Infection and transmission of dengue virus in the mosquito, Armigeres subalbatus

Abstract

The susceptibility of Armigeres subalbatus to dengue 2 virus increased with incubation time. The infection rate of Ar. subalbatus also increased in relation to raising temperature. In comparison with the infection routes, the infection rate in which the mosquitoes were incubated with intrathoracic inoculation is greater than those with oral feeding. After intrathoracic inoculation for 4 days, 54.17% and 66.67% of the mosquitoes were infected at 25℃and 30℃, respectively. After 7 days of intrathoracic inoculation, the infection rates increased to 95.83% at 25℃and 30℃. As the infection via oral feeding, the infection rates after 10 days post-infection were 4.17% and 20.83% at 25℃ and 30℃, respectively. After oral feeding for 14 days, 79.17% and 83.33% of the mosquitoes were infected at 25℃and 30℃, respectively. In infected mosquitoes, the head and salivary glands were the major infected tissues , and the salivary glands were more susceptible than the head. Midgut and reproductive system appeared to have little role in dengue 2 virus infection. Further study on the ability of the oral transmission of Ar. subalbatus revealed that the infected mosquitoes had the ability to transmit dengue 2 virus. Once the salivary glands of the mosquitoes were infected, the oral transmission rate reached 90%. Study on the susceptibility of Ar. subalbatus to four dengue virus serotypes demonstrated that Ar. subalbatus was less susceptible to dengue 1 virus than other serotypes. In general, the head and salivary glands were susceptible to all four dengue virus serotypes; while the midgut and the reproductive system were less susceptible. In conclusion, Ar. subalbatus can be infected with four serotypes of dengue virus and has the ability of oral transmission, indicating that this species could potentially serve as a vector of dengue; however, it still needs to be confirmed whether it can be a vector of dengue in nature as well.

探討白腹叢蚊(Armigeres subalbatus)雌蚊對於登革二型病毒(dengue 2 virus)之感受性，結果顯示經由吸食方式及胸部接種法感染病毒之白腹叢蚊，其登革病毒的感染率會隨著培養天數而增加。在20、25及30℃飼養條件下，蚊體之病毒感染率隨溫度升高而提高。比較感染途徑的試驗顯示，經由胸部注射方式的病毒感染率較人工薄膜給食器的經口感染率高，蚊體在注射病毒後4天已可分別檢測出54.17% (25℃)與66.67% (30℃)的感染率，至第7天其感染率已提高至95.83% (25與30℃)；然人工薄膜給食器的經口感染則須經10天才能檢測到病毒，且其感染率只有4.17% (25℃)與20.83% (30℃)，於感染後第14天則分別提高至79.17% (25℃)與83.33% (30℃)。比較白腹叢蚊各組織對登革二型病毒之感受性，結果顯示登革病毒主要感染唾腺與頭部，而唾腺組織又較頭部組織敏感，至於中腸與生殖系統的感染率則較低。進一步探討雌蚊經口傳播登革病毒之能力，結果不但顯示感染登革二型病毒之雌蚊具有經口傳播登革病毒的能力，且其可傳播的比例與唾腺感染率相關性極高，唾腺呈陽性反應的雌蚊，有九成具經口傳播能力。探討四種不同血清型登革病毒感染白腹叢蚊之情形，結果顯示白腹叢蚊對於登革一型病毒的感受性較其他三種血清型為低；整體而言，頭部與唾腺組織對此四種血清型之登革病毒具有較高的感受性，中腸與生殖系統的感受性則較低。於實驗室中進行試驗的結果顯示登革病毒確實可感染白腹叢蚊，且白腹叢蚊亦可傳播此病毒，因此白腹叢蚊似可媒介登革病毒；至於在自然界中，白腹叢蚊是否扮演登革熱病媒蚊的角色，則有待進一步探討。