Prevalence of Toxoplasma antibodies in Chiang Mai population.

Five hundred sera from blood donors were examined for antibodies to Toxoplasma by the indirect hemagglutination antibody (IHA) and the indirect fluorescent antibody (IFA) techniques. In addition, the IHA test was used to detect Toxoplasma antibodies in 500 pregnant women's sera. It was found that 4.6% of the blood donors were positive by the IHA and only 1.2% by the IFA methods. The seroprevalence, however, was less in pregnant women as only 2.8% were positive. Interestingly, 7.5% of the blood donors and 15.2% of pregnant women showed no detectable antibodies. The frequency distribution curves of IHA titers were unimodal in both groups studied. From the basis of these findings, it was concluded that there was a low degree of Toxoplasma transmission in Chiang Mai.