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Noel T Kavanagh. Control of foodborne pathogens in pigs[EB/OL]. (2007-11-01). http://en./MA-pig-industry/management/articles/control-foodborne-pathogens-pigs-t685/124-p0.htm
A zoonosis is an infectious disease naturally transmissible between vertebrates and man. At first sight the list of potential zoonoses is quite imposing; however when the exotic and rare zoonoses are removed from the list it is easier to focus on a relatively short list of important pathogens. Whilst the threat of zoonoses from pig meat is significantly lower than that from other species, it is vitally important that all parties involved in the pig industry focus on reducing the risk of zoonoses to an insignificant level in view of the fact that food safety has assumed a role of increased importance in pig meat. Control programmes designed to reduce the prevalence of foodborne pathogens in pig meat must commence on the farm with the objective of reducing the prevalence of the organisms in pigs at slaughter. Butchering and processing procedures should be designed to prevent cross-contamination of carcasses. The main foodborne zoonotic pathogens in pigs are probably salmonella, yersinia, campylobacter and toxoplasma, with salmonella being by far the most important (Table 1). There are two primary species of campylobacter, coli and jejuni. Pigs primarily carry C. coli, but can also carry C. jejuni. Food poisoning in humans is more often associated with C. jejuni, which is mainly sourced from poultry, other meats, unpasteurised milk, contaminated water and contact with other animals such as dogs. The pig is the primary source of Yersinia enterocolitica. The organism is harboured in the pig’s tonsils and intestine so carcass contamination may occur in the slaughterhouse. Toxoplasma gondii is spread from cats to pigs. It is not host-specific and can also be associated with abortions in sheep. It can cause abortions in women. Davies et al. (1998b) reported that management practices in modern production systems in North Carolina in the US appear to virtually eliminate the risk of infecting finishing pigs with either T. gondii and Trichinella spiralis. Food poisoning caused by other organisms such as Listeria monocytogenes and clostridia species can be associated with incorrect food storage procedures. The Erysipelas bacterium Erysipelothrix rhusiopathiae can infect sheep, turkeys and fish as well as pigs. It is also commonly found in soil. Erysipeloid in humans is primarily an occupational hazard to slaughterhouse and fish factory workers. Abscesses, associated with Staphylococcus aureus, are rarely associated with food poisoning in humans. S. aureus food poisoning in humans is more commonly associated with poor storage conditions and post processing contamination. In general, the strains found in red meat differ from human strains of S. aureus (Roberts, 1982). Staphylococcus aureus associated abscesses are, however, aesthetically unacceptable and therefore strict hygiene procedures must be followed so that lesions are detected, removed, and prevented from entering the food chain. Influenza viruses may be transmitted from humans to pigs and vice versa. It is important that the pig veterinarian have a sound working knowledge of pig zoonoses such that the relatively rare and exotic ones be identified, thus allowing him to focus on the important ones such as salmonella and in particular multi-antibiotic resistant phage types of Salmonella typhimurium. Salmonella control must commence at farm level with a view to reducing the exposure rate of pigs to salmonella on the farm. This should be supported by sound butchering, transporter and lairage hygiene procedures in order to prevent pig exposure to salmonella at slaughter and contamination of carcasses during the butchering process. The importance of good hygiene procedures in the kitchen cannot be over emphasised, since salmonella can be killed by exposure to a temperature of 71.5wC for a period of only 15 seconds. As salmonella control progresses, it is important that an intensive control programme be introduced in those herds containing multi-antibiotic resistant salmonellae.  SOURCES OF FOODBORNE PATHOGENS The route of infection of the most important food pathogens listed in Table 2 is the oral route. Therefore the prevalence of the organism in sows and finishing pigs at slaughter will be influenced by the rate of exposure of pigs to contaminated faeces of mainly pigs, birds, mice and cats. The identification and characterisation of the main foodborne pathogens in pigs are also documented. The methods of dissemination of foodborne pathogens are listed in Table 3 where the period of survival in the environment varies from three weeks to 18 months. Because the primary route of infection of the most important food pathogens is oral, the prevalence of the organism at slaughter will be influenced by exposure to contaminated faeces.   CAMPYLOBACTER In the United Kingdom the reported number of cases of human campylobacter infection exceeds that of salmonella and is still rising. Most epidemiological studies have indicated that poultry meat is the major risk factor for campylobacter (Kapperud et al., 1992). The majority (over 90%) of campylobacter isolates from pig faeces are C. coli (Madden et al., 1996) while most (about 90%) human clinical isolates are C. jejunii (Newell, 1997). Nevertheless, C. jejunii can be isolated from pig carcasses (Stern et al., 1985). Surveys of pigs at slaughter indicate that 50-100% of normal pigs are colonised with thermophilic campylobacters before and at the time of slaughter (Rosef et al., 1983). The organism can survive in pig slurry for 24 days and infected pigs can shed the organism in the faeces for several months. Transmission from pig to pig is via faecal contamination of the pens, feed or water. ARCOBACTER Evidence is now accumulating that Arcobacter spp., in particular A. butzleri, are pathogenic in man where they induce diarrhoea (Marinescu et al., 1996) and abdominal cramps (Vandamme and Goosens, 1992). These organisms can also be isolated from poultry and cattle. In the pig they have been associated with late term abortions and vaginal discharges, and in cattle with abortions. Being closely related to campylobacter these organisms colonise the pig’s intestine and pig exposure is primarily by the faecal/oral route. YERSINIA ENTEROCOLITICA Yersinia enterocolitica, the cause of human yersiniosis, is harboured by healthy pigs. Studies of the dissemination of infection in pig facilities indicate that infection is transmitted in contaminated pens where the organism can persist on the floors for three to 12 weeks (Fukushima et al., 1983). Transmission from pig to pig is via faecal contamination of the accommodation, water or feed. Following exposure of pigs to Y. enterocolitica, the organism is shed in the faeces within two to three weeks and shedding continues for approximately 30 weeks so pigs are capable of spreading disease for approximately 32 weeks following exposure to the organism (Fukushima et al., 1984). Y. enterocolitica is more frequently isolated in finishing pigs than in sows. Following exposure to contaminated pens shortly after weaning, the prevalence of yersinia-positive pigs reaches a peak at 12-21 weeks of age and then gradually decreases, such that the organisms are not commonly isolated from pigs over 30 weeks of age. The cessation of yersinia excretion in faeces at greater than 30 weeks of age may be associated with the establishment of local immunity in the gut, and this could explain why the rate of excretion from older sows is relatively low as compared with finishers. Y. enterocolitica is best known for its cross reaction with Brucella which gives false positives on Brucella serological tests. TOXOPLASMA GONDII Humans usually become infected with Toxoplasma gondii by ingesting oocysts in food and water contaminated by cat faeces or by consuming tissue cysts in under-cooked meat (Dubey and Beattie, 1988). Toxoplasmosis occurs worldwide, and the prevalence in finisher pigs varies in different parts of the world. T. gondii is a coccidian parasite, of which the cat is the definitive host. The oocysts are shed in cat faeces and may contaminate feed, water and soil that could be ingested by pigs. The oocysts become infective in less than seven days. Ingestion of oocysts by the pig results in the production of tissue cysts which cause a human health risk if consumed. Exposure of women to T. gondii for the first time during pregnancy can result in perinatal mortality and birth defects. Infection of immuno-compromised humans, eg., HIV patients, can result in encephalitis, blindness and death. Management factors can influence the level of toxoplasma in pigs. Lubroth et al., (1983) demonstrated that the prevalence of T. gondii in pigs raised in total confinement was low since they rarely had contact with wildlife which can have a high carrier rate of T. gondii. Assadi-Rad et al. (1995) studied the risk factors associated with the transmission of T. gondii to sows kept in different management systems and demonstrated that sows kept outdoors at any time were 23 times more likely to be seropositive than sows kept indoors. Sows on farms known to have cats were 2.6 times more likely to be seropositive than those on farms without cats. They concluded that the high risk of toxoplasmosis in outdoor sows was due to environmental contamination in addition to known exposure to cats which are the definitive host for T. gondii. Efficient rodent control also plays a role, since previously toxoplasma-free cats can become seropositive due to consumption of infected rodents. Smith et al. (1992) also demonstrated that the prevalence of T. gondii antibodies in pigs increased with age and that the prevalence could be reduced through total confinement. SALMONELLA The epidemiology of salmonella infection in pigs is complex and involves two-way transmission between man and pigs, the environment, animal feedstuffs, rodents, birds and flies. Whilst a high percentage of sows in a herd may be serologically positive for salmonella, where hygiene procedures are satisfactory and the farrowing area is operated on an all in/all out system, the rate of transmission of salmonella from sows to piglets may be relatively low, particularly where early weaning (<21 days) is practised. However, if pigs are weaned at more than 28 days of age, the rate of salmonella transmission from sows to piglets may increase due to loss of maternal antibodies in the pigs. A minimum weaning age of 21 days is set by EU regulations. Rodents (mice and rats) can infect pigs with salmonella and be infected by pigs. Flies can mechanically transmit salmonella between groups of pigs. Birds, particularly pigeons, seagulls and sparrows can introduce salmonella to pigs by direct contamination of troughs or pens where they have access to pig feed (Wray and Davies, 1996). They can also contaminate cereals which are grown and subsequently fed to pigs. Carrier pigs can shed the organism in passageways, loading ramps, pig transporters and in lairages such that the organism can be spread to other pigs if hygiene procedures in these areas are inadequate. The majority of pigs are infected with salmonella by the oral/fecal route; however the organism can also be spread by aerosol transmission (Fedorka-Cray et al., 1995). Powerwashing and disinfection of partly depopulated pig houses could enhance the spread of salmonella to the remaining pigs in a house through aerosol contamination created by the power-washer. As a result it is imperative that rooms be operated strictly on an all-in all-out basis. Salmonellae are almost ubiquitous and can be found in the environment of many animal species.Given that complete eradication is unrealistic, the objective is to reduce pig exposure to a level that constitutes a minimal human health risk. Human cases of foodborne salmonella infection are less commonly associated with pigs than with other animal products, particularly eggs and poultry. MYCOBACTERIUM AVIUM-INTRACELLULARE Mycobacterium avium-intracellulare sometimes occurs in pigs, causing lesions in cervical and occasionally mesenteric lymph nodes. These lesions are readily detected by meat inspectors and the affected head or offal condemned. Similar lesions can also be caused by yersinia and Mycobacterium bovis, however, M. bovis is not a significant disease of pigs in Ireland. M. avium infections of humans are rarely derived frominfected pigs and are more commonly associated with infections which humans derive from the environment. As a result M. avium infected pig carcasses pose no risk to humans (Brown and Tollison, 1979). STAPHYLOCOCCUS AUREUS Abscesses associated with Staphylococcus aureus, are rarely associated with food poisoning in humans. S. aureus food poisoning in humans is more commonly associated with poor storage conditions and post-processing contamination. In general, the strains found in red meat differ from strains of found in humans (Roberts, 1982). S. aureus abscesses are, however, aesthetically unacceptable. Therefore strict hygiene procedures should be followed so that lesions are detected, removed and prevented from entering the food chain. HELICOBACTER PYLORI Helicobacter pylori is associated with gastritis, peptic ulcers and gastric cancer in humans (Marshall, 1994). Many domestic species including the pig can harbour the organism; however there is no evidence that occupational exposure to domestic animals increases the risk of human infection (Thomas et al., 1994). TYPES OF SALMONELLA ISOLATED FROM PIGS IN IRELAND During the period 1995-1997 approximately two thirds of the salmonella strains isolated from Irish pigs were Salmonella typhimurium (Figure 1) and the balance made up of S. derby, choleraesuis, bredeny, goldcoast, london, mbandaka, panama, and infantis. (Table 4). These findings are broadly similar to those reported from Great Britain where S. typhimurium and derby are ranked 1 and 2; however choleraesuis is more prevalent in Ireland, making up 9% of isolates compared with 2.5% in Britain.   ANTIBIOTIC RESISTANCE PATTERNS OF SALMONELLA ISOLATES FROM PIGS IN IRELAND Isolates were classified as multi-resistant if resistance to ampicillin, chloramphenicol and tetracylines was demonstrated. Of the S. typhimurium isolates, 44.6% were classified as multi-resistant (Table 5). In Britain approximately 95% of salmonella DT104 isolates were multiresistant in 1996 (Threfall et al., 1997). None of the remaining salmonella serovars demonstrated multi resistance.  METHODS OF IDENTIFYING CARRIER PIGS AND PIGS PREVIOUSLY EXPOSED TO SALMONELLA Kazboher et al. (1997) compared the results of salmonella cultures from faecal samples, mesenteric lymph nodes and carcass surface swabs and found a salmonella prevalence rate of 3.7, 3.3 and 4.7%, respectively. The results suggest that faecal samples are a reliable indicator of salmonella carrier rates as are mesenteric lymph nodes and, by extension, caecal contents. They also found that serological tests using polymerase chain reaction (PCR) technology identified a similar prevalence rate to that of bacteriological tests using culture procedures. While test results on individual animals gave poor correlation between the tests, as a screening procedure good correlation between test procedures was recorded. They concluded that the serological method was a suitable technique for use in the context of a continuous monitoring programme. The serological method has the further advantages in that it can detect herds with a history of salmonella infection, it is inexpensive and sample handling procedures are convenient. In Denmark the Danish Mix ELISA (enzyme-linked immunosorbent assay) test is used on either meat juice or serum as a method of establishing the exposure rate to salmonella during production. They have also established a correlation between positive ELISA test results (the presence of salmonella antibodies in serum or meat juice) and the salmonella carrier rate. SALMONELLA CONTROL IN IRELAND The traditional method of identifying carrier pigs involved specialised culture techniques using pre-enrichment procedures in order to enhance the isolation rate. A range of procedures have been documented for isolation of salmonella (Bager and Peterson, 1991). The method of choice, and the one which is approved for use in accredited laboratories in Ireland, is the Rappaport and Vassiliadis (RV) procedure with pre-enrichment. This procedure produces the highest sensitivity and therefore the greatest chance of isolating salmonella organisms if present. However, enrichment culture procedures are expensive and for this reason ELISA tests were developed, initially in Denmark, and later in other countries. The ELISA test can be applied to meat juice and serum and offers the most sensitive and economic method of monitoring the incidence of exposure of pigs to salmonella. With this system the rate of exposure of pigs to salmonella can be monitored at the slaughter house and also at various stages during the production cycle. Thus it is possible to establish the point of exposure and then to facilitate the introduction of control procedures designed to reduce the exposure rate. For example, pigs could be exposed to salmonella in one house at a particular stage of the production cycle and therefore all pigs going through that house could experience a high exposure rate. At the same time pigs in other houses could remain unexposed. Identification of the area of exposure facilitates tailoring the control programme to focus on the area of exposure. Meat samples are identified, collected and frozen at the slaughterhouse. All samples are forwarded to the laboratory and the meat juice is obtained when the frozen samples are thawed. All the meat juice samples are examined by an indirect ELISA based on a combination of the lipopolysaccharide (LPS) antigens 0:1, 4, 5, 6, 7 and 12 (Table 6). The Mix ELISA detects about 95% of all salmonella serotypes occurring in Irish pigs (Kavanagh, 1998b). Herds are categorised on the basis of the prevalence of seropositives using a rolling average of three tests (24 samples per test) conducted at four-monthly intervals (Table 7).   SOURCE OF SALMONELLA INFECTION IN PIGS RODENTS AND BIRDS AS SALMONELLA CARRIERS Davies and Wray (1995) reported that 35% of mice carried Salmonella enteritidis in the liver, 46% in the intestine and 10% in droppings. This confirms that mice can be a major source of salmonella to pigs. In a further study with mice artificially infected with S. enteritidis they found that mice shed 1,000-10,000 salmonella per 100 droppings for 3-4 weeks following exposure. Salmonella shedding in the droppings continued for a further five months but at a lower rate. As 104 colony forming units (CFU) of S. typhimurium is sufficient to infect one pig this highlights the importance of good rodent control at farm level, since mice can shed up to 100 faecal pellets per day and one faecal pellet is sufficient to infect a pig. It is therefore conceivable that one mouse could infect up to 100 pigs per day. In addition, seagulls, sparrows and pigeons can contaminate feed mills and pig farms with Salmonella typhimurium (Wray and Davies, 1996). SALMONELLA IN PIG FEEDS Salmonella typhimurium is occasionally isolated from raw materials from finished feed in the UK (MAFF, 1995). S. typhimurium is not, however, amongst the top five pig feed salmonella isolates (MAFF, 1995) (Table 8). Salmonella kedouga and senftenberg isolates are common to both UK pig feed and pigs, suggesting that these two salmonella serotypes may be transmitted by pig feed (MAFF, 1995) (Table 9). THE INFLUENCE OF FEED TYPE ON SALMONELLA PREVALENCE In Denmark, the prevalence of salmonella seropositives is three times higher when finishers are fed purchased, heat treated, pelleted feed instead of home-mixed meal. (Dahl andWingstrand, 1997; Bager, 1994). This does not suggest that the pelleted feed is a source of S. typhimurium, since S. typhimurium has never been isolated in Danish feedstuffs. It has been suggested that the larger particle size of the home-mixed feed (rolled grain) compared to that of the purchased heat treated pelleted feed may partly explain the difference in seropositivity between pigs fed pelleted and homemixed feed.   The relative risk of salmonella seropositivity at pig level is 2.7 times higher when finishers are fed dry pelleted feed in contrast to fermented wet feed (Dahl and Wingstrand, 1997; Bager 1994). This may be associated with an altered gut fermentation process due to the feeding of fermented wet feeds or feeds of larger particle size providing an unsuitable environment for salmonella proliferation in the gut. Salmonella favour a pH higher than 4. In most wet feeding systems, where the product is allowed to ferment, a natural fermentation process results in the growth of lactic acid-producing bacteria and yeast. The protective effect of feeding fermented wet feed may be underestimated. The Danish results to date would suggest that more specific research should be carried out on the influence of particle size and fermented wet feed on salmonella seropositivity in finishers. The influence of enzymes, organic acids and dietary raw materials on the salmonella carrier rate deserves further research. Kavanagh and Spillane (unpublished) established in a survey of pigs at slaughter that the prevalence of salmonella antibodies in pigs fed a diet containing whey was less than one third that of pigs fed a liquid diet without whey (Table 10 and 11). Meat juice samples were tested by the Mix ELISA test.  THE INFLUENCE OF FLOOR TYPE ON PREVALENCE OF SALMONELLA IN FAECAL SAMPLES Davies et al. (1997) reported that the prevalence of salmonella in faecal samples was lowest in pigs housed on fully slatted floors compared with all other floor types and was highest in pigs raised on dirt lots. Unfortunately, many slatted floors are of poor quality and design in which circumstances the welfare requirements of the pig might not be satisfied. However, good quality, well designed slatted floors can increase pig comfort, and by reducing pig faecal contact reduce the rate of pig exposure to potential foodborne pathogens. The actual choice of slat design will vary, depending on the type and age of pigs. Sow housing type could also influence the prevalence of foodborne pathogens in sows at slaughter. It has been demonstrated that outdoor sows can have a significantly higher carrier rate of Toxoplasma gondii than sows housed indoors. As efficient salmonella control progresses at farm level, the role of the sow in transmission may assume greater importance than at present. Housing systems that minimise the sow’s contact with contaminated faeces may be needed, especially when piglets are weaned at more than four weeks of age. Davies et al. (1998a) identified a high prevalence of Salmonella shedding in breeding animals and suggested food products derived from culled breeding pigs may be an important source of foodborne disease. SALMONELLA CARRIERS The results of recent investigations have indicated that following oral exposure of pigs to S. typhimurium, the bacterium may be isolated from caecal contents within 4-6 hrs (Fedorka-Cray et al., 1995). Consequently, pigs could become carriers as a result of exposure to dirty loading ramps, dirty transporters and contaminated lairages. Influence of herd size on the prevalence of salmonella carriers A survey in the USA revealed that the percent of farms with at least one salmonella positive sample increased as herd size increased, from 32% of farms selling <2,000 pigs annually to 57% selling >10,000 pigs (Bush and Fedorka-Cray, 1997). This trend has been observed in Ireland by Kavanagh (1997) where the mean herd size from which S. typhimurium was isolated was 910 sows compared with a mean herd of 410 sows without an isolation. A similar trend was observed in Denmark (Bagges en et al., 1996). The conclusion is that the highest prevalence of salmonella is most likely to be found in the larger pig farms. In the Danish studies S. typhimurium was isolated in 23.1% of large herds (producing >2,600 pigs per year) compared with 14.7% of small herds (annual production 500-550 slaughter pigs per year). Carstensen and Christensen (1998) reported that whilst herd size was positively associated with the seroprevalence of S. enteriticia, it was of little significance because the within-herd and betweenherd variations were relatively larger in comparison. PRODUCTION OF SALMONELLA-FREE PIGS EARLY WEANING, ALL IN/ALL OUT MANAGEMENT Early weaning has been practised in the US to produce salmonella-free pigs in conjunction with multi-site production systems. A survey of nine farms by Fedorka-Cray et al. (1994b) found that all pigs, with the exception of one, when tested at 142 days post-weaning were negative on culture for salmonella. With multi-site production systems each unit is operated on an all in/all out production system. This highlights the importance of all in/all out management and demonstrates quite clearly that piglets are generally free or have a low carrier rate at weaning. If combined with good hygiene procedures, all in/all out production and elimination of crosscontamination, this negative salmonella status can be maintained through to slaughter. SURVIVAL OF SALMONELLA IN THE ENVIRONMENT Salmonellae are ubiquitous organisms. It is unlikely that the eradication of salmonella in domestic animals is possible in the foreseeable future. In the circumstances a sustained effort should be made to reduce and control the incidence of infection in animals and the prevalence of carriers. Not only can salmonellae from animals be a direct source of contamination in humans, but the recycling of salmonellae from man to animals occurs through direct transmission or environment pollution with sewage effluent and sewage sludge. Effluent can be a source of environmental contamination of pastures and crops which subsequently act as a source of salmonella to other animal species consuming the crops produced on the contaminated area. Salmonellae can grow either aerobically or anaerobically at temperatures between about 7 and 48wC (optimum 37wC). They prefer a pH of between 4 and 8. They are readily killed by heat (e.g. 71.7wC for 15 seconds) and by acid (e.g. REDUCING CARCASS CONTAMINATION AT SLAUGHTER TRANSPORT AND LAIRAGE Withdraw feed at least 12 hours before slaughter in order to reduce the risk of stomach rupture during evisceration. Transport pigs in clean, previously disinfected transporters and ensure that pigs are as clean as possible. Keep transportation and lairage stress to a minimum, since stress increases the risk of cross-contamination due to shedding of salmonella. Therefore, stress of transport and lairage time should be kept to aminimum. Research has shown (Morgan et al., 1987) that as lairage time increases the Salmonella carrier rate increases. Lairage water supply should be checked regularly in order to ensure that it is of suitable quality. Protected nipple drinkers should be used rather than drinking bowls or troughs. ORGAN RUPTURE The primary source of cross-contamination at slaughter is associated with contamination by the rectum, rupture of the gallbladder or viscera and contamination from the tongue and tonsils during butchering procedures. The application of rectal seals as the rectum is removed reduces the risk of cross contamination during butchering (Nielsen et al., 1997). Great care should be taken during butchering to avoid the gallbladder when the midline incision is made. The gallbladder should be removed intact before brisket splitting. Avoid rupturing the viscera during evisceration. For this reason it is important that the stomach be empty and feed be withdrawn from pigs at least 12 hours before slaughter. Instrument hygiene should be such that cross-contamination by contaminated instruments is avoided. This is particularly important when the viscera, gallbladder or stomach have been ruptured and the instruments contaminated. Ideally the head, heart, liver, esophagus and lungs should be removed without exposing the tonsils in order to eliminate the risk of crosscontamination by exposure to the tongue and tonsils. This, however, contravenes current EU regulations. The primary organisms associated with cross-contamination occurring during this procedure are salmonella, Yersinia enterocolitica and campylobacter. MEAT INSPECTION Cross-contamination can also occur during meat inspection. S. typhimurium could be isolated from 70% of tonsils 22 weeks after pigs had been exposed to the organism (Wood et al., 1989). Next to the tonsils, the mucosa of the caecum, ileum and colon yielded S. typhimurium most consistently at necropsy. S. typhimurium was isolated from 55% of submandibular lymph nodes on necropsy. The submandibular lymph node drains the tonsils. These lymph nodes are incised during meat inspection and as a result there is a high risk of cross-contamination of carcasses in association with routine meat hygiene procedures. For this reason it is imperative that the meat inspector and butcher sterilise their instruments after incising the lymph nodes. In contrast, salmonella was not isolated from the liver, heart or spleen of pigs more than two weeks after exposure to S. typhimurium. This suggests that the primary source of cross-contamination is likely to be the rectum, the tonsil and the submandibular lymph nodes in pigs that had been exposed to S. typhimurium more than two weeks before slaughter, providing the viscera and gallbladder were removed intact. TRENDS IN MEAT INSPECTION SYSTEMS In early 1996 the EC veterinary committee recommended that visual postmortem inspection of pig meat be accepted for pigs coming from pig units in which antemortem inspection is conducted within a HACCP-based quality system (EU Directive (Fresh Meat) 91/497/EEC). This is based on the following rationale:
This is an innovative approach to meat hygiene procedures which reduces the emphasis on palpation and incision of glands in the slaughterhouse, provided satisfactory guidelines are followed from farm to slaughterhouse.Where tuberculosis is not a problem there is little benefit in palpation and incision of submandibular glands in the slaughterhouse and indeed this can create a risk of cross-contamination by salmonella from contaminated instruments. The directive requires that a HACCP plan be in place on the supplying farms for a period of at least 12 months. Further, the farms must carry out a pre-delivery inspection of pigs and identify those needing special attention on the slaughter line. Normal pigs are pre-selected on the farm before delivery and subjected to a visual inspection only. Abnormals are then inspected using traditional meat inspection procedures. |
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