LAUSR

BACKGROUND Anthelmintic resistance is commonly reported in horse populations in developed countries, but evidence in some working horse populations is either lacking or inconclusive. OBJECTIVES To estimate prevalence of GI nematode infections in working horses in Egypt and to evaluate strongyle resistance to ivermectin, doramectin and fenbendazole. STUDY DESIGN Cross-sectional study. METHODS Faecal egg count was performed on 644 working horses from 2 provinces in Egypt. A short questionnaire about horse signalment and worming history was completed for each horse. Horses identified with ≥50 strongyle type egg/g (n = 146) underwent faecal egg count reduction testing (FECRT) following treatment with ivermectin (n = 33), doramectin (n = 33) or fenbendazole (n = 30). Risk factors for strongyle (≥200 egg/g) and Parascaris equorum (>0 egg/g) infection were investigated using multivariable logistic regression analyses. RESULTS The prevalence of low (0-199 epg), medium (200-500 epg) and high (>500 epg) strongyle infection was 88.4%, 5.9% and 5.8%, respectively. P. equorum eggs were detected in 5.1% (n = 33) of horses. Strongyle FECR was 100%, 99.97% and 100% following treatment with ivermectin, doramectin and fenbendazole, respectively. Anthelmintic treatment in the 12 months preceding examination was associated with reduced likelihood of strongyle infection (odds ratio [OR] = 0.26, 95% confidence interval [CI] = 0.14, 0.47, P <0.001). The likelihood of P. equorum infection was significantly associated with horses' age (OR = 0.78, 95% CI = 0.69, 0.90; P <0.001). Male horses were more likely to have P. equorum infection (OR = 2.86, 95% CI = 1.37, 5.93, P = 0.005). MAIN LIMITATIONS Nonrandomised selection of study areas and larval cultures were unsuccessful for some samples CONCLUSIONS: There were low prevalence of strongyle and P. equorum infection and no evidence of macrocyclic lactones or benzimidazole resistance in strongyles in the studied working horse population.