Antibodies Against Sarcocystis neurona, Neospora spp., and Toxoplasma gondii in Horses and Mules From the Northern Pantanal Wetland of Brazil

The present study evaluated the prevalence of antibodies against Sarcocystis neurona, Neospora spp., and Toxoplasma gondii in 547 equids (500 horses and 47 mules) from 25 ranches in the Brazilian Pantanal wetlands. The indirect fluorescent antibody test (IFAT) using the appropriate parasite antigens was used as a screening test, and all positive samples for Sarcocystis spp. and Neospora spp. were subsequently evaluated by the rSnSAG2/4/3 and rNhp29 enzyme-linked immunosorbent assays (ELISAs) for S. neurona and Neospora hughesi, respectively. According to the IFAT, 112 of 547 (20.4%) samples were positive for Sarcocystis spp., 65 (11.8%) were positive for Neospora spp., and 138 (25.2%) for T. gondii. In the follow-up analyses, 33 of 112 Sarcocystis spp. IFAT-positive samples were positive by rSnSAG2/4/3 ELISA, and 5 of 65 Neospora spp. IFAT-positive samples were rNhp29 ELISA positive. Western blot (WB) analysis of a subset of samples confirmed the Sarcocystis rSnSAG2/4/3 ELISA results. In contrast, WB analysis using Neospora antigen did not confirm the rNhp29 ELISA results, and further revealed that only two samples were true positives. Interestingly, the two samples seroreacted against immunodominant antigens of N. hughesi but showed stronger reaction to the same antigens of Neospora caninum in the WB. Our results demonstrate that equids from the Brazilian Pantanal wetlands have antibodies to S. neurona and T. gondii, but antibodies to Neospora spp. are uncommon in these animals.