Oestrus ovis infection in Niger: prevalence survey and closantel treatment

Abstract

A prevalence survey was performed between January and December 1996 at Niamey slaughterhouse (Niger). Of the 95 sheep heads examined 63 (66.3%) were infected with Oestrus ovis. From March to June, in the height of the hot and dry season, the infection rate was 20-50% with less than two larvae per head. From July to February, during and after the rainy season, the infection rate was 70-100% with up to 23 larvae per head in October at the end of the rainy season. There was no evidence of larval hypobiosis although parasite development stopped in March-June, during the hot and dry season, when very few residual larvae 2 (L2) were recovered. In a trial carried out in a traditional sheep flock, closantel was administered orally twice, at two-months’ interval, during the infestation period. Two groups of 49 sheep were treated with drench formulations. The control group was drenched with mebendazole only, and the treated group with a combination of closantel and mebendazole. Weight gain and especially improvement in the clinical condition of the closantel-treated group were significantly different from those of the control group (single anthelmintic treatment). The economic advantages of this approach are discussed.