Molecular Analysis of the Bloodmeals ofCulexspp. Mosquitoes at Natural Habitats in Singapore to Investigate the Potential Risk of Japanese Encephalitis Virus and West Nile Virus Transmission

Abstract

Japanese encephalitis virus (JEV) and West Nile virus (WNV) are arboviruses primarily transmitted by Culex spp. mosquitoes. Birds are the primary hosts for JEV and WNV. Recent WNV outbreaks in Europe and United States and their association with migratory birds highlight the importance of understanding the feeding host preference of potential vectors for outbreak preparedness, especially in nonendemic settings. Singapore is nonendemic to JEV and WNV, but is a stopover site for migratory birds of the East Asian-Australasian Flyway. Therefore, we elucidated the feeding host range of Culex spp. mosquitoes captured in four natural (bird) habitats in Singapore from January 2011 to December 2012. We characterized feeding host DNA in field-caught mosquitoes using a PCR sequencing-based assay targeting the mitochondrial gene regions. Of 22,648 mosquitoes captured, 21,287 belonged to the Culex vishnui subgroup. The host DNA analysis showed that mosquitoes from the Cx. vishnui subgroup are opportunistic biters, feeding on a range of birds and mammals. Cx. vishnui subgroup, Culex sitiens and Culex bitaeniorhynchus, was primarily ornithophagic, although they fed opportunistically on mammals, including humans. Culex gelidus and Culex quinquefasciatus, in contrast, fed mainly on mammals. The presence of ornitho-and anthropophilic mosquito vectors and susceptible avian and mammalian hosts poses a risk spill-over transmission of JEV and WNV among humans, should these viruses be introduced through migratory birds and establish persistent transmission in resident birds and animal hosts in Singapore.

Blood meal source identification and RNA virome determination in Japanese encephalitis virus vectors collected in Ishikawa Prefecture, Japan, show distinct avian/mammalian host preference

“…Here, we found that the principal vector for JEV fed on both mammalian and avian hosts or was in contact with more than one host during a single gonotrophic cycle, similar to the findings in villages in India (Arunachalam et al 2005) and natural bird habitats in Singapore (Yeo et al 2020). In line with this study, Cx .…”

“…tritaeniorhynchus , Kamoike in Kaga City, showed true ornithophilic feeding patterns. Yeo et al (2020) similarly reported a blood-feeding preference for Cx . bitaeniorhynchus as “primarily ornithophilic,” albeit occasionally opportunistic feeders on humans.…”

Japanese encephalitis in Bali, Indonesia: ecological and socio-cultural perspectives

“…Information and education on public to use bed-nets or insect-repellents as their personal protection measures along with implementation of a good sanitation may contribute to reduce contact with the mosquito vector. Similarly, housing the pigs indoor with anti-mosquito nets or screens especially during the peak of vector activity may minimize contact the mosquitoes to the animals [ 87 , 88 ]. Modification of rice paddy fields management for water and fertilizer usage and separating the paddy fields or preventing stagnant water around the pig farms are other strategies that may also limit contact between mosquitoes, pigs and humans.…”

Isolation and Genetic Characterization of Japanese Encephalitis Virus Two Decades after Its Elimination in Singapore

“…Although JEV has only been detected in the rural forested areas of Singapore thus far, increasing urbanization and the push for ecological conservation [67,68] result in close interactions between human dwellings and the habitats that are favored by culicine vectors and JEV hosts. A survey of bloodmeals of Culex mosquitoes in Singapore showed that JEV vectors opportunistically feed on humans [69], while a study of changing JEV epidemiological characteristics in metropolitan areas showed an apparent correlation between the presence of herons and the number of JE cases in the absence of pig farming [70]. It is thus necessary to maintain entomological and virological surveillance to keep track of possible enzootic JEV variants, thereby allowing for more leeway in containing any vector-human transmission events.…”