INFLUENCE OF HUMANS AND DOMESTIC-ANIMALS ON THE HOUSEHOLD PREVALENCE OF TRYPANOSOMA-CRUZI IN TRIATOMA-INFESTANS POPULATIONS IN NORTHWEST ARGENTINA

In three rural villages of northwest Argentina, the overall proportion of domiciliary Triatoma infestans infected with Trypanosoma cruzi was 49% among 1,316 bugs individually examined for infection in March and October 1992). Most of the variation among individual households in t he proportion of infected triatomines was explained by variations amon g houses in the proportion of bugs that fed on dogs or cats, the preva lence of infected dogs or cats, and the proportion of bugs that fed on humans, according to a logistic multiple regression analysis. The eff ects of human infection rates on bug infection rates were not statisti cally significant. After adjusting for the effects of other predictors , the presence of chickens in bedroom areas had negative and significa nt effects on the proportion of infected Triatoma infestans, and posit ive and significant effects on the number of T, cruzi-infected triatom ines collected per person-hr per house. Dog or cat infection rates and the proportion of bugs that fed on dogs or cats and on chickens expla ined 80% of the total variance of infected-bug numbers in a linear mul tiple regression modal. This is the first study to use detailed field data to show that variations in triatomine infection rates depend on b ug host feeding patterns and dog or cat infection rates, while the pre sence of chickens in bedroom areas exerts opposite effects on the prop ortion and number of infected triatomines. Domestic animals play a cru cial role in the domiciliary transmission of T. cruzi.