Potential animal health hazards of pork and pork products

Rev sci tech Off int Epiz , 16 (1), 65 78 Potential animal health hazards of pork and pork products S Farez R S Morley Animal and Plant Health Risk Assessment Network, Canadian Food Inspection Agenc.

Rev sci tech Off int Epiz., 16 (1), 65-78 Potential animal health hazards of pork and pork products S Farez & R.S Morley Animal and Plant Health Risk Assessment Network, Canadian Food Inspection Agency, 3851 Fallowfield Road, Nepean, Ontario K2H 8P9, Canada Summary The animal health hazards associated with the importation of pork and pork products include four viral agents: foot and mouth disease, classical swine fever (hog cholera), African swine fever, and swine vesicular disease viruses The safety of importing pork from a zone infected with one or more of these diseases can be adequately determined only through risk assessment This also applies for the safety of importing pork products which have undergone some form of processing (fully cooked pork products are not counted here) For each disease, the agent (pH and temperature lability), target organs, agent survival in pork and pork products, and agent quantification are discussed Agent quantification is an input of the risk assessment which measures the viral titres in waste pork and pork products in relation to the oral infective dose estimated for each disease Two other viral diseases, transmissible gastroenteritis of pigs and porcine reproductive and respiratory syndrome, are presented to illustrate w h y these two diseases are not hazards when associated with pork and pork products Keywords African swine fever - Classical swine fever (hog cholera) - Foot and mouth disease Porcine reproductive and respiratory syndrome - Risk assessment - Swine vesicular disease - Transmissible gastroenteritis of pigs Introduction T h e risk assessment m u s t determine, quantify the following factors: The introduction of animal diseases t h r o u g h t h e i m p o r t a t i o n of p o r k a n d p o r k p r o d u c t s is a c o n c e r n for all swine-rearing countries W h i l e t h e trade in p o r k is i n t e n d e d for h u m a n consumption, t h e intentional or inadvertent feeding of any u n c o o k e d waste to pigs could i n t r o d u c e animal disease a) the potential of the source to release a risk h a z a r d or risk agent The Office International des Epizooties (OIE) International Animal Health Code ( , 69) describes t h e sanitary m e a s u r e s for the safe i m p o r t a t i o n of p o r k a n d p o r k p r o d u c t s from zones infected w i t h certain swine diseases T h e i m p o r t a t i o n of p o r k (other t h a n fully c o o k e d p r o d u c t s ) from these zones is generally considered a h i g h risk It is therefore advisable to conduct a risk assessment for b o t h chilled or frozen p o r k a n d for p o r k p r o d u c t s w h i c h have b e e n subjected to a process such as heat treatment, freezing, m a t u r a t i o n a n d ageing, deboning, acidification, additives, curing, desiccation, etc Preceding risk assessment is the h a z a r d identification H a z a r d identification is the process w h i c h identifies potential risk agents a n d t h e conditions u n d e r w h i c h they m a y p r o d u c e adverse reactions Each h a z a r d necessitates a risk assessment characterise, and b) the intensity, frequency, a n d d u r a t i o n of exposure, a n d t h e n a t u r e of t h e animal a n d h u m a n p o p u l a t i o n s w h i c h m i g h t b e exposed c) the relationship b e t w e e n e x p o s u r e a n d biological a n d e c o n o m i c consequences the resulting T h e final o u t p u t s of this process are estimates of the m a g n i t u d e s of possible adverse health a n d e c o n o m i c conse­ quences, including a characterisation of the probabilities, uncertainties, or degree of confidence associated w i t h these estimates (16) In this paper, the a u t h o r s discuss t h e potential hazards associated w i t h trade i n p o r k a n d p o r k p r o d u c t s a n d p r e s e n t s o m e of t h e i n p u t s a n d t h e relevant information for a risk assessment o n t h e safety of i m p o r t i n g from zones w h e r e these h a z a r d s exist T h e p a p e r is restricted to a discussion of the 66 commodity-related i n p u t s These are as follows: agent ( p H a n d temperature lability), target organs, agent survival i n p o r k a n d p o r k p r o d u c t s , a n d agent quantification Agent quantification is an i n p u t of the risk assessment w h i c h quantifies the viral titres in waste p o r k a n d p o r k p r o d u c t s i n relation to the oral infective dose for each disease T h e risk assessment i n p u t s of incidence or prevalence of disease, d u r a t i o n of infection/viraemia, swine p o p u l a t i o n demographics, detection systems (in the h e r d , ante- a n d p o s t - m o r t e m inspections), surveillance a n d monitoring p r o g r a m m e s , disease control a n d eradication p r o g r a m m e s and exposure are m o r e clearly elaborated o n an individual country basis a n d are n o t discussed in this paper Hazard identification Rev sci tech Off int Epiz., 16 (1) O u t b r e a k s of CSF have often b e e n traced to the feeding of garbage from ships or aircraft Notable examples include two occasions, i n a n d , w h e n t h e disease w a s i n t r o d u c e d into N e w Zealand (47) T h e feeding of swill, presumably containing u n c o o k e d waste p o r k a n d p o r k p r o d u c t s , to pigs w a s incriminated i n CSF outbreaks i n t h e United K i n g d o m in (98), i n Switzerland in 9 , i n Bulgaria (65), G e r m a n y (66) a n d Poland (67) i n 9 a n d in Austria i n 9 (64) a n d 9 (68) Of SVD outbreaks w h i c h occurred in Great Britain b e t w e e n a n d , were attributed to feeding of contaminated waste food (38) There is n o evidence of oral transmission of PRRS t h r o u g h u n c o o k e d waste of p o r k or p o r k p r o d u c t s either in an enzootically infected z o n e or in the spread of the disease to a previously disease-free z o n e (5, , , 78) Experimental oral transmission is possible following administration of doses of T C I D virus (55) T h e potential hazards associated with trade in p o r k a n d p o r k p r o d u c t s are the viral agents of foot a n d m o u t h disease (FMD), classical swine fever (CSF) (hog cholera), African swine fever (ASF), a n d swine vesicular disease (SVD) T h e viral agents of transmissible gastroenteritis of pigs (TGE) a n d porcine reproductive a n d respiratory s y n d r o m e (PRRS), although perceived as potential hazards b y s o m e countries, are discussed to illustrate the differences b e t w e e n these two agents a n d actual hazards of p o r k a n d p o r k p r o d u c t s Excluded from the discussion is the parasitic agent of trichinellosis Although the agent of this disease represents a potential animal health hazard of p o r k a n d p o r k products, the disease is principally a food safety concern that w o u l d manifest itself in h u m a n s m u c h earlier a n d w i t h a m u c h greater impact t h a n i n pigs In the past a n d recently, p o r k a n d p o r k p r o d u c t s have b e e n incriminated as sources of disease introduction for all four hazards T h e disease introduction often occurs as outbreaks i n h e r d s w h i c h are fed r a w food waste in their swill, despite regulations that m a y b e in place requiring the cooking of s u c h waste before feeding However, disease introduction of PRRS a n d TGE h a s never b e e n attributed to the importation of p o r k a n d p o r k p r o d u c t s from infected zones Similarly, t h e transmission of TGE t h r o u g h t h e feeding of waste p o r k or p o r k p r o d u c t s h a s never b e e n reported O n l y experimental oral infection of one-week-old piglets w i t h h o m o g e n a t e s of muscle of t h e h i n d leg, l y m p h n o d e s (internal iliac, sub-maxillary a n d cervical) a n d b o n e m a r r o w from t h e femur of 16 six-month-old pigs w h i c h h a d b e e n i n contact w i t h experimentally infected piglets h a s b e e n demonstrated Twelve three-week-old pigs fed about 1.5 k g of t h e s a m e tissues each over days failed to b e c o m e infected, yet all b e c a m e serologically positive for neutralizing antibody to TGE virus (27) C o o k et al (13) achieved transmission of TGE i n six-day-old piglets b y oral dosing daily for days w i t h a h o m o g e n a t e of brachiocephalic m u s c l e a n d parotid l y m p h n o d e These two studies involved dosing w i t h a rather artificial m i x t u r e considering t h e h o m o g e n i s a t i o n of t h e tissues a n d t h e h i g h p r o p o r t i o n of l y m p h n o d e tissue Inputs for risk assessments on the importation of pork and pork products Many primary outbreaks of FMD have b e e n attributed to i m p o r t e d meat a n d meat p r o d u c t s , although p o r k a n d p o r k products were n o t necessarily implicated (6, 92) Agent pH and temperature lability It is almost certain that the long-distance spread of ASF from Angola to Portugal in t o o k place as a result of u n c o o k e d waste food being fed to pigs near Lisbon airport Subsequent outbreaks in Cuba in a n d , Malta, Sardinia, Brazil and the Dominican Republic i n 1978 a n d Belgium i n have also b e e n attributed to feeding pigs o n swill from ports or airports (97) T h e p H a n d temperature lability of t h e viral agents represent the two m o s t i m p o r t a n t biological properties for a n assessment o n t h e safety of i m p o r t i n g meat T h e anaerobic glycolysis w h i c h ensues in muscle after slaughter results in the conversion of glycogen to lactic acid I n one s t u d y o n m e a t quality i n different swine breeds, t h e p H of the s e m i m e m b r a n o s u s a n d longissimus dorsi muscles at m i n u t e s post m o r t e m ranged from a l o w of 6.17 to a h i g h of 6.71 (88) T h e final p H attained is generally about 5.4-5.5 67 Rev sci tech Off int Epiz., 16 (1) in typical m a m m a l i a n muscles a n d is referred to as t h e ultimate p H ' Between individual pigs there is a considerable variation i n t h e time t a k e n for the p H of latissimus dorsi muscle to fall from a p H of 6.5 to an ultimate p H of 5.5 at 37°C, a range of a b o u t 150 to j u s t over 0 m i n u t e s (45) In the commercial p r o d u c t i o n of p o r k , t h e time a n d temperatures at w h i c h the carcasses are h e l d s e l d o m allow t h e p o r k to fall b e l o w a p H of 5.7 (10) F M D virus is the only hazard w h i c h is labile to p H levels found in p o r k : however, viral inactivation as seen i n the m a t u r a t i o n of beef m a y n o t b e as dramatic Beef m a t u r e d for - h o u r s safely achieves a p H of 5.7 (3) a n d any virus p r e s e n t i n t h e m u s c l e tissues would b e readily inactivated T h e significance of this is that the p H of p o r k a n d p o r k p r o d u c t s represents a n i m p o r t a n t input in t h e risk assessment o n p o r k from F M D infected zones O t h e r organs a n d tissues s u c h as t h e p a r e n c h y m a t o u s organs, l y m p h n o d e s a n d b o n e m a r r o w w o u l d b e unlikely to achieve t h e l o w p H values as evidenced in m u s c l e Temperature lability is t h e m o s t i m p o r t a n t consideration for p o r k p r o d u c t s w h i c h u n d e r g o s o m e t h e r m a l processing Although there is a difference b e t w e e n the t e m p e r a t u r e lability of the viral agents i n culture m e d i a a n d that i n p o r k , the laboratory data give s o m e indication of t h e ease of inactivation Generally the studies involving t h e r m a l processing of p o r k i n w h i c h particular core temperatures achieve an a p p a r e n t inactivation w o u l d b e better to assess F o r the four viral hazards, a t e m p e r a t u r e of 69°C w h i c h is reached by the very i n n e r core of a p o r t i o n of p o r k appears to readily inactivate t h e virus A m i n i m a l time p e r i o d of less t h a n 15 m i n u t e s at this temperature, however, m a y b e necessary to inactivate CSF virus i n p o r k t h e epithelium of t h e coronary b a n d , t o n g u e , s n o u t a n d lips a n d in t h e m y o c a r d i u m , tonsils a n d brain stem (90) D u r i n g t h e i n c u b a t i o n period, the virus m a y only b e f o u n d at t h e site of entry a n d the adjacent l y m p h n o d e s , s u c h as t h e tonsils a n d m a n d i b u l a r a n d parotid l y m p h n o d e s for CSF, ASF a n d SVD or the popliteal l y m p h n o d e s of the h i n d legs for SVD following agent entry t h r o u g h b r o k e n s k i n o n t h e foot Despite this tissue tropism, titres are detected i n almost all tissues d u r i n g t h e state of viraemia Viral titres i n skeletal m u s c l e of viraemic pigs w i t h SVD or F M D m a y represent m o r e a function of the viral litre w t h i n b l o o d capillaries Viral titres i n skeletal m u s c l e of pigs d u r i n g the viraemic p h a s e of ASF are a reflection of h i g h b l o o d titres, the target cells (lymphocytes, endothelial cells, reticular cells, m o n o c y t e s a n d macrophages) (76) a n d loss i n vascular integrity Highly vascularised organs s u c h as t h e spleen, kidney, a n d liver a n d b o n e m a r r o w w o u l d b e expected to exhibit viral titres d u r i n g t h e state of viraemia Generally, only t h e viraemic p e r i o d a n d its d u r a t i o n are of significance i n the i m p o r t a t i o n of p o r k T h e d u r a t i o n of viraemia m a y b e quite short, as observed w i t h SVD, or prolonged, as in s o m e of t h e clinical forms of CSF a n d ASF T h e mortality as seen in t h e peracute, acute a n d s u b a c u t e forms of CSF a n d ASF naturally limits t h e viraemic period A carrier state is n o t e d w i t h ASF b u t n o t w i t h CSF, SVD or F M D i n pigs T h e carrier state for diseases s u c h as TGE a n d PRRS is characterised b y predilection a n d m a i n t e n a n c e of the virus i n tissues other t h a n p o r k , that is t h e tonsils, l u n g s a n d intestinal tract for TGE a n d the l u n g a n d tonsils for PRRS T h e carrier state of ASF in surviving pigs is confined to l y m p h n o d e s , tonsils a n d to a lesser extent kidney, spleen a n d b o n e m a r r o w (53) Target organs Before discussing t h e target organs a n d predilection sites of the viral agents, it is necessary to m a k e a clear distinction between the organs a n d tissues w h i c h constitute p o r k a n d p o r k p r o d u c t s a n d n o n - p o r k organs P o r k a n d p o r k p r o d u c t s are comprised principally of skeletal muscle, b o n e a n d fat Bone m a r r o w , b l o o d w i t h i n t h e capillaries of skeletal muscles and l y m p h n o d e s (prepectoral, presternal, precrural, superficial inguinal, popliteal, iliac, l u m b a r a n d renal) (32) a m o u n t to a very small fraction of t h e swine carcass W i t h respect to p o r k portions, l y m p h n o d e s a n d b o n e m a r r o w m a y not b e present as a result of trimming, d e b o n i n g a n d depending o n the particular cut M a n y of t h e l y m p h n o d e s indicated above are r e m o v e d t h r o u g h carcass t r i m m i n g d u e to their superficial, fat-embedded location o n the carcass Obviously, the blood, the respiratory, gastro-intestinal a n d reproductive tracts, t h e h e a d , t h e respective l y m p h n o d e s of these parts a n d the tonsils are n o t p o r k tissues The cell a n d tissues for w h i c h the agent h a s a n affinity a n d i n which the agent replicates are therefore an i m p o r t a n t consideration in t h e i m p o r t a t i o n of p o r k Virus titres i n p o r k derived from infected pigs m a y b e very l o w in c o m p a r i s o n to the predilection sites of the agent (e.g SVD virus replicates i n Agent survival in pork and pork products Survival i n t h e p r o d u c t d e p e n d s o n t h e agent properties, especially lability to time, t e m p e r a t u r e a n d p H a n d o n t h e i n h e r e n t properties of the p r o d u c t (e.g p H , water activity, moisture:protein ratio, t e m p e r a t u r e of processing a n d storage, salinity, additives, etc.) T h e interaction of these p r o d u c t properties a n d t h e enzymatic proteolysis w h i c h occurs i n m a n y p r o d u c t s are significant factors i n the inactivation of viral agents Survival of agents in various p o r k p r o d u c t s h a s b e e n investigated a n d r e p o r t e d in t h e scientific literature Most of these studies m u s t b e statistically interpreted, b a s e d o n t h e n u m b e r of samples tested for virus isolation or the data points o n t h e r e d u c t i o n of viral litre of a n agent over time Multiple studies a n d other information m a y b e c o m b i n e d a n d statistically evaluated to estimate the inactivation curve associated with s o m e form of processing Agent survival b e y o n d the usual processing time a n d t h e time required for i m p o r t a t i o n a n d distribution i n the i m p o r t i n g c o u n t r y are part of the considerations of this i n p u t Changes in t h e technology of m e a t processing a n d curing, a n d t h e efficiency of m o d e r n abattoir practices a n d international transportation a n d distribution, m u s t b e considered here 68 Rev sci tech Off int Epiz., 16 (1) Agent quantification conditions (82) In tissue culture suspensions, t h e virus survived less t h a n 15 s e c o n d s at p H a n d p H , t w o m i n u t e s at p H a n d for several weeks at p H (25, ) At a p H of 7.5, the virus i n simple media survived seconds at 61°C, two m i n u t e s at 55°C yet as long as 18 weeks at 4°C (1) Viral titres Data o n titres i n tissues, i n particular muscle, quantify the a m o u n t of agent present p e r gram Quantification of viral titres is generally obtained from experimental infection of swine with a specific strain of virus T h e viral titres in muscle a n d other tissues a r e m e a s u r e d , often at t h e p e a k of viraemia Titres at other times i n the disease course are n o t available, as experimental studies are frequendy looking for t h e 'worst-case scenario' w h e n titres are expected to b e at their highest level Employing these data to represent the titres for any day of the duration of infection or viraemia is an extrapolation Nonetheless, the data m a y represent the best available biological information Oral infective dose U n c o o k e d waste of p o r k or p o r k p r o d u c t s being ingested b y swine b y one or m o r e scenarios represents the only m o d e of transmission of interest here T h e target species is the pig, t h e portals of entry are the tonsils, oral abrasions, respiratory tract and the gastro-intestinal tract After contact exposure, ASF virus primarily gains entry t h r o u g h t h e tonsils a n d i n s o m e instances across t h e nasal, bronchial a n d (possibly) gastric mucosae (34) Similarly with exposure to pigs infected w i t h SVD, the tonsils appear to b e the m a i n site of entry, however, other entry sites m a y include the skin of t h e h e a d a n d lower limbs, u p p e r respiratory a n d digestive tract epithelium, a n d intestinal m u c o s a e (56) Virus in p o r k or p o r k p r o d u c t s h a s to contact t h e tonsils, t h e u p p e r respiratory tract epithelium or gain entry t h r o u g h oral abrasions Failing these routes of entry, t h e gastro-intestinal m u c o s a e m a y serve as sites of entry providing the virus survives the low p H of the gastric juices T h e a m o u n t of mastication of the food a n d the rapidity of swallowing a b o l u s of p o r k w o u l d d e t e r m i n e the site of viral entry It is for this reason that the oral pig infective dose % ( P D ) for the viral diseases w o u l d b e expected to b e considerably higher for feeding of infected p o r k t h a n for instilling virus i n culture m e d i a o n t h e t o n g u e of a pig, feeding the virus s u s p e n d e d in a liquid m e d i u m s u c h as m i l k or force-feeding h o m o g e n i s e d infected tissues T h e P I D h a s n o t b e e n estimated for F M D , CSF, a n d SVD Instead, an infective dose at w h i c h infection was achieved experimentally in one or m o r e pigs is available in the literature In the case of SVD, skin abrasions, especially a r o u n d the coronary b a n d s of the feet m a y serve as a portal of entry following contact w i t h infected waste p o r k (56) 50 Foot and mouth disease Target cells and tissues T h e virus is distributed t h r o u g h o u t the b o d y of the infected animal a n d can be found in different concentrations for varying periods in the tissues In pigs, t h e greatest quantities of virus are in t h e blood, epithelium, a n d liver ( , 86) T h e specific lesions i n their early stages are microscopic a n d are limited t o t h e epithelium at sites of predilection s u c h as t h e m u c o s a of the m o u t h , including the tongue, lips, g u m s , p h a r y n x , a n d palate (9) T h e incubation period of F M D is generally within t h e range of - days (82) T h e virus is excreted o n e to ten days before clinical signs appear, a n d continues for four to ten days Virus w a s detected i n b l o o d h o u r s a n d i n m u s c l e h o u r s before the appearance of a p h t h a e or the beginning of a rise in t e m p e r a t u r e (21) I n pigs, t h e virus d o e s n o t persist for m o r e t h a n a m o n t h (57) O n e characteristic w h i c h distinguishes pigs from cattle a n d s h e e p is that they a p p e a r to h a r b o u r the virus only d u r i n g clinical stages of t h e disease a n d therefore d o n o t act as carriers (15) Survival in pork and pork products T h e a p p a r e n t d u r a t i o n of survival of FMD virus in the listed p o r k a n d p o r k p r o d u c t s is as follows: - days i n different chilled organs s u c h as lungs, stomach, tongue, intestine (83) - h o u r s in chilled spleen, liver a n d k i d n e y (83) - days in frozen lungs, intestine, stomach, tongue, kidney, spleen a n d liver (83) - 170 days in Parma h a m s (52) - 182 days in t h e w h i t e Serrano h a m (58) - 168 days i n Iberian h a m (58) - 112 days in Iberian s h o u l d e r h a m s (58) - days in Iberian loins (58) - 190 days in salted bacon, a n d days i n h a m fat (22) - days in sausages (22) - days in processed intestinal casings (49) - days i n salami (71) - 10 days in t o n g u e a n d day in m u s c l e (14) Apparent thermal inactivation of FMD virus is obtained w i t h an internal t e m p e r a t u r e of 69°C (50) Agent quantification Agent pH and temperature lability FMD virus is acid, alkali a n d h e a t labile, b u t can survive for long periods at neutral p H (7 to 9) a n d u n d e r low temperature Viral titres Sellers (86) found h i g h titres of ' p l a q u e forming u n i t s (PFU)/ml in blood, 10 PFU/g i n b o n e m a r r o w a n d 66 69 Rev sci tech Off int Epiz., 16(1) ' PFU/g in liver of infected pigs Similarly h i g h virus titres of greater t h a n PFU/ml were detected b y extraction from b o t h fat a n d m u s c l e tissues of infected pigs (71) Viral titres were m e a s u r e d in each of 62 pigs two days after intravenous inoculation w i t h m l of a 1:10 dilution of a stock virus (serotype C) having a titre of ' T C D p e r ml T h e m e a n and standard deviation of t h e viral titres i n muscle, fat, b o n e marrow, b l o o d a n d l y m p h n o d e are p r e s e n t e d i n Table (58) The m e a n viral titres i n m u s c l e a n d fat as p r e s e n t e d in Table I are significandy lower t h a n t h e titres detected b y Panina et al (71) Table I Foot and mouth disease viral titres in tissues of 62 pigs two days after experimental infection (58) Titre (plaque forming units [PFU] per ml or g) Mean Standard deviation Blood Lymph node Bone marrow Fat Muscle 3.5 10 - 1(F 10 - 1 D 0 10 D.O3 Survival in pork and pork products 10 10'.5 6-10 days before d e a t h in t h e h y p e r a c u t e , acute a n d s u b a c u t e forms of t h e disease, respectively (70) W i t h o n e ASF viral strain, viraemia was d e m o n s t r a t e d two days before t h e onset of fever (34) Pigs surviving the s u b a c u t e form m a y exhibit t h e chronic form of t h e disease w h i c h m a y last for several m o n t h s T h e carrier state i n these chronically affected pigs a n d i n pigs manifesting a subclinical or i n a p p a r e n t form of t h e disease m a y b e confined to l y m p h n o d e s , tonsils a n d to a lesser extent kidney, spleen a n d b o n e m a r r o w ( , 70, ) T h e virus replicates principally i n t h e cells of t h e lymphoreticular system, b o t h the fixed cells i n t h e l y m p h n o d e s , liver a n d spleen ( , ) , a n d i n m o n o c y t e s a n d m a c r o p h a g e s (97) Endothelial cells lining b l o o d vessels are severely d a m a g e d , w i t h resulting o e d e m a , h a e m o r r h a g e a n d necrosis Lesions are m o s t p r o m i n e n t i n t h e spleen, l y m p h n o d e s , l u n g a n d liver, b u t m a y b e f o u n d i n any l y m p h o i d tissue or infiltrate of l y m p h o i d cells (46) 0.8 1(F Oral infective dose A viral titre of TCID of F M D O-strain initiated infection i n two of pigs fed m i n c e d offal (liver, k i d n e y a n d l y m p h n o d e s ) (39) T h e a p p a r e n t d u r a t i o n of survival of ASF virus i n t h e listed p o r k a n d p o r k p r o d u c t s is as follows: - days in frozen m e a t or chilled m e a t (44) - 140 days i n Iberian h a m s (58) - 140 days i n Iberian s h o u l d e r h a m s (58) - 112 days i n Iberian loins (58) - 140 days i n w h i t e Serrano h a m s (58) - 9 days i n P a r m a h a m s (52) - days in p e p p e r o n i sausage (49) - days i n salami sausage (49) A p p a r e n t thermal inactivation of ASF virus is obtained w i t h an internal t e m p e r a t u r e of 69°C (50) African swine fever Agent pH and temperature lability Agent quantification Viral titres Viral titres of m e a t samples from four pigs infected w i t h ASF ranged from " to ' haemadsorbing units % ( H A d ) p e r g i n b o t h w h o l e a n d g r o u n d meat, two days after slaughter; " ° - ' i n salami, three days after slaughter; 10 "°-10 ' i n p e p p e r o n i , three days after slaughter; 10 ' -10 ' in b r i n e d h a m , two days after slaughter; " - i n p e p p e r o n i sausage, eight days after slaughter; a n d i n salami sausage, n i n e days after slaughter (49) Viral titres were m e a s u r e d i n each of pigs five days after intramuscular inoculation of m l of u n d i l u t e d stock virus having a titre of H A d p e r m l (58) T h e m e a n a n d s t a n d a r d deviation of t h e viral titres i n muscle, fat, b o n e m a r r o w , b l o o d a n d l y m p h n o d e are presented in Table II The sensitivity of t h e ASF virus to different temperatures has been studied widely Infected b l o o d h e a t e d for m i n u t e s at 60°C loses infectivity At 56°C, the resistance of t h e virus will d e p e n d o n the presence of s e r u m S o m e strains could r e m a i n virulent after 3.5 h o u r s at 56°C (12) Kovalenko et al (44) found that t h e virus could survive years at 5°C w i t h n o light ASF virus is very resistant to acid p H , even m o r e t h a n CSF viras Plowright et al (74) have found that the ASF virus could survive 2 h o u r s at p H T h e virus is rapidly inactivated at p H 11.5 a n d the inactivation rate decreases rapidly at lower p H values (12) Target cells and tissues 5 2 5 _ , 5 Oral infective dose In one experimental study, the P I D was ' H A d (34) McVicar (53) found the P I D of a moderately virulent strain of ASF virus to b e ' H A d b y oral experimental infection The ASF virus usually enters the pig t h r o u g h t h e m o u t h or u p p e r respiratory system, a n d infection is established i n t h e nasopharyngeal region T h e virus spreads rapidly to t h e mandibular l y m p h n o d e s a n d t h r o u g h o u t the b o d y t h r o u g h l y m p h a n d b l o o d (46) Following the i n c u b a t i o n period, t h e duration of viraemia m a y last 1-3 days, - days, a n d 5 Experiments suspensions administered were c o n d u c t e d i n w h i c h l y m p h from naturally infected warthogs to domestic swine T h e results of node were these Rev sci tech Off int Epiz., 16(1) 70 Table II African swine fever viral titres in tissues of 65 pigs five days after experimental infection (58) Tissue Blood Lymph node Bone marrow Fat Muscle Titre (haemadsorbing units 50% [ H A d J per ml or g) Mean Standard deviation 12 10 - 10 1(F 10" 10° 10 9.5 oa 1(P B B 10 o.5 experiments m a d e it evident that well-homogenised tissue suspension, containing to ' H A d of ASF virus failed to infect pigs w h e n administered either i n liquid or moistened solid food (75) Classical swine fever (hog cholera) Agent pH and temperature lability While the virus is very resistant at temperatures b e l o w 0°C, research has s h o w n t h e sensitivity of the virus above this temperature It can survive three days at 50°C, seven to 15 days at 37°C a n d years at - ° C T h e virus is, however, susceptible to rapid changes i n temperature s u c h as thawing a n d refreezing T h e effect of heat treatment o n CSF virus is influenced b y the physical m e d i u m in w h i c h t h e virus is heated T h u s cell culture fluid infectivity is lost after 10 m i n u t e s at 60°C, whereas in defibrinated b l o o d t h e virus is n o t inactivated after m i n u t e s at 68°C (94) T h e virus is stable over a wide p H range, b u t is rapidly inactivated below p H a n d above p H 11 (89) Target cells and tissues T h e virus initially infects epithelial cells of the tonsillar crypts a n d subsequently spreads to the s u r r o u n d i n g lymphoreticular tissue F r o m the tonsil, CSF virus is drained to t h e regional l y m p h n o d e s , w h e r e replication occurs T h e virus reaches the peripheral b l o o d and t h e n attains h i g h titres in the spleen, b o n e marrow, visceral l y m p h n o d e s , a n d l y m p h o i d structures lining the small intestine As a result of t h e replication i n lymphoid tissue and in circulating leukocytes and m o n o n u c l e a r cells, the level of viraemia is high T h e virus probably does n o t invade p a r e n c h y m a t o u s organs until late in the viraemic p h a s e (94) Viraemia can b e detected i n pigs from b e t w e e n two to four days after infection Viraemia follows the incubation period as the spread of virulent virus t h r o u g h o u t the pig is usually completed in five to six days (77) In the peracute form, death m a y appear w i t h i n five days post-infection In the acute a n d subacute forms of the disease, t h e viraemia persists at a high level until d e a t h w h i c h m a y o c c u r b e t w e e n 10 a n d days post-infection for the acute form a n d b e t w e e n a n d days post infection for the subacute form In the chronic form, the d u r a t i o n of t h e disease could b e or m o r e days (18) In the chronic form, the viraemia m a y subside d u r i n g the course of the infection whereas viraemia persists at a h i g h level for life i n t h e late-onset form of CSF ( , 96) T h e late-onset disease, a sequel of congenital CSF virus infection, is characterised b y a period of a few m o n t h s d u r i n g w h i c h pigs r e m a i n free of disease Most pigs survive for m o r e t h a n m o n t h s b u t all eventually die T h e viraemia persists for life (95) CSF virus strains of l o w virulence can i n d u c e m i l d disease w i t h s u b s e q u e n t recovery w i t h o u t a carrier state (89) Virulent virus infects b o t h epithelial a n d reticular cells, m a c r o p h a g e s a n d tonsillar cells, whereas t h e g r o w t h of virus of r e d u c e d virulence is mainly restricted to cells of t h e epithelial tonsillar crypts (93) Survival in pork and pork products T h e a p p a r e n t d u r a t i o n of survival of CSF virus i n the listed p o r k a n d p o r k p r o d u c t s is as follows: - 4.5 years i n frozen m e a t (96) - m o n t h in t h e m e a t of salt-cured p o r k (96) - m o n t h s i n t h e b o n e m a r r o w of salt-cured p o r k (96) - 90 75 90 70 days days days days in in in in salami (84) Italian salami (72) h a m (muscle a n d fat) (84) neck, lard a n d b o n e m a r r o w (84) - 2 days i n frozen liver at - 4°C a n d - 6°C (12) - days in Iberian h a m s (58) - days in Iberian s h o u l d e r h a m s (58) - 126 days i n Iberian loins (58) - 140 days in W h i t e Serrano h a m s (58) - 189 days in Parma h a m s (52) - days i n intestinal casings processed i n w a t e r at ° C for m i n u t e s (50) Apparent thermal inactivation of CSF virus is obtained u s i n g t h e following procedures: - pasteurisation at core temperatures over 67°C of c u r e d a n d c a n n e d h a m s (89) - exposure of c u b e s (2 c m ) of h a m to a 'flash' t e m p e r a t u r e of 71°C for m i n (87) - heating to 69°C for 15 m i n (50) Agent quantification Viral titres W o o d et al (99) studied t h e titres of virus i n tissues of pigs experimentally inoculated w i t h CSF a n d slaughtered b e t w e e n seven a n d days after infection Pigs w e r e infected b y intranasal inoculation w i t h T C I D / p i g CSF virus titres i n m u s c l e r a n g e d from to ' T C I D / g a n d titres i n l y m p h n o d e s ranged from to ' T C I D / g Titres 50 4 5 50 71 fíev sci tech Off int Epiz., 16(1] ( T C I D / g ) of CSF viras i n q u a d r i c e p s m u s c l e w e r e obtained on different days after infection as follows: o n day 7, ' o n day 1 , ' o n day a n d ' o n day A comparison s t u d y of t h e pathogenicity of two strains of CSF virus revealed titres w i t h a virulent strain of ' to 10 TQD p e r m l starting o n day three of t h e infection, whereas w i t h a l o w virulent strain the viraemia w a s n o t detected in pigs until day six T h e range of titres in the pigs was 10 to T C I D p e r m l (42) W i t h t h e late-onset form of the disease, t h e viraemia persists as l o n g as t h e animal lives, w i t h plasma titres ranging b e t w e e n and ' plaque forming units (PFU)/ml Virus is continuously present in the buffy coat cells (95) 50 , 4 4 at - ° C w e r e s a m p l e d after approximately 11 m o n t h s a n d s h o w e d n o significant d r o p i n infectivity resulting from storage (20) Target cells and tissues 5 15 5 Viral titres w e r e m e a s u r e d i n each of pigs five days after intravenous inoculation w i t h m l of a 1:100 dilution of a stock virus having a titre of ' T C I D p e r m l (58) T h e m e a n a n d s t a n d a r d deviation of the viral titres i n muscle, fat, b o n e m a r r o w , b l o o d a n d l y m p h n o d e are p r e s e n t e d i n Table III 5 Table III Classical swine fever (hog cholera) viral titres in tissues of 64 pigs four or five days after experimental infection (58) Tissue Blood Lymph nods Bone marrow Fat Muscle Titre (plaque forming units [PFU] per ml or g) Mean Standard deviation 10 3.s 10 10 10 10 - Swine vesicular disease virus h a s a n affinity for, a n d replicates in, t h e epithelium of t h e coronary b a n d , tongue, s n o u t a n d lips, as well as t h e m y o c a r d i u m , t h e tonsils a n d t h e b r a i n s t e m (90) T h e s t r a t u m s p i n o s u m is t h e p r i m a r y site of viral replication i n t h e epithelium (41) I n cell cultures of epithelial a n d salivary gland tissues, SVD virus reached significant titres w h e r e a s little or n o g r o w t h w a s detected i n cell cultures of m u s c l e , l y m p h n o d e or parts of t h e digestive tract (56) Eight healthy pigs w e r e inoculated i n the coronary b a n d of t h e h i n d legs w i t h cell culture SVD virus a n d w e r e slaughtered at t h e p e a k temperature Samples of different tissues w e r e collected d u r i n g necropsy T h e virus could n o t b e isolated from t h e muscles, b u t w a s detected i n o n e fat sample Tests were performed o n fresh samples a n d at 12, , , a n d 0 days after storage at ° C (28) T h e p e a k of viraemia occurs 2-4 days post-exposure to SVD virus a n d persists for six days Virus persists for at least 10 days i n the tissues of t h e snout, tongue, coronary b a n d , tonsil, cardiac muscle, a n d central n e r v o u s system Following experimental infection, swine s h e d virus i n their faeces for u p to days (41) 12 39 10" o.a i.o Survival in pork and pork products 10 '° 10 1Q T h e a p p a r e n t d u r a t i o n of survival of SVD virus in the listed M 10 p o r k a n d p o r k p r o d u c t s is as follows: - 0 days i n P a r m a h a m s (51) - 0 days i n dry salami sausage, d r y p e p p e r o n i sausage a n d Oral infective dose intestinal casings (48) A CSF virus titration in w e a n e r pigs u s i n g the highly virulent strain Alfort' s h o w e d that t h e m i n i m a l infective dose resulting in fatal disease was less t h a n 10 T Q D (18) In c o m p a r i s o n to the three other viral h a z a r d s , this represents a very l o w oral infective dose It m a y indicate that an infective dose for p o r k and p o r k p r o d u c t s is likewise comparatively very low - 0 days in dried p e p p e r o n i a n d salami sausage (33) - days in processed intestinal casings (33) - days in salami a n d p e p p e r o n i sausages (38) - days i n u n p r o c e s s e d intestinal casings (38) - days i n Iberian loins (59) - 112 days in Iberian s h o u l d e r h a m s (59) - days i n Iberian h a m s (59) Swine vesicular disease - days i n white Serrano h a m s (59) A p p a r e n t thermal inactivation of SVD virus is obtained b y Agent pH and temperature lability SVD virus is relatively stable over a p H range of - , depending o n t e m p e r a t u r e a n d time (38): days at a p H of 5.10 a n d 7.54 at 5°C, b u t a r e d u c t i o n of over log i n titre occurred at p H values of 8 a n d 10.14 b y days a n d at p H values of 1.92 a n d 11.96 at days (40) SVD virus is also stable i n infected tissue k e p t at ambient or higher temperatures for four m o n t h s or m o r e (90) Carcass materials heating to at least 69°C ( , ) Agent quantification Viral titres D a w e (20) reported that 1 - m o n t h - o l d frozen carcass material h a d T C I D p e r g of SVD virus in the skin, T C I D i n intercostal m u s c l e a n d T C I D p e r g i n 5 Rev sci tech Off int Epiz., 16(1) 72 b o t h rib b o n e a n d k i d n e y cortex These virus titres were n o t significantly b e l o w titres from similar samples taken at the beginning of t h e storage In h a m s h e l d at 0-4°C for h o u r s after slaughter, m e a n titres, expressed as PFU p e r g of muscle, b o n e m a r r o w a n d fat w e r e ' , ' a n d ' , respectively 1 Viral titres were m e a s u r e d in each of pigs three days after intravenous inoculation w i t h m l of a 1:3 dilution of a stock virus having a titre of 4.5 X P F U p e r m l (59) T h e m e a n a n d s t a n d a r d deviation of the viral titres i n muscle, fat, b o n e m a r r o w , b l o o d a n d l y m p h n o d e are presented i n Table IV Table IV Swine vesicular disease viral titres in tissues of 64 pigs three days after experimental infection (59) Titre (plaque forming units [PFU] per ml or g) Tissue Mean Blood Lymph node Bone marrow 1Q Standard deviation 2.e u 10 10 1.2 10 - 1(F 1D 10 10° Fat Muscle Q 10° 0.2 O.B Oral infective dose A dose of ' PFU p r o d u c e d clinical signs within to days in three of t h e six pigs infected orally (instillation in t h e m o u t h ) , while the dose required to p r o d u c e infection w h e n the a m o u n t of virus was applied to abraded skin surfaces w a s PFU (56) 1036 McKercher et al (48) fed swine w i t h infected m e a t w h i c h h a d a titre of to ' T C I D p e r gram In s o m e tests, the swine b e c a m e infected w h e n fed g of infected m e a t a n d in other instances w h e n fed 0 g In o n e feeding test, the animals d i d n o t s h o w any clinical manifestations of SVD; however, five of 18 developed neutralising antibody; three of these five were contact swine Six feeding tests involving 39 swine were u s e d to indicate that swine m a y b e c o m e infected w h e n fed p r o d u c t s from m e a t from infected animals However, in these tests, only 12 of the swine s h o w e d clinical evidence of SVD illustrated the short half-life time of the PRRS virus at p H 5.0: 0.65 h o u r s at 37°C a n d 18.8 h o u r s at 4°C Survival time of PRRS virus i n plasma is believed to b e less t h a n two days At - ° C the virus retains infectivity for 18 m o n t h s ; at 4°C, for m o n t h ; at 37°C, % r e d u c t i o n occurs after 12 h o u r s a n d complete inactivation after h o u r s a n d at 56°C, complete inactivation after m i n u t e s (61) Target cells and tissues T h e porcine reproductive a n d respiratory s y n d r o m e is a multi-system disease characterised initially b y viraemia w i t h s u b s e q u e n t virus distribution a n d replication in multiple organs causing interstitial pneumonia, vasculitis, l y m p h a d e n o p a t h y , myocarditis a n d encephalitis (79) T h e duration of viraemia as either plasma- or cell-associated viraemia h a s b e e n portrayed experimentally b y Mengeling et al (60) T h e duration of viraemia in experimentally infected six-week-old pigs varied from two days to u n d e r days T h e d u r a t i o n of viraemia portrayed above is s u p p o r t e d i n part b y other studies (11) T h e l y m p h o i d a n d respiratory systems have t h e m o s t remarkable lesions a n d appear to b e t h e major sites of replication of PRRS virus (35) A tropism for vascular tissues is a s s u m e d from the lesions of vasculitis of t h e m e d i u m \ sized arteries a n d occasionally of t h e veins, n o t only in t h e lungs b u t also in other organs, including the m e n i n g e s a n d t h e brain w h e r e a perivascular lymphoplasmacytic infiltrate h a s b e e n described (19) Persistence of the virus occurs mainly i n alveolar m a c r o p h a g e s a n d in the oropharyngeal l y m p h o i d tissue Viral persistence has b e e n detected as l o n g as 157 days after initial challenge (4, 5, ) Survival in pork and pork products There are n o studies o n t h e survival of PRRS virus in p o r k a n d pork products 5 Porcine reproductive and respiratory syndrome Agent pH and temperature lability T h e PRRS virus h a s b e e n classified a n arterivirus ( , ) T h e virus is sensitive to p H : infectivity titres are r e d u c e d b y over % below p H or above p H (61) Bloemraad et al (7) Agent quantification Viral titres Bloemraad et al (7) intranasally exposed four - m o n t h - o l d SPF pigs to TCID of the PRRS virus Virus w a s detected in the s e m i m e m b r a n o s u s m u s c l e i n t h e two pigs killed five days post-exposure, at h o u r s post m o r t e m (a titre of 10 T C I D i n o n e of the pigs) b u t n o t at h o u r s N o virus w a s detected i n any of three samples representing 0, a n d h o u r s post m o r t e m from n e c k m u s c u l a t u r e , longissimus dorsi a n d b o n e m a r r o w (a total of samples) In the two pigs killed at 10 days post-infection, only o n e of the samples from n e c k m u s c u l a t u r e , longisssimus dorsi, s e m i m e m b r a n o s u s a n d b o n e m a r r o w at 0, a n d h o u r s post m o r t e m revealed virus T h e virus positive sample w a s obtained from the n e c k m u s c u l a t u r e at h o u r s post m o r t e m Titres were obtained in certain viscera a n d l y m p h n o d e s a n d in s e r u m samples at 0, a n d h o u r s post m o r t e m T h e authors a d d that t h e sporadic recovery of virus from muscle tissue m o s t likely originated from b l o o d plasma 5 29 73 Rev sci tech Off int Epiz., 16(1) and that the titres in m u s c l e d i m i n i s h e d after slaughter d u r i n g the 12 h o u r cooling period, p r o b a b l y d u e to a decrease i n the p H of the m u s c l e to a p H of b e t w e e n a n d a n d mesenteric l y m p h n o d e s In view of t h e small n u m b e r s of infected cells i n t h e tonsils, spleen, kidney, liver a n d lung, these tissues were not considered to be preferential multiplication sites A n attenuated strain replicated only in t h e Mengeling et al (60) isolated virus only from h a m a n d b o n e m a r r o w of one pig b u t n o t from samples of b o n e m a r r o w , intercostal muscle, loin, shoulder, a n d r u m p from six other viraemic pigs T h e six-week-old pigs w e r e experimentally infected t h r o u g h oronasal inoculation w i t h m l of median cell culture infective dose % ( M C I D ) / m l of PRRS virus i l e u m a n d t h e mesenteric l y m p h n o d e s T h e variation i n t h e tropism for particular parts of t h e intestine (with the preferential localisation of t h e virus i n t h e i l e u m rather t h a n the jejunum), could b e related to t h e h i g h degree of attenuation (17) 50 TGE virus h a s b e e n transmitted b y h o m o g e n a t e s of kidney, spleen, liver, lungs a n d brain, as well as gastrointestinal tract Magar et al (54) could n o t detect PRRS virus or antigens in either l y m p h n o d e s or m u s c l e of two experimentally infected slaughter-age (6 m o n t h s old) pigs 14 days post-exposure At days post-exposure i n two pigs, virus w a s detected in these tissues T h e pigs h a d b e e n inoculated intranasally a n d orally with ' T C I D a n d T C I D of PRRS virus p e r pig Samples from l u n g a n d tonsils revealed PRRS virus at b o t h and 14 days post-exposure T h e m u s c l e tissues i n c l u d e d a pool of samples from neck, chest a n d pelvic region a n d a p o o l of samples from longissimus dorsi a n d s e m i m e m b r a n o s u s muscles 5 of y o u n g pigs (2) In pigs aged 12 h o u r s to days, w h i c h w e r e orally infected w i t h TGE virus or were allowed to c o m e i n contact w i t h these inoculated pigs, the virus w a s recovered from t h e digestive tract, nasal a n d tracheal m e m b r a n e s , l u n g a n d l y m p h n o d e s draining t h e affected organs Virus was 5 4-5 m o n t h s of age inoculated orally or intratracheally, virus w a s recovered from t h e same tissues b u t n o t from the p a r e n c h y m a t o u s organs or b l o o d (37) N o virus w a s isolated from b l o o d samples t a k e n daily from 16 s i x - m o n t h - o l d pigs i n contact w i t h TGE infected piglets TGE virus w a s detected i n Oral infective dose A m i n i m u m oral infective dose or an oral P I D recovered from t h e p a r e n c h y m a t o u s organs s u c h as liver, spleen, kidney, brain a n d b l o o d (29, ) In older pigs of intestinal samples b u t n o t in pharyngeal swabs, m u s c l e of the has not been h i n d leg, l y m p h n o d e or b o n e m a r r o w samples (27) reported for PRRS TGE virus h a s an i n c u b a t i o n p e r i o d as short as 12 to 18 h (30) a n d u p to three days (81) In growing a n d finishing pigs, a Transmissible gastroenteritis of pigs watery diarrhoea developed a n d lasted 5-7 days (73) Pigs infected w i t h TGE virus m a y b e c o m e convalescent carriers, t h e virus being isolated from intestinal a n d respiratory tissues for u p to days p o s t - e x p o s u r e (91) However, long-term s h e d d i n g of viable virus a n d the role of TGE virus carriers i n Agent pH and temperature lability Transmissible gastroenteritis virus is very stable w h e n stored frozen Storage of t h e virus i n cell cultures at - ° C , - ° C , and - ° C for days d i d n o t result i n any significant d r o p in titre However, storage at 37°C for four days eliminated infectivity Similarly, virus of pig intestine origin h e l d at 37°C exhibited o n e l o g r e d u c t i o n i n viral titre every h o u r s Field strains of TGE virus are stable at p H (36) transmitting t h e disease have n o t b e e n fully assessed (80) Long-term carrier pigs m a y b e the exception rather t h a n t h e rule (73) Viraemia does n o t appear to b e a c o m p o n e n t of the pathogenesis of TGE i n t h e growing a n d finishing pig (27, 37) A l t h o u g h t h e virus was recovered from the m i l k of sows d u r i n g the acute stage of infection, these sows h a d b e e n intravenously, intranasally, or i n t r a m a m m a r i l y inoculated w i t h h i g h titres of t h e virus (43) Target cells and tissues Survival in pork and pork products Ingestion is the m o s t c o m m o n r o u t e of virus entry, a l t h o u g h nasal a n d airborne infections can occur (8) After ingestion, the virus passes u n h a r m e d t h r o u g h t h e s t o m a c h a n d replicates in t h e enterocytes of microvilli t h r o u g h o u t t h e small intestine, resulting in rapid a n d massive epithelial cell sloughing, m a r k e d villous shortening or atrophy, leading to malabsorption a n d diarrhoea (73) T h e pathogenicity a n d the sites of viral multiplication were c o m p a r e d for three strains of TGE virus, administered orally to one-week-old w e a n e d piglets T w o of the strains multiplied w i t h i n t h e intestinal tract in the enterocytes of t h e j e j u n u m a n d ileum, Peyer's patches T h e r e are n o studies o n t h e survival of TGE virus i n p o r k a n d p o r k p r o d u c t s , p r e s u m a b l y because t h e viral agent is n o t found i n p o r k tissues of TGE-infected slaughter age pigs Agent quantification Viral titres Viral titres i n p o r k tissues of slaughter age pigs d o n o t exist since a viraemic p h a s e of TGE does n o t occur in this age of pigs 74 Rev sci tech Off int Epiz., 16 (1) TGE viruses are n o t hazards of these commodities T h e Oral infective dose importation of any p o r k a n d p o r k p r o d u c t s from zones A m i n i m u m oral infective dose or an oral P I D has n o t b e e n reported for TGE, other t h a n a significant difference i n t h e virus titre required to infect slaughter age pigs versus neonatal infected w i t h o n e of these hazards necessitates a risk assessment to ensure t h e animal health security of the i m p o r t i n g country C o m m o d i t y related i n p u t s w h i c h are required for the risk assessment include: the agent p H a n d temperature lability, target organs, agent survival i n p o r k a n d pigs- p o r k p r o d u c t s , a n d t h e quantification of the agent as to viral titres in relation to a m i n i m u m infective dose Conclusions T h e potential animal health hazards associated with t h e importation of p o r k a n d p o r k p r o d u c t s , excepting fully cooked products, are FMD, ASF, CSF a n d SVD PRRS a n d Risques zoosanitaires potentiels liés la viande de porc et aux produits de charcuterie S Farez & R.S Morley Résumé Les risques zoosanitaires liés l'importation de viande de porc et de produits de charcuterie concernent quatre virus : ceux de la fièvre aphteuse, de la peste porcine classique, de la peste porcine africaine et de la maladie vésiculeuse du porc Seule l'évaluation des risques permet de déterminer correctement l'innocuité des importations de viande de porc partir d'une zone infectée par une ou plusieurs de ces maladies Cela vaut également pour l'importation de produits dérivés du porc ayant subi un certain degré de transformation (abstraction faite de la charcuterie cuite) Les auteurs analysent, pour chaque maladie, la sensibilité de l'agent responsable (aux variations de pH et de température), les organes cibles, la persistance de l'agent dans la viande de porc et la charcuterie ainsi qu'une évolution quantifiée de la présence de cet agent Cette évaluation est une donnée de l'appréciation du risque qui consiste mesurer le titre de virus présent dans les déchets de viande de porc et de charcuterie par rapport la dose infectieuse orale estimée pour chaque maladie Les auteurs présentent également deux autres maladies virales du porc, la gastro-entérite transmissible et le syndrome dysgénésique et respiratoire, et expliquent pourquoi elles ne présentent pas de risque pour la viande de porc et la charcuterie Mots-clés Evaluation des risques - Fièvre aphteuse - Gastro-entérite transmissible du porc Maladie vésiculeuse du porc - Peste porcine africaine - Peste porcine classique Syndrome dysgénésique et respiratoire du porc 75 Rev sci tech Off int Epiz., KW Potenciales riesgos zoosanitarios asociados a la carne de cerdo y embutidos S Farez & R.S Morley Resumen Cuatro son los agentes víricos que representan los principales riesgos zoosanitarios asociados a la importación de carne de cerdo y embutidos, a saber, los virus de la fiebre aftosa, la peste porcina clásica, la peste porcina africana y la enfermedad vesicular porcina La evaluación de riesgos constituye el único modo correcto de determinar el nivel de seguridad que ofrece la importación de 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