Circulation of West Nile virus in mosquitoes approximate to the migratory bird stopover in West Coast Malaysia

• Main Authors: Natasha, Jafar Ali, Yasmin, Abd Rahaman, Sharma, Reuben Sunil Kumar, Nur-Fazila, Saulol Hamid, Nur-Mahiza, Md Isa, Arshad, Siti Suri, Mohammed, Hussni Omar, Kumar, Kiven, Loong, Shih Keng, Ahmad Khusaini, Mohd Kharip Shah
• Format: Article
• Published: Public Library of Science 2023
• Subjects: QR355 Virology; R Medicine (General)
• Online Access: http://eprints.um.edu.my/38355/
• Institution: Universiti Malaya

Author summaryWest Nile virus (WNV) is considered to be one of the neglected diseases in Malaysia as most vector-borne febrile illnesses in humans are predominantly diagnosed as dengue-like illnesses. Nevertheless, WNV might be an additional virus causing the mosquito-borne disease in Malaysia based on data from previous studies. Our group previously identified the presence of WNV RNA and antibodies in the migratory and resident birds, macaques, bats and swine. However, there is no current data that could confirm the presence of WNV in the vector responsible for transmission of WNV to a wide range of hosts. Using molecular analysis, WNV RNA was detected from Culex (Cx.) tritaeniorhynchus, Cx. vishnui, Cx. pseudovishnui, Cx. gelidus, Armigeres subalbatus, and Coquillettidia spp. The sequence of WNV RNA detected in mosquitoes was similar to the WNV lineage recovered from wild birds at the same location. These findings confirm the presence of an enzootic cycle of WNV in Malaysia and the risk for spill-over to humans and other vertebrates. Being a tropical country with a conducive environment for mosquitoes, mosquito-borne illnesses such as dengue, chikungunya, lymphatic filariasis, malaria, and Japanese encephalitis are prevalent in Malaysia. Recent studies reported asymptomatic infection of West Nile virus (WNV) in animals and humans, but none of the studies included mosquitoes, except for one report made half a century ago. Considering the scarcity of information, our study sampled mosquitoes near migratory bird stopover wetland areas of West Coast Malaysia located in the Kuala Gula Bird Sanctuary and Kapar Energy Venture, during the southward migration period in October 2017 and September 2018. Our previous publication reported that migratory birds were positive for WNV antibody and RNA. Using a nested RT-PCR analysis, WNV RNA was detected in 35 (12.8%) out of 285 mosquito pools consisting of 2,635 mosquitoes, most of which were Culex spp. (species). Sanger sequencing and phylogenetic analysis revealed that the sequences grouped within lineage 2 and shared 90.12%-97.01% similarity with sequences found locally as well as those from Africa, Germany, Romania, Italy, and Israel. Evidence of WNV in the mosquitoes substantiates the need for continued surveillance of WNV in Malaysia.