A scoping review of evidence of naturally occurring Japanese encephalitis infection in vertebrate animals other than humans, ardeid birds and pigs

Abstract

Japanese encephalitis virus (JEV) is the leading cause of human encephalitis in Asia. JEV is a vector-borne disease, mainly transmitted by Culex mosquitoes, with Ardeidae birds as maintenance hosts and pigs as amplifying hosts. Other vertebrate animal hosts have been suggested to play a role in the epidemiology of JEV. This scoping review followed PRISMA guidelines to identify species in which evidence of naturally occurring JEV infection was detected in vertebrates other than ardeid birds, pigs and people. Following systematic searches, 4372 records were screened, and data were extracted from 62 eligible studies. Direct evidence (virus, viral antigen or viral RNA ) of JEV infection was identified in a variety of mammals and birds (not always identified to the species level), including bats, passerine birds (family Turdidae), livestock (cattle [Bos taurus] and a goat [Capra hircus]), carnivores (two meerkats [Suricata suricatta]), and one horse (Equus caballus). Bat families included Pteropodidae, Vespertilionidae, Rhinolophidae, Miniopteridae, Hipposideridae. Indirect evidence suggestive of JEV infection (antibodies) was detected in several mammalian and avian orders, as well as reported in two reptile species. However, a major limitation of the evidence of JEV infection identified in this review was diagnostic test accuracy, particularly for serological testing. Studies generally did not report diagnostic sensitivity or specificity. Although we hypothesise that bats and passerine birds could play an underappreciated role in JEV epidemiology, development of diagnostic tests to differentiate JEV from other orthoflaviviruses will be critical for effective surveillance in these, as well as the companion and livestock species that could be used to evaluate JEV control measures in currently endemic regions.

Scoping review of Japanese encephalitis virus transmission models

“…In their review on the ecology of JEV, Mulvey et al (2021) noted the detection of JEV in various domestic animals and wildlife beyond ardeid wading birds and pigs. While pigs are recognised as amplifying hosts, overlooking other potential competent hosts may lead to underestimating the true extent of JEV transmission (Le Flohic et al 2013;Levesque et al 2024). Notably, JEV transmission in animal hosts has been observed to continue despite the phasing out of pig farming in Singapore over 30 years ago (Yap et al 2019).…”