Assessment of trichostrongyles resistance against anthelmintics commonly used in sheep reared in Dakahlia governorate, Egypt

Abstract

Objective: To investigate, for the first time, the anthelmintic resistance of different trichostrongyles infecting sheep in Dakahlia governorate, Egypt. Design: Randomized controlled study. Animals: 820 sheep reared within 10 freely grazing herds with infrequent deworming practices.Procedures: Fresh fecal samples were collected; their floats were examined for the trichostrongyle eggs, which were then identified employing the fecal cultures and/or ITS2-PCR amplifications. Sheep (n=500) whose samples had egg counts ≥ 150 eggs per gram (EPG) of feces were selected and divided in each herd into 5 equal groups; each group received one of the tested anthelmintics including albendazole (5 mg/kg BW), levamisole (7.5 mg/kg BW), ivermectin (0.2 mg/kg BW) and doramectin (0.2 mg/kg BW), whereas the fifth group were kept untreated. The EPGs were detected for all groups at the time of treatment and weekly for 10 times post-treatment. Fecal egg counts reduction percentage (FECR%) and egg reappearance periods (ERP) were estimated.Results: The examined herds were mostly infected with Haemonchus contortus; however, few larvae of Trichostrongylus species were detected in fecal cultures of 2 herds. In the untreated groups, the EPGs increased gradually over the time of the experiment; however, no eggs were detected in samples of all treated groups 7 days post treatment resulting in 100% FECR. The macrocyclic lactones (ivermectin and doramectin) displayed longer ERPs than the benzimidazoles (levamisole and albendazole). Conclusion: No anthelmintic resistance was noticed in trichostrongyles-infected sheep population from Dakahlia governorate, Egypt, and the use of ivermectin to treat the trichostrongyles-infected sheep is recommended.