13th February 2025

Parasitic causes of uveitis

Toxoplasmosis

The causative organism is Toxoplasma gondii. Cats are the definitive host so contamination from cat litter into food is the most common route of infection. Infection may be congenital after maternal exposure, or acquired. Toxoplasmosis causes a posterior uveitis. Serology for Toxoplasma may be carried out to aid diagnosis.

Toxocariasis

Toxocariasis is an infestation by a common roundworm found in dogs, so may be transmitted by contaminated soil or food. Usually, it is unilateral. Variable findings include chronic endophthalmitis and a posterior pole or peripheral granuloma seen during fundoscopy. Red reflex may be reduced in the affected eye.

Onchocerciasis (river blindness)

Caused by the helminth Onchocerca volvulus. Systemic features are mostly an intensely itchy maculopapular rash and ‘leopard skin’, which describes hypo-and hyperpigmentation mostly affecting the shins. Anterior uveitis may be an early feature, and it may be possible to visualise live microfilariae in the anterior chamber if the patient is face down prior to examination. Treatment is most commonly with ivermectin, which targets larvae.