A follow-up study of Toxoplasma gondii infection in southern Brazil

To understand better the natural history of ocular toxoplasmosis by reexamining a well-characterized population in Southern Brazil.

Ophthalmological examination and serologic tests for Toxoplasma gondii infection were performed in 1997 on 383 individuals who had undergone the same evaluation in 1990.

Of 109 seronegative subjects in 1990, 21 (19.3%) became seropositive by 1997, and 2 (1.5% of previously seronegative patients; 9.5% of those known to have seroconverted) developed ocular toxoplasmosis. Seroconversion occurred more frequently in individuals under 17 years of age (16 of 46 patients, 34.8%) than in those greater than 17 years of age (5 of 63 patients, 7.9%; p = 0.002). Of 131 seropositive individuals who did not have ocular lesions in 1990, 11 (8.3%) had typical toxoplasmic lesions in 1997. Of the 13 individuals with non-specific hyperpigmented small retinal lesions in 1990, 3 (23%) presented with typical lesions in 1997.

Acquired T. gondii infection can result in late development of ocular lesions. Small, non-specific hyperpigmented retinal lesions may represent sites of T. gondii infection in seropositive individuals.