Prevalence and genetic characterization of Toxoplasma gondii in pigs from Northern Italy and its implication for consumers

Objectives: Toxoplasmosis is a worldwide zoonosis. The consumption of raw or undercooked pork and products thereof such as fresh sausages containing T. gondii cysts may be a source of toxoplasmosis in humans. In Nord America and Europe, T. gondii isolates can be classified into 3 main clonal Types (I, II, III). Type I is highly virulent to out-bred mice and Type II and III strains are significantly less virulent. Currently, there are few data on both the occurrence of T. gondii in pigs destined to be transformed into high value Italian food products and its genotypes circulating in Italy. The aim of this study was to evaluate the occurrence of T. gondii and genetically characterize the isolates in industrial pigs slaughtered in Northern Italy. Materials and Methods: From January to June 2014, blood, diaphragm and heart samples were collected from 505 slaughtered pigs (large white or hybrids, 9-month-old, ≈160 Kg of weight) from 73 farms located in Lombardy and Emilia Romagna. Sera were examined for IgG antibodies to T. gondii by modified agglutination test and titers ≥1:10 were considered positive; tissue samples (≈25 gr) from seropositive pigs were processed for the presence of T. gondii DNA (B1 locus) by EvaGreen® RealTime PCR and HRM analysis. Results: Anti-Toxoplasma antibodies were detected in 1.6% of pigs with titers from 1:10 to 1:320. T. gondii DNA was found in all seropositive animals and in 12/18 muscular samples. Types III, II, or both were identified in 5, 2, and 1 subjects, respectively. Conclusions: This is the largest epidemiological study on T. gondii in pigs in Italy; less pathogenic Toxoplasma types (Type II and III) were found by high sensitive and rapid molecular techniques (RealTime + HRM). The low prevalence combined with the finding of less virulent strains show that industrial pigs play a limited role in the epidemiology of T. gondii. The extent of the infection in pigs depends on the management system. Industrial pigs are unlikely to ingest rodents harboring tissue cysts and food or water contaminated with sporulated oocysts. Our results also suggest that the consumption of cured products prepared from these animals represents a very low risk to consumers of acquiring toxoplasmosis. Indeed, when pork is processed for curing (salting, drying, smoking), it is unlikely that T. gondii survives the processing procedures.