Deveplomental Characteristics Of Aedes Albopictus And Its Vector Competence Exposed To Dengue Virus In Guangzhou

Objective:To understand the effects of annual climate change on the growth and development of Aedes albopictus larvae,adult mosquito density,and dengue epidemic trends in Guangzhou.To explore the susceptibility of Aedes albopictus to dengue virus and the its ability to spread dengue fever under simulated field conditions and standard laboratory conditions(control group).It will lay the foundation for the follow-up study on the difference in susceptibility of Aedes albopictus to dengue virus under different environmental conditions in China.Methods:Two strains of Aedes albopictus(Guangzhou strain and laboratory strain)were used to conduct larval life table experiments in the wild conditions and standard laboratory conditions to record the growth and development stages of larvae and analyze the differences of larvae development time in different seasons.Adult mosquito life table experiments were performed in the wild environment to record and analyze the survival and spawning of adult mosquitoes in summer and winter.BG sentinel trap(BG trap)was used to investigate the population density of mosquitoes in three different habitats of campus,park and community in Guangzhou.The generalized estimating equation(GEE)was used to analyze the relationship between monthly reported dengue cases with temperature,precipitation,and female Ae.albopictus density.Simulating the wild and laboratory conditions in summer in artificial climate chambers,orally infest the Aedes albopictus dengue virus,and detect whether the mosquito head,ovary,and midgut were infected with the virus on the 7thand 14th days after the infection by RT-PCR.Results:Under wild condition,there was no statistical differences in the pupation rate and emergence rate of Aedes albopictus in Guangzhou in different seasons.The development time from larval to emergence was not the same in different seasons,.It’s about 15 days in spring,9 days in summer and autumn,and 22 days winter.There were statistically significant differences in development time between other seasons except for summer and autumn.According to the theory of effective accumulated temperature,the initial temperature T0 of Aedes albopictus emergence is estimated to be 15.178℃,and the effective accumulated temperature required for emergence is estimated to be 97.185 degrees·day.The median survival time of adult mosquitoes is 18 days in summer and 4 days in winter,and the survival rate of adult mosquitoes can be significantly reduced when the temperature is lower than 15℃.6853 adult mosquitoes in the three habitats were collected,including 1028 Ae.albopictus and 534 female Ae.albopictus.It was found that,for 1℃ increase in the monthly maximum temperature at 1-month lag,the number of dengue cases increased by 1.806 times;For 1 mm increase in monthly rainfall,the number of current month’s dengue cases reduced by 0.012 times;A 1/(trap·day)increase in the density of female A albopictus resulted in 0.779-fold increased number of dengue cases.In the simulated field condition of Guangzhou in summer,the infection rates of midgut,ovary and head on the 7th day of Aedes albopictus infection with dengue virus were 93.3%.83.3%,and 73.3%,respectively.There was no statistical difference in infection rates between the three tissues on day 7 and day 14.On the 7th day under simulated field conditions,the ovarian infection rate and head infection rate were higher than those under standard laboratory conditions.Conclusion:There was no significant differences in the pupation rate and emergence rate of larvae in different seasons in the wild conditions,and the development time in summer and autumn was shorter than that in spring and winter.When temperature drops below 15℃,about half of adult mosquitoes cannot survive.There were differences in the composition of mosquito species in the three habitats.There were no significant differences in the monthly average density of Ae albopictus and its sex ratio in the three habitats,but maximum temperature at 1-month lag and current month’s female density were positively associated with monthly reported dengue cases.In Guangzhou this summer,the optimal time for the virus to spread to Aedes albopictus’s head after the dengue virus has infected does not exceed 7 days.