• Written By: Ira G. Wong, MD

    This Swiss study is based on questionnaires returned and correctly completed by 63 of 139 patients with ocular toxoplasmosis (OT). Results of the survey, supplemented by chart review, indicated that patients younger than 21 years had a higher risk of TO recurrence than patients age 21 and older.

    The infection recurred in 66% of the younger survey respondents compared to 39% of the older ones. The proportion of patients who developed a recurrence remained at between 54% and 63%, regardless of the number of episodes, and the interval between episodes was between 1.0 to 1.7 years for the first three recurrences. However, the time between episodes decreased as the total number of recurrences increased.

    The authors noted that there was some selection bias in the study, since less than half of the study group correctly completed the survey. Additionally, the survey relied heavily on patient recall.

    Ocular toxoplasmosis in immunocompetent patients is much less common in the United States than in Europe and Brazil. The higher occurrence rate in some countries may be related to the ingestion of uncooked foods, genetic factors, and the presence of different strains of the Toxoplasma gondii. Ocular toxoplasmosis recurrence is seen in the U.S. population, particularly in young and middle-aged groups, but not as frequently as reported in this study.