Clinical and epidemiologic studies of Chagas' disease in rural communities of Oaxaca, Mexico, and an eight-year followup: II. Chila.

In 1971 health workers drew blood samples from 238 people living in the rural Pacific coastal village of Chile in Oaxaca State Mexico to determine seroprevalence of antibodies against Trypanosoma cruzi--the parasite responsible for Chagas disease. Seroprevalence was 60 year olds. Overall seroprevalence for adults was 67%. By 1981 adult seroprevalence had fallen to 33% and childhood prevalence to 0.7%. The very low levels of T. cruzi antibodies in children corresponded with insecticide (DDT) spraying for malaria control and with the disappearance of triatomine bugs from Chile. Medical histories revealed that seropositive individuals were more likely to exhibit acute signs and symptoms of initial bite lesions (Romanas sign) furuncle like skin lesions (Chagoma) and facial or body edema (p<.05). They also tended to suffer from chronic fatigue and difficult breathing while lying down (p<.05). 1973 electrocardiogram (ECG) results showed that seropositive individuals were significantly more likely to have complete right bundle branch block (p<.005) and premature ventricular contractions (p<.05) than seronegative individuals. There were no seroconversions among 57 people examined with ECGs between 1971-1983. Even though more seropositives (21%) experienced a progression of ECG abnormalities (3% rate/year) than seronegatives (7%) the difference was not significant. Despite reductions in seroprevalence and in triatomine bug population serologic surveillance and monitoring to detect repopulation of houses by the bugs should be maintained.