The sheep nasal bot fly lays eggs in the nostrils. Animals may attempt to avoid flies by running with their head down and nosing into corners. The larvae crawl into the nose where irritation causes sneezing and mucopurulent discharge from the nostrils. Debilitating secondary bacterial infections may occur.
Infection is very common in Australian sheep and goats.
Wandering maggot-like larvae up to 20mm long may be an incidental finding at necropsy when the nasopharynx is exposed during longitudinal craniotomy for brain examination.
Ivermectin is one of a number of anthelmintics highly effective at killing larvae.
Prevention is usually achieved incidentally with helminth control programs using macrocyclic lactones.