[Does emergency vaccination make sense as a supporting element in control of foot-and-mouth disease in Switzerland]. / Ist die Notimpfung als unterstützende Massnahme zur Tilgung der Maul- und Klauenseuche in der Schweiz sinnvoll?

The outbreak of foot and mouth disease (FMD) in Great Britain in 2001 let to discussions and especially emergency vaccination was deemed as an alternative to the culling of vast numbers of healthy animals. The project emergency vaccination for FMD in Switzerland was conducted to compare the effectiveness of conventional control strategies during a FMD outbreak alone and with ring vaccination of 3 km and 10 km, respectively. The results of this project showed that emergency vaccination conducted at the beginning of an epidemic was not favorable compared to conventional disease control strategy in Switzerland. In case of an advanced FMD epidemic, a 10 km ring vaccination could support the disease control in a positive way. However, the goal of emergency vaccination to save animal live can hardly be achieved due to actual legal basis and the consequent restriction measures within vaccination zones which will lead to welfare culling.

L'épizootie de fièvre aphteuse en Grande Bretagne en 2001 a montré que les abatages de masse d'animaux sains sont plus en plus critiquée. On discute régulièrement de la vaccination d'urgence comme mesure permettant de réduire le nombre d'animaux à tuer en cas d'épizootie. Dans le cadre du projet vaccination d'urgence FA suisse, on a comparé l'effet de la seule lutte conventionnelle avec celui d'une vaccination d'urgence «vaccination to live¼ dans un périmètre de 3 km (GV3) respectivement 10 km (GV10) quant à la durée et à l'importance du foyer. Au début d'une épizootie, la vaccination d'urgence supplémentaire n'apporte pas d'avantage face à la lutte conventionnelle. Si une vaccination V10 est pratiquée plus tardivement, elle peut dans certains cas amener une diminution et un raccourcissement de l'épizootie. Le but visant, grâce à la vaccination d'urgence, à tuer moins d'animaux ne peut toutefois pas, dans les conditions actuelles, être atteint car vu les fortes limitations du trafic d'animaux à l'intérieur des zones de vaccination, on doit compter avec des abattages pour des raisons de protections des animaux.

Antimicrobial resistance of Yersinia enterocolitica strains from human patients, pigs and retail pork in Switzerland.

To obtain basic data for future resistance monitoring programs, 386 Yersinia enterocolitica strains from human patients, raw retail pork and pig feces were tested for their susceptibilities to 16 antimicrobial agents and two antimicrobial growth promoters (carbadox and olaquindox). No strains were resistant to ceftriaxone, cefuroxime, ciprofloxacine, gentamicin, kanamycin, neomycin or polymyxin. Although in Switzerland carbadox and olaquindox were used as growth promoters for pigs for over 25 years, all strains were susceptible to them. In contrast, there were high levels of resistance to ampicillin, cefalothin and amoxicillin/clavulanic acid. Less than 10% of clinical isolates and strains from pig feces were resistant to streptomycin, sulfonamide, trimethoprim/sulfamethoxazole, tetracyclin, trimethoprim and chloramphenicol, but strains from retail pork were all susceptible to these antimicrobial agents. This finding suggested that pork is probably not a major source of Y. enterocolitica that cause human infections in Switzerland. A difference between clinical isolates and strains from pork was also shown by serotyping. Clinical isolates frequently belonged to the O3 and O9 groups whereas these two serotypes were not found in strains from pork. Resistance to multiple antimicrobial agents was rare. When examined by pulsed field gel electrophoresis (PFGE), two strains of fecal origin with an identical pattern of resistance to six antimicrobial agents were shown to be unrelated. Of four clinical isolates with resistances to five antimicrobial agents, two were of the same pulsotype. Retrospectively, it was found that these strains came from two members of the same household and thus represented a mini-outbreak.

Listeria monocytogenes: food-borne pathogen and hygiene indicator.

In the past 25 years, Listeria monocytogenes has become increasingly important as a food-associated pathogen. Most European Union countries have an annual incidence of human listeriosis of between two and ten reported cases per million. Because of its high case fatality rate, listeriosis ranks among the most frequent causes of death due to food-borne illness. Listeria monocytogenes infections are responsible for the highest hospitalisation rates (91%) amongst known food-borne pathogens and have been linked to sporadic episodes and large outbreaks of human illness worldwide. The ability to persist in food-processing environments and multiply under refrigeration temperatures makes L. monocytogenes a significant threat to public health. Listeria monocytogenes contamination is one of the leading microbiological causes of food recalls, mainly of meat, poultry, seafood and dairy products. Prevention and control measures are based on hazard analysis and critical control point programmes throughout the food industry, and on specific recommendations for high-risk groups. Understanding how these micro-organisms adapt their cellular physiology to overcome stress is important in controlling L. monocytogenes in food environments.

Assessment and modification of a Western blot assay for detection of central nervous system tissue in meat products in the United States.

Health hazards associated with meat contaminated by the bovine spongiform encephalopathy agent have led to the development of tests for the presence of this agent. The objective of this study was to optimize a neuron-specific enolase Western blot assay for use in the United States. We compared the original test with a modified protocol to evaluate the detection limit for the presence of central nervous system (CNS) tissue in experimentally inoculated samples and compared and evaluated the utility of these tests for detecting CNS tissue in retail sausages. Sensitivity and specificity of the original and modified protocols were evaluated using the kappa statistic to assess agreement between the results of the two protocols. The original protocol resulted in 100% specificity and 92% sensitivity for raw samples and 92% specificity and 72% sensitivity for cooked samples. The modified protocol resulted in 92% specificity and 89% sensitivity for raw samples and 83% specificity and 75% sensitivity for cooked samples. The kappa statistic for protocol comparison was 0.94 for raw samples and 0.74 for cooked samples. Both protocols correctly identified CNS tissue in positive controls for each replicate. Although the Western blot technique should be considered for screening for the presence of bovine CNS tissue in meat samples, the techniques should be further optimized to address problems of low sensitivity. A test with higher sensitivity is needed to protect consumers from food safety threats associated with bovine CNS tissue.

Behavior of Listeria monocytogenes during processing and storage of experimentally contaminated hot-smoked trout.

Hot-smoked fish like smoked trout is quite frequently contaminated with Listeria monocytogenes. In order to estimate the potential health hazard for the consumer eating such products, the behavior of L. monocytogenes was studied during processing and storage of artificially-inoculated hot-smoked trout. Four trials were performed; in trials 1 and 3 a wild-type strain was used, while in trials 2 and 4 a serological reference strain, SLCC 2755, was used. In the first two trials, raw trout was surface inoculated with L. monocytogenes, marinated, hot-smoked (core temperature 65 degrees C during 20 min), and stored at 4 and 8-10 degrees C, respectively, for up to 20 days. At different times during processing and storage, samples were taken and, by means of a MPN-method, quantitatively analysed for L. monocytogenes. The initial Listeria levels in the trout were 10(6) MPN/g. Until smoking, the concentrations remained about the same. After the hot-smoking process and during storage, however, L. monocytogenes could no longer be detected. In trials 3 and 4, the trout were inoculated after hot-smoking at a final concentration of 4.5 x 10(1) MPN/g and 3.1 x 10(1) MPN/g, respectively. During storage at 4 degrees C, neither an increase nor a decrease of L. monocytogenes was observed. At 8-10 degrees C, however, a significant increase up to 10(7) MPN/g occurred. By hot-smoking, low level contaminations of raw fish with L. monocytogenes will easily be eliminated. Nevertheless, it is of great importance to prevent postprocessing contamination, because during storage at refrigeration temperatures growth of L. monocytogenes is possible.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of mesophilic Aeromonas species in raw and ready-to-eat fish and meat products in Switzerland.

A total of 829 poultry, meat, shellfish and fish products commonly consumed in Switzerland were qualitatively and quantitatively examined for the presence of mesophilic Aeromonas spp. Overall, aeromonads occurred in 24.1% of the samples. Raw food products were frequently contaminated (e.g. 94.1% in minced meat), with colony counts up to 6.0 x 10(6)/g. Some ready-to-eat products had a relatively high percentage of positive samples as well, such as cooked ham in slices (38.2%), mortadella (12.9%), smoked cooked sausage (15.6%), hot and cold smoked fish (10.9-14.3%) and gravad salmon (10.5%). Colony counts, however, were somewhat lower (up to 1.7 x 10(3)/g). The high contamination rate of cooked or hot smoked foods suggests recontamination after cooking or smoking, e.g., at the slicing and packaging stage. 61.2% of the identified strains were Aeromonas hydrophila, followed by 22.5% Aeromonas caviae and 16.3% Aeromonas sobria.

Comparison of seven selective media for the isolation of mesophilic Aeromonas species in fish and meat.

Seven selective agar media and two enrichment broths were evaluated for their suitability for the isolation of mesophilic Aeromonas species from meat, fish, and shellfish samples. In a first trial, aeromonads were inoculated in fish and meat samples and reisolated using all selected media. For qualitative isolation, enrichment in alkaline peptone water (pH 8.7 +/- 0.1) at 28 degrees C and subsequent plating onto sheep blood agar supplemented with 30 mg/L ampicillin (ASBA 30) and bile salts-irgasan-brilliant green agar (BIBG) at 35 degrees C led to the best results. For quantitative assays, direct plating on the same agar media is recommended. In a second trial, 829 meat, fish, and shellfish samples were investigated with the same methods. The results show that BIBG is the most selective medium and that presumptive identification of aeromonads on ASBA 30 is very easy. Finally, we could confirm the opinion of other workers that optimal recovery of mesophilic Aeromonas spp. requires the use of more than one agar medium.

A PCR-based test for species-specific determination of heat treatment conditions of animal meals as an effective prophylactic method for bovine spongiform encephalopathy.

Efficiency of animal waste sterilization prescribed by the European Union and Switzerland was verified using a pork-based ELISA and two PCR assays (tRNA(Glu)/cytochrome b specific for vertebrates; bovine species-specific cytochrome b mitochondrial genome). A total of 204 samples of feedingstuffs were analysed including reference materials subjected to known heat treatments. Both ELISA and PCR assays were able to detect poorly heat-treated feedingstuffs if there was enough pork-based material present. The proposed species-specific PCR test, however, showed a higher sensitivity and specificity as it specifically detected bovine material. Nevertheless, the PCR assay will not detect bovine material in properly heat-treated feeds as the DNA is too fragmented. It is, however, very useful as a rapid, sensitive, and specific method for the routine screening of animal meals with regard to prophylaxis of BSE.

[Residues of antibiotics and chemotherapeutics in meat]. / Rückstände von Antibiotika und Chemotherapeutika in Fleisch.

Antibiotics and chemotherapeutics in food may only be present in concentrations below a toxicologically approved level. To check the established limits laboratories depend on reliable methods: on the one hand rapid and inexpensive screening tests (biological and immunological methods), on the other hand rather costly but very specific chemical-analytical reference methods. The results of residue testing in a big slaughter plant are presented. Residues of antibiotics were mainly found in calves. The most frequently detected drugs were tetracyclines, sulfonamides and aminoglycosides.

[Zoonoses as a risk when associating with livestock or animal products]. / Zoonosen als Risiko im Umgang mit Tieren und tierischen Produkten.

The risk of zoonotic disease transmission when handling livestock or animal products is substantial. In industrialized countries, the classical zoonotic diseases such as tuberculosis or brucellosis are no longer in the foreground. Latent zoonoses such as salmonellosis and campylobacteriosis can cause serious disease in humans and have become a major public health problem during the past years. Since animals infected with these pathogens show only mild transient disease or no clinical signs at all, new concepts in the entire production line ("stable to table") are necessary in order to avoid human infection. Two emerging viruses with zoonotic potential--avian influenza virus and Nipah virus--have been found in Asia in 1997 and 1999. Both diseases had a major impact on disease control and public health in the countries of origin. In order to cope threats from infectious diseases, in particular those of public health relevance, a combined effort among all institutions involved will be necessary. The proposed "European Center for Infectious Diseases" and the "Swiss center for zoonotic diseases" could be a potential approach in order to achieve this goal.

[The prevalence of salmonella, yersinia and mycobacteria in slaughtered pigs in Switzerland]. / Verbreitung von Salmonellen, Yersinien und Mykobakterien bei Schlachtschweinen in der Schweiz.

Clinically healthy food animals can be reservoirs for various foodborne pathogens. In general, such animals do not have lesions that are visible during meat inspection. Pigs are considered to be carriers of salmonella, yersinia and mycobacteria, but the risk of transmission to humans is difficult to assess. The aim of this study was to estimate the actual prevalence of the three above mentioned pathogens in the Swiss pig population and to comment on their significance. A total of 570 samples each of tonsils and mesenteric lymphnodes, were collected at two slaughterhouses from carcasses of apparently healthy pigs and analyzed for the presence of salmonella, yersinia and mycobacteria. The prevalence of salmonella (0.9%) was found to be lower than--while that of yersinia (8.1%) and mycobacteria (12.8%) about equal to--results reported from other European countries. Yersinia typing showed that serotype O:9 of Yersinia enterocolitica (2.5%) was 6 to 7 times more frequent than serotype O:3 (0.4%)--formerly the most frequent serotype. Mycobacterium avium was the most frequent isolate (90.7%) among the mycobacteria isolated. Although all three pathogens are present in the Swiss pig population, we consider the risk of transmission to humans via consumption of pork as low. Appropriate preventive measures and quality management should contribute to keep the risk under control.

[Trichinellosis in slaughtered and wild animals in Switzerland using a digestion method and a serologic method (E/S-ELISA)]. / Untersuchungen von Schlacht- und Wildtieren in der Schweiz auf Trichinellose mit der Verdauungsmethode und einem serologischen Verfahren (E/S-ELISA).

For many decades trichinellosis has not been reported among Swiss domestic pigs. Considering the fact that Trichinella occurs in a sylvatic cycle in Switzerland, a study was designed to reevaluate the present epidemiologic situation by investigating 10,904 fattening pigs, 218 pigs with free access to pasturage or being kept on an alp, 104 domestic boars, 106 horses, 44 wild boars and 538 foxes using a direct and an indirect diagnostic technique (digestion method and serology with ELISA and an excretory/secretory antigen, respectively). The digestion method was performed according to EC-guidelines. Furthermore, 25,239 sera originating from a Swiss sow-serum bank were tested retrospectively for anti-Trichinella antibodies. Trichinella was not detectable in all domestic pigs using the digestion method. Serologically, 3 fattening pigs (0.027%) and 9 sows (0.036%) demonstrated weak antibody reactivities against the Trichinella E/S-antigen. Based upon statistical calculations for the negative-positive threshold, these antibody-reactions were considered to be within the normal range of variability of the test. Although statistically restricted, the results of the present study indicate the absence of Trichinella within the Swiss pig population. Based upon the rational applicability of the ELISA and its diagnostic sensitivity and specificity, this test appears as the most suitable method to perform large-scale screenings among slaughter pigs. Pigs with free access to pasturage and boars were all parasitologically and serologically negative for Trichinella. The digestion method showed that horses and wild boars were all parasitologically negative, whereas 1.3% of the foxes were positive for Trichinella larvae.

Detection of Mycobacterium avium subspecies paratuberculosis in Swiss dairy cattle by culture and serology.

Faecal samples from 186 dairy cows representing ten commercial dairy herds with sporadic clinical paratuberculosis (group A), and from 100 dairy cows from herds without a history of paratuberculosis (group B) were cultured for Mycobacterium avium subspecies paratuberculosis (MAP). Two different decontamination methods, a NaOH/oxalic acid method and treatment with 0.75% hexadecylpyridinium chloride (HPC) were performed prior to inoculation of Loewenstein-Jensen agar slants with and without mycobactin. Cultures were incubated for 16 weeks. Acid-fast staining bacteria were identified as MAP on the basis of mycobactin dependency and by PCR-RFLP analysis of the IS 1311-insertion element of M. avium. MAP was grown from 15 out of 186 group A animals (8.1%) whereas faecal culture for MAP was consistently negative in group B. The growth rate of MAP was significantly higher (8.1% vs. 1.6%) and the contamination rate of cultures was significantly lower (17.6% vs. 21.5%) in faecal samples decontaminated with NaOH/oxalic acid than with HPC-treated faecal samples (p<0.01, McNemar's test). Atypical mycobacteria which were grown from 46.8% of NaOH/oxalic acid treated specimens were not obtained from any of the HPC-treated samples. A commercial ELISA with MAP-lipoarabinomannan as the antigen was used to detect MAP-antibodies in unabsorbed sera from all animals. The percentage of ELISA-positive cows was 16.8%. Overall agreement between antibody detection and MAP-positive faecal culture was 15.4%.

Policy-driven development of cost-effective, risk-based surveillance strategies.

Animal health and residue surveillance verifies the good health status of the animal population, thereby supporting international free trade of animals and animal products. However, active surveillance is costly and time-consuming. The development of cost-effective tools for animal health and food hazard surveillance is therefore a priority for decision-makers in the field of veterinary public health. The assumption of this paper is that outcome-based formulation of standards, legislation leaving room for risk-based approaches and close collaboration and a mutual understanding and exchange between scientists and policy makers are essential for cost-effective surveillance. We illustrate this using the following examples: (i) a risk-based sample size calculation for surveys to substantiate freedom from diseases/infection, (ii) a cost-effective national surveillance system for Bluetongue using scenario tree modelling and (iii) a framework for risk-based residue monitoring. Surveys to substantiate freedom from infectious bovine rhinotracheitis and enzootic bovine leucosis between 2002 and 2009 saved over 6 million € by applying a risk-based sample size calculation approach, and by taking into account prior information from repeated surveys. An open, progressive policy making process stimulates research and science to develop risk-based and cost-efficient survey methodologies. Early involvement of policy makers in scientific developments facilitates implementation of new findings and full exploitation of benefits for producers and consumers.

Patterns of animal diseases and their control.

Despite enormous progress in scientific knowledge and improvements in sanitary standards in livestock production, the world has recently been confronted with several animal disease epidemics which have caused significant economic losses. General awareness regarding unusual clinical signs and prompt reporting of disease is an important requirement in disease detection and control and needs to be promoted among farmers and veterinarians. Unexpected clinical syndromes are of increasing importance for public health. Syndromic surveillance has been shown to be a key element in detecting emerging diseases. Once detected and diagnosed, surveillance programmes constitute the first step towards determining the disease pattern with regard to time and space. This pattern of disease occurrence becomes the basis for selecting approaches for further disease investigation and for disease control.

Detection of Mycobacterium avium subspecies paratuberculosis in Swiss dairy cattle by real-time PCR and culture: a comparison of the two assays.

AIMS: To compare the two different diagnostic assays for the detection of Mycobacterium avium ssp. paratuberculosis, the aetiological agent of paratuberculosis. METHODS AND RESULTS: Faecal samples were derived from 310 cows, representing 13 commercial dairy herds in various locations in Switzerland with expected increased risk because of a past history of disease. Detection assays for M. avium ssp. paratuberculosis were culture (gold standard) and a newly designed real-time PCR. Real-time PCR identified 31 of 310 animals as positive within this risk population whereas culture identified 20 positive animals. The specificity of real-time PCR was confirmed by DNA sequencing of the PCR product. Depending on the test used, the paratuberculosis prevalence in our tested risk population ranged from 6.5 to 10%. CONCLUSIONS: Real-time PCR and culture data were in good agreement, and real-time PCR generates data in a short time in contrast to culture. SIGNIFICANCE AND IMPACT OF THE STUDY: We consider real-time PCR as a suitable alternative method to culture for the detection of M. avium ssp. paratuberculosis in a national surveillance programme.

Behavior of Listeria monocytogenes during fabrication and storage of experimentally contaminated smoked salmon.

Experiments were carried out to examine the behavior of Listeria monocytogenes in the course of fabrication and storage of smoked salmon. In three trials, raw salmon fillets were surface inoculated with L. monocytogenes, marinated, smoked at 26 to 30 degrees C, and stored at 4 or 10 degrees C for up to 30 days. At different times during the fabrication and storage, samples were taken and, by means of the three-tube most probable number (MPN) method, quantitatively analyzed for the concentration of L. monocytogenes. The initial Listeria levels in the raw fillets were 10(4) MPN/g in trial 1, 10(1) MPN/g in trial 2, and 10(2) MPN/g in trial 3. During the fabrication, neither an increase nor a decrease of the inoculated quantities was observed. During the storage, however, a significant growth was measured in two of three trials; in trial 1, a 2.5 log10 MPN/g increase and in trial 3, an increase of even 4.5 log10 MPN/g. In the second trial, the Listeria level remained about the same. The results indicate the importance of preventing pre- and postprocessing contamination of L. monocytogenes in raw and smoked salmon. Because a significant increase of L. monocytogenes was measured during storage, there might be an increasing risk of infection for the consumer by storing such fish for a long time.

Subtyping Listeria monocytogenes isolates genetically related to the Swiss epidemic clone.

Macrorestriction analysis by pulsed-field gel electrophoresis was used to assess the diversity of strains within the epidemic-associated electrophoretic type 1 (ET1) clone of Listeria monocytogenes. For this purpose, a total of 144 isolates from Switzerland shown by multilocus enzyme electrophoresis to belong to the ET1 were examined. These isolates were subtyped by macrorestriction analysis using the enzymes ApaI and SmaI and field inversion gel electrophoresis. Among these 144 isolates, 45 were isolated in human listeriosis cases of the postepidemic period of 1988 to 1993 and 44 were isolated in animal listeriosis cases of the same period. Forty-seven isolates were from the epidemic period of 1983 to 1987, and eight additional isolates were from cattle from two different farms. Twenty-nine different subtypes could be identified among the 144 isolates tested. Five major subtypes were found more frequently than the others during the postepidemic period, both in humans and in animals. Two of these subtypes had been previously implicated in outbreaks of listeriosis, thus suggesting that particular pulsed-field gel electrophoresis subtypes may be frequently associated with disease in humans and animals. Two of these frequent subtypes were also suspected to be related to small clusters of listeriosis cases during the postepidemic period. The results obtained by typing epidemiologically related isolates from different animals within the same farms and from different body sites of a given patient confirmed the potential of macrorestriction analysis for epidemiological studies restricted to short periods of time and to small number of isolates. The analysis of 47 isolates related to the Swiss listeriosis epidemic period of 1983 to 1987 and the use of Southern blotting and hybridization experiments show that the interpretation of relatedness between isolates presenting slightly different macrorestriction patterns may be more complex than commonly accepted. In such cases, careful interpretation of the potential molecular mechanisms leading to the differences observed between patterns is necessary.

Genotypic characterization of Mycobacterium avium strains recovered from animals and their comparison to human strains.

Mycobacterium avium was recovered from 21 birds and 10 pigs. Bird isolates carried IS901 and a few copies of IS1245 and appeared highly related by pulsed-field gel electrophoresis. Pig isolates showed features previously described in human isolates: a lack of IS901, a high copy number of IS1245, and marked polymorphism by pulsed-field gel electrophoresis.