Exploring the Seroprevalence and Molecular Epidemiology of Toxoplasma gondii in Sheep Populations of Uruguay

Toxoplasmosis poses a substantial risk as a globally prevalent foodborne zoonotic disease. This disease does not only impact public health, but also results in noteworthy economic losses for countries dependent on rural activities, particularly those associated to the livestock industry, particularly pronounced in sheep and goats, where reproductive failure is a prevailing consequence. With a history deeply rooted in sheep farming, Uruguay ranks as the fifth-largest global exporter of sheep meat and the third-largest exporter of combed wool. However, the reproductive performance of sheep flocks remains suboptimal in the country. Our previous studies unveiled a concerning proportion of abortions attributable to Toxoplasma gondii 27% among aborted fetuses/placentas subjected to laboratory diagnostic investigations to assess for abortion causality. However, the overall prevalence of the parasite and the genotypes infecting Uruguayan sheep flocks have not been investigated. In this study, we aimed to assess T. gondii seroprevalence in sheep using an in-house ELISA assay, elucidate the prevailing genotypes in sheep employing molecular and serological typing, and characterize the impact of genetic diversity on parasite phenotype. Our findings indicate that around 17% of sheep in Uruguay are seropositive for T. gondii, and there is notable genetic variability in T. gondii detected in aborted ovine fetuses. In addition, we detected a predominance of type III strains, along with atypical and previously unreported genetic types. Furthermore, isolation and characterization of two Uruguayan strains obtained from aborted sheep, named TgUru1 and TgUru2, revealed diversity in terms of virulence and the ability to cause chronic/persistent infections. Thorough genetic and phenotypic analysis of these strains, encompassing in vivo and in vitro assessments revealed that both exhibit markedly distinct phenotypes, with TgUru1 displaying high virulence and rapid growth, and TgUru2 exhibiting slow growth and high rates of spontaneous cystogenesis. These differences extend to in vivo studies and gene-specific developmental stage expression. We are currently delving into the genetic and transcriptomic underpinnings of these variations, aiming to comprehend their potential impact on disease outcome. Additionally, our research extends to exploring the correlation between our animal findings and the human population in Uruguay concerning the prevalent strain's genetic background.