A Case and Review of Ophthalmomyiasis Caused by Oestrus ovis in the Central Valley of California, United States.

Ophthalmomyiasis externa is the infestation of external ocular structures most commonly by Oestrus ovis, sheep nasal bot fly, which have a pupal stage in soil. Farmers and shepherds are commonly affected but rarely in urban areas. This is the first case of Oestrus ovis ophthalmomyiasis externa in California since Catalina Island 1986. No livestock exposure was noted. Manure fertilizer sourced from grazing fields of natural hosts was used on a local urban sports field and is the suspected source.