Serosurvey Reveals Exposure to West Nile Virus in Asymptomatic Horse Populations in Central Spain Prior to Recent Disease Foci

Summary West Nile fever/encephalitis (WNF) is an infectious disease affecting horses, birds and humans, with a cycle involving birds as natural reservoirs and mosquitoes as transmission vectors. It is a notifiable disease, re‐emerging in Europe. In Spain, it first appeared in horses in the south (An...

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Bibliographic Details
Published in:Transboundary and emerging diseases 2017-10, Vol.64 (5), p.1387-1392
Main Authors: Abad‐Cobo, A., Llorente, F., Barbero, M. del Carmen, Cruz‐López, F., Forés, P., Jiménez‐Clavero, M. Á.
Format: Article
Language:English
Subjects:
Animal populations
Animals
Antibodies, Viral - blood
Aquatic insects
Birds
Circulation
Disease Outbreaks - veterinary
Disease transmission
Encephalitis
Enzyme-linked immunosorbent assay
Enzyme-Linked Immunosorbent Assay - veterinary
Epidemics
Fever
horse
Horse Diseases - epidemiology
Horse Diseases - virology
Horses
IgM
Immunoglobulin M
Immunoglobulin M - blood
Infectious diseases
Mosquitoes
Neutralization
Neutralization Tests - veterinary
Outbreaks
Populations
Retrospective Studies
Seroconversion
serosurvey
Spain
Spain - epidemiology
Titration
Vector-borne diseases
Vectors
virus neutralization
Viruses
West Nile Fever - epidemiology
West Nile Fever - veterinary
West Nile Fever - virology
West Nile virus
West Nile virus - immunology
West Nile virus - isolation & purification
Wildlife
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Summary:Summary West Nile fever/encephalitis (WNF) is an infectious disease affecting horses, birds and humans, with a cycle involving birds as natural reservoirs and mosquitoes as transmission vectors. It is a notifiable disease, re‐emerging in Europe. In Spain, it first appeared in horses in the south (Andalusia) in 2010, where outbreaks occur every year since. However, in 2014, an outbreak was declared in horses in central Spain, approximately 200 km away from the closest foci in Andalusia. Before that, evidence of West Nile virus (WNV) circulation in central Spain had been obtained only from wildlife, but never in horses. The purpose of this work was to perform a serosurvey to retrospectively detect West Nile virus infections in asymptomatic horses in central Spain from 2011 to 2013, that is before the occurrence of the first outbreaks in the area. For that, serum samples from 369 horses, collected between September 2011 and November 2013 in central Spain, were analysed by ELISA (blocking and IgM) and confirmed by virus neutralization, proving its specificity using parallel titration with another flavivirus (Usutu virus). As a result, 10 of 369 horse serum samples analysed gave positive results by competitive ELISA, 5 of which were confirmed as positive to WNV by virus neutralization (seropositivity rate: 1.35%). One of these WNV seropositive samples was IgM‐positive. Chronologically, the first positive samples, including the IgM‐positive, corresponded to sera collected in 2012 in Madrid province. From these results, we concluded that WNV circulated in asymptomatic equine populations of central Spain at least since 2012, before the first disease outbreak reported in this area.
ISSN:1865-1674
1865-1682
DOI:10.1111/tbed.12510