Residual effect of a micro-encapsulated formulation of organophosphates and piriproxifen on the mortality of deltamethrin resistant Triatoma infestans populations in rural houses of the bolivian Chaco region

ABRAHAM GEMIO ALARICO; NAHUEL ROMERO; LAURA HERNÁNDEZ; SILVIA CATALÁ; DAVID GORLA

MEMóRIAS DO INSTITUTO OSWALDO CRUZ.

FUNDACO OSWALDO CRUZ

Lugar: Rio de Janeiro; Año: 2010 vol. 105 p. 752 - 756

0074-0276

The Bolivian chaco is endemic for Chagas disease, and is the place where the discovery of pyrethroid resistant Triatoma infestans (Hemiptera, Reduviidae) populations was identified by WHO as an important focus for research. The objective of this study was to evaluate the residual effect of a micro-encapsulated formulation containing organophosphate active ingredients and a juvenile hormone analogue (Inesfly 5A IGR), on the mortality of T. infestans in rural houses of the bolivian chaco treated up to 34 months before, and to evaluate the susceptibility to pyrethroids of the offspring of field collected insects. Thirty houses were randomly selected within three communities to carry out wall bio-assays with T. infestans nymphs. Mortality was recorded 24, 48 and 72 hours after wall contact. Eggs laid by females collected in the area were used to obtain first instar nymphs and carry out pyrethroid susceptibility tests. The wall bio-assays showed that the micro-encapsulated insecticide eliminates T. infestans populations and produces detectable mortality of insects exposed to walls treated 34 months before. The discriminant dose of deltamethrin (0.01 mg/ml), showed 65% nymph survival, whereas at the highest tested dose (1.0 mg/ml) 14% of the nymphs survived. These results show that Inesfly 5A IGR is an appropriate tool for the elimination of intradomestic and peridomestic populations of T. infestans resistant to pyrethroids.