Molecular epidemiology of Toxoplasma gondii in impala (Aepyceros melampus) from the Greater Kruger in South Africa : detection of the Africa 4 lineage

Background
Toxoplasma gondii is an apicomplexan parasite that causes toxoplasmosis, a widespread zoonotic disease. Despite the clinical significance of this zoonotic parasite, little is known regarding its prevalence in South Africa, particularly in wildlife. Considering the possible presence of the parasite in wildlife species and the popularity of South African game meat, in a 'One Health context', the consumption of undercooked game meat by people could represent a public health issue. The objective of this study was to determine the prevalence of T. gondii and any genotypes in impala from the Greater Kruger region destined for game meat.
Methods
Serum and seven different tissue samples were collected from 138 impala (Aepyceros melampus) from the Timbavati Private Nature Reserve in South Africa. The seroprevalence of T. gondii was determined using the Modified Agglutination Test (MAT). The presence of T. gondii DNA within the impala tissues and possible tissue tropism were determined using a quantitative PCR (qPCR). For strong qPCR-positive samples, T. gondii DNA was genotyped using a panel of 15 microsatellite markers.
Results
The seroprevalence was determined to be 8.7%. The qPCR identified T. gondii DNA in at least one tissue type of 7.2% of the impala. The T. gondii DNA was detected in the brain and tongue samples from two impala respectively, and were genotyped as belonging to the Africa 4 lineage. To place the two genotypes identified in this study within the broader context of the genetic diversity of T. gondii in Africa, a genetic tree was constructed using all African strains genotyped with 15 microsatellite markers.
Conclusion
These results shed light on serological versus molecular techniques in determining infection of T. gondii in impala, and also point to possible tissue tropism during infection. The results identify Africa 4 strains circulating in South African wildlife intended for human consumption, and the importance of genotype and phenotype characterisation to assess the potential public health risks.