Temperature Increase Enhances Aedes albopictus Competence to Transmit Dengue Virus

Abstract

Dengue is a mosquito-borne disease that has been an epidemic in China for many years. <i>Aedes albopictus</i> is the dominant <i>Aedes</i> mosquito species and the main vector of dengue in China. Epidemiologically, dengue mainly occurs in Guangdong Province; it does not occur or rarely occurs in other areas of mainland China. This distribution may be associated with climate, mosquito density, and other factors in different regions; however, the effect of temperature on the vector competence of <i>Ae. albopictus</i> for dengue viruses (DENV) remains unclear. In this study, <i>Ae. albopictus</i> was orally infected with dengue virus 2 (DENV-2) and reared at constant temperatures (18, 23, 28, and 32°C) and a fluctuating temperature (28-23-18°C). The infection status of the midguts, ovaries, and salivary glands of each mosquito was detected by polymerase chain reaction (PCR) at 0, 5, 10, and 15 days post-infection (dpi). DENV-2 RNA copies from positive tissues were quantified by quantitative real time PCR (qRT-PCR). At 18°C, DENV-2 proliferated slowly in the midgut of <i>Ae. albopictus</i>, and the virus could not spread to the salivary glands. At 23 and 28°C, DENV-2 was detected in the ovaries and salivary glands at 10 dpi. The rates of infection, dissemination, population transmission, and DENV-2 copies at 28°C were higher than those at 23°C at any time point. At 32°C, the extrinsic incubation period (EIP) for DENV-2 in <i>Ae. albopictus</i> was only 5 dpi, and the vector competence was the highest among all the temperatures. Compared with 28°C, at 28-23-18°C, the positive rate and the amount of DENV-2 in the salivary glands were significantly lower. Therefore, temperature is an important factor affecting the vector competence of <i>Ae. albopictus</i> for DENV-2. Within the suitable temperature range, the replication of DENV-2 in <i>Ae. albopictus</i> accelerated, and the EIP was shorter with a higher temperature. Our results provide a guide for vector control and an experimental basis for differences in the spatial distribution of dengue cases.