Coprological prevalence and intensity of helminth infection in working horses in Lesotho.

This study aimed to (1) estimate infection prevalence of strongyle, Oxyuris equi and Parascaris equorum species and the intensity of infection with strongyles in working horses in lowland Lesotho and (2) investigate associations between infection and horse age, sex and owner-reported use of anthelmintics. In a cross-sectional survey, fresh faecal samples were obtained from 305 randomly selected horses and worm egg counts performed using a validated field laboratory kit. Details of anthelmintic use were collected using a standardised face-to-face owner questionnaire. Infection prevalence estimates for each species were calculated, as were infection intensity estimates for strongyle species. Logistic regression was used to investigate associations between exposure variables and infection status/intensity. Prevalence of strongyle infection was 88.2%; 11.8% of horses were not infected and infection intensity was low (1-500 eggs per gram (epg)) in 19.7%, medium (501-1,000 epg) in 19.7%) and high (>1,001 epg) in 48.8%. Decreasing strongyle infection intensity was associated with the use of proprietary equine anthelmintic products (OR 0.18, 95%CI 0.11-0.30, p<0.0001). Prevalence of O. equi infection was 6.2%; the odds of infection with this parasite decreased with increasing horse age (OR 0.84, 95%CI 0.72-0.97, p = 0.02). P. equorum infection prevalence was 21.6%; no statistically significant associations with the investigated exposure variables were found. In conclusion, strongyle infection is endemic in working horses in lowland Lesotho, but proprietary equine anthelmintics assist in managing infection. The apparent lack of age-acquired immunity to P. equorum infection may deserve further investigation. Although O. equi infection is less widespread, measures to protect younger animals may be appropriate.