DEET Efficacy Increases With Age in the Vector Mosquitoes Anopheles gambiae s.s. and Aedes albopictus (Diptera: Culicidae)

Abstract

Old mosquitoes are the most likely to transmit pathogens due to the higher probability that they will be exposed to pathogens, and the time required before a mosquito becomes infectious, the extrinsic incubation period (EIP). However, old mosquitoes are rarely considered in the evaluation of control tools. This study evaluated the effect of mosquito aging on the repellent efficacy of N,N-diethyl-3-methylbenzamide (DEET) in two vector mosquitoes, Anopheles gambiae s.s. (Giles) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae), respective vectors of malaria parasites and arboviruses such as dengue, chikungunya, and Zika viruses. For both mosquito species, DEET-induced inhibition of blood-feeding was assessed in three age classes. Life-history traits related to mosquito fecundity and survival following DEET exposure were also measured. Results showed that, in both species, bloodmeal inhibition induced by DEET was significantly higher in old females (>18 d old) than in younger ones (<13 d old). Life history traits recording showed no combined effects of DEET and aging on mosquito blood engorgement, oviposition rate, number of eggs laid nor survival; however, age effects are reported for all these traits. These results highlight the need for taking into account mosquito age in the evaluation of integrated mosquito management tools. They also suggest that the control of vector-borne pathogens with a long EIP could be improved by targeting old mosquitoes and supports the efficacy of repellents in the fight against mosquito-borne diseases.

The Impact of Insecticide Pre-Exposure on Longevity, Feeding Succession, and Egg Batch Size of Wild Anopheles gambiae s.l.

“…In this study, the longevity of a vector was defined as the time mosquitoes survived the first 24 hours after exposure to deltamethrin/permethrin until actual death. Longevity is an important parameter when considering mosquito competence in transmitting malaria disease; the mosquito must survive long enough so that the Plasmodium life cycle will be complete and be transferred to the salivary gland of the vector [ 57 ]. The difference in longevity between wild mosquitoes and susceptible colonies showed that the resistant population had shown to survive longer than susceptible ones.…”

“…The tested vectors were offered blood meal twice a week; the first blood meal was given 48 hours after the susceptibility test was performed. The blood meal was always given in the morning times between 07 : 00 and 09 : 00 h after being sugar-deprived for one hour before the blood meal [ 57 ]. Rabbits' fur was shaved dorsal ventrally, and then, they were kept in a restrainer, which limited their movement and exposed the shaven part to mosquitoes to feed for 30 minutes, but the number of successfully fed mosquitoes was recorded after one hour.…”

MAÏA® Topical Repellent Ointment Provides Long-Lasting Protection Against Anopheles Gambiae s.s., Anopheles Arabiensis and Aedes Aegypti Under Semi-Field Conditions in Tanzania

“…Moreover, semi-eld environments allow volunteers to be accessible to a known number of mosquitoes of known age, physiological status, and avidity and it minimizes heterogeneity in the data allowing a more precise estimation of true repellent e cacy. The study is also conservative as it used young, never blood-fed mosquitoes raised under optimal conditions to maximize body size and then sugar starved, which are less repelled by DEET than older or smaller mosquitoes [36,37].…”

Single blinded semi-field evaluation of&nbsp;MAÏA®&nbsp;topical&nbsp;repellent&nbsp;ointment compared to unformulated 20% DEET against&nbsp;Anopheles gambiae s.s., Anopheles&nbsp;arabiensis&nbsp;and&nbsp;Aedes aegypti&nbsp;in&nbsp;Tanzania

“…Moreover, semi-eld environments allow volunteers to be accessible to a known number of mosquitoes of known age, physiological status, and avidity, and minimize heterogeneity in the data allowing a more precise estimation of true repellent e cacy. The study is also conservative as it used young, never blood-fed mosquitoes raised under optimal conditions to maximize body size and then sugar starved, which are less repelled by DEET than older or smaller mosquitoes [36,37].…”