Efficacy and residual effect of two pyrethroid insecticides against Triatoma infestans in three types of houses. Field evaluation in Arequipa, Perú

Abstract

Objetives. To compare the residual efficacy of two insecticides for the vector control of Triatoma infestans on three type of housing in two localities from Arequipa, Peru. Material and methods. Field assay, were used wet powder formulations of deltamethrin and lambdacyhalothrin on different substrates (concrete, brick and sillar [white local volcanic rock]) at doses of 25 and 30 mg/m2 respectively. 1445 Triatoma infestans V nymphs were used in bioassays, where they were exposed for 48 hours on the sprayed wall and were observed for 14 days to assess mortality. The exhibition was held in each type of surface and insecticide for 24 hours, 30 and 90 days after treatment. Results. At 24 h the lambdacyhalothrin was more effective than deltamethrin in brick and sillar (p <0.01). For the 30 days deltamethrin had better residual effect in brick and sillar (p <0.01) and 90 days was higher than the lambdacihalothrin in concrete (73 vs 35%, p <0.001), brick (62 vs 23% p <0.001) and sillar (63 vs 27%, p <0.001). The reduction in mortality in deltamethrin was evident to the third month, were similar to the 24h and the first month (p> 0.05). Lambdacyhalothrin reduced its effectiveness at 23% per month since the first evaluation (p <0.001, r2 : 0.95). Conclusions. Lambdacyhalothrin is effective in the first days after its residual effect is poor but, unlike deltamethrin. These results should be taken into account to calculate the time of spraying of each pesticide on vector control of Chagas disease by type of construction material.