Resistência á ivermectina em ovinos

Abstract

One of the limiting factors for meat sheep farming is gastrointestinal parasites. This occurs due to the direct damage imposed by parasites on animals, but also to increasing reports of resistance to antiparasitic drugs. Therefore, it is essential for rural producers to monitor the effectiveness of the drug, as well as seek alternative therapeutic tools. In herds whose resistance to all available drugs has already been detected, an alternative is to evaluate whether any of the drugs used at a higher dose would still be effective. The present work aimed to evaluate the post-treatment efficacy with ivermectin used at a dose of 630 mcg/kg, in sheep from a herd in the Uberlândia region, Minas Gerais, where there is already a report of multiple resistance to antiparasitic drugs. For this, 20 Santa Ines x Dorper crossbreed sheep were divided into two experimental groups. One of them received ivermectin, subcutaneously, at a dose of 630 mcg/kg, and the other remained as an untreated control. Fecal samples were collected to determine the number of strongyle eggs per gram (OPG) on the day of treatment (day zero), and also 7 and 14 days later. The mean OPG and efficacy reduction values ​​were -163 and -155, respectively, for day 7; 38.4 and 44.6% for day 14. These numbers indicate that the active ingredient remains completely ineffective, even when applied three times above the therapeutic dose described for the sheep species.