Standing at the crossroads: the emergence of Japanese encephalitis in Australia
J. R. Gilkerson A *A
James Gilkerson is an equine veterinarian whose research interests focus on the diagnosis, epidemiology and prevention of infectious diseases. James is currently a professor of veterinary microbiology and director of the Centre for Equine Infectious Disease at the Melbourne Veterinary School. |
Abstract
Japanese encephalitis virus (JEV) was detected in pigs (Sus scrofa) in four Australian states in 2022. Human cases, including three deaths, were also reported. Japanese encephalitis virus is maintained in nature in an infection cycle between mosquitos and waterbirds. This outbreak was the first report of ongoing JEV transmission on the Australian mainland. Other members of the JE serogroup, West Nile virus and Murray Valley encephalitis virus, are already established in endemic cycles in Australia and large outbreaks of infection with these viruses have been reported following widespread flooding events. As an arbovirus that affects both domestic and wild animals, as well as people, JEV is a classical One Health issue. The effects of climate change drive longer, warmer and wetter conditions that favour expansion of invertebrate vectors and vertebrate reservoir hosts, which in turn increases the likelihood of spillover events, which affects domestic animals and humans. Horses and humans are considered to be ‘dead-end’ hosts of viruses in the JEV serogroup, as there is insufficient viraemic titre for subsequent transmission to mosquitos. However, pigs are considered amplifying hosts of JEV infection and contribute to maintenance of ongoing infection cycles. The 2022 outbreak highlighted the importance of a One Health approach in responding to arbovirus outbreaks. A focus on human cases and a lack of sensitive and specific diagnostic tests limits the capacity of authorities to undertake effective surveillance of the distribution of an outbreak in other animal species that are more important to the ecology of JEV.
Keywords: arbovirus, Australia, equine, flavivirus, Japanese encephalitis, JEV, mosquito, One Health, porcine.
James Gilkerson is an equine veterinarian whose research interests focus on the diagnosis, epidemiology and prevention of infectious diseases. James is currently a professor of veterinary microbiology and director of the Centre for Equine Infectious Disease at the Melbourne Veterinary School. |
References
1 Hanna JN et al. (1996) An outbreak of Japanese encephalitis in the Torres Strait, Australia, 1995. Med J Aust 165, 256-260.
| Crossref | Google Scholar | PubMed |
2 van den Hurk AF et al. (2019) Japanese encephalitis virus in Australia: from known known to known unknown. Trop Med Infect Dis 4, 38.
| Crossref | Google Scholar | PubMed |
3 Waller C et al. (2022) Japanese encephalitis in Australia – a sentinel case. N Engl J Med 387, 661-662.
| Crossref | Google Scholar | PubMed |
4 Kuwata R et al. (2020) Distribution of Japanese encephalitis virus, Japan and Southeast Asia, 2016–2018. Emerg Infect Dis 26, 125-128.
| Crossref | Google Scholar | PubMed |
5 World Health Organization (2022) Disease Outbreak News, Japanese Encephalitis – Australia, 28 April 2022. WHO. https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON365
7 Scherer WF et al. (1959) Ecologic studies of Japanese encephalitis virus in Japan. VI. Swine infection. Am J Trop Med Hyg 8, 698-706.
| Crossref | Google Scholar | PubMed |
8 Matsuda S (1962) An epidemiologic study of Japanese B encephalitis with special reference to the effectiveness of the vaccination. Bull Inst Publ Hlth, Tokyo 11, 173-190.
| Google Scholar |
9 Solomon T, Winter PM (2004) Neurovirulence and host factors in flavivirus encephalitis – evidence from clinical epidemiology. In Emergence and Control of Zoonotic Viral Encephalitides (Calisher CH, Griffin DE, eds). Archives of Virology, vol. 18(suppl. a), pp. 161–170. Springer, Vienna, Austria. 10.1007/978-3-7091-0572-6_14
11 Holmes JM et al. (2012) Murray Valley encephalomyelitis in a horse. Aust Vet J 90, 252-254.
| Crossref | Google Scholar | PubMed |
12 Roche SE et al. (2013) Descriptive overview of the 2011 epidemic of arboviral disease in horses in Australia. Aust Vet J 91, 5-13.
| Crossref | Google Scholar | PubMed |
13 Tee SY et al. (2012) Kunjin flaviviral encephalomyelitis in an Arabian gelding in New South Wales, Australia. Aust Vet J 90, 321-324.
| Crossref | Google Scholar | PubMed |
14 World Organisation for Animal Health (2022) Australia – Japanese encephalitis – Immediate notification. (WAHIS) https://wahis.woah.org/#/in-review/4338?reportId=154328&fromPage=event-dashboard-url
15 Yang D-K (2024) Chapter 3.1.10. Japanese encephalitis. In Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. World Organisation for Animal Health. https://www.oie.int/fileadmin/Home/eng/Health_standards/tahm/3.01.10_JEV.pdf
