Long-term effects of a nationwide control program on the seropositivity for Trypanosoma cruzi infection in young men from Argentina.
Unselected nationwide cohorts of Argentine men 18 years of age summoned for military service were tested for antibodies to Trypanosoma cruzi each year from 1981 to 1993. After an initial screening using indirect hemagglutination test, the positive sera were retested by titrated indirect hemagglutination and immunofluorescence antibody tests at 39 laboratories or at the national reference center in Buenos Aires. Nearly 1.8 million men were examined for T. cruzi antibodies using the same standardized procedures under a quality assurance program. The prevalence of seropositivity for T. cruzi decreased significantly from 5.8% in 1981 to 1.9% in 1993, but the decrease was not homogeneous among provinces within each region or constant over time. Prior to the nationwide control campaign initiated in 1961-1962, 15 provinces had high (> 20%) percentages of houses with domiciliary infestation by Triatoma infestans bugs, which decreased to nine provinces in 1982, and four provinces in 1992. The observed decrease in the prevalence of seropositivity for T. cruzi may be mostly attributed to the spraying with insecticides to eliminate the domiciliary populations of Triatoma infestans. The lack of a sustainable triatomine surveillance program set a limit to the decrease of seropositivity rates and prompted a revised strategy based on community participation.