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West Nile virus seroprevalence survey of UK equines - SE0554

Description
This proposal supports Disease threat and mitigation.

This piece of work would investigate the current West Nile virus (WNV) seroprevalence in horses in England. Following the emergence of this virus in northern Germany in 2018 and its suspected overwintering, the risk of emergence in the UK has increased. Seroprevalence will be established within the study cohort through the measurement of WNV antibody levels within individual equine serum samples. Only a small proportion of horses develop clinical disease signs so this study will assess whether there has been cryptic transmission of this virus and provide a baseline for prior exposure in horses with which to compare future surveys that may be required if the risk of WNV introduction continues to increase.
Objective
Virus transmission by mosquitoes in Europe has been dominated by the emergence of West Nile virus (WNV). Infection with WNV causes West Nile fever in humans and horses, and is notifiable in horses in the United Kingdom. However, the majority of equine infections are asymptomatic with seroconversion being the only means of confirming exposure to WNV. The virus has become endemic across southern and central Europe being detected annually in many countries. However, in 2018 there was a dramatic increase in the number of cases in both humans and horses. To November, there were 285 outbreaks of WNV in equids across Europe. This includes cases from Germany, the furthest north the virus has been reported and on a similar latitude with the UK. The risk of WNV incursion into the UK in future years is likely to increase. The main mechanism of WNV translocation is through the movement of migrating birds. Current surveillance for WNV is restricted to detection of virus in wild birds and investigation of horses displaying neurological disease signs. This project proposes to measure the WNV seroprevalence of a cohort of UK horse sera obtained from a number of sources between 2018 and 2019.
Knowledge acquisition:
Equine serum samples will be acquired from APHAs own archive from submissions and supplemented with samples from academic and charitable collaborators e.g. University of Nottingham. The criteria for addition to the cohort will be:
1. Sample obtained either within 18 months of the study starting or during the lifetime of the survey.
2. The horse was resident within a county within south and east England (e.g. Norfolk, Suffolk, Essex, Cambridgeshire, Kent, Surrey, West Suffolk, East Suffolk, Berkshire, Hampshire). These are the most likely sites for migratory passerine birds entering the country from mainland Europe.
3. Wherever possible WNV vaccinated horse samples will be excluded from the survey and serum samples will have been maintained in a cold chain (-20oC or lower) prior to entering the study.

WNV antibody will be measured using a capture ELISA that detects all anti-WNV antibodies present in a sample (pan-immunoglobulin; IgM and IgG) indicating prior exposure. Samples positive by this first assay will be tested by the IgM specific ELISA test to determine whether there is evidence for a recent infection.

A report of the findings of the study will be prepared within the project and any opportunity to publish the results will be taken.


Time-Scale and Cost
From: 2019

To: 2020

Cost: £24,636
Contractor / Funded Organisations
APHA (Animal and Plant Health Agency)
Keywords
African Swine Fever              
Fields of Study
Animal Health