Tissue cyst-based quantitative risk assessment of human toxoplasmosis from consuming pork in Denmark: A farm-to-fork approach

Toxoplasma gondii is an important foodborne pathogen. The aim of this study was to develop a tissue cyst-based quantitative risk assessment model to estimate the probability of human infection with T. gondii from consuming pork in Denmark. A 'farm-to-fork' model was developed to trace the path of T. gondii infection, beginning with the true seroprevalence in pigs and proceeding to the estimation of tissue cysts in portions of pork. The model then accounted for the number of infectious portions post preparation and prior to consumption. Thereafter, the model estimated the probability of human infection from consumption of infectious portions using a doseresponse model. The model predicted the prevalence of T. gondii infections in humans, with the assumption that infections did not equate clinical illness. The average estimated prevalence at the age of 75 years ranged from 58.8% to 88.8%, depending on specific model scenarios. Furthermore, the predicted prevalence was higher for portions originating from conventionally raised pigs compared to those from organic pigs. This was due to the significantly higher proportion of consumption of conventional pork compared to organic pork, and despite the per-portion risk being higher for organic pork. The model identified that undercooked pork, dry-cured sausages, and smoked products pose a risk of infection. The probabilities of human infection per portion consumed were estimated at 7.3 x 10-4, 4.7 x 10-4, and 1.2 x 10-5, respectively. However, the actual risk posed by dry-cured sausages remains uncertain due to limited data on the effectiveness of salting applied in dry-cured sausage processing. It was epidemiologically challenging to build the model due to the lack of comprehensive data on salting processes and the complexity of accurately reflecting industry standards. The age-specific prevalence offers limited value for public health decision-making; however, attribution of risk to specific pork products and in comparing organic and conventional pork provides more actionable insights for the future.