Mosquito-Disseminated Insecticide for Citywide Vector Control and Its Potential to Block Arbovirus Epidemics: Entomological Observations and Modeling Results from Amazonian Brazil

Background: mosquito-borne viruses threaten public health worldwide. when the ratio of competent vectors to susceptible humans is low enough,the virus’s basic reproductive number (r0) falls below 1.0 (each case generating,on average,<1.0 additional case) and the infection fades out from the population. conventional mosquito control tactics,however,seldom yield r0< 1.0. a promising alternative uses mosquitoes to disseminate a potent growth-regulator larvicide,pyriproxyfen (ppf),to aquatic larval habitats; this kills most mosquito juveniles and substantially reduces adult mosquito emergence. we tested mosquito-disseminated ppf in manacapuru,a 60,000-inhabitant city (~650 ha) in amazonian brazil. methods and findings: we sampled juvenile mosquitoes monthly in 100 dwellings over four periods in february 2014–january 2016: 12 baseline months,5 mo of citywide ppf dissemination,3 mo of focal ppf dissemination around aedes-infested dwellings,and 3 mo after dissemination ended. we caught 19,434 juvenile mosquitoes (66% aedes albopictus,28% ae. aegypti) in 8,271 trap-months. using generalized linear mixed models,we estimated intervention effects on juvenile catch and adult emergence while adjusting for dwelling-level clustering,unequal sampling effort,and weather-related confounders. following ppf dissemination,aedes juvenile catch decreased by 79%–92% and juvenile mortality increased from 2%–7% to 80%–90%. mean adult aedes emergence fell from 1,077 per month (range 653–1,635) at baseline to 50.4 per month during ppf dissemination (range 2–117). female aedes emergence dropped by 96%–98%,such that the number of females emerging per person decreased to 0.06 females per person-month (range 0.002–0.129). deterministic models predict,under plausible biological-epidemiological scenarios,that the r0of typical aedes-borne viruses would fall from 3–45 at baseline to 0.004–0.06 during ppf dissemination. the main limitations of our study were that it was a before–after trial lacking truly independent replicates and that we did not measure mosquito-borne virus transmission empirically. conclusions: mosquito-disseminated ppf has potential to block mosquito-borne virus transmission citywide,even under adverse scenarios. our results signal new avenues for mosquito-borne disease prevention,likely including the effective control of aedes-borne dengue,zika,and chikungunya epidemics. cluster-randomized controlled trials will help determine whether mosquito-disseminated ppf can,as our findings suggest,develop into a major tool for improving global public health. © 2017 abad-franch et al.