Toxoplasma gondiiprevalence in confinement pig herds measured by meat juice serology at slaughter

The new European food safety legislative demands a risk-based improvement of the processes of meat production from farm to fork instead of just inspecting the carcasses of each slaughtered pig. One major tool to include the pre-harvest stage of meat production is profiling herds serologically especially for latent zoonotic infections. The paper describes the inclusion of continuously serological testing for Toxoplasma gondii antibodies using meat juice samples. This concept was applied at two abattoirs in the Northwest of Germany using meat juice according to the sampling for the German Salmonella monitoring programme. The results of testing 39 pig herds demonstrated an unexpected high frequency of Toxoplasma gondii antibody positive pigs (> 90% herd prevalence, up to 80% intra-herd-prevalence) although only confinement herds were included into the study. Introduction Human cases of Toxoplasmosis are caused by contact to Toxoplasma shedding cats, resp. to their excretions, transmission from pregnant women to their foetuses or by eating Toxoplasma burdened raw or undercooked meat. The latter is the major reason, why Toxoplasma gondii infections of pigs are of public health relevance, especially in countries like Germany with a high proportion of raw pork consumption. Toxoplasma burdened carcasses cannot be detected by the tools of the traditional meat inspection (visual inspection, palpation, incision) and they enter the food chain, which potentially pose a risk to pregnant women and immune-deficient persons. In contrast to the traditional meat inspection, a core element of the risk-based meat inspection is process control and process optimization on the basis of the so-called “food chain information” (mortality, morbidity, drug-use in the herd of origin) as required by the Reg. (EC) 853/2004. To add data on subclinical zoonotic infections of pig herds to this food chain information, it is necessary to detect subclinical diseases like Salmonellosis, Yersiniosis, and Toxoplasmosis by means of targeted, specific diagnostic tests (e.g. by serology). Serological monitoring results are valuable for deciding on the appropriate inspection method and selecting carcasses for e.g. the production of minced meat. The paper gives an overview on ways to integrate the Toxoplasma seroprevalence of pig herds into meat juice multi-serology programmes for implementing the risk-based meat inspection. Material and Methods Testing the comparability of blood serum and meat juice: For assessing the reliability of meat juice instead of blood serum as samples for the detection of antibodies against Toxoplasma gondii, 291 paired samples from pigs (i.e. 291 times serum and meat juice from exactly the same pig) out of six herds supplying slaughter pigs to one abattoir were tested together with six different ELISA-tests for detecting antibodies against Salmonella, Yersinia, Trichinella, Mycoplasma hyopneumoniae, Influenza A H1N1 and H3N2. For detecting Toxoplasma gondii antibodies, the ANIMALTYPE Toxoplasma Ab ELISA (LDL, Leipzig, Germany) was used. This test is based on a recombinant antigen and contains a multispecies conjugate, which has been developed and validated for the use of blood serum and meat juice. Since a relatively low seroprevalence for Toxoplasma gondii was expected, several assuredly positive Toxoplasma control sera and meat juices (produced via experimental infections) were provided by the Institute for Parasitology of the University of Veterinary Medicine Hannover, Foundation, Germany, were simultaneously tested with the field sera and meat juices.