A Multihousehold Study Reveals a Positive Correlation between Age, Severity of Ocular Toxoplasmosis, and Levels of Glycoinositolphospholipid-Specific Immunoglobulin A

A cross-sectional household study involving 499 individuals was undertaken in an area of Minas Gerais state, Brazil, where infection with Toxoplasma gondii is endemic. Nearly 50% (n = 247) of the sample had T. gondii-specific antibodies, even individuals in the 5 –9-year-old age group. Approximately 12.5% (n = 28) of a random subsample of participants who were positive for T. gondii antibodies had ocular lesions associated with T gondii infection. The frequency of ocular toxoplasmosis increased significantly with age, with ∼50% of individuals >60 years of age having lesions. The size of the ocular lesion correlated positively (r = 0.85; Ρ = .01) with the serum level of immunoglobulin A specific for tachyzoite-derived glycoinositolphospholipids. We found that sharing the same residence accounted for 30% of the variation in infectivity among residents in the sample, whereas age was the main risk factor for development of ocular toxoplasmosis in patients who were positive for T. gondii antibodies.