High genetic diversity in Toxoplasma gondii isolates from pigs at slaughterhouses in Paraíba state, northeastern Brazil: Circulation of new genotypes and Brazilian clonal lineages

Abstract

The consumption of raw or undercooked pig meat containing Toxoplasma gondii cysts is an important transmission route of this protozoon to animals and humans. This study aimed to serologically diagnose, isolate and genotype T. gondii from pigs slaughtered for human consumption in the state of Paraíba, northeastern Brazil. Blood and tissue samples (heart, tongue and brain) were collected from 120 pigs at slaughterhouses in the state of Paraíba. Serological examinations were performed with an indirect immunofluorescent antibody test (IFAT) with a cut-off point of 1:64. Tissues from positive animals were subjected to bioassays in mice to isolate the parasite. A total of 12.5% (15/120) of the animals were positive according to the IFAT, with titres ranging from 64 to 2048. Viable parasites were isolated in 80% (12/15) of the bioassays. The twelve T. gondii isolates obtained in this study and an additional 13 previously described isolates were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) using 11 genetic markers. Additionally, microsatellite (MS) analysis was performed using 15 markers. Nineteen of the 25 isolates completely genotyped using PCR-RFLP had 12 different genotypes, six of which were newly identified. One isolate had a mixed infection. The same 18 non-mixed isolates had 16 different genotypes based on the MS analysis. Genotype #13 (Caribbean 1), which is commonly encountered in northeastern Brazil and is probably a clonal lineage circulating in this region, was the most frequent genotype detected through both the PCR-RFLP and MS analyses. These results demonstrate that T. gondii is widespread among pigs slaughtered in the state of Paraíba. The results also confirm that this parasite has high genetic diversity in this region and that non-archetypal genotypes commonly circulate between different hosts and across different regions of Brazil.