Children at high risk of vision loss through parasitic infection from pets

June 24, 2011

A first national survey of ophthalmology specialists reveals that transmission of ocular toxocariasis (OT) continues to place children at risk of debilitating ophthalmologic disease, including permanent vision loss, from unintentional ingestion of zoonotic parasites shed by dogs and cats.

A first national survey of ophthalmology specialists reveals that transmission of ocular toxocariasis (OT) continues to place children at risk of debilitating ophthalmologic disease, including permanent vision loss, from unintentional ingestion of zoonotic parasites shed by dogs and cats.

Ocular toxocariasis is caused by Toxocara canis and Toxocara cati roundworms from dogs and cats that most commonly infect humans through contact with feces-contaminated soil. Children are especially at risk through exposure to contaminated playgrounds and sandboxes.

Some 599 ophthalmologists participated in a Web-based survey intended to gather clinical, demographic, and epidemiologic information on patients with OT. Ophthalmologists reported 68 newly diagnosed patients from September 2009 through September 2010.

Of the 44 patients with available demographic information, the median age at diagnosis was 8.5 years. Twenty-five (57%) patients lived in the South; the highest number of cases occurred in Georgia, Florida, California, and Texas.

Among the 30 patients with available clinical data, the most frequently reported symptom was vision loss (83%), with 68% experiencing permanent vision loss. The most commonly reported signs included subretinal granulomatous mass/scar, vitritis, posterior pole granuloma, and peripheral granuloma with traction bands.

Twenty patients underwent testing for antibody to the Toxocara parasite; 14 (70%) tested positive. Thirty-three patients owned a pet (primarily dogs and/or cats).

The report published by the Centers for Disease Control and Prevention also notes that good hygiene practices such as hand washing after contact with pets, timely disposal of pet feces, and routine deworming of family dogs and cats are strategies that can reduce OT infection and lower the risk of associated vision loss in children.

Centers for Disease Control and Prevention (CDC). Ocular toxocariasis-United States, 2009-2010. MMWR Morb Mortal Wkly Rep. 2011;60(22):734-736.