Showing papers in "Revue Scientifique Et Technique De L Office International Des Epizooties in 1997"

The role of seafood in foodborne diseases in the United States of America

Abstract: In the United States of America, seafood ranked third on the list of products which caused foodborne disease between 1983 and 1992. Outbreaks connected with fish vectors were caused by scombroid, ciguatoxin, bacteria and unknown agents; in shellfish, unknown agents, paralytic shellfish poisoning, Vibrio spp. and other bacteria, followed by hepatitis A virus, were responsible for the outbreaks. At least ten genera of bacterial pathogens have been implicated in seafood-borne diseases. Over the past twenty-five years, bacterial pathogens associated with faecal contamination have represented only 4% of the shellfish-associated outbreaks, while naturally-occurring bacteria accounted for 20% of shellfish-related illnesses and 99% of the deaths. Most of these indigenous bacteria fall into the family Vibrionaceae which includes the genera Vibrio, Aeromonas and Plesiomonas. In general, Vibrio spp. are not associated with faecal contamination and therefore faecal indicators do not correlate with the presence of Vibrio. Viruses are the most significant cause of shellfish-associated disease: in New York State, for example, 33% and 62% of 196 outbreaks between 1981 and 1992 were caused by Norwalk virus and gastrointestinal viruses (small round structured viruses), respectively. In addition, several illnesses are a result of toxic algal blooms, the growth of naturally occurring bacteria and diatoms causing neurotoxic shellfish poisoning, paralytic shellfish poisoning, diarrhoetic shellfish poisoning, amnesic shellfish poisoning and ciguatera. Current estimates place the annual number of ciguatera cases at 20,000 world-wide. Scombroid poisoning is the most significant cause of illness associated with seafood. Scombrotoxin is of bacterial origin and halophilic Vibrio spp. causing high histamine levels are implicated as the source. Scombroid poisoning is geographically diverse and many species have been implicated, namely: tuna, mahi-mahi, bluefish, sardines, mackerel, amberjack and abalone. Temperature abuse has been cited as a major cause of scombroid poisoning. For routine work, the use of faecal indicators to predict the relative level of faecal contamination should not be disposed of. However, the main source of seafood illness is due to species which are not predicted by these organisms. In order to protect public health, routine surveillance using new pathogen-specific techniques such as polymerase chain reaction should be used. This, in combination with risk assessment methods and hazard analysis and critical control points, will begin to address the need for improvement in the safety of seafood.

Contagious agalactia of small ruminants: current knowledge concerning epidemiology, diagnosis and control.

Abstract: Contagious agalactia of small ruminants is a syndrome which principally affects the mammary glands, joints and eyes. The main causal agents are Mycoplasma agalactiae in sheep, and M. agalactiae, M. mycoides subsp. mycoides large colony type and M. capricolum subsp. capricolum in goats. In addition, M. putrefaciens can produce a similar clinical picture, particularly in goats. Contagious agalactia occurs on all five continents and is often enzootic. The evolution of the infection tends to be chronic in affected animals and herds. Symptomless shedding of mycoplasmas, mainly in the milk, may persist for a long time. These insidious infections, associated with carriage in the ears of healthy animals, are difficult to diagnose and to control. The main mode of transmission between flocks is related to the sale of carrier animals and contact during transhumance, whereas transmission within a flock occurs through contact, suckling and milking. This review discusses the clinical features, epidemiology, treatment, prevention and control of the disease.

Risk of spread of penaeid shrimp viruses in the Americas by the international movement of live and frozen shrimp.

Abstract: Within the past decade, viral diseases have emerged as serious economic impediments to successful shrimp farming in many of the shrimp-farming countries of the world. In the western hemisphere, the viral agents of Taura syndrome (TS) and infectious hypodermal and haematopoietic necrosis have caused serious disease epizootics throughout the shrimp-growing regions of the Americas and Hawaii, while in Asia the viral agents of white spot syndrome (WSS) and yellow head (YH) have caused pandemics with catastrophic losses. The international transfer of live shrimp for aquaculture purposes is an obvious mechanism by which the viruses have spread within and between regions in which they have occurred. Shrimp-eating gulls, other seabirds and aquatic insects may also be factors in the spread of shrimp viruses between and within regions. Another potentially important mechanism for the international spread of these pathogens is the trade in frozen commodity shrimp, which may contain viruses exotic to the importing countries. The viral agents of WSS, YH and TS have been found, and demonstrated to be infectious, in frozen shrimp imported into the United States market. Mechanisms identified for the potential transfer of virus in imported frozen products to domestic populations of cultured or wild penaeid shrimp stocks include: the release of untreated liquid or solid wastes from shrimp importing and processing plants directly into coastal waters, improper disposal of solid waste from shrimp importing and processing plants in landfills so that the waste is accessible to gulls and other seabirds, and the use of imported shrimp as bait by sports fishermen.

Epidemiology and control of egg-associated Salmonella enteritidis in the United States of America.

Abstract: The isolation rate for Salmonella enterica serotype Enteritidis (SE) in humans in the United States of America (USA) increased from 1,207 sporadic isolates identified in 1976 (0.6 isolates/100,000 population) to 10,201 identified in 1995 (4.0/100,000 population). The proportion of reported Salmonella isolates which were SE increased from 5% to 25% during the same time period. In 1990, 1994, and 1995, SE was the most commonly reported reported Salmonella serotype in the USA. Much of this increase has been associated with the consumption of contaminated shell eggs. An examination of the results of a United States Department of Agriculture (USDA) survey of spent hens at slaughter and unpasteurised liquid egg at breaker plants (liquid egg processors) in 1991 and 1995 reveals an increase in the prevalence of SE isolates overall and in most regions of the USA. SE phage type 4 (pt 4), the predominant SE phage type in other parts of the world, has emerged in the egg industry in the western USA concurrent with a sharp increase in the number of sporadic human SE pt 4 isolates in California and Utah. Research on the molecular structure and virulence of SE pt 4 isolates from the USA as compared with isolates from other parts of the world (human and poultry) should be a priority. A comparison of DNA from pt 4 isolates from the USA and Europe may provide information about the potential threat to public health and poultry in the USA from this phage type. Some regional success in the reduction of human illness as a result of SE control efforts is apparent. The Pennsylvania Egg Quality Assurance Program has shown progress in reducing SE infection in participating flocks. At a national level, however, neither the incidence of human illness due to SE nor the prevalence of SE in flocks and unpasteurised liquid eggs have decreased significantly, despite the implementation of the USDA 'trace back' regulation from 1990 to 1995, and intensified efforts to educate food handlers and to enforce safe food handling practices. More effort is needed to control SE at every stage of the egg continuum, from production through to consumption. A risk-reduction approach, with barriers to the introduction and multiplication of the pathogen throughout the farm-to-table continuum, is the most practical method for reducing human illness from SE in shell eggs at present. An effective long-term solution will require interdisciplinary efforts involving government, industry, consumers, and academics. Interventions should be developed and evaluated in compliance with the potential for reducing the risk to human health and cost-effectiveness.

Parasites of fish and risks to public health.

Abstract: A multitude of parasites have been reported in fish, but only a few species are capable of infecting humans. The most important of the helminths acquired by humans from fish are the anisakid nematodes (particularly Anisakis simplex and Pseudoterranova decipiens), cestodes of the genus Diphyllobothrium and digenetic trematodes of the families Heterophyidae, Opisthorchiidae and Nanophyetidae. Seafood-associated infections by acanthocephalans are rarely reported in humans. All of the helminths mentioned above are associated with social-cultural and behavioural factors, in particular the consumption of raw or undercooked seafood. Measures can be taken during harvesting, processing or post-processing (e.g., by the consumer) to mitigate the risks of infection. The seafood industry and government authorities can apply various programmes to reduce these risks, including good manufacturing practices (GMPs) and hazard analysis and critical control point (HACCP) systems. Such measures may include avoiding particular harvest areas, sizes of fish, or even particular species of fish. The method of capture, handling and storage of the catch can directly affect the quality of the seafood with regard to the presence and numbers of parasites. The extent of processing--including heading and gutting, candling and trimming--and the type of product derived (fresh, frozen, salted or pickled) can all contribute to the control of the risks posed by helminths. The most effective means of killing the parasites are either freezing or heat inactivation.

Milk pasteurisation and safety: a brief history and update

Abstract: A brief history of the development of milk pasteurisation is presented and updated. Concerns about the margin of safety provided by current pasteurisation standards in terms of milk-borne pathogens such as mycobacteria (in particular Mycobacterium paratuberculosis) and other emerging pathogens such as Listeria monocytogenes and Escherichia coli O157:H7 are discussed. With the exception of the endospores of Bacillus cereus, current standards appear to be adequate for public health assurance of milk safety provided good manufacturing practices are followed.

Strategies to control Salmonella and Campylobacter in raw poultry products

Abstract: Foodborne illness is a major public health concern. The largest number of foodborne illness cases attributed to poultry and poultry products are caused by paratyphoid serotypes of Salmonella and by Campylobacter jejuni. The effective prevention of foodborne disease requires an understanding that contamination can be introduced into foods at numerous points along the food chain. Since multiple entry points exist for foodborne pathogens, multifaceted intervention approaches are required to successfully control contamination of poultry during the various phases of the growth period and processing procedure of broiler chickens. Strategies during the grow-out period (the period during which day-old chicks are raised to six- to seven-week-old broiler chickens) include sanitation, biosecurity, vaccine and drug therapy, and biological control procedures, such as those aimed at preventing colonisation. There are also many critical control points identified in the processing plant which reduce contamination. These include temperature controls (washer and product), chemical interventions, water replacements and counter-flow technology in the scalder and chiller, and equipment maintenance. Transportation and food handling at retail outlets and by the consumer (i.e., storage at the proper temperature and adequate cooking) are the final critical control points in the farm-to-table continuum. It is important to apply risk reduction strategies throughout the food chain. These include: easing the development and implementation of voluntary animal production 'best management practices', implementing in-plant hazard analysis and critical control point systems, developing effective transportation and refrigeration standards, working to facilitate adoption of the model Food Code in all States and providing educational materials and support for public health activities nationwide.

Therapeutic antibiotics in animal feeds and antibiotic resistance.

Abstract: Recent statutory changes involving animal drugs are expected to facilitate the therapeutic use of antibiotics in animal feeds in the United States of America. The use of antibiotics in animal feeds is controversial due to the potential development of resistant bacterial pathogens in food-producing animals which are exposed to the antibiotics and the resultant public health risk. Zoonotic micro-organisms can be transmitted to humans through contact with animal populations, either directly or through the consumption of contaminated food. Recommendations to address the public health concerns include the strengthening of professional education in the areas of infectious diseases and the appropriate selection and use of antimicrobial agents, the development of a comprehensive food safety education programme for food-animal veterinarians and animal producers, and the development of surveillance programmes to monitor antimicrobial resistance among zoonotic pathogens. Early identification of emerging resistance can facilitate a timely and appropriate public health response.

Potential animal health hazards of pork and pork products

Abstract: 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 why these two diseases are not hazards when associated with pork and pork products.

Disease risks to animal health from artificial insemination with bovine semen

Abstract: Two of the major goals of artificial insemination of domesticated animals are to achieve continuous genetic improvement and to prevent or eliminate venereal disease. In comparison with natural service, fewer males are needed to artificially inseminate the same number of females and to produce the same number of offspring. However, there are risks associated with artificial insemination, which has the potential to disseminate genetic defects and also to spread infectious disease nationally and internationally. This paper focuses on the risk of six specific diseases which are transmitted in bull semen and outlines the appropriate measures to prevent these risks.

Public health and pork and pork products: regional perspectives of Denmark

Abstract: An ambitious programme to eliminate pork as an important source of human salmonellosis was initiated in Denmark in 1993 by the Ministry of Food, Agriculture and Fisheries. The programme comprises control of feedmills, breeding and multiplying herds, slaughter herds and slaughter plants, as well as the final product, fresh pork. As a consequence, the level of occurrence of Salmonella spp. in fresh pork produced in Denmark is approximately 1%. Yersinia enterocolitica 0:3 infections are common in slaughter pig herds in Denmark, and pork is considered to be the only source of human infection in the country. The incidence of pork-related occurrences of human salmonellosis and yersiniosis in 1996 was approximately nine cases per 100,000 inhabitants for both diseases. All swine in Denmark are screened for Trichinella spp. infection, although no positive results have been obtained since 1930. Swine are not considered to be a source for Campylobacter jejuni or enterohaemorrhagic Escherichia coli in Denmark. Listeria monocytogenes can be detected in relatively high rates in pork: however, the incidence of human listeriosis is only 0.5 cases per 100,000 inhabitants. Toxoplasma gondii antibodies have been demonstrated in 3% of slaughter pigs, though the importance of pork as a source of infection is probably very low. Denmark is officially free from Brucella abortus, B. melitensis and Mycobacterium bovis.

Meat from dairy cows: possible microbiological hazards and risks.

Abstract: Summary The authors provide an overview of the circumstances associated with culling of dairy cattle in the United States of America (USA) and focus on the possible significant microbiological hazards associated with meat from cull dairy cows. Cull dairy cows are an important source of food in the USA, accounting for at least approximately 17% of ground beef. The potential microbiological hazards for foodborne illness from cull dairy cows discussed here include Salmonella (with special attention to 5. Typhimurium DT104), Escherichia coli 0157:H7, Campylobacter jejuni, Listeria monocytogenes, Clostridium perfringens and Staphylococcus aureus. Possible sources and means of contamination are pointed out, as are the potential foodborne risks from Bacillus cereus and Aeromonas spp. In conclusion, widespread microbiological studies are needed to determine the prevalence and risk of foodborne pathogens in cull dairy cattle.

Risks of spreading foot and mouth disease through milk and dairy products

Abstract: A review of epidemics of foot and mouth disease (FMD) has highlighted the important role which raw (untreated) milk can play in the spread of the disease in a country which is normally free of FMD and whose cattle are not routinely vaccinated. The greatest hazard is likely to be in the early stages of an outbreak, before disease control measures have been implemented. The spread of FMD through milk can be prevented by the effective application of control measures combined with 'codes of practice' for the treatment of potentially infected milk. The author considers the probable mechanisms of transmission of FMD by milk and dairy products. These mechanisms are based on the quantities of virus excreted in milk, the survival of the virus under various management and manufacturing conditions and the minimum doses required to initiate infection in susceptible animals by different routes. The key points for consideration when making a risk assessment of the importation of milk and dairy products are also discussed.

Risk analysis in relation to the importation and exportation of animal products.

Abstract: The design of a quantitative risk analysis model has to be dictated by the questions it seeks to answer. The model should also be as objective as the available data will allow. Animal and animal product import risks usually have three characteristics which make the design of a good quantitative risk analysis model quite difficult, namely:--the probabilities of the steps leading to the undesired outcome are frequently inter-related--the probability of the undesired outcome itself is in many cases very small, making direct simulation impractical--important variables within the model often cannot be quantified through analysis of data, thus these variables must be modelled with probability distributions to reflect the degree of uncertainty, usually determined by expert opinion. This paper provides a tutorial on some modelling techniques which are essential to the risk assessment of animal and animal product imports and which help overcome these problems. A number of probability distributions, their uses and inter-relationships, are examined. The application of these distributions, coupled with some general modelling techniques, is then demonstrated to produce rigorous and transparent animal import risk analyses.

Seafood-associated diseases and control in canada

Abstract: Paralytic shellfish poisoning (PSP) has been documented for two centuries and control programmes have been operated for fifty years. Although some illnesses are reported almost every year, the last known death from PSP occurred in 1981. In more recent years, amnesic shellfish poisoning, ciguatera poisoning, diarrhoetic shellfish poisoning, scombroid (histamine) poisoning and tetramine poisoning have been documented. The most frequently observed of these diseases is scombroid poisoning from improperly stored fish, but PSP and ciguatera poisoning have the most serious consequences. Vibrio infections arising from naturally-contaminated shellfish are virtually unknown, and viral illnesses from polluted harvested waters are rare. Control is achieved through monitoring of waters for indicators of human pathogens. Inspection systems based on the hazard analysis and critical control point principles are being introduced into all areas of fish and shellfish harvesting. The Inspection Directorate of the Department of Fisheries and Oceans joined the new Canadian Food Inspection Agency in 1997, which co-ordinates all Federal control measures for food in Canada.

Public health and the safety of milk and milk products from sheep and goats.

Abstract: Goats and sheep rank third and fourth in terms of global milk production from different species, but unlike cow milk, which has stringent hygiene and quality regulations, microbiological standards for the production and distribution of goat milk and sheep milk are more relaxed. Difficulties in managing the sanitary quality of sheep and goat milk derive from a series of factors including the low level of production per head, the milking system, the difficulty involved in machine milking, the conditions under which the herds or flocks are raised, adverse climatic conditions and the spread of production over a wide geographic area. Fresh goat milk is consumed by infants and others with allergies to cow milk and is also used for on-farm manufactured cheese, with or without thermal treatment. The high fat content and peculiar taste of cheeses made from ewe milk are also very popular. These cheese varieties, which are mostly still of 'artisan-type', are not covered by regulatory definitions and the dispute over the use of raw versus pasteurised milk is still alive. However, in documented intoxications recorded after the consumption of cheese, there has always been evidence of incorrect temperature control during pasteurisation, the deliberate addition of raw milk, or contamination during storage. Compositional differences between the milk from cows, ewes and goats (chemical composition of lipids, phosphatase level, freezing point, natural bacterial inhibitor levels, somatic cell count, etc.) preclude the nondiscriminatory use of bovine standards for regulatory purposes. Quality standards adjusted for the specifics of ewe/goat milk should be considered. The production of safe cheese is linked to a series of conditions which ensure consumer health, primarily pasteurisation. In the absence of pasteurisation, all cheeses made from raw milk should be subjected to strict periodic controls.

Parasites associated with pork and pork products.

Abstract: Three parasites pose a public health risk from the ingestion of raw or undercooked pork, namely: Trichinella spiralis, Taenia solium and Toxoplasma gondii. Inspection procedures, when practised according to prescribed methods, are effective in eliminating the majority of risks from T. spiralis and T. solium. No suitable methods for the post-slaughter detection of T. gondii are available. All three parasites are inactivated by various methods of cooking, freezing and curing; some information is also available on inactivation by irradiation. Good production practices, including a high level of sanitation, rodent and cat control on farms, can prevent opportunities for exposure of pigs to these parasites. Alternatively, meat inspection, proper commercial processing and adherence to guidelines for in-home preparation of meat are effective methods for reduction of risks for human exposure.

Public health hazards from small ruminant meat products in Europe

Abstract: Foodborne diseases, in particular those related to meat and meat products, have recently become a matter of great public concern. Sheep and goat meat can transmit infections and diseases either through handling during preparation procedures or as a result of ingestion by the consumer. The authors highlight the second route of contamination in relation to meat and meat products from small ruminants in European countries. Among the most important diseases transmitted by mutton and goat meat, toxoplasmosis remains the greatest threat, particularly in immuno-compromised people and in pregnant women. Other pathogens which may be associated with the consumption of meat from small ruminants include: Clostridium perfringens, Cryptosporidium parvum and Campylobacter jejuni. As with other ruminant species, Escherichia coli O157:H7 can be considered as an emerging pathogen, for which control efforts must be made. The classical zoonoses (brucellosis, Q fever, hydatidosis) are also presented here, although the major source of contamination for these diseases remains contact with infected animals or the handling of carcasses. The fact that the association of foodborne diseases with mutton and goat meat is less frequent than with the meat of other animal species should be noted, for the following reasons: a) lower levels of production; b) less intensive production, leading to a weaker microbial contamination; c) mutton and goat meat are subjected to processing less often than other meats; d) the usual boiling or cooking processes.

Standardisations internationale et régionale des épreuves immuno-enzymatiques : méthodes, intérêts et limites

Abstract: Numerous attempts have been made to standardise immuno-enzyme techniques (enzyme-linked immunosorbent assay: ELISA) used for the diagnosis of infectious diseases, in order to improve the reproducibility of the tests, expression of results, choice of a positive threshold, and selection of reference samples. The international standardisation of reagents and test protocols appears essential for quality control and the comparison of results between laboratories, but the interpretation of results can encounter major differences depending on the geographical sector under study. Based on these studies, and in the light of a model indirect ELISA for detecting antibodies against Trypanosoma vivax in cattle, the author proposes the international standardisation of reagents, test protocol, and the expression of results of ELISA using international reference samples. For local standardisation, the following proposals are made: sampling of representative local populations. Establishment of the distribution patterns of infected and uninfected local populations. Selection of representative controls from local populations (secondary reference samples). Expression of test results in comparison with these controls. Establishment of internal quality control based on the response of controls. Determination of a positive threshold, in accordance with the requirements of the user. Adaptation of the positive threshold according to the prevalence observed in the geographical sector under study.

Contamination of animal products : the minimum pathogen dose required to initiate infection

Abstract: When an animal product contains a low level of contamination (perhaps less than the minimum infective dose of a pathogen as determined experimentally), the theoretical probability remains that if a large number of animals are exposed to that product, at least one animal in the group will become infected. Such an infected animal could start an outbreak of the disease. These aspects, therefore, should be considered when risk assessments are performed. Foot and mouth disease virus in milk is used as an example.

Public health risks of ostrich and crocodile meat.

Abstract: Summary This paper discusses the infectious agents and chemical substances potentially capable of contaminating the meat of ostriches and crocodiles and which thus pose a danger to human handlers and consumers. For ostrich meat, there is no danger from Crimean-Congo haemorrhagic fever or spongiform encephalopathy. Contamination of ostrich meat with salmonellae, chlamydia, pasteurellae, mycobacteria and erysipelas might be possible, but has never been reported. No parasites are known which could be transmitted through ostrich meat to human consumers. Residues from growth hormones, antibiotics and acaricides are potential public health hazards. For crocodile meat, there is a distinct possibility of contamination with salmonellae, depending on housing, feed, slaughter technique and hygiene practices under which the animal is reared. Chlamydial infections are common on some crocodile farms in southern Africa. Mycobacteriosis is extremely rare. Tapeworm cysts have been found in crocodile meat in two cases only. Trichinellosis has been reported on several crocodile farms in Zimbabwe. A generalised coccidiosis with invasion of organs and tissues has been seen in several species of crocodiles, but should present no danger to consumers.

[Contamination of bee products and risk for human health: situation in France].

Abstract: To meet the needs of a colony, bees collect honey, honey-dew, pollen and water from an environment exposed to various bacterial and chemical contaminants, which might be incorporated in products for human consumption. In addition to this environmental pollution, contamination of bee products may also occur during packing. In France, tests for various pollutants are performed more or less systematically, at the request of the Ministry of Agriculture, merchants or producers. Honey and royal jelly contain very little bacterial or chemical contamination, due to both the ability of colonies to eliminate pathogenic and non-pathogenic micro-organisms present in their environment, and to the physico-chemical properties of these products, as well as the role of bees in filtering chemical pollutants. To create the framework for European legislation on the testing of products, bacterial and chemical standards should be created and should be based on standardised techniques. The testing of imported bee products requires greater attention.

Bovine spongiform encephalopathy: the causal role of ruminant-derived protein in cattle diets

Abstract: Although bovine spongiform encephalopathy (BSE) has occurred in other European countries, the major epidemic has been in the United Kingdom (UK), where there have been more than 163,000 cases so far. BSE has been linked to the practice of feeding meat-and-bone meal (MBM), putatively contaminated with scrapie agent, to cattle. A ban on the feeding of MBM to ruminants in the UK has resulted in a significant decline in the number of reported cases. It is considered that BSE in other European countries probably originated through the use of British MBM in the diets of cattle in these affected countries. Recently, in the UK, a new variant form of Creutzfeldt-Jakob disease in humans has been discovered, which does not appear to have occurred before the advent of BSE. It may have been caused by BSE agent, possibly as a consequence of dietary exposure. The use of MBM in the diets of any livestock species has now been prohibited in the UK.

Problems associated with drug residues in beef from feeds and therapy.

Abstract: Drug residues in beef have been reported internationally. These include antimicrobials, anti-inflammatories, growth promotants, parasiticides and insecticides. The main factors associated with residues are animal age and use, and failure to observe withdrawal time for regular or extra-label use. Public health concerns include toxic and anaphylactic reactions, and development of drug-resistant strains of bacteria. The maximum residue level (MRL) is the current standard for residues in food adopted by the Codex Committees of the Food and Agriculture Organisation and World Health Organisation, but is not universally accepted or standardised. Detection of residues at slaughter is a critical point in residue control. Several live animal tests are available, but these vary in reliability and usage. After slaughter, tissues sampled and tests used are more uniform. To prevent international trade barriers associated with drug residues in beef, the following conditions should be implemented: standardisation of testing methods used to detect drug residues; standardisation of methods for determining MRLs; establishment of active surveillance programmes to monitor residues.

Risks and economic consequences of introducing classical swine fever into the Netherlands by feeding swill to swine.

Abstract: An effective animal disease prevention and eradication programme is of great importance for meat-exporting countries such as the Netherlands. If a serious outbreak of disease were to occur, the eradication measures required by the European Union and a possible ban on meat exports would have severe economic consequences. However, historical and experimental information on which these programmes can be based is scarce. Furthermore, until recently, an integrated approach which combined the various aspects of outbreaks and risks with economic consequences was lacking. This paper describes a project based on such an integrated approach. The project covered the elicitation of expert knowledge and the development of the virus introduction risk simulation model (VIRiS). VIRiS integrates objective and subjective information concerning risks and consequences of virus introduction, and thus presents policy-makers with a useful tool for the evaluation of existing prevention programmes and possible alternatives. VIRiS is illustrated for classical swine fever. A comparison is made between the current situation and a hypothetical situation where the risk factor 'swill feeding' is completely eliminated.

Risks and prevention of contamination of beef carcasses during the slaughter process in the United States of America

Abstract: Summary A brief general description of the beef cattle slaughter process used in the United States of America is presented Considerable variation in prevalence of microbial contamination at beef processing establishments has been reported Primary factors which may explain this variation include: a) pathogen load on, or in, live animals entering the establishment b) sanitation practices used by the establishment Pathogen load on, or in, live animals depends on environmental exposure to contaminants, the health of the animal, and on situations stressful to the animal which may increase microbial shedding, such as disrupted access to feed and water, transport, handling and contact with other animals Processing stations and slaughter practices which are potential sources of carcass contamination are listed, and points on carcasses where contamination is most likely to occur are noted Contamination risk-reduction measures within an establishment include carcass treatments with anti-microbial agents, trimming, washing, steaming, chilling and gamma irradiation Several good sanitation practices are described Microbial monitoring is a necessary step for determining whether sanitation practices are efficacious, but the usefulness of microbial monitoring depends on the microbial tests selected, sampling procedures, frequency of sampling, the rapidity of receiving test results and consistent and accurate record-keeping and analysis Federal inspection to ensure that processing establishments comply with new Federal regulations regarding the implementation of standard sanitation procedures and microbial testing should result in greater vigilance of good sanitation practices by establishments

The public health risks associated with wild and feral swine

Abstract: Summary Wild swine populations {Sus scrofa) are present in many regions of the world. Large feral populations in North America and Australia are principally derived from introduced domestic pigs. In Europe, most wild boar are found in Germany and Poland. While wild swine are certainly a significant reservoir of infection for domestic swine diseases (for example, African swine fever virus in wild boar in Sardinia), these swine generally do not constitute a major public health risk. Brucella suis infections and trichinellosis are the most important zoonotic threats to public health.

Risks of transmitting scrapie and bovine spongiform encephalopathy by semen and embryos.

Abstract: This paper reviews current knowledge on transmission of scrapie and bovine spongiform encephalopathy (BSE) by semen and embryos. In sheep, in particular, it is difficult to distinguish between the genetic transmission of susceptibility to scrapie and vertical transmission of the infection. Nevertheless, there is evidence that vertical transmission of infection does occur, probably across the placenta, but none to suggest a significant scrapie risk from semen. Two teams have studied scrapie transmission from experimentally infected sheep using embryo transfer. Whereas one team found no evidence for transmission, the results from the other team suggest that embryos, even after washing, might carry the disease into the offspring. In regard to goats, although genetic differences in susceptibility exist, they are much less obvious than in sheep. There is no evidence for vertical transmission or for transmission through semen and embryos. With regard to BSE, although it appears that genetic differences in susceptibility are absent or unimportant, some recent work does suggest that the disease may be passed from cow to calf. The route of transmission and stage or stages when this takes place are unclear, however. In conclusion, despite growing evidence to indicate that scrapie and BSE are unlikely to be transmitted through semen and embryos, more research is needed to confirm this. Furthermore, until all possibility of risk is ruled out, risk reduction methods must be considered, especially when semen and embryos are being imported into countries where the diseases do not exist.

Oral rabies vaccination of red foxes and golden jackals in Israel: preliminary bait evaluation.

Abstract: Summary Field trials were conducted in late April to early May of 1995 and 1996 in central Israel to assess the potential for controlling rabies in red foxes (Vulpes vulpes) and golden jackals [Canis aureus) by using vaccine-laden baits. Of the bait types which were field tested, polymer fish meal baits were selected as the most suitable for both species. Fish meal baits containing tetracycline hydrochloride, an oral biomarker, were distributed by four-wheel-drive vehicle at a density of ~ 30 baits/km2 in two test areas of 35 km2. Of the animals which were trapped and euthanased seven to ten days after treatment, 65% of foxes and 56% of jackals gave positive results when tested for the biomarker. These results indicate the potential effectiveness of oral rabies vaccination of these species in Israel and possibly elsewhere in the Middle East, where rabies is a problem in wild canids.

National surveillance of poultry diseases in Lebanon.

Abstract: From 1992 to mid-1996, a national survey of poultry diseases in Lebanon was conducted. This surveillance included meat breeder, layer breeder, commercial layer and chicken broiler flocks. The history, signs, lesions and laboratory tests of poultry were used in the diagnosis of prevalent poultry diseases. Culture techniques were used to screen for bacterial diseases; serological techniques and, to a lesser extent, culture techniques were used to diagnose viral diseases; and both serological and culture techniques were used to diagnose Mycoplasma infections. The outbreaks of diseases detected in broiler breeder flocks and the number of such flocks experiencing these diseases were as follows: femoral head necrosis (6), egg-drop syndrome (3), reovirus-associated malabsorption syndrome (3), synovitis (Mycoplasma synoviae infection) (7), swollen head syndrome (SHS) (3), tenosynovitis (viral arthritis) (1), lymphoid leukosis (3), avian encephalomyelitis (1), fowl pox (1) and aortic rupture (1). The disease outbreaks detected in layer breeders were as follows: SHS (2), bumble foot (2), egg-drop syndrome (3) and avian infectious bronchitis (IB) (1). The disease outbreaks detected in commercial layer flocks were as follows: egg-drop syndrome (5), avian infectious laryngotracheitis (2), avian IB (nephrogenic strain) (1), malabsorption (1), avian tuberculosis (Mycobacterium avium) (1), Marek's disease (1), fowl pox (1), Salmonella enterica subsp. enterica Enteritidis infection (1), salpingitis (1) and Heterakis gallinae infestation (1). The disease outbreaks detected in broiler flocks were as follows: colibacillosis (40), infectious bursal disease (Gumboro disease) (15), malabsorption syndrome (8), avian infectious laryngotracheitis (8), paratyphoids (salmonellosis) (7), femoral head necrosis (8), SHS (6), avian mycoplasmosis (Mycoplasma gallisepticum infection) (6), synovitis (7), avian IB (6), botulism (1), avian encephalomyelitis (1) and gangrenous dermatitis (1). Diseases which occurred and which were reported for the first time in Lebanon were as follows: bumble foot, femoral head necrosis, avian IB (nephrogenic strain), malabsorption syndrome and SHS. This surveillance helped to establish baseline data concerning the predominant poultry diseases in Lebanon. Such information is a prerequisite for future regional and international collaboration to identify the source of the aetiological agents and to control their spread to neighbouring countries.