Isolation and genotyping of Toxoplasma gondii in sheep meat from Northern Parana state, Brazil

Introduction: Toxoplasmosis is caused by Toxoplasma gondii, an intracellular protozoan that can infect humans and all warm-blooded animals. Objective: The present study aimed to isolate and genetically characterize T. gondii in sheep meat. Methods: The study was conducted in a sheep slaughterhouse, and samples of masseter muscles, tongue, heart, diaphragm, and blood were collected from 50 sheep. The sheep sera were subjected to an indirect immunofluorescence assay (IFA) to detect anti-Toxoplasma gondii IgG antibodies. The cutoff point used was 1:64. Tissue samples from seropositive animals were subjected to mouse bioassay. Inoculating mice determined the virulence of isolated strains. Genotyping was performed using multilocus PCR-RFLP with 11 genetic markers. Kaplan-Meier was used to build a survival curve. Results: IFAT showed 12% (6/50) of seropositivity, and the antibody titers were 64 (4/50, 8%) and 256 (2/ 50, 4%). The isolates were named TgShBrPr01 and TgShBrPr02. Genetic characterization of the isolate TgShBrPr01 showed the genotype ToxoDB #183. The isolated TgShBrPr02 did not amplify all markers; however, the available typing data indicate a new genotype. The survival curve of TgShBrPr01 showed a high virulence strain and killed all the Swiss Webster mice infected with 102 and 103 T. gondii tachyzoites. Conclusion: This study isolated two new atypical (nonclonal) T. gondii strains from sheep, underscoring the potential risk of this transmission source to humans, especially when meat is consumed raw or undercooked.