Effects of partial housing improvement and insecticide spraying on the reinfestation dynamics of Triatoma infestans in rural northwestern Argentina

M. C. Cecere^{, , a}, R. E. Gürtler^a, D. M. Canale^b, R. Chuit^c and J. E. Cohen<sup>d

a</sup> Laboratory of General Ecology, Department of Ecology, Genetics and Evolution, Faculty of Exact and Natural Sciences, University of Buenos Aires, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina
^b National Chagas Service, Center for Chagas Disease Reservoirs and Vectors, 9 de Julio 356, 5000, Córdoba, Argentina
^c Academia Nacional de Medicina, Centro de Investigaciones Epidemiológicas, Pacheco de Melo 2081, Buenos Aires, Argentina
^d Laboratory of Populations, Rockefeller University and Columbia University, 1230 York Ave., Box 20, New York, NY 10021-6399, USA

Received 21 December 2001;  revised 10 June 2002;  accepted 18 June 2002.  Available online 6 November 2002.

Abstract

The long-term effects on domiciliary reinfestation by Triatoma infestans of smoothing the plaster of indoor walls prior to insecticide application (in Amamá village) relative to only insecticide application (in Trinidad–Mercedes villages) were evaluated in rural northwestern Argentina from 1992 to 1997. All domestic and peridomestic areas of each house were sprayed with 2.5% suspension concentrate deltamethrin at 25 mg/m² in October 1992, and infestations were assessed by various methods every 6 months. Domiciliary infestation decreased from 72–88% in 1992 to 6–17% in late 1995, to increase moderately thereafter without returning to baseline rates. Peridomestic sites were the first in becoming reinfested, and reached more abundant T. infestans populations than domiciliary areas. Domiciliary infestation rates and bug abundances were not significantly different between communities during surveillance. Domiciliary infestation rates in well-plastered houses were very low (5–9%) and approximately stable until 1996, but in houses with regular or bad plaster they consistently increased from 5 to 19–21% in both communities. Logistic multiple regression analysis showed that the likelihood of domestic infestation assessed through householders' collections was significantly and positively associated with the occurrence of an infested peridomestic site in the respective house, the occurrence of high-density domestic infestations before interventions, and well-plastered walls in 1996. Combining insecticide spraying and partial improvement of walls controlled domestic infestations and transmission of Trypanosoma cruzi effectively, but was not sufficient to eliminate T. infestans from the study area or increase the effectiveness of careful chemical control.

Author Keywords: Triatoma infestans; Chagas disease; Control; Surveillance; Insecticide; Environmental management

Corresponding author. Tel.: +54-11-4576-3300x214; fax: +54-11-4576-3384; email: carla@bg.fcen.uba.ar