Gastrointestinal parasite burdens and associated factors in free-ranging cattle in Buno Bedele Zone, Southwestern Ethiopia: a cross-sectional study

Gastrointestinal (GI) helminthiasis poses a persistent challenge to smallholder cattle production in free-ranging grazing systems. Designing targeted control strategies requires understanding how host and agroecological factors influence parasite distribution. This study aimed to determine the prevalence and egg-shedding intensity of GI helminth infections in free-ranging cattle across the Buno Bedele Zone, Southwestern Ethiopia. A cross-sectional study was conducted on 384 cattle across midland and lowland agroecological settings. Faecal samples were evaluated using flotation, sedimentation, and McMaster egg-counting techniques, with coproculture and Baermann recovery used to differentiate GI strongyle third-stage larvae (L3). Associations were examined using univariable analyses followed by multivariable generalized linear mixed-effects models (GLMMs), with body condition, age, sex, and altitude category as fixed effects and peasant association nested within district as random intercepts. The highest prevalence values were observed for GI strongyles (41.67%) and Fasciola spp. (19.53%). Coproculture revealed a strongyle larval profile dominated by Bunostomum spp. (28.42%), followed by Trichostrongylus spp. (21.62%). For GI strongyles, body condition and altitude interacted significantly (interaction aOR = 7.05, p < 0.001). Among midland cattle, those in poor body condition had higher odds of GI strongyle detection than those in good body condition (aOR = 8.40, 95% CI: 3.25–21.67, p < 0.001), but this was not observed among lowland cattle. For Fasciola spp., poor body condition (aOR = 3.58, 95% CI: 1.71–7.49) and midland altitude (aOR = 4.23, 95% CI: 2.32–7.69) were independently associated with higher odds of detection. Young and adult cattle had higher odds than calves (aOR = 4.02 and 5.50, respectively), while males had lower odds than females (aOR = 0.50, 95% CI: 0.29–0.87). Moniezia spp. showed low prevalence and no significant associations with the evaluated risk factors. Infection was strongly clustered within households (design effects 3.7 and 6.7); in household-clustered sensitivity analyses the Fasciola spp. associations were not retained. GI helminth infections were common among free-ranging cattle, with strongyles and Fasciola spp. predominating. The association between body condition and GI strongyle infection varied by agroecological setting, whereas body condition and midland setting were independently associated with Fasciola spp. detection. These findings support locally adapted parasite management and continued surveillance.