Serological and molecular detection of Theileria equi in horses from Sinop, Mato Grosso state, Brazil
Equine piroplasmosis is the most important tick-borne disease to affect horses in Brazil. Theileria equi is one of the causative agents of equine piroplasmosis. Chronic cases are expected, in which the animals show no apparent signs of infection and remain asymptomatic but constitute a source of the infectious agent that ticks can spread. This study was conducted across 81 ranches located in the municipality of Sinop, State of Mato Grosso, Brazil. A sample calculation was performed to estimate the apparent prevalence of T. equi among horses. A total of 1,853 animals were included in the sampling analysis based on the information available from the Institute of Agricultural and Livestock Defense of Mato Grosso State. The serological analysis of 367 serum samples using an indirect enzyme-linked immunosorbent assay (ELISA) to detect anti-T. equi antibodies revealed that 337 animals were positive, representing a frequency of 90.70%. The molecular analysis designed to amplify the EMA-1 gene, which T. equi harbors, showed positivity in 20 of 89 tested samples. The fragments of four samples were sequenced and analyzed to determine their similarities to sequences from other species, based on sequences deposited at GenBank, and all showed 100% similarity with T. equi. Our study represents the first report of T. equi antibodies among the equids in northwestern Mato Grosso, revealing the widespread distribution of seropositive animals.