The objective of the study was to evaluate the antiparasitic resistance against horse nematodes in the South of Rio Grande do Sul, Brazil. The results concerning the tests of anthelmintic efficacy on horses, stored in the database of the Parasitic Diseases Study Group (GEEP) - Veterinary Faculty, at the Federal University of Pelotas (UFPel), were carried out in the laboratory from 2018 to 2019. Stool samples were received from farms with breeding of adult female and male Criollo horses naturally infected, located in municipalities in the country’s southern region. The antiparasitic agents tested were Triclorfon + Fenbendazole, Closantel + Albendazole, Ivermectin + Praziquantel, Fenbendazole, Ivermectin, Doramectin, Mebendazole and Moxidectin. Techniques such as Gordon and Whitlock, Coproculture and Fecal Egg Count Reduction Test were performed. Of all the antiparasitic drugs tested, it was observed that only treatments with Ivermectin 2% showed desired values. The observed results indicate that resistance to macrocyclic lactones is usual in equine parasites in this Brazilian region, despite the results with isolated Ivermectin.

Resumo. O objetivo do estudo foi estimar a prevalência de nematódeos intestinais em equinos da região sul do Rio Grande do Sul, Brasil. Doze propriedades foram incluídas no estudo. Foram analisados 385 equinos, machos e fêmeas, com idade entre seis meses e 27 anos. As fazendas foram consideradas infectadas quando pelo menos um equino analisado foi positivo. A pesquisa parasitológica foi realizada por meio das técnicas de McMaster e Coprocultura. Ciatostomíneos foram encontrados em todas as propriedades e Strongylus vulgaris em apenas duas. A prevalência de nematódeos intestinais nos equinos foi: Ciatostomíneos (96,36%), Parascaris equorum (12,21%), Oxyuris equi (10,13%) e Strongyloides westeri (3,12%). O conhecimento acerca da prevalência dos nematódeos intestinais poderá contribuir para elaboração de programas de controle parasitário na região.

No abstract