Parity and Longevity of Aedes aegypti According to Temperatures in Controlled Conditions and Consequences on Dengue Transmission Risks

Abstract

BackgroundIn Guadeloupe, Aedes aegypti mosquitoes are the only vectors of dengue and chikungunya viruses. For both diseases, vector control is the only tool for preventing epidemics since no vaccine or specific treatment is available. However, to efficiently implement control of mosquitoes vectors, a reliable estimation of the transmission risks is necessary. To become infective an Ae. aegypti female must ingest the virus during a blood meal and will not be able to transmit the virus during another blood-meal until the extrinsic incubation period is completed. Consequently the aged females will carry more infectious risks. The objectives of the present study were to estimate under controlled conditions the expectation of infective life for females and thus the transmission risks in relation with their reproductive cycle and parity status.Methodology/Principal FindingsLarvae of Ae. aegypti were collected in central Guadeloupe and breed under laboratory conditions until adult emergence. The experiments were performed at constant temperatures (± 1.5°C) of 24°C, 27°C and 30°C on adults females from first generation (F1). Females were kept and fed individually and records of blood-feeding, egg-laying and survival were done daily. Some females were dissected at different physiological stages to observe the ovaries development. The data were analyzed to follow the evolution of parity rates, the number of gonotrophic cycles, the fecundity and to study the mean expectation of life and the mean expectation of infective life for Ae. aegypti females according to temperatures. The expectation of life varies with the parity rates and according to the temperatures, with durations from about 10 days at low parity rates at the higher temperature to an optimal duration of about 35 days when 70% of females are parous at 27°C. Infective life expectancy was found highly variable in the lower parous rates and again the optimal durations were found when more than 50% of females are parous for the mean temperatures of 27°C and 30°C.ConclusionParity rates can be determined for field collected females and could be a good proxy of the expectation of infective life according to temperatures. However, for the same parity rates, the estimation of infective life expectation is very different between Ae. aegypti and Anopheles gambiae mosquitoes. Correlation of field parity rates with transmission risks requires absolutely to be based on Ae. aegypti models, since available Anopheles sp. models underestimate greatly the females longevity.

Forest cover and climate as potential drivers for dengue fever in Sumatra and Kalimantan 2006–2016: a spatiotemporal analysis

“…Other studies have shown that warmer temperature enhances dengue virus multiplication through shortening the extrinsic incubation period [59][60][61] and shortens the extrinsic incubation period of DENV within mosquitoes [60,62]. The best temperature range for survival of Aedes mosquitoes is between 18 and 27°C [10,[63][64][65][66][67]. During the dry season with no piped water, people are forced to store water in containers especially in areas with water shortage, which in turn provides a breeding site form Aedes mosquitoes [68,69].…”

Determination of Environmental Factors Affecting Dengue Incidence in Sleman District, Yogyakarta, Indonesia

“…Low environmental temperatures will prolong the mosquito reproduction cycle thus decreasing the frequency of blood sucking. Low environmental temperatures will also prolong the EIP of dengue virus (Goindin et al, 2015) (Table 2) is likely to be that rainfall can have a negative or positive impact on the capacity of mosquito's vectors. More in-depth research is needed to discover the effects of precipitation on dengue cases more precisely.…”

The tortoise strategy as an arbovirus fitness phenotype within the mosquito as revealed by a novel formulation of age-structured vectorial capacity

“…In this case, it was the difference between declaring a risk for outbreak or not ( Figure 5). Many things affect vector competence including vector species, discrete populations within species, and environmental factors [1, 14,19,20,28,40,42,43]. Several recent studies have focused on environmental factors such as temperature, and found that temperature not only affects vector competence of many arboviruses, especially in Aedes aegypti, but also several life traits of the mosquito [27,39,41].…”

“…Cartons were checked daily and, when present, dead mosquitoes were counted and removed up to 28 dpe (approximately 1 month), as this has been shown to be the upper limit of believed survival of Ae. aegypti and is similar to the range used in Tesla, et al [27,28]. Only mosquitoes that took all offered bloodmeals were included in the mortality analyses.…”

“…For example, we consider a hypothetical EIPmax of EIP50 (the time it takes for 50% of exposed mosquitoes to transmit) to demonstrate how these group-specific mortality rates and the age-structure of willingness to bite interact to drive vectorial capacity in the context of Ageacquisition [28,38]. The S.OLDER group would require an EIP50 of 11 dpi or 9 dpi for biting rates of 2 and 1, respectively.…”