Chagas disease in north-west Argentina: risk of domestic reinfestation by Triatoma infestans after a single community-wide application of deltamethrin

Abstract

The risk of domestic reinfestation by Triatoma infestans after a single community-wide application of delta-methrin (2.5% suspension concentrate at 25 mg active ingredient/m2) was studied in Amamá, north-west Argentina, where no insecticide spraying had been done by official control services. The percentage of infested houses fell from 88% before spraying in 1985 to nil during the 6 months after spraying, and thereafter increased from 5% in 1986 to 96% before a second treatment in 1992, fitting closely to a logistic model (r2 = 0.997). Significant risk factors associated with domestic reinfestation determined from stepwise logistic regression and one-factor analysis were the density of T. infestans in bedrooms just before spraying and the surface structure of indoor walls. Peak densities of bugs in 1988-1989 significantly differed between levels of both risk factors. Our study suggests the existence of stable determinants of infestation linked to the household which, in the absence of effective control measures, would also determine the speed of house recolonization and the ensuing bug densities. Plastering of mud walls before application of insecticides to all domestic and peridomestic structures is supported by the study.

Trypanosoma cruzi infection in Triatoma infestans and other triatomines: long-term effects of a control program in rural northwestern Argentina

“…Previous articles described the area and its history of infestation by T. infestans (5,11). Amamá is located on a paved road, 6-10 km from the other villages.…”

Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma infestans (Heteroptera: Reduviidae)

“…In northwestern Argentina, in the absence of effective surveillance, sustained control actions and socioeconomic or environmental improvements, domestic populations of T. infestans increased exponentially to return to baseline levels 3-5 years after spraying (Gürtler et al, 1994). The reestablishment of bug populations following a blanket application of insecticide may be attributed to persistence of residual insect foci or immigration of bugs.…”

Identification and characterization of microsatellite markers in the Chagas disease vector Triatoma dimidiata

“…Vector control programs in South America have proven highly successful at reducing both home infestation rates and the incidence of new infections in affected areas (Schmunis et al, 1996). Unfortunately, reinfestation rates among treated houses have ranged from 3 to 88%, up to 7 years post spraying (Gurtler et al, 1994;Cecere et al, 1997;Dujardin et al, 1997;Rojas de Arias et al, 1999). In Guatemala, infestation rates of almost 20% have been reported in villages 1 year following insecticide spraying (C.C.R., unpublished data).…”