Risk factors for equine trypanosomosis and hematological analysis of horses in Paraguay.

Animal trypanosomosis, caused by Trypanozoon trypanosomes (Trypanosoma evansi and T. equiperdum), and Trypanosoma vivax, is endemic to South American countries and has a negative impact on the livestock industry. However, the risk factors for trypanosomosis in Paraguay remain unknown. This study aimed to determine the risk factors for equine trypanosomosis in Paraguay based on a PCR-based molecular survey and individual horse sampling data. In this study, 739 blood samples were collected from horses in 16 departments of Paraguay between August 2019 and November 2020. To elucidate the risk factors for trypanosome infection, the relationship between trypanosome infection status detected by PCR and the location, sex, age, breed of horses, and season of sample collection was analyzed. There were no significant differences in trypanosome prevalence in horses between the eastern and western regions, ages, or breeds of horses in Paraguay. Sex and season were identified as risk factors for trypanosome infection in horses in Paraguay in the current study. These results suggest that the rainy-summer season, when vectors increase in number and their blood-sucking activity, could be the most important risk factor for trypanosome infection in Paraguay horses. Preventive measures and treatments should be developed to address these factors.