A prospective study of seroprevalence of Toxoplasmosis in general population, and in HIV/AIDS patients in Bombay, India.

Two hundred and seventy nine sera (age group 13-50 years) were tested for antitoxoplasma IgG/IgM antibodies by ELISA techniques; the diagnostic titer for positive test is 10 iu/ml or > 1:100. Sera were obtained from (i) 165 (100 men/65 women) healthy adult voluntary blood donors (HIV, HBsAg, VDRL negative); (ii) 89 consecutive HIV/AIDS patients (82 men/7 women); and (iii) 25 patients (HIV negative: 12 men/13 women) treated for cerebral Tuberculoma or Neurocysticercosis during this study from January 1996-June 1997. The overall seroprevalence was 30.9% (51/165) in the immunocompetent adult (group i) 34% (34/100) men and 26.2% (17/65) in women [range: 10-899 iu/ml; (mean: 376.8)]. In HIV infected hosts the seroprevalence [range: 21-340 iu/ml; (mean; 180)] was 67.8% (56/82 men, 04/07 women). The seroprevalence was 20.5% (8/39), 32.8% (22/67), 34.8% (16/46) and 38.4% (5/13) in the 2nd, 3rd, 4th and 5th decades respectively in healthy adults. In HIV/AIDS patients, 69% (29/42) in the 3rd and 70.6% (24/34) in 4th decade were seropositive. The risk of cerebral Toxoplasmosis (encephalitis-02, granuloma-24) was 43.3% (26/60, mean 250 iu/ml). The seroprevalence was 28% in group iii (range 12-80 iu/ml, mean 21 iu/ml). Anti-toxo IgM was negative in all. Primary Toxoplasma infection appears to be subclinical and prevalent throughout life. T. gondii has emerged as an important opportunistic infection in HIV/AIDS patients in Bombay. Recrudescence of cerebral toxoplasmosis (CTOX) is observed with low IgG response during mid-late stage of the disease, as seen in our patients (mean IgG 250 iu/ml, CD4+ = 283/cmm (range 43-504 in 5 patients). Primary prophylaxis for CTOX seems rationale and can be targeted to asymptomatic HIV/AIDS population at risk who are seropositive for T. gondii (mean IgG 111.5 iu/ml in our study). The very high predictive value of a negative test for TOX remains the best serological parameter for excluding acute episode of TOX.