April 2023

More than just allergies...

​A one-year old Spanish goat was submitted to the Oklahoma Animal Disease Diagnostic Lab for necropsy examination.  As an incidental finding during necropsy, the following (Video) was discovered in the right frontal sinus.

Video 1: Larva recovered at necropsy

Image 1: Posterior spiracles of recovered larva

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What's your diagnosis?

​Oestrus ovis, larva third stage (L3).  The nasal botfly, is a small fly ~ 1cm long with vestigial mouthparts. They are active during warmer hours of the day, depositing larvae (L1) in the nostril of sheep.  The L1 crawls onto the mucous membrane of the nasal passage remaining there for about 2 weeks, or in arrested stage during the winter. The larva then moves to the frontal sinuses where they reach the L3 stage.  After full development, the L3 larva crawl down into the nasal passages and is expelled by the sheep’s sneezing.
O. ovis larvae are not pathogenic, but heavy infestation can cause, nasal discharge, sneezing and partial blockage of the nasal passages.  Diagnosis is made by location of the larva on the host and morphology of spiracles. (Image 1)  Although these larvae are commonly called the sheep botfly, larvae have been also found in deer, goats, and cattle. There are also reports of horse, dog and human infestation.