[Prevention of Recurrence of Ocular Toxoplasmosis - When? How? For Whom?]

Ocular toxoplasmosis (OT) leads to permanent visual disturbances in a high proportion of patients. A combination of antibiotics and corticosteroids may reduce the risk of permanent visual impairment and may delay recurrence. In this overview, we summarise the current state of knowledge regarding the recurrence prophylaxis of OT.

The basis of this review is a literature search in PubMed with the key words (MeSH terms) "human ocular toxoplasmosis" or "retinochoroiditis" and "recurrence" and "prophylaxis" or "prevention". The resulting publications included case series with more than 20 patients, prospective clinical studies and meta-analyses published within the last 25 years, as well as other publications mentioned therein, and was evaluated on the basis of the experience of the authors.

The frequency of recurrences does not differ between Latin America, North America and Europe, and is around 12 - 15% in the first two years and then decreases, with recurrences observed up to 49 years after an active infection. According to two placebo-controlled double-blind studies from Brazil, where particularly serious relapses occur, antibiotic prophylaxis with 160 mg trimethoprim combined with 800 mg sulfamethoxazole three times a week for 12 months can reduce the occurrence of relapses from 22 to 3% for up to three years. After that, the likelihood of recurrence is as high as in patients who have never received prophylaxis.

Relapses can be effectively prevented, if this is medically indicated. Among other considerations are central location of the lesion, insufficient immune competence and frequent relapses. Prophylaxis should be carried out for at least 12 months, since the risk of recurrence is highest in the first two years.