Evaluation of vector competence of Culex tritaeniorhynchus and Culex pipiens pallens for Japanese encephalitis virus genotype III and V

TL;DR

This study compares how well two mosquito species transmit Japanese encephalitis virus, finding that one is a highly effective carrier while the other may contribute to urban spread.

Contribution

The study provides new insights into the vector competence of Cx. pipiens pallens for JEV genotypes in urban settings.

Findings

Cx. tritaeniorhynchus showed over 95% infection and transmission rates for both JEV genotypes.

Cx. pipiens pallens had lower infection rates but high dissemination and transmission among infected mosquitoes.

Viral loads were significantly higher in Cx. tritaeniorhynchus compared to Cx. pipiens pallens.

Abstract

Japanese encephalitis virus (JEV) is a major mosquito-borne pathogen, primarily transmitted by Culex tritaeniorhynchus in rural regions. In the Republic of Korea (ROK), genotype V (GV) has become the dominant JEV strain since 2010, raising suspicion about the vector competence of urban mosquitoes like Culex pipiens pallens.

This study evaluated the vector competence of Cx. tritaeniorhynchus and Cx. pipiens pallens for JEV GIII and GV under laboratory conditions. Mosquitoes were orally infected, and the infection rate (IR), dissemination rate (DR), and transmission rate (TR) were assessed at days 7 and 14 post-infection.

Culex tritaeniorhynchus showed consistently high IR, DR, and TR for both genotypes, with over 95% of mosquitoes infected and actively transmitting the virus. In contrast, Cx. pipiens pallens exhibited a markedly lower IR, ranging from 23.1 to 39.2%; however, among infected mosquitoes, DR and TR were comparatively high. Viral load and titers were also markedly higher in Cx. tritaeniorhynchus than in Cx. pipiens pallens, particularly in the head-thorax and salivation samples.

These findings confirm that Cx. tritaeniorhynchus is a highly competent vector for JEV GIII and GV and suggest that Cx. pipiens pallens may play a notable role in the transmission of Japanese encephalitis virus in urban areas. This study emphasizes the importance of targeted vector surveillance and control strategies for multiple mosquito species, especially given the recent urbanization of JE cases in the ROK.

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