Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti

Abstract

Background There is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS. Methods We evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify “delayed mortality”. Results Mean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80–97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months). Conclusions Chlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.

Influence of testing modality on bioefficacy for the evaluation of Interceptor® G2 mosquito nets to combat malaria mosquitoes in Tanzania

“…Conversely, in both the West African hut and I-ACT, mosquitoes cannot exit and are therefore more likely to make repeated contacts with the nets and sleeping humans. Hut design clearly influences both 72-h mosquito mortality and blood-feeding endpoints as seen in this study and others for Anopheles [ 34 , 43 , 44 ] and Aedes [ 46 ]. However, when considering the odds ratios, it was possible to detect differences between products with increased bioefficacy of Interceptor ® G2 compared to Interceptor ® in all hut designs, the tunnel test and the I-ACT, underlining the importance of comparing between products using well-powered studies with a rationale for the margins of acceptable difference between products [ 47 ].…”

Preventive residual insecticide applications successfully controlled Aedes aegypti in Yucatan, Mexico

“…Clothianidin targets the nicotinic acetylcholine receptor (nAChR) in the insect central nervous system 50 , leading to a delayed effect on the mortality of mosquitoes. As seen with other insecticide, chlorfenapyr 51 , clothianidin increases its efficacy when mosquitoes are free-flying.…”

“…Clothianidin targets the nicotinic acetylcholine receptor (nAChR) in the insect central nervous system 50 , leading to a delayed effect on the mortality of mosquitoes. As seen with other insecticide, chlorfenapyr 51 , clothianidin increases its efficacy when mosquitoes are free-flying. www.nature.com/scientificreports/ A recent study, conducted in towns surrounding Merida, estimated a weekly cost of releasing Wolbachiacarrying male Ae.…”

Residual efficacy of the neonicotinoid insecticide clothianidin against pyrethroid‐resistant Aedes aegypti

“…The mosquitoes originated from a pyrethroid‐resistant population from Merida (Juan Pablo strain, from F4 generation) used for resistance evolution and operational studies 21 kept at the insectary of Unidad Colaborativa para Bioensayos Entomologicos of the Universidad Autonoma de Yucatan (UCBE‐UADY). The strain undergoes mixing with field populations every 6 months and undergoes routine Centers for Disease Control and Prevention (CDC) cone bioassays to quantify levels of phenotypic resistance to the four major groups of insecticides (pyrethroid, carbamate, organophosphate, organochlorine).…”

“…Methods were similar to those previously described by Che‐Mendoza et al 21 . Briefly, three experimental houses (typical middle‐ to low‐income housing) were equally furnished and double‐screened with mosquito mesh on outdoor and interior doors and windows to impede mosquito entry/exit (see Dunbar et al 20 .…”