Sheep-pest
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Oestrus ovis
sheep bot fly, sheep nostril fly
Oestrus ovis is an obligate parasitic fly (Diptera: Oestridae) that develops exclusively within the nasal and sinus cavities of sheep and related ungulates. Females are larviparous, depositing live first-instar larvae directly into host nostrils during flight. Larvae develop through three instars within the host before exiting to pupate in soil. The species causes oestrosis, a condition marked by nasal discharge, respiratory distress, and reduced productivity in livestock. Human infestations, though uncommon, have been documented worldwide.