Parasite control practices and anthelmintic efficacy field study on gastrointestinal nematode infections of Horro sheep in Western Oromiya, Ethiopia

Gastrointestinal nematodes are one of the rampant parasitic diseases constraining sheep farming in western Oromiya. A study aimed at assessing parasite control practices in use and to determine the efficacy of three brands of anthelmintics commonly used on the farms was conducted. Questionnaire survey and faecal egg count reduction tests (FECRT) were used to collect data. Majority of respondents (95.3%) indicated that anthelmintic treatment was the only method used to manage nematode infections in sheep. Many farmers (60.0%) followed prescription orders to determine dosage while others (40.0%) were reliant on visual appraisals. In most responses (38.7%) two treatments were given per year and more deworming can be done directed to animals exhibiting general syndromes such as emaciation, diarrhea and loss of production. Most of the treatments (49.3%) were performed on the farms by the owners. Efficacy tests showed a suspected resistance against albendazole by Haemonchus contortus and Trichostrongylus spp. whereas tetraclozan and ivermectin demonstrated high efficacy against all nematode genera isolated on the farms. Some worm control practices which are thought to enhance selection of resistant strains have been evident. These involved mainly risk of underdosing and continued use of one class of anthelmintics, irrespective of its efficacy status, which may accelerate selection dynamics. To preserve the efficacy of anthelmintics, targeted selective treatments traditionally practiced by farmers should be encouraged and supported by laboratory tests to identify animals in need of treatments. Anthelmintic efficacy evaluations should be part of the control strategies to monitor treatment failures in the study areas. Key words: Gastrointestinal nematode, parasite control, anthelmintic efficacy, questionnaire, horro sheep, Ethiopia.