Abstract
BackgroundThe mosquito Aedes albopictus is a vector of dengue and Zika viruses. Insecticide-resistant mosquito populations have evolved in recent decades, suggesting that new control strategies are needed. Hong Kong has a monsoon-influenced humid subtropical climate, which favours the spread of mosquitoes. However, baseline information on the composition and dynamics of the occurrence of endosymbiont Wolbachia in local Ae. albopictus is lacking, hindering the development of scientifically-informed control measures. This study identifies the presence and absence of dengue and Zika viruses, and Wolbachia infection in Aedes albopictus in Hong Kong.MethodsOviposition traps were set at 57 areas in Hong Kong, and both immature and adult mosquitoes were collected on a monthly basis between April 2018 and April 2019 as the study sample. Each individual mosquito in this sample was processed and screened for the presence of the dengue and Zika viruses and the endosymbionts Wolbachia wAlbA and wAlbB with PCR.ResultsTotals of 967 and 984 mosquitoes were tested respectively for the presence of dengue and Zika viruses, and no trace of either infection was found in these samples. The presence of wAlbA and wAlbB was also tested in 1582 individuals. Over 80% of these individuals were found to be stably infected with Wolbachia throughout the thirteen-month collection period (~ 47% singly-infected; ~ 36.8% doubly infected with both wAlbA and wAlbB).ConclusionsThe high degree of Wolbachia wAlbA and wAlbB infection in Ae. albopictus mosquitoes in Hong Kong, coupled with the absence of any signs of infection by dengue and Zika viruses, contrasts significantly with the pattern of mosquito infection in other parts of Asia. Further studies of the infection pattern in local mosquitoes are warranted before mosquito control strategies used in other regions are implemented in Hong Kong.
Highlights
The mosquito Aedes albopictus is a vector of dengue and Zika viruses
Individuals collected from areas with an ovitrap index (= number of Aedes-positive ovitraps/total number of ovitraps retrieved from a particular area × 100%) above 10% were reared to adulthood at room temperature for 3 weeks in dechlorinated tap water using a mosquito breeder (BioQuip, California, USA)
There was a significant drop in the number of samples collected in August 2018, probably because additional mosquito controls were deployed in that month to tackle a local outbreak of dengue fever in Hong Kong
Summary
The mosquito Aedes albopictus is a vector of dengue and Zika viruses. This study identifies the presence and absence of dengue and Zika viruses, and Wolbachia infection in Aedes albopictus in Hong Kong. Dengue virus is a single positive-stranded RNA virus of the family Flaviviridae, and can cause dengue fever (including breakbone fever, dandy fever, dengue hemorrhagic fever and dengue shock syndrome) in humans after transmission by the Aedes mosquito. Acquired dengue fever has been reported, with the first confirmed case occurring in 2003 [8]. The number of dengue cases reported in Hong Kong usually correlates with the occurrence of outbreaks in other Southeast Asian countries, such as those reported in 2007 or the more recent outbreak in Guangdong Province which affected 40,000 people in 2014
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