A THESIS SUBMITTED TO THE DEPARTMENT OF ANIMAL SCIENCE, COLLEGE OF AGRICULTURE, SCHOOL OF GRADUATE STUDIES, ARBA MINCH UNIVERSITY

Abstract

Goats are a crucial livestock resource for smallholder communities, providing significant livelihood support. However, abomasal nematode parasites in these animals are a major contributor to health problems and productivity losses. This study identified and quantified abomasal nematodes in slaughtered goats, assessed drug usage practices and evaluated anthelmintic resistance in Arba Minch Zuriya district. A cross-sectional and laboratory based experimental study designs were used to collect data from October 2023 to August 2024 through structured questionnaires, postmortem worm recovery techniques, and in-vitro drug resistance assays. Accordingly, of 120 examined goat abomasums, 108 (90%) harbored at least one nematode species. Haemonchus contortus, Teladorsagia circumcincta, and Trichostrongylus axei were the worm species identified as sole (21%) or mixed infections (79%). The mean burden of Haemonchus contortus (757.5) was significantly higher than that of Teladorsagia circumcincta (415.8) and Trichostrongylus axei (363.3) (p<0.05). Animals' sex, age, and body condition significantly influenced the mean burden of abomasal nematode infection (p<0.001). The survey results reveal the majority of respondents (80%) used albendazole bolus to control parasitism in goats. In vitro assays on Haemonchus contortus showed that this drug significantly (p<0.05) inhibited egg hatching in a dose-dependent manner, with a maximum rate of 97.9% at 60 µg/µl. The minimum concentration of albendazole that inhibits 50% of egg hatching and embryonation (IC50) was 0.0096 µg/µl. Additionally, there was a statistically significant (p<0.05) dose-dependent inhibition of H. contortus larval motility observed for ivermectin, with predicted IC50 of 0.257 µg/µl. Moreover, the inhibition of larvae motility by the tetramisole hydrochloride did not significantly vary among different concentrations, with an expected IC50 value of 0.00068 µg/µl. In conclusion, the high burden of H. contortus in the abomasum of slaughtered goats indicates its endemic nature in the area. The higher IC50 value for ivermectin suggests a risk of ivermectin resistance in the study area. Therefore, caprine haemonchosis, teladorsagiosis and trichostrongylosis should be considered during clinical procedures and combining antihelminthic treatments, creating farmer awareness, and rotating anthelmintic drugs can help reduce the risk of ivermectin resistance.