Comparison of Japanese Encephalitis Force of Infection in Pigs, Poultry and Dogs in Cambodian Villages.

Héléna Ladreyt,Véronique Chevalier,Leangyi Heng,Saraden In,Sreymom Ken,Sokchea Lay,Sowath Ly,Philippe Dussart,Veasna Duong,Benoit Durand,Sothyra Tum,Heidi Auerswald,Chakriyouth Top

doi:10.3390/pathogens9090719

Abstract

Japanese encephalitis virus (JEV) is the main cause of human viral encephalitis in Asia, with a mortality rate reaching 30%, mostly affecting children. The traditionally described cycle involving wild birds as reservoirs, pigs as amplifying hosts and Culex mosquitoes as vectors is questioned, with increasing evidence of a more complex multi-host system involved in areas where densities of pigs are low, such as in Cambodia. In 2018, we examined pigs, chickens, ducks and dogs from Kandal province, Cambodia, for antibody response against JEV by hemagglutination inhibition and virus neutralization assays. Forces of infection (FOI) for flaviviruses and JEV were estimated per species and per unit of body surface area (BSA). JEV seroprevalence reached 31% (95% CI: 23–41%) in pigs, 1% (95% CI: 0.1–3%) in chickens, 12% (95% CI: 7–19%) in ducks and 35% (95% CI: 28–42%) in dogs. Pigs were most likely to be infected (FOI: 0.09 per month), but the FOI was higher in ducks than in pigs for a given BSA (ratio of 0.13). Dogs had a lower FOI than ducks but a higher FOI than chickens (0.01 per month). For a given BSA, dogs were less likely to be infected than pigs (ratio of 1.9). In Cambodia, the virus may be circulating between multiple hosts. Dogs live in close contact with humans, and estimating their exposure to JEV infection could be a relevant indicator of the risk for humans to get infected, which is poorly known due to underdiagnosis. Understanding the JEV cycle and developing tools to quantify the exposure of humans is essential to adapt and support control measures for this vaccine-preventable disease.

Highlights

IntroductionJapanese encephalitis virus (JEV) is the major cause of human viral encephalitis in Southeast Asia
Japanese encephalitis virus (JEV) is the major cause of human viral encephalitis in Southeast Asia.JE is detected in the rest of Asia, from India in the west to China in the north and Japan in the east, as well as in northern Australia
Out of the 666 sampled animals, seven pigs and eight chickens were excluded because their age was unknown, and three pigs were excluded because there was insufficient serum to undergo a foci reduction neutralization test (FRNT)

Summary

Introduction

Japanese encephalitis virus (JEV) is the major cause of human viral encephalitis in Southeast Asia. JE is detected in the rest of Asia, from India in the west to China in the north and Japan in the east, as well as in northern Australia. Its annual incidence has been estimated at around 68,000 cases per year, these figures may be underestimated since the disease occurs mainly in developing countries where access to care and case identification may be limited [1,2,3]. Three quarters of cases concern children and JE remains a substantial public health issue even in areas where human vaccination programs are implemented [1]. It is commonly accepted that JEV is transmitted between reservoirs (Ardeid birds) or amplification hosts (pigs) through the bites of Culex mosquitoes and probably some Aedes mosquitoes [5,6,7]

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