Serological evidence of continued Japanese encephalitis virus transmission in Singapore nearly three decades after end of pig farming

Yap, Grace; Lim, Xiao Fang; Chan, Sharon; How, Choon Beng; Humaidi, Mahathir; Yeo, Gladys; Mailepessov, Diyar; Kong, Marcella; Lai, Yee Ling; Okumura, Chiharu; Ng, Lee Ching

doi:10.1186/s13071-019-3501-0

Cited by 32 publications

(39 citation statements)

References 31 publications

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“…Japanese encephalitis is endemic in many Asian countries and contributes to an annual disease burden of *30,000-50,000 reported cases and 10,000 deaths (Solomon 2006, Erlanger et al 2009, Tiwari et al 2012. Subsequent to abolishment of pig farms in 1992, the incidence of Japanese encephalitis in Singapore dropped sharply (See et al 2002, Ting et al 2004, Koh et al 2006, Wang and Liang 2015, Yap et al 2019. However, serological surveys revealed exposure to Japanese encephalitis virus ( JEV) in wild boars, dogs, chickens, cows, and goats, suggesting the likelihood of an enzootic transmission cycle in local animal populations (See et al 2002, Ting et al 2004, Yap et al 2019.…”

Section: Introductionmentioning

confidence: 99%

Molecular Analysis of the Bloodmeals ofCulexspp. Mosquitoes at Natural Habitats in Singapore to Investigate the Potential Risk of Japanese Encephalitis Virus and West Nile Virus Transmission

Yeo

Chan

How

et al. 2020

Vector-Borne and Zoonotic Diseases

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Japanese encephalitis virus (JEV) and West Nile virus (WNV) are arboviruses primarily transmitted by Culex spp. mosquitoes. Birds are the primary hosts for JEV and WNV. Recent WNV outbreaks in Europe and United States and their association with migratory birds highlight the importance of understanding the feeding host preference of potential vectors for outbreak preparedness, especially in nonendemic settings. Singapore is nonendemic to JEV and WNV, but is a stopover site for migratory birds of the East Asian-Australasian Flyway. Therefore, we elucidated the feeding host range of Culex spp. mosquitoes captured in four natural (bird) habitats in Singapore from January 2011 to December 2012. We characterized feeding host DNA in field-caught mosquitoes using a PCR sequencing-based assay targeting the mitochondrial gene regions. Of 22,648 mosquitoes captured, 21,287 belonged to the Culex vishnui subgroup. The host DNA analysis showed that mosquitoes from the Cx. vishnui subgroup are opportunistic biters, feeding on a range of birds and mammals. Cx. vishnui subgroup, Culex sitiens and Culex bitaeniorhynchus, was primarily ornithophagic, although they fed opportunistically on mammals, including humans. Culex gelidus and Culex quinquefasciatus, in contrast, fed mainly on mammals. The presence of ornitho-and anthropophilic mosquito vectors and susceptible avian and mammalian hosts poses a risk spill-over transmission of JEV and WNV among humans, should these viruses be introduced through migratory birds and establish persistent transmission in resident birds and animal hosts in Singapore.

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Section: Introductionmentioning

confidence: 99%

Molecular Analysis of the Bloodmeals ofCulexspp. Mosquitoes at Natural Habitats in Singapore to Investigate the Potential Risk of Japanese Encephalitis Virus and West Nile Virus Transmission

Yeo

Chan

How

et al. 2020

Vector-Borne and Zoonotic Diseases

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“…However, seroprevalence of local wild pigs in Singapore remains relatively high at 15.2% for a country without recent clinical cases. From our study, it is shown that local birds have JEV seropositivity rate of 3.2% and the JEV antibody is detected mainly in herons and raptors [27]. This indicates possible sylvatic transmission between the vector and both the amplifying and reservoir hosts.…”

Section: Discussionmentioning

confidence: 60%

“…Further evidence of JEV seropositivity in ardeid birds, raptors, wild boars and sentinel chickens from 2010 till 2017 demonstrated that JEV transmission in animal hosts has continued despite the abolishment of pig farms [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Spatial Analysis of Japanese Encephalitis Virus Transmission Risk Factors in Singapore

Humaidi

Kwan

Xinli

et al. 2020

Preprint

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Abstract Background Singapore was previously endemic for JEV but the threat of JE remains. There is continued JEV transmission in animal hosts despite the banning of pig farming in 1992. Surveillance of mosquitoes, ardeid birds and swine gives public health officials useful warning signs for the monitoring of JEV. In this study, we aim to develop a JE Risk Map based on the data gathered by spatial and quantitative survey of the JE-associated vectors and animal hosts. Methods For over a year across the island, the distribution and population of herons were visually surveyed and the distribution of wild boars was captured with wildlife camera traps. Mosquito population data was collected from 16 sites with ecological factors suitable for JE transmission. The animal and vector data were then spatially analysed using open-sourced GIS software. Results Four JE high risk clusters were interpolated from the combined risk factors of data points. A JEV positive Culex tritaeniorynchus pool was subsequently detected in the largest of these JE high risk clusters.

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“…Pigs act as an amplifier host of JEV, thus can be a key suspect of spreading infection to human living in close proximity [4]. The detection of JEV in pigs was reported earlier from Cambodia, Singapore, Vietnam, Australia, Japan, China, Thailand, Laos, Indonesia, India etc (Fig 6) [22, 34-42], however the studies on pigs for the presence of JE virus and its genotypes in circulation among pigs in India are limited [19]. Hence, the current investigation was mainly focused on the JE virus detection in pig serum and tonsil in three different JE endemic states of India namely Odisha, Assam and Manipur.…”

Section: Discussionmentioning

confidence: 95%

Molecular epidemiology of Japanese Encephalitis Virus in pig population of Odisha, Assam and Manipur states of India

Datey

Singh²,

Rajkhowa

et al. 2019

Preprint

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AbstractJapanese encephalitis virus (JEV) comes under the family Flaviviridae and genus flavivirus. It predominantly infects the children under the age of 10 years and the case fatality rate can stretch out as high as 30%. Pigs act as reservoir and amplifying intermediate host for JEV. Recent report suggested longer persistence of JEV in tonsil than in circulation of experimentally infected pigs. The current investigation was conducted to understand the prevalence and molecular epidemiology of JEV infection in pigs in three different geographical sites in India (Odisha, Assam and Manipur). Serum samples were tested by ELISA and RT-PCR for detection of JEV, while only RT-PCR was done in case of tonsils tissues collected from pigs slaughtered in abattoir. Prevalence of JEV was highest in Manipur (25.45% in serum and 10.08% in tonsil) but lower in Assam (3.75% in serum and 0% in tonsils) and Odisha (1.49% in serum and 3.7% in tonsils). The percentage of sero-positivity was found to be 3.75% of IgM and 9.9% of IgG in Assam and Odisha respectively. Genotype III (GIII) of JEV was the dominant genotype and sporadic mutations of S83G, H76P, E78Q, C55S, and S64W along with two consistent mutations V46S and V51I were observed in all the GIII strains. Analysis of the E gene sequence revealed a single mutation, S118N in the GI strain. Older pigs (above 7 months) were found to be infected relatively more (8.6%) than younger pigs (age group 3-7 months). In conclusion, the high JE virus infection rate of pig in the current locations suggests the need for continuous surveillance of this virus in pigs which will ultimately help to adopt an effective control strategy to prevent the spread of JE infection to human.Author summaryJapanese encephalitis is one of the contributing factors in acute encephalitis syndrome cases reported across India as well as Asia. Primarily young naive human population are affected with JEV. The death rate can be as high as 30% and in about 30%-50% surviving population paralysis, brain damage or other serious permanent sequelae may be observed. The viral load gets amplified in pigs and thus plays a crucial role in transmitting the infection in human communities living in close proximity to pig dwelling. The current study was conducted to demonstrate prevalence of JEV in pig population of three geographical regions of India viz. the States of Odisha, Assam and Manipur that have reported JE outbreaks in human population. The current study demonstrates that the rate of infection is 3.28% among pigs in Manipur followed by Assam and Odisha. GIII was found to be the most predominant JEV genotype, while only one GI genotype strain was detected from Odisha region. These findings suggested the need of continuous surveillance of this virus in pigs and proper implementation of human and animal vaccination programme to control the infection.

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Serological evidence of continued Japanese encephalitis virus transmission in Singapore nearly three decades after end of pig farming

Cited by 32 publications

References 31 publications

Molecular Analysis of the Bloodmeals ofCulexspp. Mosquitoes at Natural Habitats in Singapore to Investigate the Potential Risk of Japanese Encephalitis Virus and West Nile Virus Transmission

Molecular Analysis of the Bloodmeals ofCulexspp. Mosquitoes at Natural Habitats in Singapore to Investigate the Potential Risk of Japanese Encephalitis Virus and West Nile Virus Transmission

Spatial Analysis of Japanese Encephalitis Virus Transmission Risk Factors in Singapore

Molecular epidemiology of Japanese Encephalitis Virus in pig population of Odisha, Assam and Manipur states of India

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