Field evaluation of the deltametrin residual effect on mortality and knockdown for Triatoma infestans, on three types of substrates in Arequipa, Perú

Abstract

Objectives: To determine knockdown and mortality in the measurement of the residual efficacy of deltamethrin formulated insecticide 5% SC used in Chagas disease vector control on three types of substrates (sillar [white local volcanic rock], brick and concrete) to doses of 25mg/m2. Material and methods: We applied the deltamethrin in house with different construction material in an endemic zone of Arequipa, Peru, 87 to 120 third-stage nymphs V of Triatoma infestans was exposed by 72 hours to the treated surfaces, the nymphs were transferred to clean containers to determine mortality to 15 days, as well as knockdown and recovery. This experiment was carried out at 24 hours, 30, 60, 90 and 120 days post-treatment. Results: The mortality of the deltamethrin was reduced from 95% in the fist 24 hours to 34% in the fourth month after exposure, regardless of the type of substrate, to a monthly rate of 14,5% (p<0,001; r2=0,79), the knockdown was maintained above 75% in the fourth month recovery was increased over time (p<0,001; r2=0,77). According substrate, we found a persistent mortality >50% to 60 days for sillar, and 90 days for the brick and concrete. Conclusions: We showed the low effectiveness of deltamethrin 5% SC to four months after the treatment on different substrates (sillar, brick and concrete). It is necessary to take into account these results to calculate the time of application of this pesticide on vector control programmes.