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

CECERE MC; GURTLER RE; CANALE MD; CHUIT R; COHEN J

ACTA TROPICA

Año: 2002 vol. 84 p. 101 - 116

0001-706X

The long-term effects on domiciliary reinfestation by Triatoma infestans of smoothing the plaster of indoor walls/prior to insecticide application(in Amama´ 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.The long-term effects on domiciliary reinfestation by Triatoma infestans of smoothing the plaster of indoor walls/prior to insecticide application(in Amama´ 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.