The Emergence of Japanese Encephalitis Virus in Australia in 2022: Existing Knowledge of Mosquito Vectors

Hurk, Andrew van den; Skinner, Eloise B; Ritchie, Scott A.; Mackenzie, John S.

doi:10.3390/v14061208

Cited by 50 publications

(70 citation statements)

References 96 publications

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“…gelidus, both of which are well-established JEV vectors across the Indo-Pacific region, and Cx. quinquefasciatus, which is well established throughout Australia [21].…”

Section: Introductionmentioning

confidence: 99%

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Little pig, little pig, let me come in: The influence of landscape structure and La Niña climatic anomalies on the emergence of Japanese encephalitis virus in Australian piggeries in 2022

Walsh

Webb

Brookes

2022

Preprint

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The widespread activity of Japanese encephalitis virus (JEV) in previously unaffected regions of eastern and southern Australia in 2022 represents the most significant local arbovirus emergency in almost 50 years. Japanese encephalitis virus is transmitted by mosquitoes and maintained in wild ardeid birds and amplified in pigs, the latter of which suffer significant reproductive losses as a result of infection. The landscape of JEV outbreak risk in mainland Australia is almost entirely unknown, particularly in the eastern and southern parts of the country where the virus has not been previously documented. Although other areas with endemic JEV circulation in the Indo-Pacific region have demonstrated the importance of wild waterbird-livestock interface in agricultural-wetland mosaics, no such investigation has yet determined the configuration of pathogenic landscapes for Australia. Moreover, the recent emergence in Australia has followed substantial precipitation and temperature anomalies associated with the La Niña phase of the El Niño Southern Oscillation. This study investigated the landscape epidemiology of JEV outbreaks in Australian piggeries recorded between January and April of 2022 to determine the influence of ardeid habitat suitability, hydrogeography, hydrology, land cover and La Niña-associated climate anomalies in demarcating risk. Outbreaks of JEV in domestic pigs were associated with ardeid species richness, agricultural and riparian landscape mosaics, hydrological flow accumulation, and grasslands. This study has identified the composition and configuration of landscape features that delineated risk for piggeries during the 2022 emergence of JEV in Australia. Although preliminary, these findings can inform actionable strategies for the development of new One Health JEV surveillance specific to the needs of Australia.

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“…gelidus, both of which are well-established JEV vectors across the Indo-Pacific region, and Cx. quinquefasciatus, which is well established throughout Australia [21].…”

Section: Introductionmentioning

confidence: 99%

“…gelidus , both of which are well-established JEV vectors across the Indo-Pacific region, and Cx. quinquefasciatus , which is well established throughout Australia[21]. There remains much to learn about the role of local mosquito species, their abundance, and diversity in driving transmission and spillover in Australia.…”

Section: Introductionmentioning

confidence: 99%

Little pig, little pig, let me come in: The influence of landscape structure and La Niña climatic anomalies on the emergence of Japanese encephalitis virus in Australian piggeries in 2022

Walsh

Webb

Brookes

2022

Preprint

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“…Other than Cx . annulirostris , few studies have been undertaken on the competence of other mosquito species to transmit the different JEV genotypes [ 73 ].…”

Section: Discussionmentioning

confidence: 99%

Molecular detection and characterisation of the first Japanese encephalitis virus belonging to genotype IV acquired in Australia

et al. 2022

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Background A fatal case of Japanese encephalitis (JE) occurred in a resident of the Tiwi Islands, in the Northern Territory of Australia in February 2021, preceding the large JE outbreak in south-eastern Australia in 2022. This study reports the detection, whole genome sequencing and analysis of the virus responsible (designated JEV/Australia/NT_Tiwi Islands/2021). Methods Reverse transcription quantitative PCR (RT-qPCR) testing was performed on post-mortem brain specimens using a range of JE virus (JEV)-specific assays. Virus isolation from brain specimens was attempted by inoculation of mosquito and mammalian cells or embryonated chicken eggs. Whole genome sequencing was undertaken using a combination of Illumina next generation sequencing methodologies, including a tiling amplicon approach. Phylogenetic and selection analyses were performed using alignments of the Tiwi Islands JEV genome and envelope (E) protein gene sequences and publicly available JEV sequences. Results Virus isolation was unsuccessful and JEV RNA was detected only by RT-qPCR assays capable of detecting all JEV genotypes. Phylogenetic analysis revealed that the Tiwi Islands strain is a divergent member of genotype IV (GIV) and is closely related to the 2022 Australian outbreak virus (99.8% nucleotide identity). The Australian strains share highest levels of nucleotide identity with Indonesian viruses from 2017 and 2019 (96.7–96.8%). The most recent common ancestor of this Australian-Indonesian clade was estimated to have emerged in 2007 (95% HPD range: 1998–2014). Positive selection was detected using two methods (MEME and FEL) at several sites in the E and non-structural protein genes, including a single site in the E protein (S194N) unique to the Australian GIV strains. Conclusion This case represents the first detection of GIV JEV acquired in Australia, and only the second confirmed fatal human infection with a GIV JEV strain. The close phylogenetic relationship between the Tiwi Islands strain and recent Indonesian viruses is indicative of the origin of this novel GIV lineage, which we estimate has circulated in the region for several years prior to the Tiwi Islands case.

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“…Recently, JEV has spread in Australia to new geographic regions. 168 Geographic expansion of flaviviruses pathogenic for equids should thus always be considered a realistic threat, and their detection should be included in surveillance programs.…”

Section: Discussionmentioning

confidence: 99%

European College of Equine Internal Medicine consensus statement on equine flaviviridae infections in Europe

Cavalleri

Korbacska-Kutasi

Leblond

et al. 2022

Veterinary Internal Medicne

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Horses and other equids can be infected with several viruses of the family Flaviviridae, belonging to the genus Flavivirus and Hepacivirus. This consensus statement focuses on viruses with known occurrence in Europe, with the objective to summarize the current literature and formulate clinically relevant evidence‐based recommendations regarding clinical disease, diagnosis, treatment, and prevention. The viruses circulating in Europe include West Nile virus, tick‐borne encephalitis virus, Usutu virus, Louping ill virus and the equine hepacivirus. West Nile virus and Usutu virus are mosquito‐borne, while tick‐borne encephalitis virus and Louping ill virus are tick‐borne. The natural route of transmission for equine hepacivirus remains speculative. West Nile virus and tick‐borne encephalitis virus can induce encephalitis in infected horses. In the British Isle, rare equine cases of encephalitis associated with Louping ill virus are reported. In contrast, equine hepacivirus infections are associated with mild acute hepatitis and possibly chronic hepatitis. Diagnosis of flavivirus infections is made primarily by serology, although cross‐reactivity occurs. Virus neutralization testing is considered the gold standard to differentiate between flavivirus infections in horses. Hepacivirus infection is detected by serum or liver RT‐PCR. No direct antiviral treatment against flavi‐ or hepacivirus infections in horses is currently available and thus, treatment is supportive. Three vaccines against West Nile virus are licensed in the European Union. Geographic expansion of flaviviruses pathogenic for equids should always be considered a realistic threat, and it would be beneficial if their detection was included in surveillance programs.

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The Emergence of Japanese Encephalitis Virus in Australia in 2022: Existing Knowledge of Mosquito Vectors

Cited by 50 publications

References 96 publications

Little pig, little pig, let me come in: The influence of landscape structure and La Niña climatic anomalies on the emergence of Japanese encephalitis virus in Australian piggeries in 2022

Little pig, little pig, let me come in: The influence of landscape structure and La Niña climatic anomalies on the emergence of Japanese encephalitis virus in Australian piggeries in 2022

Molecular detection and characterisation of the first Japanese encephalitis virus belonging to genotype IV acquired in Australia

European College of Equine Internal Medicine consensus statement on equine flaviviridae infections in Europe

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