Risk factors for toxoplasmic encephalitis in HIV-infected patients: a case-control study in Brazil

A case-control study to identify the risk factors for toxoplasmic encephalitis (TE) among HIV-infected patients with latent Toxoplasma gondii infection was performed in a teaching hospital in south-eastern Brazil. Although the subjects were all positive for serum IgG antibodies to Toxoplasma, some (the cases) developed TE during routine follow-up at the hospital whereas others (the controls) did not. Adjusted odds ratios (aOR) were estimated by multiple logistic regression after controlling for potential confounders. Only 46 (22%) of the 210 cases but 93 (45%) of the 205 controls were on prophylactic regimens with co-trimoxazole [aOR = 0.30; 95% confidence interval (CI) = 0.15-0.60]. Subjects with fewer than 100 (aOR = 37.09; CI =7.49-183.67) or between 100 and 200 CD4 cells/microl (aOR = 10.20; CI =2.00-51.90) were at substantially increased risk of developing TE than those with >400 CD4 cells/microl. Although the results of preliminary, unadjusted data analysis indicated that male sex and homosexual or bisexual activity might be additional risk factors, these associations were not found to be statistically significant by multiple regression analysis. In conclusion, no risk factors for TE other than low CD4 cell counts and failure to receive prophylaxis were found among HIV-infected Brazilian patients with past exposure to Toxoplasma. Seropositive patients with CD4 cell counts above 100/microl (the point at which specific prophylaxis is usually recommended) but below 200/microl might also benefit from effective anti-TE prophylaxis.