Circulation of Japanese encephalitis virus in pigs and mosquito vectors within Can Tho city, Vietnam.

Johanna F Lindahl,Ho Thi Viet Thu,Sofia Boqvist,Jan Chirico,Karl Ståhl,Ulf Magnusson,Michael J Turell

doi:10.1371/journal.pntd.0002153

Abstract

Japanese encephalitis virus (JEV) is a mosquito-borne, zoonotic flavivirus causing encephalitis in humans and reproductive disorder in pigs. JEV is present in large parts of Asia, where urbanization is high. Households within and outside Can Tho city, South Vietnam, were selected to monitor circulation of JEV. A nested RT-PCR was established to detect the presence of JEV in mosquitoes whereas sera from pigs belonging to households within the province were analyzed for the presence of antibodies to JEV. A total of 7885 mosquitoes were collected and divided into 352 pools whereof seven were JEV-positive, six of which were collected within the city. Fragments from four pools clustered with JEV genotype III and three with genotype I. Of the 43 pigs sampled inside the city 100% had JEV antibodies. Our study demonstrates exposure to JEV in pigs, and co-circulation of JEV genotype I and III in mosquitoes within an urban environment in South Vietnam. Thus, although JEV has mainly been considered a rural disease, the potential for transmission in urban areas cannot be ignored.

Highlights

Japanese encephalitis (JE) is a zoonotic disease spread over large parts of Asia
Japanese encephalitis virus is a mosquito-borne flavivirus which is divided into five genotypes [4], and the virus has been isolated from more than 25 mosquito species, not all are important in the epidemiology of JEV [5]
The authors show that of 43 pigs sampled in Can Tho city, South Vietnam, all had antibodies to JE virus (JEV), and since some of these were born in the city, they must have been infected within the urban area

Summary

Introduction

Japanese encephalitis (JE) is a zoonotic disease spread over large parts of Asia. It is one of the most important arboviral encephalitis in humans, with an estimated 10 million cases over the last 60 years, with 30% case fatality [1]. It has been shown that two prerequisites for spreading JEV, the presence of competent vectors and the main amplifying host (the pig), are met in urban settings [9,10]. The presence of JEV in urban areas has not been studied extensively previously, previous studies in other cities in Asia have shown seropositivity in humans [11,12]

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