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. Aedes albopictus is the dominant Aedes 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 Ae. albopictus for dengue viruses (DENV) remains unclear. In this study, Ae. albopictus 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 Ae. albopictus, 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 Ae. albopictus 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 Ae. albopictus for DENV-2. Within the suitable temperature range, the replication of DENV-2 in Ae. albopictus 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.

Keywords: Aedes albopictus; dengue virus 2; temperature; vector competence; viral titration.

FIGURE 1

Vector competence of Ae. albopictus orally infected with DENV-2 at different temperatures. Ae. albopictus orally infected with DENV-2 were reared at 18, 23, 28, and 32°C. The midguts, ovaries, and salivary glands of mosquitoes reared at each temperature were dissected at 0, 5, 10, and 15 days post-infection and detected by PCR. (A) Infection rate (IR): no. positive midguts/total no. midguts; (B) Dissemination rate (DR): no. positive ovaries/no. positive midguts; (C) Population transmission rate (PTR): no. positive salivary glands/total no. mosquitoes. Error bars represent 95% confidence interval (CI).

FIGURE 2

Comparison of vector competence of Ae. albopictus between constant and fluctuating temperatures. The IR, DR, and PTR of Ae. albopictus reared at 28°C and 28–23–18°C were compared at 0, 5, 10, and 15 dpi. (A) IR; (B) DR; (C) PTR. Error bars represent 95% CI. ^∗P < 0.05; ^∗∗P < 0.01.

FIGURE 3

DENV-2 RNA copies in tissues of Ae. albopictus at the constant temperature. The amount of DENV-2 in the positive tissues of Ae. albopictus was further detected by qRT-PCR. (A) Midguts; (B) ovaries; (C) salivary glands. Horizontal black lines show median DENV-2 copies (log₁₀) at each temperature.

FIGURE 4

Comparison of DENV-2 RNA copies in tissues of Ae. albopictus between constant and fluctuating temperatures. The amount of DENV-2 in tissues of Ae. albopictus reared at 28°C and 28–23–18°C was compared at 0, 5, 10, and 15 dpi. (A) Midguts; (B) ovaries; (C) salivary glands. Horizontal black lines show median DENV-2 copies (log₁₀) at each temperature. ^∗P < 0.05.