Cross-Species Transmission and Molecular Diversity of Toxoplasma gondii in Domestic Animals from Erbil, Iraq

Toxoplasma gondii is a significant global zoonotic parasite found in a variety of domestic animals. This study aimed to determine the prevalence of Toxoplasma gondii and its genotypic associations in hens, equines, sheep and goats in Erbil Governorate, Iraq. A total of 778 whole blood samples, consisting of 85 cocks, 107 hens, 102 horses, 44 mules, 230 sheep and 210 goats, were subjected to a polymerase chain reaction (PCR) using the Toxoplasma gondii B1 gene. DNA sequencing and phylogenetic analysis were then performed. The PCR positivity rate was 12.9% (11/85) for cocks and 17.8% (19/107) for hens, with no statistically significant location-based variation (P < 0.426). Mules were much more prevalent (P < 0.054) at 15 (34.1%) than horses at 19 (18.6%) and were infected slightly more frequently than horses of either sex. The highest prevalence rate was found in sheep (22.6%), with ewes that had previously aborted having a higher infection rate (P < 0.003), at 29% (54.7%), compared to 23% (29.1%) for those without a history of abortion. Although the increase in infection depended on age, it was numerically higher but not statistically significant (P < 0.113). The prevalence of goats (29.0%) varied significantly by district (P < 0.004), with a significantly lower prevalence among pregnant goats (22.4%). Phylogenetic analysis of five local isolates (from chicken, goat, horse, mule and sheep) revealed close genetic proximity, forming a clade (bootstrap: 99.7–100%), suggesting possible cross-species circulation of similar genotypes. These isolates showed intermediate genetic proximity between strains from epidemiologically related areas, but gross divergence between strains from geographically separated areas. The results indicate that environmental pollution and local livestock practices contribute to the spread of Toxoplasma gondii and that specific control interventions are necessary to reduce the risk of zoonotic transmission. This article provides important information on the epidemiology and genetic characteristics of Toxoplasma gondii in Erbil, which may contribute to efforts to control toxoplasmosis in livestock and humans.