Human infection and risk of transmission of Chagas disease in Hidalgo State, Mexico.

New zones with risk of infection for Chagas disease were reported in San Antonio Tezoquipan, Caltimacan, and El Ahorcado in the Hidalgo State of Mexico. Antibodies to Trypanosoma cruzi were detected by enzyme-linked immunosorbent assay and indirect hemagglutination assay in human serum samples. Study subjects were also given an electrocardiogram. Trypanosoma cruzi was isolated from triatomines collected and its virulence was determined in BALB/c mice. Seropositive persons were found in the three regions studied and seroprevalence of T. cruzi ranged between 3.25% and 5.13%. Six of eight seropositive persons had cardiac alterations. The species of triatomines detected were Triatoma barberi, Triatoma mexicana, and Triatoma dimidiata, and at least one of each species was infected with T. cruzi. Entomologic indexes from the zones were determined, and El Ahorcado showed the greatest risk of infection. In this region, we found more virulent isolates of T. cruzi in Triatoma barberi, and the highest human seroprevalence for T. cruzi.