Assessment of the feasibility of serological monitoring and on-farm information about health status for the future meat inspection of fattening pigs.

Current macroscopic meat inspection cannot detect the most common pork-borne pathogens (Salmonella spp., Yersinia enterocolitica and Toxoplasma gondii). Furthermore, food chain information (FCI) may not provide sufficient data for visual-only inspection, which is supposed to be the common way of inspection of pigs in the European Union. Our observational study aimed to evaluate the serological monitoring and the clinical evaluation of on-farm health status of pigs and assess the feasibility of these data as part of the FCI in meat inspection. We studied the serological status of Salmonella spp., Yersinia spp. and T. gondii in pigs during the fattening period. Additionally, we evaluated the association between on-farm health status and meat inspection findings. On 57 indoor fattening pig farms in Finland, we collected blood samples (mean of 20 pigs/farm) and assessed the on-farm health (coughing, tail biting, lameness) at the end of the fattening period. We visited 34 of these farms also at the beginning of the fattening for sampling and on-farm health evaluation of the same pigs. Meat inspection results were obtained after slaughter for all 57 farms. Salmonella seroprevalence was low at the end of the fattening period: it was 17.6%, 10.6% or 1.9%, with the cut-off values of OD15% (recommended by the test manufacturer), OD20% (used by Danish monitoring programme) and OD40% (used by German monitoring programme), respectively. The overall seroprevalence of Salmonella spp. and Yersinia spp. increased significantly (P < 0.001) during the fattening period (from 8.1% to 17.2% and from 30.3% to 72.3%, respectively), while the seroprevalence of T. gondii remained low (<1%). The within-farm seroprevalences of Salmonella spp. and Yersinia spp. differed significantly between the farms and this farm-level serological data could be used as FCI for risk-based decisions to improve food safety. Such potentially feasible decisions could include additional carcass testing, carcass decontamination, carcass processing, slaughtering arrangements and improved biosecurity measures at the farm. However, risk mitigation targets and procedures must be carefully adjusted for each pathogen regarding also economic aspects. Tail biting observed on farm was associated with partial carcass condemnations and arthritis at slaughter. This information could be included in the FCI and used when making decisions regarding meat inspection procedure: visual-only or additional inspections.

Comparison of commercial ELISA tests for the detection of Toxoplasma antibodies in the meat juice of naturally infected pigs.

Toxoplasmosis is a globally distributed protozoal zoonosis. Pigs are considered an important reservoir of Toxoplasma gondii and pork a major infection source of human toxoplasmosis. ELISA methods are commonly used diagnostic tools for detecting Toxoplasma infections. They are also used for slaughterhouse-based serological monitoring of toxoplasmosis in pigs to identify positive farms. The methods used are non-standardised with varying sensitivity and specificity. In our study, four commercial ELISA tests for the detection of Toxoplasma antibodies in the meat juice of slaughter pigs were compared with a modified agglutination test (MAT) as a reference. The cut-off values of the ELISA tests provided by the manufacturer varied between 0.20 and 0.50, and clearly influenced prevalence. The sensitivity of tests I, II and III varied between 96.4 and 78.6. Sensitivity was unacceptably low (3.6) for test IV (cut-off=0.30). Tests I, II and III had the highest accuracy and the best agreement with the reference test when a cut-off of 0.30 was used. Test II and III showed very good agreement (K=0.92 and 0.84, respectively) with the MAT. A very strong correlation (Pearson correlation >0.89) was observed between the S/P values of tests I, II and III. Our results demonstrate that the test and cut-off value used influence the results of the apparent seroprevalence studies.

Current food chain information provides insufficient information for modern meat inspection of pigs.

Meat inspection now incorporates a more risk-based approach for protecting human health against meat-borne biological hazards. Official post-mortem meat inspection of pigs has shifted to visual meat inspection. The official veterinarian decides on additional post-mortem inspection procedures, such as incisions and palpations. The decision is based on declarations in the food chain information (FCI), ante-mortem inspection and post-mortem inspection. However, a smooth slaughter and inspection process is essential. Therefore, one should be able to assess prior to slaughter which pigs are suitable for visual meat inspection only, and which need more profound inspection procedures. This study evaluates the usability of the FCI provided by pig producers and considered the possibility for risk ranking of incoming slaughter batches according to the previous meat inspection data and the current FCI. Eighty-five slaughter batches comprising 8954 fattening pigs were randomly selected at a slaughterhouse that receives animals from across Finland. The mortality rate, the FCI and the meat inspection results for each batch were obtained. The current FCI alone provided insufficient and inaccurate information for risk ranking purposes for meat inspection. The partial condemnation rate for a batch was best predicted by the partial condemnation rate calculated for all the pigs sent for slaughter from the same holding in the previous year (p<0.001) and by prior information on cough declared in the current FCI (p=0.02) statement. Training and information to producers are needed to make the FCI reporting procedures more accurate. Historical meat inspection data on pigs slaughtered from the same holdings and well-chosen symptoms/signs for reporting, should be included in the FCI to facilitate the allocation of pigs for visual inspection. The introduced simple scoring system can be easily used for additional information for directing batches to appropriate meat inspection procedures. To control the main biological public health hazards related to pork, serological surveillance should be done and the information obtained from analyses should be used as part of the FCI.