A CLINICAL-PARASITOLOGICAL MONOTHERAPY CURE IN THE TREATMENT OF EXPERIMENTAL-INFECTION BY A HIGHLY VIRULENT-STRAIN OF TOXOPLASMA-GONDII

Toxoplasmic encephalitis in patients with the acquired immunodeficienc y syndrome (AIDS) is treated classically with pyrimethamine plus sulfa diazine. Unfortunately: up to 40% of these patients are unable to comp lete the course of therapy because of adverse reactions to sulfonamide s. This study considers the possible usefulness of monotherapies in th e treatment of acute toxoplasmosis, producing parasitological cures 2- 3 months after the date of infection. With this therapy, the main adve rse effects are suppressed. Groups of mice infected with the RH strain of Toxoplasma gondii were treated with pyrimethamine alone, sulfadiaz ine alone, and pyrimethamine plus sulfadiazine for 7 d. Treatment with pyrimethamine plus sulfadiazine produced clinical cures in 100% of th e infected mice 1 month after infection. Treatment with pyrimethamine gave a 60% survival rate (clinical cure) at 1 month postinfection. Fin ally, treatment with sulfadiazine produced a 60 % survival rate at 1 m onth postinfection. Although the antitoxoplasmic regimen with pyrimeth amine plus sulfadiazine has proven to be effective in intensive treatm ent of toxoplasmic encephalitis, relapses occur in more than 80% of ca ses after cessation of antitoxoplasmic therapy, making secondary proph ylaxis mandatory. In this study the efficacy of treatment was also eva luated in terms of parasitological cure. None of the three therapies s howed parasitological cure after 1 month of treatment. When the interv als were extended to a 3-month observation, monotherapy with pyrimetha mine and sulfadiazine alone produced a parasitological cure.