Reconsidering the pathogenesis of ocular toxoplasmosis

PURPOSE: To review recent observations regarding the sources of Toxoplasma gondii infection and rates of ocular involvement in cases of infection acquired after birth, and to reconcile them with older observations and widely held beliefs about the pathogenesis of ocular toxoplasmosis. METHOD: A review of pertinent reports from the medical literature. RESULTS: There are several potential sources and routes of infection, including inhalation of spores and ingestion of contaminated drinking water, that were previously unrecognized. Ocular involvement in cases of acquired infection appears to be more common than heretofore believed. A variety of host and parasitic factors may influence rates of ocular infection and the characteristics of ocular disease. CONCLUSIONS: The scars from which recurrent toxoplasmic retinochoroiditis arise may be the result of remote, acquired infections in many cases, rather than the residua of congenital infections, as commonly assumed. A better understanding of the epidemiology of T. gondii infection, as well as the host and parasitic factors that influence disease presentation, is important for developing strategies for prevention and management of ocular toxoplasmosis.