Reactivity of Horse Sera to Antigens Derived From -Like and .

and are protozoan parasites endemic to the Americas. The former is the major cause of equine protozoal myeloencephalitis, and the latter is associated with pulmonary sarcocystosis in birds. The opossum is the definitive host of these parasites in North America. Four species are found in Brazil, and in most reports in this country, species shed by opossums have been classified as -like. It is unknown whether reports on -seropositive horses in Brazil are also derived from exposure of horses to -like. The aim of this study was to test the sera reactivity of 409 horses in Brazil using antigens derived from a Brazilian strain of like (Sarco-BA1) and from a North American strain of (SN138). Samples were examined by immunofluorescent antibody tests (IFATs) at start dilutions of 1:20, and a selected number of samples was tested by Western blot (WB). Sera from 43/409 (10.5%) horses were reactive to -like and 70 of 409 (17.1%) were reactive to antigen; sera from 25 animals (6.1%) were positive for both parasites by IFAT. A poor agreement was observed between the two employed IFATs (κ = 0.364), indicating that horses were exposed to more than one species. Horse sera evaluated by WB consisted of four sera reactive to -like by IFAT, six sera positive to by IFAT, two sera that tested negative to both parasites by IFAT, and a negative control horse serum from New Zealand. Proteins in the range of 16 and 30 kDa were recognized by part of IFAT-positive sera using both antigen preparations. We concluded that Brazilian horses are exposed to distinct species that generate different serological responses in exposed animals. Antigens in the range of 16 and 30 kDa are probably homologous in the two parasites. Exposure of the tested horses to other species, such as , and , or cannot be excluded in the current study.