In order to estimate possible focus of resistance of bovine gastrointestinal helminths to ivermectin, levamisole phosphate and albendazole sulphoxide, 39 properties in the Santa Catarina Plateau were evaluated. In each location a mean number of 60 samples of feces was collected from animals between seven and 18 months of age, for the evaluation of the number of eggs per gram of feces (EPG), for culture and for larvae identification. Three groups with similar EPG mean were comprised, with the mean EPG being considered the group control. Animal from each group received a different subcutaneous treatment: a) 0.2mg kg-1 ivermectin, b) 5mg kg-1 levamisole phosphate, and c) 2.5mg kg-1 albendazole sulphoxide). The fecal evaluation, per group, was repeated seven days later. Resistance was considered when the efficacy of the drug was lesser than 95% and when the inferior limit of the confidence interval CI95% was lesser than 90%. From the properties examined, 82.1% presented animals with helminths resistant to ivermectin, 15.4% to levamisole phosphate, and 7.8% to albendazole sulphoxide. In only 10.3% of the properties the efficacy of all the anthelmintics was superior to 95%. Based on the generic diagnosis, through the larvae identification, Cooperia spp and Haemonchus spp were the prevailing resistant genus to ivermectin, Ostertagia spp, Cooperia spp and Trichostrongylus spp were associated with resistance to levamisole phosphate, and Cooperia spp. to albendazole sulphoxide.
Trichostrongylidae; albendazole sulphoxide; levamisole phosphate; ivermectin
