Gastrointestinal nematodes of goats and their anthelmintic resistance around Hawassa, Ethiopia

Gastrointestinal nematodes are seriously affecting the health of goats and negatively impacting their productivity and welfare. A cross-sectional study was conducted from December 2023 to September 2024 to estimate the prevalence of gastrointestinal (GI) nematode infection in goats. A field experiment was also conducted to assess the anthelmintic drug resistance status of goat GI nematodes in Hawassa. Fecal samples were collected from 750 goats selected using systematic random sampling. The fecal samples were examined using the flotation and McMaster egg counting techniques. The overall prevalence of GI nematode infection in goats was 46.5% (95% CI: 43.0-50.1). The multivariable logistic regression analysis showed that age and flock size affected (p < 0.05) infection of goats by GI nematodes. The number of eggs per gram of feces (EPG) ranged from 50 to 2300, and the overall mean EPG was 850 (95% CI: 778.1-991.9). Four hundred and fifty-eight third stage larvae were recovered from the culture of fecal samples, pooled from 349 goats positive for strongyle type eggs, for species identification. The nematode genera identified were Trichostrongylus (32.3%), Haemonchus (26.9%), Oesophagostomum (16.6%), Teladorsagia (12.5%), Strongyloides (6.8%) and Bunostomum (5.0%). The post-treatment fecal egg count reduction of the field anthelmintic resistance test for albendazole, tetramisole, and ivermectin were 69.7% (95% CL: 39.4- 84.8), 95.7% (95% CL: 90.2-98.1) and 80.3% (95% CL: 72.8-85.7), respectively revealing the presence of resistance for albendazole and ivermectin. Culture of pooled post-treatment fecal samples from each treatment group resulted in the recovery of Trichostrongylus spp. and Haemonchus spp. from albendazoletreated goats, and Trichostrongylus spp. and Teladorsagia spp. from ivermectin treated goats, suggesting the respective genera of GI nematodes that developed resistance to these commonly used anthelmintics. The results of the study indicated that it is time to think about developing effective strategies to slow and manage anthelmintic resistance development in Ethiopia and implement methods such as rotation of anthelmintic classes in large farms and village flocks to delay the development of resistance.