Parasite to patient: A quantitative risk model for Trichinella spp. in pork and wild boar meat

Consumption of raw or inadequately cooked pork meat may result in trichinellosis, a human disease due to nematodes of the genus Trichinella. In many countries worldwide, individual control of pig carcasses at meat inspection is mandatory but incurs high costs in relation to absence of positive carcasses from pigs reared under controlled housing. EU regulation 2015/1375 implements an alternative risk-based approach, in view of absence of positive findings in pigs under controlled housing conditions. Moreover, Codex Alimentarius guidelines for the control of Trichinella spp. in meat of suidae have been published (CAC, 2015) and used in conjunction with the OIE terrestrial Animal health code, to provide guidance to governments and industry on risk based control measures to prevent human exposure to Trichinella spp. and to facilitate international pork trade. To further support such a risk-based approach, we model the risk of human trichinellosis due to consumption of meat from infected pigs, raised under non-controlled housing and wild boar, using Quantitative Microbial Risk Assessment (QMRA) methods. Our model quantifies the distribution of Trichinella muscle larve (ML) in swine, test sensitivity at carcass control, partitioning of edible pork parts, Trichinella ML distribution in edible muscle types, heat inactivation by cooking and portion sizes. The resulting exposure estimate is combined with a dose response model for Trichinella species to estimate the incidence of human illness after consumption of infected meat. Paramater estimation is based on experimental and observational datasets. In Poland, which served as example, we estimated an average incidence of 0.90 (95%CI: 0.00-3.68) trichinellosis cases per million persons per year (Mpy) due to consumption of pork from pigs that were reared under non-controlled housing, and 1.97 (95%CI: 0.82-4.00) cases per Mpy due to consumption of wild boar. The total estimated incidence of human trichinellosis attributed to pigs from non-controlled housing and wild boar in Poland, is similar to the incidence of human trichinellosis in that country reported by EFSA. Overall, in Europe, we estimated an upper incidence limit of 5.3×10^-4 cases per Mpy, or less than one predicted case of trichinellosis in the European Union every 4years, due to consumption of pork from controlled housing. Therefore, Trichinella testing of pigs under controlled housing is not adding any value to protect human health. We suggest applying our farm-to-fork QMRA model to further support decision making on the global scale.