Investigations on latent zoonoses in the context of the Swiss Swein 99 - project

Livestock producers in developed countries, such as pig producers, are facing the challenge to produce high quality products which satisfy their customers. Quality assurance programmes therefore are likely to become more important in the near future (Blaha, 1997). A prerequisite to the development of such programmes is the knowledge of animal health data, including zoonoses. In this context, an epidemiological study of the pig health and productivity in Switzerland, called Schwein 99 , has been initiated. This study has the overall objective to study the health and production profile of swine in a broad approach, where pigs are expected to be followed from birth to slaughter. Thus it will be carried out at three levels, i.e. at the breeding units, the fattening units and the abattoirs, respectively. This paper presents preliminary results from a pilot study carried out prior to the larger project to investigate the importance of selected zoonoses, Salmonella, Yersinia enterocolilica and Mycobacterium avium, in slaughtered healthy pigs

Investigations on latent zoonoses in the context of the Swiss "Swein 99"- project

Livestock producers in developed countries, such as pig producers, are facing the challenge to produce high quality products which satisfy their customers. Quality assurance programmes therefore are likely to become more important in the near future (Blaha, 1997). A prerequisite to the development of such programmes is the knowledge of animal health data, including zoonoses. In this context, an epidemiological study of the pig health and productivity in Switzerland, called "Schwein 99", has been initiated. This study has the overall objective to study the health and production profile of swine in a broad approach, where pigs are expected to be followed from birth to slaughter. Thus it will be carried out at three levels, i.e. at the breeding units, the fattening units and the abattoirs, respectively. This paper presents preliminary results from a pilot study carried out prior to the larger project to investigate the importance of selected zoonoses, Salmonella, Yersinia enterocolilica and Mycobacterium avium, in slaughtered healthy pigs.</p

[Trichinellosis in slaughtered and wild animals in Switzerland using a digestion method and a serologic method (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

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

Typing Listeria monocytogenes isolates from fish products and human listeriosis cases.

Seventy-two Listeria monocytogenes isolates originating from 10 different fish products of 12 producers and 47 isolates from human listeriosis cases were typed by serotyping and multilocus enzyme electrophoresis. Seventy-five of these isolates were further subtyped by restriction analysis of genomic DNA with the enzyme XhoI and by pulsed-field gel electrophoresis using the enzymes ApaI and SmaI. The results show that several L. monocytogenes clones identified by multilocus enzyme electrophoresis are frequently found in fish products of different origins. One of these clones is the same as another previously shown to be frequently associated with meat and meat products. The epidemic-associated electrophoretic type 1 was only rarely found in fish products. No association was found between any type of fish product and a particular lineage of L. monocytogenes. Both long-term persistence of a strain and simultaneous presence of several clearly distinct strains in the products of single producers were observed. The comparison of L. monocytogenes isolates from human clinical listeriosis cases in Switzerland and those from imported fish products by use of multilocus enzyme electrophoresis showed that they do not form two clearly distinct lineages but nevertheless belong to two separate populations. None of the 48 subtypes distinguished by the combination of all four typing methods could be found in both populations of human origin and those of fish origin