Impact of single and multiple residual sprayings of pyrethroid insecticides against Triatoma dimidiata (Reduviiade; Triatominae), the principal vector of Chagas disease in Jutiapa, Guatemala.

This study investigated the impact of single, double, and triple insecticide sprayings on indoor infestation of Triatoma dimidiata in Jutiapa, Guatemala. Up to three successive insecticide sprayings were applied in villages, where the indoor infestation index was > 5% before each spraying round or located adjacent to the persistently infested villages. Among 64 villages with single spraying, the mean indoor infestation index reduced from 20.8% to 1.4% after 12 months, but rose to 8.1% after 33 months. In 40 double-sprayed villages, it decreased from 41.9% to 11.9% by the first spraying and to 4.8% by the second spraying. For 12 villages with triple spraying, it reduced from 40.6% to 13.2%, 10.9%, and 4.1% through each spraying round. Geographic analysis showed that originally highly infested villages were spatially clustered and were likely to remain infested after the sprayings. Indoor infestation of T. dimidiata can be controlled with less than three rounds of spraying.