Effects of Hibernation Site, Temperature, and Humidity on the Abundance and Survival of Overwintering Culex pipiens pipiens and Anopheles messeae (Diptera: Culicidae)

Abstract

Knowledge of the hibernation site preferences and the factors which influence winter survival in these hibernation sites may enhance understanding of mosquito population dynamics after winter and how arboviruses persist in temperate regions. Our study quantified the number of adult overwintering mosquitoes in cellars and aboveground constructions and analyzed survival rates in relation to the environmental conditions in these sites. During the winters 2016/2017 and 2018/2019, 149 different constructions in Northwest Germany were sampled for mosquitoes. Mosquitoes were detected in 44% of the cellars and in 33% of the aboveground constructions. Culex p. pipiens Linnaeus was the most abundant species in cellars, whereas high numbers of Anopheles messeae Falleroni were collected from a single barn. Subsequently, an enclosure study was conducted during 2019/2020. Overwintering field-collected Cx. p. pipiens and An. messeae were divided into groups with or without fructose availability, and placed in cages with different man-made hibernations sites, where temperature and relative humidity were recorded hourly. For both species, increasing mean temperatures (5–16°C) but not mean relative humidity (58–94%) were correlated with winter mortality rates of the mosquitoes. The lipid measurements were greater and mortality rates were lower when both species were provided fructose. Larger specimens (determined by wing length) stored more lipids, and in Cx. p pipiens, but not in An. messeae, survival probability of large specimens was significantly greater than for small females. Mosquitoes showed a distinct pattern in the selection of overwintering sites, while temperature was an important driver for survival.

Mosquitoes from Europe Are Able to Transmit Snowshoe Hare Virus

“…Transovarial transmission, a known mechanism for several CSG viruses in Aedes mosquitoes, appears feasible for SSHV in European Aedes species [ 63 ]. The investigated Culex mosquitoes from Germany, which overwinter as adults similar to Culiseta mosquitoes from Northern America, could also facilitate SSHV maintenance [ 64 , 65 , 66 ]. Whether SSHV can establish an enzootic cycle in Europe would also depend on the hosts.…”

The Effects of Indoor Residual Spraying on Prevalence of Malaria among Under-five Children in Zambia; A Retrospective Cohort Study

“…When rains come, and the temperatures become suitable, the adults emerge and begin foraging and reproducing to replenish the populations of mosquito vectors (28). During winters with extremely low temperatures, adult mosquitoes are also known to hibernate in cellars and other above-ground structures where they hide, lower their basal metabolic rates and can survive for longer periods until conditions improve (29).…”

The Ongoing Epidemic of West Nile Virus in Greece: The Contribution of Biological Vectors and Reservoirs and the Importance of Climate and Socioeconomic Factors Revisited

“…Lower mean annual winter and higher spring and summer temperatures have all been associated with the increased risk for epidemic outbreaks. However, evidence is not always conclusive [ 31 , 32 , 33 , 34 ]. Vectors, in this case mosquitoes, replicate, and in general function above a threshold temperature of 10 °C [ 35 ].…”

“…The increased relative humidity was associated with and increased survival rate of Aedes albopictus , but not Culex sp. in separate reports [ 31 , 40 ]. However, observed biting rates consistently relate to drier conditions [ 41 , 42 ].…”