Decontamination of broilers with hydrogen peroxide stabilised with glycerol during processing.

Experiments were conducted to assess the effects of different concentrations of hydrogen peroxide stabilised by glycerol solution in potable water on the bacteriological and organoleptic quality of freshly slaughtered broiler carcasses. Skin-pH and colour were measured 3.5 and 24 h after treatment and compared to untreated carcasses. Bacterial colonisation was determined 3.5 and 24 h and, 7 days after treatment, carcasses being stored at 1 degrees C. None of the concentrations used affected the appearance and "bloom" of the carcasses as could be measured by colorimeter and changing of the acidity. Mean microbial counts were significantly reduced (P<0.01) when treated and control broilers were compared. Average reductions of 0.3 up to1.4 log N for the mesophilic aerobic counts were achieved and from 0.4 up to 1.2 log N for Enterobacteriaceae. A 3% w/w solution made from a commercially available stock solution (Glyroxyl), which consists of 44% hydrogen peroxide, 44% demineralised water and 12% glycerol proved to lower colonisation more effectively than a 2% solution.

Suggestions for the construction, analysis and use of descriptive epidemiological models for the modernization of meat inspection.

There is consensus that scientifically validated, quantitative assessments of actual public health risks are a prerequisite for any sound modernization of current meat inspection procedures. This article outlines how such analyses could be conducted. Approaches that rely heavily upon extrapolations from theoretical dose-effect relationships are inadequate for the assessment of microbiological health risks associated with the production and consumption of meat. The use of highly structured and very elaborate descriptive epidemiological models covering the entire period from stable to table can be considered a promising solution. Health risks can be quantified by means of incidence rates and the influence of risk factors by means of odds ratios and (population) attributable fractions. A great advantage is that when it is not possible to quantify risks exactly, the descriptive models are detailed enough to be used in a hazard analysis critical control point (HACCP)-like approach and for writing validated codes of good manufacturing practice (GMP). There are, however, several conditions which have to be met before risk assessment can become the foundation of safety assurances for meat, such as active legislative support and the setting up of monitoring systems for zoonoses and other health hazards in animals and humans.

Salmonella in slaughter pigs: the effect of logistic slaughter procedures of pigs on the prevalence of Salmonella in pork.

A substantial part of the finishing pigs in the Netherlands is infected with Salmonella. Infection of pigs with Salmonella can occur already on the farm. Pigs can also get infected or contaminated during transport, lairage or slaughter. The aim of this study was to evaluate the effect of separating pigs from Salmonella-infected farms from pigs from Salmonella-free farms during transport, lairage and slaughter on the prevalence of Salmonella on pork after slaughter. Two experiments were carried out. In the first experiment, farms were selected to participate, based on serology of the pigs (Dutch Salmonella ELISA). The pigs were slaughtered at the beginning of the day: firstly, sero-negative herds, secondly, sero-positive herds and thirdly, again sero-negative herds. The latter were slaughtered to investigate the effect of a contaminated slaughterline due to a previously slaughtered positive herd. In the second experiment, farms were selected to participate, based on both serology and bacteriology of the pigs on the farm. Two hundred pigs from Salmonella-free farms were slaughtered after 200 pigs from Salmonella-infected farms. Results showed that the prevalence of Salmonella in pork samples of sero-negative herds was lower than in samples of sero-positive herds. Results also showed that Salmonella contamination of carcasses after slaughter was partially caused by Salmonella-infected herds that were slaughtered before, and partially by residential flora of the slaughterhouse. It is concluded that separate slaughter of sero-negative pig herds can be useful to decrease the prevalence of Salmonella-contaminated pork after slaughter. To avoid cross-contamination by residential flora from trucks, lairage and slaughterline, cleaning and disinfection have to be improved.

Salmonella in slaughter pigs: prevalence, serotypes and critical control points during slaughter in two slaughterhouses.

The purpose of this study was to show the distribution of Salmonella in slaughtered pigs and the environment of the slaughterhouse. 1,114 samples of slaughtered pigs (six different samples for Salmonella isolation and one serum sample for ELISA on antibodies per pig) and 477 samples of the slaughterhouse environment were collected in two slaughterhouses on two sampling days per slaughterhouse. Salmonella was isolated from one or more samples of 47% of the pigs. The highest prevalence of Salmonella was observed in rectal content samples (25.6%), whereas the lowest prevalence of Salmonella was observed on the carcasses (1.4%). The prevalence of Salmonella in other samples was: 19.6% in tonsils, 9.3% on livers, 9.3% on tongues, and 9.3% in mesenterial lymphnodes. The prevalence of Salmonella in environmental samples was high in the drain water samples in both slaughterhouses (61%) and on the carcass splitter in one slaughterhouse (33%). Salmonella typhimurium was the most frequently isolated serotype in pig samples and environmental samples in both slaughterhouses: 43% of the Salmonella isolates from pigs and 33% of the Salmonella isolates from the environment was S. typhimurium. The results of this study show that Salmonella prevalences in pigs differ a lot, depending on which part of the pig is sampled. Not all different samples of the pig will become available for human consumption, but collecting more than one sample per pig showed that Salmonella can be found in almost the whole pig. The result of surface samples of carcass and liver gives information about hygiene during the slaughter process; the result of tonsils, lymphnodes and rectal contents, combined with the serological result, gives information about infection of the pig before the slaughter process (on the farm, during transport or in lairage). It can be concluded that results of Salmonella isolation of slaughter pigs should always be carefully interpreted, depending on the type of sample that has been collected.

Identification and quantification of risk factors in animal management and transport regarding Salmonella spp. in pigs.

This article discusses the main elements of a descriptive epidemiological model for Salmonella spp. in the pre-harvest stages of pork production, and the subsequent quantification of risk factors. About two thirds of all Dutch pig farms are more or less permanently infected. At infected finishing farms, the current probability that Salmonella-free pigs will become infected is about 85%. In the case that a certain pen is infected, the current probability that further pen-to-pen transmission will occur is about 90% and that (human) vectors will also spread the infection 60%. Between 5-30% of the animals may still excrete Salmonella spp. at the end of the finishing period, and this percentage can double during transport and lairage. In infected pigs at slaughter weight, the Salmonella spp. are foremost located in the digestive tract, its contents and the closely associated lymph nodes. Under the current circumstances, the lack of farm hygiene (odds ratio (OR) 39.7), (re)contaminated feed (OR 1.6), the use of broad spectrum antibiotics (OR 5.6), a positive Salmonella-status of animals before transport (roughly estimated OR 4.0), the lack of transport hygiene (roughly estimated OR 1.1) and transport stress (OR 1.9) are the most important risk factors regarding infections with Salmonella spp. Currently the role of on-farm contamination cycles with endemic ('house flora') Salmonella spp. is so important, that the role of other factors is difficult to ascertain. It is also concluded that the farm-phase forms the core of all current problems, and that better prevention and control can be achieved by, (i) very strict and consistent farm hygiene in combination with promotion of the colonization resistance of animals kept together with a prudent use of broad spectrum antibiotics; (ii) simultaneous execution of control programmes at breeding farms, multiplying farms and finishing farms; (iii) separate transport, lairage and slaughter of the animals thus produced.

Identification and quantification of risk factors regarding Salmonella spp. on pork carcasses.

The main elements of a descriptive epidemiological model for Salmonella spp. in Dutch pig slaughterlines, and the subsequent quantification of risk factors regarding the contamination of carcasses, are described. There is a strong correlation between the number of live animals that carry Salmonella spp. in their faeces and the number of contaminated carcasses at the end of the slaughterline. Live animals that carry Salmonella spp. are 3-4 times more likely to end up as a positive carcass than Salmonella-free animals. Currently, about 70% of all carcass contamination results from the animals themselves being carriers, and 30% because other animals were carriers (i.e. cross contamination). Furthermore, it is estimated that in general between 5-30% of the carcasses produced may contain Salmonella spp. With respect to carcass contamination with Enterobacteriaceae and Salmonella spp., inadequately cleaned polishing machines (odds ratio, OR, 6) and 'inapt procedures during evisceration' (OR 11), i.e. faulty evisceration and hygiene practices, are the most important risk factors. An estimated 5-15% of all carcass contamination with Salmonella spp. occurs during polishing after singeing. The remainder is the result of current evisceration practices (55-90%) and, to a lesser extent, further processing (5-35%), i.e dressing, splitting and meat inspection. Less likely Salmonella spp. already present on the skin of the live animals survive scalding and singeing. However, because pigs are the only important source for the Salmonella contamination of the line and the carcasses produced, it can also be concluded that if Salmonella-free pigs were produced, consumers could be provided with virtually Salmonella-free pork. As long as Salmonella-positive animals enter abattoirs, there will always be transmission of Salmonella spp. to consumers, even if the process is carried out according to stringent codes of good manufacturing practices (GMP). EU regulations should, therefore, allow for the decontamination of caracasses with a safe substance, e.g. lactic acid, on the condition that the slaughterhouse strictly adhers to GMP principles.

Salmonella spp. on pork at cutting plants and at the retail level and the influence of particular risk factors.

This article describes the contamination of pork with Salmonella spp. in cutting plants and butchers' shops in The Netherlands and quantifies the influence of several risk factors. When contaminated carcasses are being processed, the main risk factors regarding cross contamination are inapt cleaning and disinfection (OR 12.8), manipulation of contaminated materials as such (OR 4.7) and (re)contaminated surfaces (OR 4.4). However, in the current situation, where contaminated carcasses are constantly being brought into cutting lines, interim cleaning and disinfection of surfaces and utensils during breaks and at the end of the working day will most likely prevent not more than about 10% of all cross contamination that takes place during a working day. Thus, as long as contaminated carcasses are being processed, about 90% of the cross contamination that occurs in cutting plants is practically unavoidable. It can therefore also be concluded that under these circumstances the implementation of codes of good manufacturing practices (GMP) and Hazard Analysis Critical Control Point (HACCP)-inspired production methods will only be marginally effective in the control of Salmonella spp. cross contamination in cutting lines. The same is more or less true for the processing of contaminated cuts or carcasses by butchers in shops and supermarkets. Furthermore, in contrast to the situation in cutting plants, it may be that up to 10% of butcher's shops or kitchens of restaurants become colonized for several weeks or months with their own endemic 'house flora' of Salmonella spp., which are originally introduced via the purchased contaminated products of animal origin. Though there are no hard data to substantiate this, it can be suspected that these shops and restaurants represent the more badly managed, i.e. poorly cleaned and disinfected, enterprises. However, several analytical limitations hinder an exact determination of the prevalence of Salmonella spp. contaminated pork and an exact quantification the influence of risk factors. The diagnostic value (i.e. the sensitivity, specificity, precision and predictive value) of the combination of swabbing of carcasses and cuts and the usually employed culturing methods, in particular, is largely unknown, and there are indications that it may be seriously questioned. Without a more thorough knowledge about the diagnostic value of current and future methods of sampling and identification, it is impossible to provide for more accurate estimations of the prevalence of Salmonella positive carcasses and cuts. Based on the research data, the incidence of contaminated cuts and retail-ready pork can not be estimated more precise than as somewhere between 5-40%. When compensating for the discussed methodological flaws, it must be assumed that currently the true prevalence of contaminated primal cuts and retail-ready pork in butchers' shops is about 25-30%, and that of minced pork and pork sausages about 50-55%. Lastly it is concluded that if carcasses were Salmonella-free, consumers could in principle be provided with virtually Salmonella-free pork. It is therefore recommended that the EU allows for a decontamination step in slaughterhouses with a substance that is generally recognized as safe, provided that the producers strictly adhere to GMP-principles.

Impact on human health of Salmonella spp. on pork in The Netherlands and the anticipated effects of some currently proposed control strategies.

The impact on human health of Salmonella spp. on pork in The Netherlands is described. Subsequently, the effects of some currently proposed control strategies in the Dutch pork production chain are evaluated and quantified with the aid of a simple mathematical model. The estimated average incidence of cases of salmonellosis in the Netherlands is about 450 cases per 100,000 person years at risk (pyar). Some special risk groups for which the risks could be quantified are (1) persons with underlying diseases, such as neoplasms or diabetes mellitus (1200 cases/100,000 pyar); (2) persons with achlorhydria or who excessively use antacids (1100 cases/100,000 pyar); (3) persons who have recently been treated with antibiotics that disturb the normal gut flora (1700 cases/100,000 pyar); (4) nurses (900 cases/100,000 pyar); (5) caterers (900 cases/100,000 pyar); (6) slaughterline personnel (1800 cases/100,000 pyar). Furthermore, it is estimated that 15% (5-25%) of all cases of salmonellosis in The Netherlands are associated with the consumption of pork. Currently, proposed control measures regarding Salmonella in pigs and on pork in The Netherlands are codes of good manufacturing practices (GMP) that, in fact, formalize recommendations that can be found in many handbooks about pig breeding and pig slaughtering. When evaluated by a mathematical model constructed for this purpose, the proposed GMP codes from farm to cutting/retail could, at best, reduce the current levels of Salmonella-positive pigs and pork by 50-60%. If pigs were bred according to the rather costly specific pathogen-free concept (SPF), the prevalence of contaminated carcasses and pork could in total be reduced by 95% or more. However, implementing GMP codes from the transport phase up to the cutting/retail phase coupled with a decontamination step at the end of the slaughterline would be just as effective as GMP in combination with breeding using the SPF-concept. It is therefore concluded that the most efficient and cost-effective way of reducing the 'Salmonella problem' entailed by the consumption of pork would be to decontaminate carcasses under the precondition that the entire production chain strictly adheres to GMP principles. Therefore, the EU should also allow for more possibilities regarding the decontamination of carcasses than is currently the case. It is also concluded that current EU regulations relying on hazard analysis of critical control points (HACCP)-inspired production in cutting plants will not be effective in reducing the prevalence of Salmonella spp. on pork. This is mainly because (1) there is currently an almost steady stream of Salmonella-positive carcasses that enter the cutting process; (2) when contaminated carcasses are being processed, further cross-contamination during working hours is unavoidable; (3) no steps in the cutting process are intentionally designed to effectively reduce the risks or consequences of cross contamination of cuts and retail-ready products.

Monitoring of transmission of Salmonella enterica serovars in pigs using bacteriological and serological detection methods.

The standard method to detect Salmonella positive pigs is bacteriological examination of the faeces, but in recent years the use of Salmonella-ELISA's have become available to screen pigs for serological evidence of infection. This study was conducted to monitor the transmission of five different Salmonella enterica serovars (S. Typhimurium, S. Brandenburg, S. Panama, S. Livingstone, and S. Goldcoast) in fattening pigs and to test the feasibility of Salmonella-ELISA, using seeder pigs as a mode of transmission. Serovar dependence in transmission was observed. The Salmonella-ELISA proved to be useful to detect S. Typhimurium and S. Brandenburg in herds but was of limited value to demonstrate S. Livingstone, S. Goldcoast, and S. Panama.

Salmonella in the lairage of pig slaughterhouses.

The purpose of this study was to determine if lairages of pig slaughterhouses can act as a source of contamination of slaughtered pigs with Salmonella. The prevalence and variety of serotypes of Salmonella in the lairages of two pig slaughterhouses were determined, and the efficacy of the usual cleaning and disinfection on the presence of Salmonella was estimated. Lairages of two pig slaughterhouses were sampled three times when pigs were present. Furthermore, these lairages were sampled after the usual cleaning and disinfection, whereas the lairage of one slaughterhouse was sampled an additional time after improved cleaning and disinfection. Samples were collected by swabbing floor and wall surfaces and collecting the residing fluids on the floor throughout the lairage. Salmonella was isolated in 70 to 90% of the samples when pigs were present. The usual cleaning and disinfection reduced the level of contamination with Salmonella to 25% positive samples, whereas improved cleaning and disinfection reduced this level to 10% positive samples. It is concluded that the waiting period in the lairage of at least 2 h contains a substantial risk for slaughter pigs to become infected with Salmonella, especially for pigs originating from Salmonella-free herds. The usual cleaning and disinfection of the lairage were not sufficient to eliminate this risk, whereas an improved procedure for cleaning and disinfection still was unsatisfactory.

Hematological and clinicochemical profiles of healthy swine and swine with inflammatory processes.

The hematological and clinicochemical profiles of healthy swine and swine with inflammatory processes were investigated. Blood was collected at slaughter and postmortem examination was performed to select healthy swine and swine with pleuritis, pneumonia or abscesses. In healthy swine, the values of several variables revealed significant differences between gilts, barrows and boars. This was caused predominantly by the values obtained for boars. Inflammatory processes altered the values of most variables investigated, particularly for erythrocyte sedimentation rate, hemoglobin and hematocrit, for the activity of alkaline phosphatase, and for concentrations of iron, phosphate, albumin and fibrinogen in plasma. Compared with healthy swine, differences were largest for swine with metastatic abscesses and swine with both abscesses and other pathological lesions; differences were less pronounced in swine with solitary abscesses and were minor in swine with pneumonia and swine with pleuritis. Porcine hematological and clinicochemical profiles reflect the degree of inflammation.

Impact of animal husbandry and slaughter technologies on microbial contamination of meat: Monitoring and control.

The microbial flora transferred to carcasses during slaughter is a reflection of the care taken on the slaughter floor and of the types and numbers of microorganisms acquired by the animal on the farm or during the period of transportation to the slaughter house. These microogranisms may include those able to cause illness in the consumer, or microorganisms responsible for spoilage of the product. Considerable progress has been made in reducing contamination at slaughter and thereby extending the shelf-life of meat. In contrast, international statistics still clearly show that meat and meat products are responsible for a major proportion of all foodborne infections. This latter aspect is not determined by the overall number of microorganisms present but by the bacterial composition of the animal's gut flora at slaughter. Preventive quality assurance along the whole productions and processing line is therefore the only effective means of controlling the microbiological safety and quality of meat. This includes hazard analysis techniques to identify critical control points and procedures for monitoring the microbiological status of both animals and carcasses since most of the critical points cannot be totally controlled. At early stages in the production line, colonisation of meat animals with pathogens should be prevented. Subsequently, good slaughter practices will ensure carcasses of good overall microbiological quality. This paper deals with microbiological monitoring systems that can be used at different stages of production and processing to control the microbiological quality of poultry and pig meat.

Number and distribution of bacteria on some beef carcasses at selected abattoirs in some member states of the European communities.

In seven member countries of the European Communities, three abattoirs were visited on three occasions in each of two surveys and at each visit ten beef carcasses were sampled, before chilling, at defined sites on the neck, brisket, forerib and medially on the round. In Survey I, samples were plated for total viable count (TVC) at 30° (ISO 2293) and Enterobacteriaceae at 37° (ISO 5552); in Survey II only TVCs were made. This paper is confined to analyses of the TVCs in the two surveys. Data from each country were analysed separately as sampling methodology may not have been sufficiently reproducible by different workers to allow between-countries comparison. Variations among visits to particular abattoirs and abattoir × site interactions made comparisons among abattoirs invalid within five of the seven countries. To effectively monitor differences between abattoirs within most countries it would be necessary to make more than three visits to each abattoir. Despite abattoir × site interactions in three countries in Survey I and four countries in Survey II, comparisons between sites were generally valid because of the consistent high contamination of the brisket. In the remainder of countries the abattoir × site interaction was too large to allow valid comparisons between sites. It is recommended that at least three or four sites are sampled in future surveys as only one site per carcass would underestimate the number of more heavily contaminated carcasses.

Critical points in meat production lines regarding the introduction of Listeria monocytogenes.

In order to elucidate critical points concerning Listeria monocytogenes during bovine and porcine slaughter, cutting and processing, 843 samples were obtained from carcasses, primal cuts, products at retail and from environmental surfaces. Only 2-7% of the carcasses and 0-10% of the environmental samples in the 'clean' part of the pork slaughterline were found to be positive for L. monocytogenes. The incidence of L. monocytogenes was increased after chilling and cutting. In the cutting room 11-36% of the primal cuts and 71-100% of the environmental samples were found positive for L. monocytogenes. Our findings indicate that contamination of pork meat with L. monocytogenes originates from the processing environment of the chilling or cutting room. The incidence of L. monocytogenes in the bovine cutting and meat processing line (0-60%) was lower than in the porcine cutting and meat processing line (11-100%).

Predictability of post mortem abnormalities in shipments of slaughter pigs as an aid for meat inspection.

This paper reports on the predictability of post mortem abnormalities in individual deliveries of pigs, shipped from the fattening herd to the slaughterhouse. The percentage of pigs in a delivery having post mortem abnormalities was expressed in a Meat Inspection Index. This index is based on data about relevant abnormalities, weighted on the specific significance of each for meat inspection. It was investigated whether Meat Inspection Indices of previous deliveries of pigs could be used for prediction of indices of future deliveries. Results suggest that the Meat Inspection Index cannot be used in such a predictive capacity, partly because of great variation among individual shipments. However, a Meat Inspection Index could play a role in signalling farms that are likely to deliver pigs with a higher level of abnormalities. More attention could then be paid to animals coming from these herds.

Lactic acid as a decontaminant in slaughter and processing procedures.

An attempt was made to interrelate the data obtained in experiments conducted by our Department along beef, veal and pig slaughter lines, using lactic acid (LA) for the decontamination of carcasses, cold and hot boned primal cuts, slaughter byproducts, and butcher's knives. First and foremost it was observed, that provided Good Manufacturing Practices are strictly followed, the microbial load of carcass surfaces will be substantially reduced. LA-decontamination may result in an additional reduction. Since in the early post-mortem period bacteria are not yet attached to the meat surface, LA-decontamination should preferably be applied to the hot carcass. It was demonstrated that, dependent on mode and duration of application, LA sprays not exceeding 1% v/v (beef), 1.25% v/v (veal) and 1.5% v/v (pork) resulted in acceptable carcass colour scores. Blood spots, which are particularly prone to discolouration by lactic acid application, should be removed at an early post-mortem stage e.g. by strong showering. The difference in surface pH between LA-treated and control carcasses disappeared within 72 hours post-mortem. Veal longissimus chops treated with LA solutions up to 2% v/v were not identified by a consumer taste panel as significantly different from controls. The 'immediate' bactericidal effect of LA-decontamination for beef, veal and pig carcasses, as well as for pig liver and veal brain, amounted to approximately 1.5 log cycles for the aerobic colony counts, strongly dependent on substrate and conditions of decontamination. In addition, a 'delayed' bacteriostatic effect was observed during storage, which is probably the result of a prolonged lag phase of acid-injured micro-organisms surviving lactic acid decontamination.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of information from pig finishing herds for meat inspection purposes.

In a field trial on Integrated Quality Control of finishing pigs we evaluated information written on Quality Information Cards (QUIC) for meat inspection purposes. These cards were sent with 3747 shipments of pigs going from the finishing herd to the slaughterhouse. Pig suppliers answered five questions dealing with health problems and the use of drugs during the finishing period. By comparing QUIC answers to recorded post-mortem abnormalities, we found that the information on the QUIC had some, albeit low, predictive value with respect to the abnormalities 'arthritis', 'condemned liver' and lung lesions. Shipments without a QUIC or with a faulty QUIC were considered 'suspect' because higher levels of abnormalities were found in these shipments. These results indicate the potential use of a QUIC.

Preselection of finishing pigs on the farm as an aid for meat inspection.

The ability of pig suppliers to separate pigs with abnormalities from pigs without abnormalities at the end of the finishing period was investigated. Nineteen hundred and seventy-eight pigs, delivered by 22 pig suppliers, were involved in the experiment. The pigs were inspected on the farm by the pig supplier and, separately, by a veterinary expert. The animals were sent in 22 deliveries to one slaughterhouse. A veterinary meat inspector carried out the ante- and post-mortem inspections. The results of the inspections were compared. The measure of agreement, Cohen's Kappa (CK), indicated a poor (CK less than 0.40) to fair (0.40 less than CK less than 0.75) agreement among the results of the different inspection procedures, depending on the abnormality under investigation. There was a fair to good agreement for the abnormality 'tail lesion' among all inspections. Some findings of the live animal, such as 'straggler', were associated with a wide range of post-mortem abnormalities. It is concluded that preselection is possible and that the economic and practical feasibility of preselection should be investigated.

Investigations with enzyme-linked immunosorbent assays for Trichinella spiralis and Toxoplasma gondii in the Dutch 'Integrated Quality Control for finishing pigs' research project.

In the framework of the Dutch field trial 'Integrated Quality Control (IQC) for finishing pigs' ELISA (screening) techniques were used to detect animals seropositive for Toxoplasma gondii and/or Trichinella spiralis. The aim was to determine whether farms which consistently delivered seropositive pigs could be detected and monitored (defined as 'problem farms'). The investigation involved 120 farms and three slaughterhouses, and a total of 23,348 serum samples were examined. In addition, all pigs were also screened for the presence of Trichinella spiralis with the digestion method (pooled samples). The prevalence of seropositivity for Trichinella spiralis and Toxoplasma gondii was 0.3% and 2.1% respectively. Parasitological examinations concerning T. spiralis were negative. Considering the characteristics of the used methodology, the conclusion was drawn that there were no parasitological or serological indications for T. spiralis infections, and that with respect to T. gondii the infection rate seemed to be equally low for all farms involved. In addition, a longitudinal pilot study during a whole finishing period was undertaken at two finishing farms. Animals seropositive for Toxoplasma gondii were found from the earliest days of the finishing period. Housing and management may (still) play an important role in the prevention of contact with this parasite.

Human health hazards associated with the administration of antimicrobials to slaughter animals. Part II. An assessment of the risks of resistant bacteria in pigs and pork.

Risks for the consumer regarding the acquisition of resistant bacteria and/or resistance genes via the consumption of pork are discussed. In general, Salmonella spp. and Escherichia coli that originate from animals do not easily transfer their resistance genes to the resident intestinal flora of humans. The prevalence of resistant E. coli in humans seems more associated with being a vegetarian (odds ratio (OR) 1.89) than with the consumption of meat and meat products. Other risk factors are treatment with antimicrobials (OR 2-5), becoming hospitalized (OR 5.93), or working in a health setting (OR 4.38). In the Netherlands, annually an estimated 45,000 people (0-150,000) become a carrier of resistant E. coli and/or resistance genes that ori ginate from pigs, while an estimated 345,000 persons (175,000-600,000) become a carrier of resistant E. coli and/or resistance genes that originate from hospitals, e.g. other patients. Any problems with resistant Salmonella spp. that stem from pigs are, in fact, an integral part of the total problem of food-borne salmonellosis. Sometimes there are outbreaks of a specific multi-resistant clone of S. typhimurium that causes problems in both farm animals and humans. The probability that in the next 30 years there is no or maximally one outbreak of a specific clone that originates from pig herds is estimated at about 75%. Antimicrobials used as a growth promoter can have a measurable influence on the prevalence of resistant bacteria. The likely chain of events regarding avoparcin and the selection and dissemination of resistance against vancomycin in the enterococci gives the impression that the impact of the use of antimicrobials in animals on the prevalence of resistance in humans is largely determined by whether resistance genes are, or become, located on a self-transferable transposon. Furthermore, consumer health risks of antimicrobials used in slaughter pigs are mainly determined by the selection and dissemination of bacterial resistance and much less by the toxicological properties of any residues in pork. It is also concluded that most of the problems with resistant bacteria in humans are associated with the medical use of antimicrobials, and that the impact of particularly the veterinary use of antimicrobials is limited. However, the impact of antimicrobials used as a feed additive appears to be much greater than that of antimicrobials used for strictly veterinary purposes. The use of antimicrobials as a feed additive should therefore be seriously reconsidered.