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

ABSTRACT

PIP: 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 5% in 16 year old children, but increased from 41% to 62% to a peak of 78% for 16-19, 20-29, and 30-39 year olds respectively then fell to 68% for 40-49 year olds only to climb again to 75% in 50-59 year olds and fell again to 47% for =or 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 (Romana's 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.