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.
