Preparedness for potential future serological surveillance of Toxoplasma gondii in the Danish pig population: A review of latest epidemiological studies from Denmark

Consumption of undercooked meat infected with Toxoplasma gondii may cause toxoplasmosis in humans. For decision making regarding potential risk mitigation, it is necessary to first investigate the actual seroprevalence in Danish pig sub-populations. It is also important to ascertain whether it is possible to identify infected herds at slaughter with a reliable serological assay.

Here, the results of three latest epidemiological studies in Danish pig herds are presented. The objectives were to quantify seroprevalence, identify the associated major risk factors and optimise the use of diagnostic methods. Our findings show that the true seroprevalence of T. gondii was high in sows, medium in organic finishers and low in conventional finishers.

Hence, age and production system were found to be good predictors of high- and low-risk herds in Denmark. Furthermore, our time-to-detection analysis showed that it would take a longer time to detect seropositive finishers from conventional herds and sow herds, but a shorter time for organic finisher herds.

Test characteristics of a commonly used commercial ELISA i.e., cut-off, sensitivity, and specificity were updated. Additionally, our investigation into the zoonotic risk revealed that the probability of exposure to T. gondii from consuming pork products was low in Denmark. Our findings are in-line with EFSA’s recommendation of auditing for biosecurity in low-risk conventional herds and monitoring of outdoor finishers.

Future studies should explore whether it would be suitable to improve existing processes e.g., freezing of pork intended for making high-risk products, and to educate consumers, compared to implementing a surveillance system.