Unterschiedliche Bewertungsmöglichkeiten von Fleischsaft- und Serum-ELISA am Beispiel der Erfassung der Seroprävalenzen von Toxoplasma gondii, Yersinia enterocolitica und Salmonella in deutschen Outdoor-Schweinehaltungen

- Different rating systems for meat juice and serum ELISA using prevalence data of Toxoplasma gondii, Yersinia enterocolitica and Salmonella in finishing pigs from German farms with outdoor-keeping - The aim of this study was to test the use of ELISA-techniques as an easy-to-do, descriptive and reliable rating system for the seroprevalence of different zoonotic pathogens in livestock. Material & Methods Meat juice and serum samples from 2,004 finishing pigs were taken at the abattoir from 41 different establishments with outdoor-keeping. Samples were tested for Toxoplasma gondii, Yersinia enterocolitica and Salmonella, using commercial ELISA-kits, in the Institute for Meat Hygiene and Technology. Results of single animals, regional prevalence and the Farm seroprevalence were determined. Subsequently, different systems for the assessment of farm-seroprevalence (manufacturer’s cut’off, double-sampling of meatjuice and serum, median-analysis and categorization), were used. Results Pigs from German farms with outdoor-keeping tested positive for Toxoplasma, Yersinia and Salmonella in serum and meat juice. The farm-seroprevalence data were different; in particular, the prevalence of Yersinia was high. The individual results for Toxoplasma and Salmonella of positive animals, needed to calculate the farm-seroprevalence, were frequently located just above the manufacturer’s cut’off. As a result of median-analysis and categorization, 2 establishments were rated as farms under risk for Toxoplasma- (serum and meat juice), 31 (serum) and 34 (meat juice) for Yersinia- and 4 (serum) and 7 (meat juice) for Salmonella. Assessment Two rating systems were used. Farms with a positive (animal based) result via manufacturer’s cut’off were categorized as positive for the respective pathogen. In comparison, the OD% of a farm was determined through the median OD% based on the individual animal data and subsequently assessed by a categorization-key (median-categorization). Such a broader approach may farm circumstances more precisely. The categories were developed based on sensitivity and specificity of the test and using the principle of a TG-ROC-analysis, which is statistically reproducible. A combination of both systems may produce a accurate picture of the farm’s situation. Conclusions Sampling at the abattoir is established with official monitoring programs and does not interfer with slaughter and processing. Commercial ELISA-kits for detection of different zoonosis pathogens are available and are used in practice. It was possible to assess the ELISA-results in a sensible way using the different procedures. Results illustrate the need of a periodical evaluation, in order to get a more accurate picture of Toxoplasma gondii, Yersinia enterocolitica and Salmonella in pig farms.