RELACIÓN ENTRE INFECCIONES ASINTOMÁTICAS CON Anaplasma marginale, Babesia spp. y Trypanosoma vivax EN TOROS Y NIVELES DE TESTOSTERONA Relationship between asymptomatic infections with Anaplasma marginale, Babesia spp. and Trypanosoma vivax in bulls and testosterone levels

Some bovine hemotropic infections are associated with decreased reproductive potential in bulls, but the underlying mechanisms involved are poorly understood. The main objective of this transversal study was to determine Anaplasma marginale, Babesia spp., and Trypanosoma vivax infections in asymptomatic bulls (n=85) of various breeds and ages, and to compare serum average testosterone levels in infected and non-infected animals. The highest prevalence by Polymerase Chain Reaction (PCR) was 46% for A. marginale, 34% for Babesia spp. and 60% for T. vivax. The greatest percentages of bulls infected with A. marginale and Babesia spp. were found in the Holstein breed (75.0 and 66.7%, respectively), and the lowest in the Carora breed (35.7 and 14.2%, respectively) with values of P<0.001. The percentage of bulls infected with T. vivax was higher in the Holstein, Carora and Mixed Breeds (75.0, 71.4 and 76.5%) as compared to the Brahman breed (38.1%). The highest percentages of infection with A. marginale and Babesia spp. were found in animals 10- 19 months old and less than 29 months old, respectively, while the highest percentage of infection with T. vivax was observed in 40-49 months old animals. These results show the importance of the breed and age in the selection of individuals for studies of prevalence, treatment and epidemiological control. Hematocrit values were statistically lower in animals infected with A. marginale as compared to the non-infected group (P<0.02). Bulls infected with T. vivax presented lower levels of serum testosterone, while bulls either infected with A. marginale or Babesia spp. or non- infected, showed no differences in this hormone. The decrease in testosterone levels in bulls appears to correlate with T. vivax chronic infection, suggesting a link between the presence of this pathogen and hormonal levels.