Ocular Toxocariasis — United States, 2009–2010

Flora C. Lum, MD; H. Dunbar Hoskins Jr, MD; Ramana S. Moorthy, MD; Russell W. Read, MD; Michelle C. Starr; Susan P. Montgomery, DVM; Jeffrey L. Jones, MD; Dana M. Woodhall, MD


Morbidity and Mortality Weekly Report. 2011;60(22):734-736. 

In This Article

Abstract and Introduction


Ocular toxocariasis (OT) is caused by the zoonotic parasites Toxocara canis and Toxocara cati, roundworms of dogs and cats. Persons become infected with Toxocara when they unintentionally ingest embryonated eggs that have been shed in the feces of infected animals. Although OT is uncommon, it most often affects young children and can cause debilitating ophthalmologic disease, including blindness. Previous studies of OT in the United States have been conducted in single institutions.[1,2,3,4] This report describes the results of a web-based survey distributed to uveitis, retinal, and pediatric ophthalmology specialists nationwide to collect epidemiologic, demographic, and clinical information on patients with OT. A total of 68 patients were newly diagnosed with OT from September 2009 through September 2010. Among the 44 patients for whom demographic information was available, the median patient age was 8.5 years (range: 1–60 years), and 25 patients (57%) lived in the South at the time of diagnosis. Among 30 patients with reported clinical data, the most common symptom was vision loss, reported by 25 (83%) patients; of these, 17 (68%) suffered permanent vision loss. The results of this first national level survey demonstrate that OT transmission continues to occur in the United States, frequently affecting children and causing permanent vision loss in the majority of reported patients. Good hygiene practices, timely disposal of pet feces, and routine deworming of pets are strategies necessary to reduce OT in humans.

In collaboration with the American Academy of Ophthalmology (AAO), a web-based survey was distributed to currently practicing ophthalmologists belonging to the American Uveitis Society (AUS), the American Society of Retina Specialists (ASRS), or the American Association for Pediatric Ophthalmology and Strabismus (AAPOS). Each ophthalmologist reported how many patients with OT were examined from September 2009 through September 2010. An OT patient was defined as a person who had a new clinical diagnosis of OT based on ophthalmologic signs and symptoms. Ophthalmologists were asked to provide epidemiologic, demographic, clinical, diagnostic, and treatment data for each OT patient.

Of the 3,020 ophthalmology specialists surveyed, 599 (19%) responded; of these, 67% were pediatric ophthalmologists, 18% were retinal specialists, and 15% were uveitis specialists. OT patients were classified as newly diagnosed if first diagnosed with OT from September 2009 through September 2010. A total of 68 newly diagnosed OT patients were reported. OT patients lived in 23 different states, the District of Columbia, and Puerto Rico (Table 1). Twenty-five of 44 (57%) OT patients lived in the South, and 21 of 33 (64%) owned a pet (Table 2). Clinical data were reported for 30 OT patients. Vision loss was observed in 25 (83%) of these 30 OT patients, 17 (68%) of whom had permanent vision loss (Table 3). Three of the top five most commonly reported ophthalmologic signs (subretinal granulomatous mass/scar, posterior pole granuloma, and peripheral granuloma with traction bands) are indicative of permanent injury to the eye.[5] Fourteen of 20 (70%) OT patients who had serum enzyme-linked immunosorbent assay (ELISA) testing for antibody to the Toxocara parasite completed had a positive test result. Corticosteroid treatment was prescribed for 11 of 12 (92%) OT patients, whereas seven of 28 (25%) OT patients underwent ophthalmologic procedures, including pars plana vitrectomy, scleral buckling, and cataract surgery, in an attempt to improve their vision.


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