Orthoflavivirus circulation in South-East Queensland, Australia, before and during the 2021-2022 incursion of Japanese encephalitis virus assessed through sero-epidemiological survey of a sentinel equine population.
Abstract: An incursion and outbreak of Japanese encephalitis virus (JEV) was reported in Australia in 2021 and 2022, respectively. There was speculation that JEV may have been circulating in Australia unknowingly prior to the detection. In this study, we determined sero-prevalence and transmission of West Nile virus (WNV), Murray Valley encephalitis virus (MVEV) and JEV, prior to and post JEV incursion in a sentinel equine population in south-east Queensland (SEQ), Australia, using blocking ELISAs (screening test) and virus neutralisation test (confirmatory). Serum samples collected between 2018 and 2020 (prior to JEV incursion; = 607) from horses residing in SEQ revealed that sero-prevalence to pathogenic orthoflaviviruses was low, specifically WNV (1.3 %; 8/607), MVEV (1.2 %; 7/607), and JEV (4.9 %; 30/607). The significantly higher prevalence of JEV ( < 0.05) was skewed by the high proportion of horses previously enrolled in one or more JEV vaccine studies (17/30; 56.7 %) and the unknown JEV vaccination history due to international travel (6/30; 20 %). Thirty-two foals were enrolled as sentinels to monitor for arbovirus transmissions in SEQ between 2020 and 2023. Results showed that JEV seroconversion was first detected in April 2022 ( = 4), with seven more seroconversions detected in the following months until November 2022. This study (i) confirms that it is highly unlikely that JEV incursion in SEQ occurred prior to February 2022; (ii) circulation of WNV in SEQ remains very low; and (iii) highlights the complexity in the interpretation of orthoflavivirus serological results. The authors propose that horses should be included as sentinels for arbovirus transmission monitoring in Australia.
© 2024 The Authors.
Publication Date: 2024-11-05 PubMed ID: 39802065PubMed Central: PMC11723196DOI: 10.1016/j.onehlt.2024.100930Google Scholar: Lookup
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- Journal Article
Summary
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Overview
- This study investigated the presence and spread of Japanese encephalitis virus (JEV) and related orthoflaviviruses in horses in South-East Queensland, Australia, before and during the 2021-2022 JEV outbreak.
- The research used serological testing to track virus exposure in horses, concluding that JEV likely did not circulate widely before 2022, and that horses can serve as effective sentinels for monitoring these viruses.
Background and Purpose
- Japanese encephalitis virus (JEV) caused a significant outbreak in Australia in 2021-2022, raising questions about whether it had previously been circulating unnoticed.
- Other orthoflaviviruses of concern include West Nile virus (WNV) and Murray Valley encephalitis virus (MVEV), which can also infect horses and humans.
- This study aimed to determine the sero-prevalence (presence of virus-specific antibodies indicating past infection or vaccination) and transmission of JEV, WNV, and MVEV in horses from South-East Queensland (SEQ), both before and after the documented JEV incursion.
- Horses were targeted as sentinels because their infections can reflect arbovirus activity in the environment, helping to monitor potential risks to humans and other animals.
Methodology
- Sample Collection:
- 607 serum samples were collected from horses in SEQ between 2018 and 2020, prior to the known JEV outbreak.
- 32 foals were enrolled and monitored longitudinally from 2020 to 2023 to detect new infections, termed seroconversions.
- Serological Testing:
- Initial screening was done using blocking ELISA, which identifies antibodies to orthoflaviviruses broadly.
- Positive ELISA results were confirmed with virus neutralisation tests, which specifically identify antibodies against individual viruses such as JEV, WNV, or MVEV.
Key Findings
- Low Prevalence Before Outbreak:
- WNV antibodies were detected in only 1.3% of horses (8/607).
- MVEV antibodies were found in 1.2% (7/607).
- JEV antibodies were detected in 4.9% (30/607), but this was influenced by previous vaccinations or unknown vaccination status related to international travel.
- JEV Seroconversion During Outbreak:
- In the foals monitored as sentinels, JEV seroconversion was first detected in April 2022.
- Additional seroconversions were recorded up until November 2022, confirming active JEV transmission during that period.
- Interpretation of Serology:
- The higher pre-outbreak JEV prevalence largely reflected vaccination history rather than natural infection.
- This complexity highlights challenges in interpreting serological data for flaviviruses, as vaccines and cross-reactive antibodies can confound results.
Conclusions and Implications
- The study strongly supports that JEV was unlikely circulating in South-East Queensland before early 2022, indicating the outbreak was indeed a new incursion.
- West Nile virus prevalence remains very low in the region, suggesting limited risk from this virus at present.
- The research underscores the need for careful consideration of vaccination status and cross-reactivity when interpreting flavivirus serology.
- Horses are validated as valuable sentinels for monitoring arbovirus transmission, providing early indicators of virus activity that can inform public health and veterinary responses.
- Inclusion of horses in routine arboviral surveillance programs in Australia is recommended to improve early detection and control efforts.
Cite This Article
APA
Yuen NKY, Harrison JJ, Wang ASW, McMahon IE, Habarugira G, Coyle MP, Bielefeldt-Ohmann H.
(2024).
Orthoflavivirus circulation in South-East Queensland, Australia, before and during the 2021-2022 incursion of Japanese encephalitis virus assessed through sero-epidemiological survey of a sentinel equine population.
One Health, 19, 100930.
https://doi.org/10.1016/j.onehlt.2024.100930 Publication
Researcher Affiliations
- School of Veterinary Science, Faculty of Science, The University of Queensland, Gatton, QLD 4343, Australia.
- School of Chemistry and Molecular Biosciences, Faculty of Science, The University of Queensland, Brisbane, QLD 4072, Australia.
- School of Veterinary Science, Faculty of Science, The University of Queensland, Gatton, QLD 4343, Australia.
- School of Chemistry and Molecular Biosciences, Faculty of Science, The University of Queensland, Brisbane, QLD 4072, Australia.
- School of Chemistry and Molecular Biosciences, Faculty of Science, The University of Queensland, Brisbane, QLD 4072, Australia.
- Equine Unit, Office of the Director Gatton Campus, The University of Queensland, Gatton, QLD 4343, Australia.
- School of Chemistry and Molecular Biosciences, Faculty of Science, The University of Queensland, Brisbane, QLD 4072, Australia.
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, QLD 4072, Australia.
- Equine Unit, Office of the Director Gatton Campus, The University of Queensland, Gatton, QLD 4343, Australia.
Conflict of Interest Statement
H.B.O. is the proprietor of the consultancy firm BIOHMPATHOLOGY. Data included in this publication are based on a patent (WO/2018/176075), on which H.B.O and J.J.H are inventors. All other authors declare no conflict of interest.
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Citations
This article has been cited 1 times.- Rusenova N, Rusenov A. First Serologic Evidence of West Nile Virus and Usutu Virus Circulation Among Dogs in the Bulgarian Danube Region and Analysis of Some Risk Factors.. Vet Sci 2025 Apr 16;12(4).
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