Effects of Guangzhou seasonal climate change on the development of Aedes albopictus and its susceptibility to DENV-2
Authors: Zheng Xueli , Wu Shanshan , He Yulan , Wei Yong , Fan Peiyang , Ni Weigui , Zhong Daibin , Zhou Guofa 
Published: August 2021

The susceptibility of Asian tiger mosquitoes to DENV-2 in different seasons was observed in simulated field environments as a reference to design dengue fever control strategies in Guangzhou. The life table experiments of mosquitoes in four seasons were carried out in the field. The susceptibility of Ae. albopictus to dengue virus was observed in both environments in Guangzhou in summer and winter. Ae. albopictus was infected with dengue virus by oral feeding. On day 7 and 14 after infection, the viral load in the head, ovary, and midgut of the mosquito was detected using real-time fluorescent quantitative PCR. Immune-associated gene expression in infected mosquitoes was performed using quantitative real-time reverse transcriptase PCR. The hatching rate and pupation rate of Ae. albopictus larvae in different seasons differed significantly. The winter hatching rate of larvae was lower than that in summer, and the incubation time was longer than in summer. In the winter field environment, Ae. albopictus still underwent basic growth and development processes. Mosquitoes in the simulated field environment were more susceptible to DENV-2 than those in the simulated laboratory environment. In the midgut, viral RNA levels on day 7 in summer were higher than those on day 7 in winter (F = 14.459, P = 0.01); ovarian viral RNA levels on day 7 in summer were higher than those on day 7 in winter (F = 8.656, P < 0.001), but there was no significant difference in the viral load at other time points (P > 0.05). Dicer-2 mRNA expression on day 7 in winter was 4.071 times than that on day 7 in summer: the viral load and Dicer-2 expression correlated moderately. Ae. albopictus could still develop and transmit dengue virus in winter in Guangzhou. Mosquitoes under simulated field conditions were more susceptible to DENV-2 than those under simulated laboratory conditions.

Author summary

Ae. albopictus is the only vector of dengue fever in Guangzhou. Observational data of Ae. albopictus development under natural conditions is important for monitoring vector population expansion, dengue virus transmission, and disease outbreak prevention. We found that Ae. albopictus could still develop in winter in Guangzhou. In addition, the viral load of mosquitoes in the simulated winter environment was lower than that in summer on the 7th day after infection; however, the difference in the viral load of mosquitoes in winter and summer on the 14th day after infection was not statistically significant. Mosquitoes in simulated field conditions were more susceptible to DENV-2 than those in simulated laboratory conditions. The results suggested that Ae. albopictus retains the ability to transmit dengue virus in winter in Guangzhou, and that improved dengue epidemic prevention and control measures are required. The findings of this study represent an important reference for the design of dengue fever control strategies in Guangzhou in response to global climate change.