The detection of Japanese encephalitis virus in Megachiropteran bats in West Kalimantan, Indonesia: A potential enzootic transmission pattern in the absence of pig holdings

Abstract

The West Kalimantan province in Borneo island, Indonesia belongs to endemic area of Japanese encephalitis (JE) that accounts for approximately 30% of total cases yearly. As the presence of pig holdings is uncommon in West Kalimantan, another reservoir host might have played a role in the local transmission of JE virus in this area. Current study aimed to identify the potential role of bats in the local transmission of JE by performing molecular detection of JE virus in bats and mosquitoes using RT-PCR. Sample collection was performed in 3 districts in West Kalimantan, covering 3 different ecosystems: forest, coastal, and residential areas. Bat collection was performed using mist net and harp net, while mosquito collection was carried out using animal-baited trap and human landing collection. A total of 373 blood samples from bats were tested for JE virus, among which 21 samples (5.6%) showed positive results, mainly from Cynopterus brachyotis (lesser short-nosed fruit bat) found in residential areas. Out of 53 mosquito pools, 3 JE-positive pools of Culex tritaeniorhynchus and Cx. vishnui were collected at the same location as JE-positive bats. Current study showed the first evidence of JE virus detection in several species of Megachiropteran bats in Indonesia, demonstrated the potential role of frugivorous bats in local transmission of JE in West Kalimantan. More aggressive measures are required in JE risk mitigation, particularly in initiating JE vaccination campaign and in avoiding disruption of bats’ natural habitats through changes in land-use.

Estimation of Japanese encephalitis virus infection prevalence in mosquitoes and bats through nationwide sentinel surveillance in Indonesia

“…The results of the current study showed overlapping of bat and mosquito flight ranges among JE-infected sample collection sites, demonstrating the possibility of viral spillover to other areas, including human dwellings. Similar findings have also been found in West Kalimantan province in our previous pilot study [ 25 ].…”

“…A total of 11 provinces were selected as study locations, and were determined based on the previous reports of human clinical cases of JE by the local health offices and previous studies [ 6 , 26 , 27 ], including West Sumatra, Riau, West Java, Yogyakarta, East Java, West Kalimantan, Bali, North Sulawesi, West Nusa Tenggara, East Nusa Tenggara, and Papua. The results of our pilot study conducted in West Kalimantan province have been published elsewhere [ 25 ], however, few data will be mentioned in this study in order to give the whole picture of JE virus infection in mosquitoes and bats in Indonesia. Sampling of bats and mosquitoes was purposively performed in 3 districts in each corresponding province and represents 3 different ecosystems: forest, coastal, and urban areas.…”

“…The viremia profiling in bats may be used to estimate the potential role of bats as the reservoir hosts for JE virus. This study depicts the national surveillance of JE virus in mosquitoes and bats in Indonesia, of which some data from West Kalimantan province have been mentioned elsewhere [ 25 ]. The implementation of the One Health concept in regard to environmental health is assessed through stratification of the ecosystem via sample collection and the measurement of climatic factors.…”

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

“…In a survey from 11 provinces in Indonesia, JEV viral RNA was detected by RT-PCR targeting the NS3 gene in blood samples from 61 of 2805 live, wild-caught pteropodid bats (2.3%) including the genera Cynopterus , Dobsonia , Eonycteris , Macroglossus , Pteropus , Rousettus , and Thoopterus [49]. Viral RNA was also detected in pteropodid bats in an earlier study in Indonesia (up to 43% of Balionycterus maculata ; other species were up to 9% prevalence) [50, 51]. The first detection of JEV infection in bats in India was in 2020, associated with a mortality event in which 52 pteropodid bats were found dead in Gorakhpur district, Uttar Pradesh, a province which has a high incidence of JE in people and JEV circulating in domestic pigs [52, 53].…”

“…Bats are known reservoirs of many viruses – for example, Hendra virus and lyssavirus – but their role in the epidemiology of orthoflaviruses, including JEV, is unknown despite research interest [76, 77]. This interest was reflected in the current review in which bats comprised >40% of all individuals sampled for direct evidence of JEV infection over an extensive spatiotemporal window (China, India, Indonesia, and Thailand from 1974 to 2022) [49–51, 54–56, 66]. Whilst ecological studies have not found evidence that bats are involved in the epidemiology of JEV, experimental investigation indicates that bats can be competent JEV hosts [78, 79].…”