies These may occur as the result of a vitamin-deficient diet, or a failure V 764 V Vitamins – in some instances – to synthesise a particular vitamin within the body ‘Secondary’ or ‘conditioned’ deficiencies may also arise from any disease which impairs absorption from the alimentary tract, injuries to the liver, infections (which increase the consumption of vitamins), metallic poisoning, and as the result of some enzyme which destroys or inactivates a vitamin (For examples of the last-mentioned cause, see ‘CHASTEK PARALYSIS’.) Biotin-producing bacteria live in intestines and contribute a variable amount But biotin deficiency is not rare – except in adult ruminants Signs of deficiency are: dermatitis on ears, neck, shoulder and tail of the pig, together with cracking of the walls and sole of the hoof; retarded growth and brittle feathering, foot dermatitis, swollen eyelids, eruptions on mouth and beak, perosis, leg weakness, poor hatchability and embryonic malformations in birds A report from Finland stated that bleeding from the navel, which was a serious problem in a breeding herd of 85 Finnish Landrace and 85 Large White sows, could be successfully controlled by vitamin C (not vitamin K as might have been expected) An ascorbic acid supplement was given to the sows for from to days before farrowing Piglets from the treated sows were also 5.5 per cent heavier than those from untreated controls at weeks of age Vitamin E (tocopherol) could with advantage be added to all compound feeds as a precautionary measure, particularly if the feed contains polyunsaturated fatty acids Less vitamin E is absorbed from the intestine if the latter are present Some feeds contain vitamin E antagonists – present in lucerne and beans The activity of vitamin E may be reduced by a high nitrate content in feed or drinking water Animals which not receive an adequate supply of the trace element selenium need extra vitamin E, because selenium has a vitamin E sparing effect Application of fertilisers rich in sulphates inhibits the absorption of selenium by plants from the soil, and in these circumstances grazing animals will require extra vitamin E Vitamin E contents of feeds as well as crops may be reduced to a dangerous level on storage (See also Muscular dystrophy under MUSCLES, DISEASES OF.) Anti-vitamin E factor may be present in barley as well as fats of animal origin Despite a current tendency to increase vitamin levels in animal feeds, cases of vitamin E deficiency appear to be becoming more prevalent in all classes of farm livestock, resulting in mulberry heart in pigs, muscular dystrophy in calves, and ‘crazy chick’ disease in poultry Perhaps this has something to with the faster growth-rates expected of animals nowadays Certainly the low vitamin E content of some cereals is important This is especially the case with some samples of barley grown on selenium-deficient soil but fed on a farm where selenium is no problem, and where the possibility of such a deficiency might well be overlooked It is generally accepted that the daily requirement of vitamin E is, for cows, g; for calves, 150 mg; for ewes, mg; and for lambs, 25 mg Vitamin E deficiency leads to white muscle disease or muscular dystrophy; and a supplement of this vitamin has been shown to reduce the incidence of retained placenta, metritis, and cysts of the ovaries when given with SELENIUM Horses Vitamin A deficiency is unlikely to occur except in town horses denied adequate green food Deficiency symptoms are stated to include night-blindness, hoof lesions, corneal lesions, respiratory symptoms, and reproductive difficulties Some of the B vitamins are synthesised by adult horses, but backward foals may benefit from vitamin supplements Infertility in the mare may sometimes be associated with a vitamin C deficiency It has been suggested that splints, sidebones, ringbones, and spavins may be associated with a vitamin D deficiency Cattle Vitamin A deficiency in cattle denied adequate green food leads to abortion or the birth of weak, blind calves, or of those suffering from diarrhoea which die within a few days Corneal lesions and blindness may also result in growing cattle For example, Hereford bulls on a diet of beet-pulp nuts, high-protein nuts, and barley straw went blind owing to a lack of vitamin A (See also HYPERKERATOSIS.) Vitamins of the B complex are mostly synthesised in the rumen, but in the newborn calf a deficiency may occur (See THIAMIN.) Vitamin C is apparently synthesised by adult cattle, but some cases of infertility may, it is believed, be due to a deficiency, and some cases of navel-ill benefit, it is said, from vitamin C treatment In some parts of Britain pasture or fodder crops contain too little vitamin D, while sunlight during the winter months is insufficient to enable the shortage to be made good within the animal’s body; the result is rickets Vitamin E deficiency is associated with muscular dystrophy Pigs Vitamin A deficiency results in failure to grow in piglets and infertility in adult pigs, as well as paralysis of the hindquarters A nicotinic acid deficiency gives rise to a condition simulating necrotic enteritis and poor growth Yeast supplements will correct deficiencies of the B complex, but excess may result in rickets Voice A vitamin E deficiency in newborn piglets can result in their sudden death after being given iron injections to prevent anaemia It is advisable to delay the injection until the piglet is a week old, when it is more tolerant of iron Gilts’ rations low in vitamin E or high in fatty acid predispose to this condition in the offspring Biotin deficiency in pigs gives rise to symptoms which include dermatitis Lameness can affect a whole herd where there is a biotin deficiency causing cracks in the sole or wall of the hooves Dog and cat Vitamin A has been used with success in the treatment of diarrhoea in kittens Corneal lesions, even blindness in extreme cases, and sometimes deafness, have also been attributed to a vitamin A deficiency Vitamin B (thiamin) deficiency results in fatigue and loss of appetite, and may be associated with cramp Yeast may prove effective in cases of depraved appetite and chorea ‘Black tongue’ in the dog and an ulcerative stomatitis in the dog are seen in the USA in naturally occurring cases of nicotinic acid deficiency Lack of riboflavin is associated with eye lesions and skin disease Rickets results from lack of vitamin D, especially in the larger breeds, but overdosage is harmful and can lead to deposits of calcium salts in or between muscles Poultry Vitamin A deficiency will occur only in birds deprived of adequate green food Maize and cod-liver oil (which must not be rancid) are alternative sources of this vitamin Lack of it leads, in chickens, to drowsiness, weakness, staggering, stunted growth, and often a discharge from the eyes and nostrils The presence of pustular lesions in the oesophagus is diagnostic Adult birds become dishevelled looking, weak and emaciated, and show a watery or cheesy discharge from eyes and nostrils Deficiency of riboflavin (vitamin B2) in the diet is not uncommon, particularly in wire-floor battery brooders, in which the chicks have no access to droppings (On solid floors chicks may correct the deficiency by eating their droppings, which contain riboflavin synthesised by organisms in the lower part of the gut, but not otherwise available to the body.) Symptoms are leg weakness and a curling inwards of the toes in chicks; also decreased egg production and poor hatchability (See also biotin under ‘Vitamin B’, above.) Thin shells, reduced hatchability, and sometimes a temporary paralysis after laying, are indications of a vitamin D deficiency Chicks are unthrifty, walk with difficulty, and later show typical symptoms of rickets Bone deformity 765 and softening of the beak occur in adult birds Sunlight, green food, and the judicious use in winter of cod-liver oil overcome this deficiency Vitamin E, necessary for hatchability, is present in whole grain and, to a lesser extent, in greenstuff The latter also contains ample vitamin K, a deficiency of which leads to anaemia as a result of internal haemorrhage Voice Voice is the sound produced as the result of the vibration of a column of air forced through the larynx by contraction of the respiratory muscles The means by which this is produced are analogous to those by which sound is produced in a reed instrument, except that in the living animal the pitch of the voice can be altered at will This is accomplished by the amount of tension exerted by muscular action upon the vocal cords; the more tense these are the higher is the pitch of the voice In the majority of mammals the vibrations are produced when a blast of air is expelled from the chest, but in the donkey the higher notes of the bray result from inspiration of air, and the lower notes from expiration The character of the voice can be altered to some extent by changes in the resonating chambers of the nose, mouth, pharynx, etc.; thus, the false nostrils of the horse are used to produce the snort of fear or excitement, the nasal cavities transmit the whinny and neigh of pleasure, and the mouth and pharynx furnish the character of the neigh of impatience, loneliness, and sometimes the challenge of anger of the jealous stallion Neighing or whinnying in the horse is an expiratory act produced partly through the mouth and partly through the nose; the bray of the ass is expiratory for the low notes and inspiratory for the high; bellowing in the ox, bleating in the sheep, barking in the dog, and the mew of the cat are all produced by expiratory efforts Animals use their voices upon widely different occasions It seems probable that they make the greatest use of this faculty for the purposes of enabling the young to recognise their dams from a distance, and to maintain cohesion of herds or flocks Stragglers getting left behind, or separated from their special companions, can be heard calling for long distances Male animals of many species will give a warning upon the approach of newcomers or danger Females may produce little cries or screams when attended by males during periods of oestrus, or when making acquaintance with their newly born progeny Almost all the domestic animals emit cries when V 766 Volar suffering pain In the horse tribe the sounds are often merely grunts or groans, especially when the pain is abdominal In other cases horses will scream when they are suddenly subjected to acute pain, or to very great fright Cattle and sheep in agony behave similarly to horses; they usually groan, but cows, ewes, and heifers may issue a long drawn-out bellow or bleat during difficult parturition The pig has a range of notes from the satisfied grunt of suckling a sow, to the frightened squeals and screams of those that are being handled by man The dog has a note for all occasions; he generally expresses all the emotions of which he is capable by differences in his bark (See also LARYNX and MUTING OF DOGS.) In rabies the character of the voice may be changed In the ‘dumb’ form, barking is suppressed Volar Refers to the back of the fore-limb Volcanic Gases Typically these comprise water vapour, carbon dioxide, sulphur dioxide, hydrogen sulphide, hydrochloric acid, hydrogen fluoride, and carbon monoxide Volvulus An intestinal obstruction is produced by the twisting of a loop of bowel round itself It is usually due to some spasmodic contraction of the muscular coat, or to the presence of gas, and is very dangerous owing to the great risk of strangulation of the blood supply and consequent necrosis Excessive gas formation in the caecum and colon of whey-fed pigs may lead to volvulus (See HAEMORRHAGIC GASTROENTERITIS OF PIGS and INTESTINES, DISEASES OF.) Vomica A cavity in the lung tissue produced by disease Vomicae are most commonly met with in cattle suffering from either tuberculosis or contagious pleuro-pneumonia Vomiting Vomiting involves not merely a contraction of V the stomach walls and a dilatation of the gullet, but is a complex act in which the abdominal muscles, the diaphragm, the muscles of the chest and larynx, and those of the lower part of the neck all play a part Before the act there is usually a profuse secretion of watery saliva which serves to lubricate the passage of the stomach contents The animal appears uneasy, and will usually seek a secluded spot Soon rhythmic contractions of the abdominal muscles commence and culminate in the ejection of a quantity of frothy material The diaphragm is generally fixed, and there is a powerful closing of the glottis to prevent any fluids from gaining access into the trachea The dog and cat vomit with relative ease They are able to induce vomiting by eating portions of the green shoots of couch grass (Triticum repens), ingestion of which brings on vomiting within to 10 minutes In the pig, the process is more exacting than in the carnivores Cattle and sheep may vomit occasionally, but it is not common and may be related to a serious stomach disorder or to rhododendron poisoning Vomiting in the horse is rare, and often is associated with a rupture of the stomach; when it occurs it should be considered a very grave symptom indeed The material always escapes through the nostrils in the horse Causes Vomiting can be considered under the following headings: Travel sickness Stress Simple indigestion When the stomach has received either a quality or a quantity of foodstuff with which it is unable to deal, the process of digestion does not proceed, or only proceeds up to a point The material brought up is recognisable as food, but it is mixed with quantities of frothy mucus, water, and perhaps may be stained brownish from bile It has a faintly sour smell which is greater the longer the process of digestion has been enabled to proceed The ejecta is generally easily brought up, and the animal soon settles down and becomes normal Indigestion from foreign bodies (See ‘CHOKING’; IMPACTION; FOREIGN BODY.) Gastritis The walls of the stomach are inflamed and thickened, the mucous membrane is swollen and painful, and the nervous system is in an irritable state Whenever food or water enters the organ, vomiting immediately takes place The vomit consists of the solid material swallowed, coated on the outside with mucus and froth If liquids have been taken they are returned almost unchanged When the inflammatory condition is very severe there are quantities of blood that have undergone partial digestion and have an appearance not unlike coffee-grounds, seen in the vomit In such animals there will be a very offensive smell both from the ejecta and from the mouth of the patient Pyloric stenosis, which may be congenital, is said to give rise to projectile vomiting Enteritis is associated with vomiting but there is diarrhoea as well Vulvovaginitis, Granular Impaction of the rectum, whether from particles of undigested bone, or hair, hard faeces, etc., generally induces vomiting in which not only does the stomach expel its contents, but masses of bowel content as well Acute nephritis is an extremely common cause of thirst and vomiting in the dog Pyometra in the bitch, cat, and sow is frequently accompanied by vomiting Accidents The shock of a severe burn or accident will cause vomiting, although the injuries have not been inflicted upon the stomach itself In other cases, where the head has been injured, the area in the case of the brain which control the act of vomiting becomes disturbed and the animal evacuates its stomach Poisons Many irritant substances will produce vomiting Of the commonest may be mentioned tartar emetic, mustard, salt, carbolic acid, areca-nut, castor oil, etc.; and of substances less common, but more drastic, the following are examples: strychnine, arsenic, phosphorus, apomorphine, croton oil, zinc and copper sulphates, and many of the metallic salts Some of these have special characteristics; for example, phosphorus vomit is luminous in the dark Diseases The symptom of vomiting is common to many other diseases – meningitis, peritonitis, nephritis, leptospirosis, rabies, vomiting and wasting syndrome in pigs, etc Treatment In the dog and cat the use of normal saline or glucose saline by injection is frequently indicated as an alternative to giving food (liquid or otherwise) by mouth during an illness (such as nephritis, uraemia, and enteritis) in which vomiting is persistent Vomiting and Wasting Syndrome This occurs in piglets days old and upwards, and is characterised by vomiting, depression, 767 loss of appetite, constipation, emaciation, and a hairy appearance It is caused by a coronavirus, haemagglutinating encephalomyelitis virus (HEV) (See also ‘ONTARIO ENCEPHALITIS’.) Von Willebrand’s Disease An inherited bleeding disorder found in some 25 breeds of dogs, and associated with an autosomal trait causing a high morbidity but a low mortality Signs may include epistaxis, haematuria, lameness, bleeding from genital mucosa, and prolonged bleeding from cut nails, etc Vultures (see TROPICS; CARCASES, DISPOSAL OF) Vulva It has in domesticated animals only simple, single labia or lips Diseases of the vulva In Kenya, squamous cell carcinoma of the vulva is common in cattle of the Ayrshire breed Cryosurgery has given good results when treatment has not been delayed until the tumour becomes too large In 62 cases, 55 were successfully treated (For persistent bleeding from the vulva, see VAGINA.) In the tropics, especially, a thick purulent discharge from the vagina may be a sign of tuberculosis involving the uterus/vagina Vulvovaginitis (see under RHINOTRACHEITIS and VULVOVAGINITIS, GRANULAR) Vulvovaginitis, Granular A venereal disease of cattle caused by Mycoplasma bovigenitalium, affecting vulva and vagina or seminal vesicles and skin of the penis The lesions are nodules V ... Alphaviruses Aphthoviruses Arboviruses Arenaviruses Bunyaviruses Caliciviruses Circoviruses Coronaviruses Enteroviruses Flaviviruses Herpesviruses Iridoviruses Lentiviruses Morbilliviruses Oncoviruses... Oncoviruses Orbiviruses Orthomyxoviruses Orthopoxviruses Papillomaviruses Paramyxoviruses Parapoxviruses V Pestiviruses Picornaviruses Poxviruses Reoviruses Retroviruses Rhabdoviruses Togaviruses Diseases... discharge from the vagina may be a sign of tuberculosis involving the uterus/vagina Vulvovaginitis (see under RHINOTRACHEITIS and VULVOVAGINITIS, GRANULAR) Vulvovaginitis, Granular A venereal disease