Toxoplasma gondii infection in advanced HIV infection

To study Toxoplasma encephalitis (TE) in advanced HIV infection, including predictive factors, possible prophylactic regimens and impact on survival.

Epidemiological analysis of data collected prospectively during the Alpha study, a double-blind, randomized clinical trial, comparing two doses of dideoxyinosine in patients with advanced HIV disease.

First episode of TE occurred in 75 out of 499 patients participating in the trial.

Kaplan-Meier estimates and semi-parametric Cox's model were used.

A low CD4 cell count and a positive Toxoplasma serology were strongly predictive of the occurrence of TE. In patients with CD4 counts < 100 x 10(6)/l and a positive Toxoplasma serology at entry to the study, the 12-month TE incidence was 25.4%. Patients who were receiving at entry any of the following potentially antitoxoplasmic drugs: trimethoprim-sulphamethoxazole, pyrimethamine, dapsone, pyrimethamine-sulphadoxine or sulphadiazine, had a lower TE incidence than those who were not; 6.2 versus 18.8%, respectively (P < 0.001). The rate of survival 12 months after TE was 29.6%. Even after adjusting the major prognostic covariates, TE was predictive of death (P < 0.001; relative risk, 1.8).

The high HIV incidence, morbidity and mortality in high-prevalence areas suggests that primary prophylaxis should be given in patients at high risk for toxoplasmic reactivation.