Toxoplasmosis is the most common retinal infection in the United States, and it can lead to severe visual impairment. It is generally believed that individuals remain infected with Toxoplasma gondii for life with intracellular cysts forming in the muscles, brain, and other organs. T. gondii IgG antibodies are also thought to remain for life. In 2003, Holland1 estimated the burden of ocular toxoplasmic eye lesions in the United States based on data from the third National Health and Nutrition Examination Survey (NHANES III), conducted in 1988–1994, and the 2000 census.1,2 We now present an update of the ocular toxoplasmosis burden based on more recent NHANES and U.S. population data.
For the burden calculations, we used (1) T. gondii antibody seroprevalence data from the NHANES 1999–20043 to determine T. gondii infection rates, (2) 2009 U.S. Census estimates,4 (3) calculations of the proportion of persons with T. gondii infection who have ocular lesions from estimates by Holland,1,2,5 and (4) the prevalence of symptomatic ocular disease from a large waterborne outbreak of toxoplasmosis in Canada6 to estimate the rate of symptomatic disease in infected persons. We also provided ranges for the estimate of symptomatic ocular toxoplasmosis (Table 1).
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