Distribution, abundance and blood-feeding behavior of Aedes albopictus (Diptera: Culicidae) in Korea

Abstract

Aedes albopictus is an invasive mosquito that can be found in all continents. This species, considered as a secondary vector of Dengue virus, has recently been suggested to play a role in the transmission of Zika virus in several countries bordering Brazil. This mosquito originated in the forests of Southeast Asia. However, this species has spread throughout the world by increased intercontinental trade during the 20th century. In this study, I surveyed the distribution, abundance and main micro habitats of Ae. albopictus in Korea. Ae. alobpictus accounted for 4% of a total of 99,625 mosquitoes examined. Ae. albopictus was first collected in May, its number increased slowly throughout August and reached the greatest number in September, then followed by rapid decrease in number during October. The larval habitats were found within 500 m distance from the bamboo forest. Most larvae were found mainly in tires (44.4% in Iksan-si, 63.6% in Damyang-gun) and artificial containers (55.6% in Iksan-si, 45.5% in Damyang-gun) including a plastic wash basin, bowl, can, styrofoam-box within the range of adult mosquito activity. Ae. albopictus activity began around sunrise with peaks in late morning (08:00–09:00) and early evening (16:00–19:00) and ended with sunset. Light intensity appears to be a major factor affecting mosquito activity: if light intensity is over some threshold, Ae. albopictus activity decreased. The main bloodmeal source of Ae. albopictus was mammals (71%) followed by birds (26%), amphibians (2%) and fish (1%). The main mammalian blood source was human (86%). This results showed that Ae. albopictus feed exclusively on human, representing the potential of this mosquito as a major vector of dengue virus, once this virus becomes domestic. In flavivirus detection, no virus was detected in the specimens of Ae. albopictus, but a total of six Japanese encephalitis virus (JEV)-positive pools were detected from Culex orientalis and Cx. pipiens except Cx tritaeniorhynchus, the main vector mosquitos of JEV. All the detected JEVs were identified as genotype V by phylogenetic analysis of the envelope gene. Our findings confirmed that a new genotype of JEV was introduced into Korea and suggested that the two mosquito species may play a role in JEV transmission. To investigate the possibility of using Wolbachia, as one of biological control strategy, I investigated the distribution of Wolbachia infection in Ae. albopictus according to geographical distribution in Korea. Over 99% of the collected mosquitoes harbored Wolbachia, and the sequence homologies of the WSP gene showed more than 98% similarity within the mosquito species. Ae. albopictus was found to be infected with two Wolbachia strains, wAlbA and wAlbB. Regional distribution analysis indicated that the wAlbA strain of Wolbachia showed more than 98% sequence similarity among Ae. albopictus collected from different regions. This study would support further functional and biocontrol-related studies of Wolbachia. Additionally, I also investigated the mosquito species composition by employing the DNA barcoding method based on the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene sequence. To this end, mtCOI genes from individual mosquitoes of 25 species were sequenced, and their phylogenetic relationship was analyzed. Phylogenetic analysis showed that most mosquito species were clustered according to morphological characteristics, except for certain Anopheles species. DNA barcoding using mtCOI genes successfully identified mosquito species, and it can be used as an effective technique to complement morphological identification.