Action needed to reduce equine flu ‘late-year’ pattern, research warns

Researchers have said more needs to be done to reduce the risk of equine influenza (EI) being brought into the UK through animal imports.

Latest analysis from the Equine Infectious Disease Surveillance (EIDS) group, based at the University of Cambridge’s vet school, has suggested the virus is not present all year round.

But it found that more than half of cases recorded between 2020 and 2024 had occurred during the final quarter of the calendar year.

‘Continued surveillance’

Lead author Fleur Whitlock argued the findings demonstrated the importance of “continued surveillance” within the equine industry.

She said: “Our work shows that in the UK, flu in horses is not simply a seasonal inevitability but is strongly influenced by horse movements and trade.

“By strengthening vaccination uptake and biosecurity measures – particularly around imports and sales during the high-risk late year period – we have a clear opportunity to reduce the scale and impact of future outbreaks.”

The paper, published in the Equine Veterinary Journal, analysed surveillance data collected since the 2019 EI epidemic, in which more than 400 cases were confirmed.

EI activity

The researchers did acknowledge a need for caution in interpreting EI activity during 2020 because of the impact of COVID-19 restrictions, which reduced opportunities both for the disease to spread and cases to be detected. But it argued there was a “repeatable late-year pattern” for much of the period from 2020 to 2024, with 52% of all cases recorded in that time occurring within the last three months of those years.

The monthly rate of outbreaks between October and December was also found to be three times higher than that recorded during the rest of the year.

Among confirmed cases that were new arrivals on affected sites, more than half (56%) were found to originate from Ireland – the largest exporter of horses to the UK – while 20% were linked to domestic movements.

But the study also highlighted an incident in late 2022 when 13 premises, which tested positive for the virus, were found to have links to one of three equine sale sites – two in England and one in Ireland.

‘Long-distance dissemination’

Although the paper stressed no evidence existed of a connection between the sales themselves, it argued that the presence of cases in the midlands, Wales and Scotland, each of which derived from an Irish sale, demonstrated the “potential for long-distance dissemination of EIV via horse movements”.

The researchers have also voiced concerns about potentially “critical” gaps in biosecurity, after the study found three-quarters (75%) of infected premises did not quarantine new arrivals, while a similar proportion of new cases (74%) were found to involve unvaccinated horses.

The paper said: “Control measures should prioritise vaccination of new arrivals, post-arrival quarantine and strengthened biosecurity during transport.”