ToxSauQMRA: Study of the tropism and persistence of Toxoplasma gondii: from pork carcass to sausage and dry ham, a quantitative microbiological risk assessment
Toxoplasma gondii is an intracellular coccidian parasite and one of the most successful parasites worldwide. Sexual reproduction resulting in shedding of oocysts occurs only in felids (definitive hosts), but virtually all warm blooded animals can carry tissue cysts and act as intermediate hosts. Humans, as intermediate hosts, become infected with T. gondii through ingestion of oocysts (e.g. when handling soil or cat litter, or on unwashed vegetables) or tissue cysts in raw or undercooked meat. If a woman becomes infected for the first time during pregnancy, T. gondii is transmitted to the fetus in approximately 30% of the occasions (Thiebaut et al., 2007). This can result in abortion or a baby born with central nervous system abnormalities, chorioretinitis, unspecific signs, or without symptoms. T. gondii is also an important cause of disease in immune‐compromised individuals, and was a major cause of death in AIDS‐patients before the introduction of highly active retroviral therapy (Luft and Remington, 1992). Postnatal T. gondii infection has long been perceived as harmless, but is now recognized as an important cause of chorioretinitis for immunocompetent individuals (Gilbert and Stanford, 2000). Meat appears to be a major source of T. gondii infections in Europe, as in an European multi‐center case control study 30 to 63% of infections in pregnant women were attributed to meat, whereas 6 to 17% were most likely soil borne (Cook et al., 2000). Pigs, like other livestock, can harbour tissue cysts following the ingestion of oocysts or dead animals. The surveillance plan conducted by the Ministry of Agriculture of France in 2013, and carried out by ANSES in collaboration with URCA, showed that 3.0% (CI95-[0.9-5.0%]) of pigs raised in an in-door system and 6.3% (CI95-[2.6-9.9%]) of pigs raised outdoor were seropositive for T. gondii. This seroprevalence reached 13.5% (CI95-[13.1-13.9%]) in out-door breeding sows. Viable parasite could be isolated in 22% (25/113) and 47% (16/34) of the indoor and outdoor pig carcasses analysed respectively. With 40.4 kg per household in 2014, pork is the first meat consumed in France, whose ¾ is eaten in the form of sausage and salami products (FranceAgriMer, 2015). Among raw cured meats, dry sausage is the most widely consumed (about 75,000 tonnes of dry sausage per year in France). France alone produced just over 108,000 tonnes of sausages and dry sausages in 2015, representing about 9% of the total tonnage of all sausages (FICT data, 2016). The health safety of these products is therefore a major issue. The share played by the consumption of pork meat in human contaminations is not known, nor is the risk of transmission of the parasite via the consumption of cured meat products. As early as 1999, the Codex Alimentarius Commission recommended that microbiological risk assessment should be based on a quantitative estimate. The high prevalence of toxoplasmosis in France in humans (32%) and the fact that the main mode of contamination is food-borne, fully justifies the conduct of a quantitative microbiological risk assessment (QMRA). If, in France, we have the T. gondii seroprevalence in various meat-producing species (ovine, bovine, pig, horses) enabling such an analysis, it lacks however the quantitative estimates concerning the distribution of parasites in the various parts (muscles) of a carcass and the reduction of the parasite load according to the cooking, preparation or preservation, as identified by an expert group of ANSES in 2005 (AFSSA, 2005). The present project aims at answering this lack of knowledge, providing though the bases for a robust QMRA analysis in France, an European country with a high Toxoplasma positive rate among humans.