Excito-repellency effect of deltamethrin on triatomines under laboratory conditions

Abstract

This work demonstrates that deltamethrin in low doses produces an excito-repellency effect on triatomines, as already observed for mosquitoes. A wooden box covered with a cloth impregnated with deltamethrin at doses of 2.5 and 5mg ai/m 2 was utilized for the experiment. The triatomine species studied were Triatoma infestans, Panstrongylus megistus, Rhodnius neglectus and Triatoma sordida. Adults were released in one of the sides of the box and their position was noted in subsequent periods. The observations were realized on the day the cloth was impregnated and subsequently repeated at 30 and 60 days for T. sordida; on day 120, the remaining species were included. Insect mortality and attempts at flight from the box were also observed. Excitorepellency was evident for all species and doses up to day 120. The only species that attempted to fly was P. megistus. The excito-repellency effect may be considered as an additional advantage to the insecticide power, as it should be able to prevent the installation of new colonies by females that fly into the homes, and at the moment of the spraying, it should promote the flushing out of triatomines from the wall crevices and from other shelters. Key-words: Excito-repellency. Triatominae. Deltamethrine. Pyrethroid. Chagas' disease. Control.Resumo No presente trabalho procurou-se constatar se a deltametrina em baixas doses produz excito-repelência em triatomíneos, conforme já observado para mosquitos. O experimento foi realizado utilizando-se uma caixa de madeira recoberta com tecido impregnado com deltametrina nas doses de 2,5 e 5mg ia/m 2 . As espécies de triatomíneos estudadas foram o T. infestans, P. megistus, R. neglectus e T. sordida. Exemplares adultos eram liberados em um dos lados da caixa, e a posição dos mesmos era anotada em períodos subseqüentes. A experiência foi realizada no dia da impregnação do tecido, e repetida aos 30 e 60 dias para o T. sordida; aos 120 dias incluíram-se as demais espécies. Também foram observadas a mortalidade dos insetos e a tentativa de fuga da caixa através do vôo. A excito-repelência foi evidente para todas as espécies e doses até o 120 o dia. A única espécie que voou foi o P. megistus. O efeito excito-repelente pode ser considerado uma vantagem adicional ao poder do inseticida pois dificultaria a instalação de novas colônias a partir de fêmeas que ingressassem nas casas através do vôo, além de promover o desalojamento de exemplares presentes nas frestas das paredes e outros esconderijos. Palavras-chaves: Excito-repelência. Triatominae. Deltametrina. Piretróide. Doença de Chagas. Controle.

Lack of Segregation between Two Species of Chagas Disease Vectors

“…5,24,26,50 Differences in dispersal rates may represent an additional dimension that could interfere in the house infestation capacity of these species. Although T. infestans and P. megistus are known to promptly initiate flight, 51,52 further studies would be necessary to analyze whether differences in flight capacity between them could be related to distinct dispersal rates and spatial distribution. It has also been found that P. megistus is more sensible to temperature shocks than T. infestans, and shows stronger effects after abrupt variations of temperature on ecdysis and survival 53,54 and that P. megistus is much more susceptible than T. infestans to deltamethrin, a piretroid insecticide.…”

“…It has also been found that P. megistus is more sensible to temperature shocks than T. infestans, and shows stronger effects after abrupt variations of temperature on ecdysis and survival 53,54 and that P. megistus is much more susceptible than T. infestans to deltamethrin, a piretroid insecticide. 51 Deltamethrin, even at sub-lethal doses, may inhibit re-colonization of households by P. megistus from sylvatic ecotopes. 51 Our results, and those of other reports, 5,24,37,51 reinforce the notion that T. infestans is better pre-adapted for exploiting domiciliary ecotopes than P. megistus.…”

“…51 Deltamethrin, even at sub-lethal doses, may inhibit re-colonization of households by P. megistus from sylvatic ecotopes. 51 Our results, and those of other reports, 5,24,37,51 reinforce the notion that T. infestans is better pre-adapted for exploiting domiciliary ecotopes than P. megistus. The study of vector behavior can provide innovative strategies for epidemiologic surveillance and control of tropical infections such as Chagas disease.…”

Response of Triatoma infestans to pour-on cypermethrin applied to chickens under laboratory conditions

“…Nymphs fed on treated chickens took 15.1 ± 14.4 mg of blood on each occasion, whereas nymphs fed on control T. infestans response to pour-on cypermethrin • Ivana Amelotti et al 484 chickens took 36.2 ± 24.2 mg. This effect might be due to a repellence response, as seen in Triatoma sordida up to 120 days after the application of 2.5 mg/m 2 of deltamethrin (Diotaiuti et al 2000). Similarly, Alzogaray et al (2000) showed that a repellent component inhibits the feeding of T. infestans third-instar nymphs.…”

History of insecticide resistance of Triatominae vectors

“…Given the specifi city of Triatomine occurrence in household annexes, but the absence of colonization, alternative means of vector control have been tested, including repellents (20) , lining, and/or impregnated curtains (21) (22) (23) . However, the effectiveness of these alternatives requires rigorous assessment.…”