EFFECTS OF CHICKENS ON THE PREVALENCE OF INFESTATION AND POPULATION-DENSITY OF TRIATOMA-INFESTANS IN RURAL HOUSES OF NORTH-WEST ARGENTINA

Effects of the presence of chickens on population density of the bug T riatoma infestans, principal vector of Chagas disease, were investigat ed by standardized sampling (indoors and peridomestically) from sixty- eight houses of three rural communities in noah-west Argentina, during March 1992. The domiciliary density of T. infestans increased linearl y with the percentage of bugs that fed on chickens, as identified by a gar double-diffusion tests. Bug density was significantly higher in ho uses where hens usually nested indoors than in those where they did no t, as determined by concurrent direct observations and interviews of h ouseholders. Multiple linear regression analysis of domiciliary bug de nsity on (a) the total number of people, dogs and cats per house; (b) the percentage of domiciliary bugs that fed on chickens,or (c) the ind oor-brooding habit of hens, showed the two variables (b,c) related to chickens as significant predictors in each regression model. Inclusion both variables representing chickens increased the fit significantly. Addition of other potentially confounding factors (domestic insectici de use, type of roof and walls of house) did not affect the significan t variables retained in the best-fitting regression model. Peridomesti c infestation was positively associated with the household number of f owls. Chickens were the main bloodmeal source of peridomestic T.infest ans populations. Human-fed bugs were detected in peridomestic sites of sixteen houses, indicating active dispersal of adults and large nymph al instars from bedroom areas. Exclusion of hens from domiciliary area s and promotion of chicken sheds, of an appropriate design that would not harbour bug populations, should limit the triatomine population gr owth rate and reduce the risk of infestation.