Análise genética de isolados do Haemonchus sp de ruminantes domésticos para identificação da resistência ao anti-helmíntico Benzimidazol

Abstract

The purpose of this study is to genetically characterize the resistance to benzimidazole (BZ) anthelmintic in Haemonchus sp helminths isolated from ruminants. With this purpose, thirty animals from herds of cattle, goats, sheep and buffalos, had stool samples collected and analyzed for the presence of trichostrongylus eggs. Properties were evaluated as for the history of using BZ to control nematodes. In herds of cattle and sheep, BZ has been used for over ten years whereas in herds of buffalos and goats, it has not been used for at least five years. Among the 120 animals tested, eighteen (~15%) had trichostrongylus eggs in their feces, with counts from 200 to 33000 eggs per gram of feces. The presence of Phe200Tyr mutation in the -tubulin gene, which confers a resistance to BZ was evaluated in all samples and its frequencies ranged from 0.074 to 0.476 (N= ~20 larvae/host). In order to identify the helminth which infected herds, nuclear DNA was sequenced at the ITS-2 region of eggs and larvae. In the herd of cattle, the main nematode was identified as Haemonchus placei and in the other herds, it was the Haemonchus contortus species. The study has shown the presence of resistant alleles in a high frequency among specimens of Haemonchus sp, particularly in properties which maintain a continuous selective pressure by using BZ. Resistance in isolates of ruminant livestock was identified through genotyping; 2 statistical tests were carried out and have not shown a significant difference among isolates of Haemonchus present in different animals from the same herd. However, significant differences were observed among herds. This study emphasizes the need to use molecular methods for monitoring the occurrence of anthelmintic resistance, encouraging the rational use of anti-parasitic drugs.