Semi-field evaluation of the exposure-free mosquito electrocuting trap and BG-Sentinel trap as an alternative to the human landing catch for measuring the efficacy of transfluthrin emanators against Aedes aegypti

Abstract

Background The human landing catch (HLC) measures human exposure to mosquito bites and evaluates the efficacy of vector control tools. However, it may expose volunteers to potentially infected mosquitoes. The mosquito electrocuting trap (MET) and BG-Sentinel traps (BGS) represent alternative, exposure-free methods for sampling host-seeking mosquitoes. This study investigates whether these methods can be effectively used as alternatives to HLC for measuring the efficacy of transfluthrin emanator against Aedes aegypti. Methods The protective efficacy (PE) of freestanding passive transfluthrin emanators (FTPEs), measured by HLC, MET and BGS, was compared in no-choice and choice tests. The collection methods were conducted 2 m from an experimental hut with FTPEs positioned at 3 m on either side of them. For the choice experiment, a competitor HLC was included 10 m from the first collection point. One hundred laboratory-reared Ae. aegypti mosquitoes were released and collected for 3 consecutive h. Results In the no-choice test, each method measured similar PE: HLC: 66% (95% confidence interval [CI]: 50–82), MET: 55% (95% CI: 48–63) and BGS: 64% (95% CI: 54–73). The proportion of mosquitoes recaptured was consistent between methods (20–24%) in treatment and varied (47–71%) in the control. However, in choice tests, the PE measured by each method varied: HLC: 37% (95% CI: 25–50%), MET: 76% (95% CI: 61–92) and BGS trap: 0% (95% CI: 0–100). Recaptured mosquitoes were no longer consistent between methods in treatment (2–26%) and remained variable in the control (7–42%). FTPE provided 50% PE to the second HLC 10 m away. In the control, the MET and the BGS were less efficacious in collecting mosquitoes in the presence of a second HLC. Conclusions Measuring the PE in isolation was fairly consistent for HLC, MET and BGS. Because HLC is not advisable, it is reasonable to use either MET or BGS as a proxy for HLC for testing volatile pyrethroid (VP) in areas of active arbovirus-endemic areas. The presence of a human host in close proximity invalidated the PE estimates from BGS and METs. Findings also indicated that transfluthrin can protect multiple people in the peridomestic area and that at short range mosquitoes select humans over the BGS.

Chikungunya fever

“…A more environmentally sound approach is to use trapping systems that result in the capture, death or sterilization of vectors 233 . For mosquito vectors, these methods include mass-trapping with sticky gravid traps placed in 60-80% of homes, dry attractive toxic sugar bait, electromechanical traps, and traps coupled with ultralow-volume spraying [234][235][236] . A novel approach is the use of inactivated yeast interfering RNA formulations that are specific for killing mosquito larvae 237 .…”

Field evaluation of a volatile pyrethroid spatial repellent and etofenprox-treated clothing for outdoor protection against forest malaria vectors in Cambodia

“…Therefore, the BB’s residual efficacy is currently unknown. Similarly to ITCs, transfluthrin-based VPSR efficacy over time is dependent on exposure to UV and other environmental parameters (rainfall, wind), as well as the susceptibility of local mosquitoes to pyrethroids [18,19,56,56,68,77]. For this field study, insecticide susceptibility testing to pyrethroids, including etofenprox and transfluthrin, was not feasible due to issues with keeping field-caught adult Anopheles alive and other logistical challenges.…”

“…The hourly human landing rate (HLR) for the control arm across the 49 collection nights was estimated as a proxy for the hourly human biting rate (HBR) [55,56].…”

CDC light traps underestimate the protective efficacy of an indoor spatial repellent against bites from wild Anopheles arabiensis mosquitoes in Tanzania

“…it can be labour intensive and taxing on volunteers when done at large scale [ 26 , 49 ], and can be challenging to standardize due to differences in human attractiveness to mosquitoes, skilfulness of collectors, and alertness throughout the collection period [ 25 , 26 ]. Evaluations of the Mosquito Electrocuting Trap (MET) and Biogents Sentinel Trap (BGS) for measurement of the PE of SR using Aedes aegypti have also shown some promise in semi-field experiments if observations are independent because it was observed that mosquitoes divert from traps to nearby humans [ 50 ].…”