Suspect West Nile virus encephalomyelitis in an imported horse in the UK

Abstract Background West Nile virus (WNV) is a single-stranded RNA virus that can cause neurological disease in both humans and horses. Due to the movement of competent vectors and viraemic hosts, WNV has repeatedly emerged globally and more recently in western Europe. Within the UK, WNV is a notifiable disease in horses, and vaccines against the virus are commercially available. However, there has been no investigation into the seroprevalence of WNV in the UK equine population to determine the extent of vaccination or to provide evidence of recent infection. Methods Equine serum samples were obtained from the Animal and Plant Health Agency’s equine testing service between August and November 2019. A total of 988 serum samples were selected for horses resident in South East England. WNV seroprevalence was determined using two enzyme-linked immunosorbent assays (ELISAs) to detect total flavivirus antibodies and WNV-specific immunoglobulin M (IgM) antibodies. Positive IgM results were investigated by contacting the submitting veterinarian to establish the clinical history or evidence of prior vaccination of the horses in question. Results Within the cohort, 274 samples tested positive for flavivirus antibodies, of which two subsequently tested positive for WNV-specific IgM antibodies. The follow-up investigation established that both horses had been vaccinated prior to serum samples being drawn, which resulted in an IgM-positive response. All the samples that tested positive by competition ELISA were from horses set to be exported to countries where WNV is endemic. Consequently, the positive results were likely due to previous vaccination. In contrast, 714 samples were seronegative, indicating that the majority of the UK equine population may be susceptible to WNV infection. Conclusions There was no evidence for cryptic WNV infection in a cohort of horses sampled in England in 2019. All IgM-seropositive cases were due to vaccination; this should be noted for future epidemiological surveys in the event of a disease outbreak, as it is not possible to distinguish vaccinated from infected horses without knowledge of their clinical histories.

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Defra assesses the risk of West Nile virus being introduced to the UK

Veterinary Record ◽

10.1136/vr.164.9.252 ◽

2009 ◽

Vol 164 (9) ◽

pp. 252-252 ◽

Cited By ~ 1

Keyword(s):

West Nile Virus ◽

West Nile ◽

The Uk

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A novel approach for predicting risk of vector-borne disease establishment in marginal temperate environments under climate change: West Nile virus in the UK

Journal of The Royal Society Interface ◽

10.1098/rsif.2021.0049 ◽

2021 ◽

Vol 18 (178) ◽

pp. 20210049

Author(s):

David A. Ewing ◽

Bethan V. Purse ◽

Christina A. Cobbold ◽

Steven M. White

Keyword(s):

Climate Change ◽

West Nile Virus ◽

Land Use Changes ◽

West Nile ◽

Vector Borne Diseases ◽

Modelling Framework ◽

Novel Approach ◽

Tick Borne Encephalitis ◽

Vector Borne ◽

The Uk

Vector-borne diseases (VBDs), such as dengue, Zika, West Nile virus (WNV) and tick-borne encephalitis, account for substantial human morbidity worldwide and have expanded their range into temperate regions in recent decades. Climate change has been proposed as a likely driver of past and future expansion, however, the complex ecology of host and vector populations and their interactions with each other, environmental variables and land-use changes makes understanding the likely impacts of climate change on VBDs challenging. We present an environmentally driven, stage-structured, host–vector mathematical modelling framework to address this challenge. We apply our framework to predict the risk of WNV outbreaks in current and future UK climates. WNV is a mosquito-borne arbovirus which has expanded its range in mainland Europe in recent years. We predict that, while risks will remain low in the coming two to three decades, the risk of WNV outbreaks in the UK will increase with projected temperature rises and outbreaks appear plausible in the latter half of this century. This risk will increase substantially if increased temperatures lead to increases in the length of the mosquito biting season or if European strains show higher replication at lower temperatures than North American strains.

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Implications for Northern Europe of the emergence of West Nile virus in the USA

Epidemiology and Infection ◽

10.1017/s0950268803008707 ◽

2003 ◽

Vol 131 (1) ◽

pp. 583-589 ◽

Cited By ~ 12

Author(s):

E. A. GOULD

Keyword(s):

United Kingdom ◽

West Nile Virus ◽

The United States ◽

Health Problems ◽

West Nile ◽

Potential Health ◽

The United Kingdom ◽

Wide Range ◽

The Usa ◽

The Uk

The unexpected appearance of fatal encephalitis in six elderly people living in New York in 1999, heralded the re-birth of arbovirology in the United States of America. The subsequent rapid spread through North America and impact of the disease on humans, birds, horses and a wide range of other species including alligators and frogs, has brought West Nile virus (WNV) to the attention of governments and the media, worldwide. The response of the public in the United Kingdom has not been hysterical, despite being fuelled by press reports that scientists have demonstrated the presence of WNV antibodies in birds in the UK. Nevertheless, concern has been expressed by government bodies either directly or indirectly connected with the potential health problems that could arise if WNV was introduced and caused the same degree of morbidity and mortality as that seen in the USA. Is the concern justified and are we likely to see significant health problems associated with WNV if this virus is confirmed to be present and circulating amongst birds in the UK? In this review I shall try to put the virus in its true context and assess the risks that WNV might pose both to animals and humans in the United Kingdom.

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Serological evidence of West Nile virus, Usutu virus and Sindbis virus infection of birds in the UK

Journal of General Virology ◽

10.1099/vir.0.19341-0 ◽

2003 ◽

Vol 84 (10) ◽

pp. 2807-2817 ◽

Cited By ~ 136

Author(s):

Alan Buckley ◽

Alistair Dawson ◽

Stephen R. Moss ◽

Shelley A. Hinsley ◽

Paul E. Bellamy ◽

...

Keyword(s):

West Nile Virus ◽

North America ◽

Neutralizing Antibodies ◽

Sindbis Virus ◽

Nucleotide Sequencing ◽

West Nile ◽

Potential Health ◽

Bird Population ◽

Usutu Virus ◽

The Uk

The introduction and rapid dispersal of the African flavivirus West Nile virus (WNV) throughout North America, and the high fatality rate due to encephalitis in birds, horses, other wildlife species and humans, has attracted major attention worldwide. Usutu virus, another flavivirus, came to prominence in 2001, when it was identified as the agent responsible for a drop in the bird population in Austria; previously this encephalitic virus was found only in birds and mosquitoes in Africa. Sindbis virus, a pathogenic alphavirus that causes arthritis, is widespread throughout Africa, Europe, Asia and Australia, infecting a range of arthropods and vertebrates and is genetically related to encephalitic viruses in North America. Currently there is no evidence that any of these viruses cause disease in the UK. Here the presence of virus-specific neutralizing antibodies is reported in the sera of resident and migrant birds in the UK, implying that each of these viruses is being introduced to UK birds, possibly by mosquitoes. This is supported by nucleotide sequencing that identified three slightly different sequences of WNV RNA in tissues of magpies and a blackbird. The detection of specific neutralizing antibodies to WNV in birds provides a plausible explanation for the lack of evidence of a decrease in the bird population in the UK compared with North America. The potential health risk posed to humans and animals by these viruses circulating in the UK is discussed.

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