Purpose: This study aimed to identify pig farms that contribute most to the pork-related foodborne toxoplasma disease burden, as prime candidates for intervention. The contribution is estimated from the true infection status at animal-level per farm, the likelihood of the presence of tissue cysts given the serological result, and the number of pigs delivered to slaughter.
Methods: The true infection status was estimated from T. gondii antibodies in serum using a general Bayesian latent class hierarchical model. From each pig herd delivered to three Dutch slaughterhouses in 2012 to 2016, one to six blood samples were collected and examined serologically with the PrioCHECK™ Toxoplasma Antibody ELISA Kit (Thermo Fisher). The likelihood of tissue cysts for serologically positive pigs was quantified from literature data. The number of pigs delivered per farm were obtained from slaughterhouse records. Sensitivity analyses were conducted to assess the effect of prior choice in the latent class model.
Results: In total, 226,839 samples of 174,583 herds delivered from 3,521 farms were tested serologically. Preliminary analyses gave estimates for diagnostic test sensitivity and specificity of approximately 80% (95% credible interval: 42 to 99%) and 99.3% (99.1 to 99.5%), respectively. Estimates for the herd-level prevalence, animal-level prevalence, and the contribution to the disease burden per pig farm are currently being finalized.
Significance: Prioritizing pig farms according to their relative contribution to the foodborne disease burden supports the highest health gain for intervention programs. This study produced a robust methodology for that purpose and showed its application in the Netherlands for the priority foodborne pathogen, T. gondii.