Study on utilization and efficacy of commonly used anthelmintics against gastrointestinal nematodes in naturally infected sheep in North Gondar, North-Western Ethiopia

Anthelmintic utilization and efficacy of commonly used anthelmintics against gastrointestinal nematodes in naturally infected sheep were assessed in North Gondar, North-Western Ethiopia. Anthelmintic utilization data were collected with a semi-structured questionnaire. An efficacy trial was conducted on 28 naturally infected sheep. The animals were randomly allocated into seven groups (four in each). Groups were treated with albendazole, ivermectin, tetramisole, levamisole, albendazole, ivermectin plus albendazole, albendazole plus levamisole, and a no-treatment control group. The faecal egg count reduction test (FECRT) was used to evaluate the efficacy of anthelmintics and identification of parasites was done by the faecal culture examination method. Data from the survey showed that different anthelmintics were used and some improper utilization was also recorded. Livestock owners had a tendency to deworm their animals throughout the year, but most commonly at the beginning of the rainy season. The highest FECRT (100%) was observed in animals receiving combined therapy, followed by albendazole (99.08%), ivermectin (96.69%), levamisole (90.06%) and the lowest reduction percentage was observed in the tetramisole group (89.51%). Parasite species surviving treatment were: albendazole, Trichuris; ivermectin, Trichuris and Haemonchus; levamisole and tetramisole, Trichuris, Haemonchus and Oesophagostomum. In summary, the different anthelmintics used in the study area did not have equal efficacy. Therefore, proper utilization and selection of anthelmintics are necessary for effective control of these parasites in Ethiopia. Key words: Anthelmintics, efficacy, gastrointestinal nematodes, sheep, Ethiopia.