Newly designed PCR assays based on the ema-10 and ema-11 genes confirm the circulation of Theileria haneyi in horses in Brazil.

Equine Piroplasmosis (EP) is a tick-borne disease caused by the protozoan parasites Babesia caballi, Theileria equi, and Theileria haneyi, characterized by intravascular hemolysis and associated systemic illness. Although T. equi and B. caballi have been widely reported in some regions of Brazil, data from other states are limited. Additionally, despite reports of T. equi genotype C, currently recognized as T. haneyi, has been identified in Brazil, there are no investigations using T. haneyi-specific molecular tools. This study assessed the presence of these three agents in horses from Baixada Maranhense microregion (n = 34), northeastern Brazil, and in horses from an equestrian center (n = 12) in Guará, southeastern Brazil. Of 46 horse DNA samples, one (2.1%) from an imported animal in the equestrian center tested positive for T. haneyi in ema-10 and ema-11-based PCR assays. Two animals tested positive for T. equi in a species-specific PCR (ema-1), and all samples were negative for B. caballi. BLASTn analysis showed ema-10 and ema-11 sequences shared 98.9% to 99.3% identity with T. haneyi detected in a horse at the U.S.-Mexico border. Despite the small sample size, this study confirms the presence of T. haneyi in Brazil and the need for monitoring imported animals.