Infection follows ingestion of Toxocara canis, most commonly found in the stools of puppies. Uveitis is rarely observed in generalized visceral larva migrans but typically occurs after only a minimal systemic infection with a few larvae. Laboratory testing should include titers for antitoxocara antibodies, both IgG and IgM. Treatment is limited to local and systemic corticosteroids. Anthelmintic drugs are not recommended. Birdshot chorioretinopathy is a chronic bilateral, intermediate, and posterior uveitis of unknown etiology, primarily affecting patients in their 5th to 7th decades of life.
Women tend to be affected more often than men.
Typical symptoms are floaters and decreased vision. Characteristic signs include moderate to severe vitritis and multiple areas of choroiditis in a distinctive radial or streaklike pattern. Cystoid macular edema is a common vision-lowering complication. Periocular and systemic corticosteroids often improve vision, although recurrences and resistance to these therapies are common. The presumed ocular histoplasmosis syndrome occurs mostly in patients coming from the Ohio, Missouri, and Mississippi river valley, a region endemic for histoplasmosis.