Vector surveillance at Narita International Airport in 2021: the detection of Japanese encephalitis virus genotype I from Culex tritaeniorhynchus and the vector control conducted by Narita Airport Quarantine Station

Abstract

Vector surveillance was conducted at Narita International Airport in 2021. A total of 8,120 adult mosquitoes were collected. The most abundant species was Culex tritaeniorhynchus (7,821 adults, 96% of the total). The second was Cx. pipiens complex (184 adults) and the third was Aedes albopictus (84 adults). Among them, 8,097 female adults were tested for pathogen genes of flavi virus (8,085 adults, 377 pools), chikungunya virus (83 adults, 18 pools), and plasmodium parasites (12 adults, 10 pools). Japanese encephalitis virus (JEV) genotype I was detected from 2 pools (30 females) of Cx. tritaeniorhynchus. All other tests were negative. In response to the collection of JEV positive mosquitoes, we put up posters reminding passengers to avoid mosquito bites. Furthermore, people working outdoors at the airport at night were warned to avoid mosquito bites and to prevent mosquitoes from entering the cabin of aircraft parked at Narita International Airport. After the detection of JEV gene, we increased the frequency of survey and intensified surveillance until no more adult female Cx. tritaeniorhynchus were collected. Based on this survey, no risk of Japanese encephalitis infection at Narita International Airport was announced to the public on October 29, 2021.