Epidemiology of and impact of insecticide spraying on vectorial Trypanosoma cruzi transmission in an area in the Bolivian Chaco

Abstract

Residual insecticide spraying has effectively eliminated vector borne transmission of Chagas disease in many areas in South America, while in others it has failed to interrupt or sustain interruption of transmission. We describe Chagas disease epidemiology in seven contiguous villages in the Bolivian Chaco and evaluate an insecticide spraying program using a catalytic model. Community members > 2 years of age were invited to participate in a serosurvey and epidemiologic risk factor analysis. Chagas seroprevalence was 19.6% in children ≤ 15 years, 87.1% in >15 year olds, and 51.7% in the overall population. Force of infection analysis did not conclusively demonstrate an interruption in transmission. Only village of residence, age (adjusted odds ratio [aOR] = 1.16; 95% confidence interval [CI] = 1.11-1.22) and cracks in the walls of sleeping structures (aOR = 2.16; CI = 1.09-4.27) were found to be associated with disease in multivariable analysis. Catalytic models may be useful for evaluating spraying programs when pre-existing incidence data are unavailable. Sealing cracks in walls may be an efficient way to mitigate disease transmission.