Oestrus ovis in Sheep in Krishna District, Andhra Pradesh

Abstract

Oestrosis, caused by larvae of Oestrus ovis, is an obligatory myiasis of sheep and goats, identified as a significant problem in small ruminants globally. The present study is aimed to focus on gross lesions and phenotypic characterization of O. ovis larvae and adult flies in infested sheep. A total 123 sheep heads were inspected during routine slaughter or necropsy, for the presence of O. ovis larvae. Of these, 45 (36. 58%) sheep heads were found to harbour the larvae. The infestation rates with respect to breed was highest in non-descript sheep (45%) compared to Nellore Brown (40.27%) and Nellore Jodipi (22.58%), without any significant difference. Age-wise highest prevalence was recorded in older sheep (>1 year, 66.66%), than young ones (< 1 year, 30.39%) with significant difference (ꭓ2=9.877, P=0.002). Gender-wise, ewes showed highest prevalence (37.5%) compared to rams (36.44%) without any significant difference. Gross examination of infested sheep revealed copious nasal discharge, varying from serous to mucopurulent type with inflamed mucous membranes of naso-cranial sinuses. The larval instars (L2 and L3) and adult flies that developed from mature larvae were identified based on stigmal plates and morphological characteristics. In conclusion, oestrosis is common in sheep in Krishna district, Andhra Pradesh, indicating the need for regular surveillance to follow appropriate control strategies.