What happened after the epidemic? Equine influenza surveillance sheds light on sources and seasonal risk in the United Kingdom.
Authors: Whitlock Fleur, Grewar John, Newton Richard
Journal: Equine veterinary journal
Summary
# Equine Influenza in the UK: Movement and Seasonality Reveal Control Priorities Between 2020 and 2024, equine influenza (EI) in the United Kingdom displayed a striking seasonal pattern largely driven by horse trade, with 52% of all outbreaks (65 of 126 premises) clustered in the final quarter—a 3.25-fold higher monthly rate than the remainder of the year. Using negative binomial regression to analyse laboratory-confirmed cases against importation data, Whitlock and colleagues identified that over 75% of affected premises had received a new arrival within two weeks, with over half of index cases originating from Ireland. When non-pure-bred horse imports from Ireland were incorporated into the model, the October–December incidence rate increased 3.9-fold compared to other seasons, and higher import volumes significantly predicted outbreak risk (incidence rate ratios of 4.5 and 3.7 for the upper quartiles). These findings underscore that EI outbreaks are fundamentally linked to movement patterns rather than purely seasonal transmission dynamics. For equine professionals—particularly those involved in purchasing, transporting or receiving horses during autumn months—this research justifies prioritising vaccination of new arrivals, enforcing strict quarantine protocols of at least two weeks, and implementing enhanced biosecurity measures around transport and sale yards, especially when acquiring animals from Irish sources or high-volume trading periods.
Read the full abstract on PubMed
Practical Takeaways
- •Implement mandatory vaccination and post-arrival quarantine protocols for all new horse arrivals, particularly during October-December when outbreak risk is highest
- •Strengthen biosecurity measures during horse transport and at sales facilities, especially for non-breeding stock imported from Ireland
- •Monitor Irish horse imports as a key surveillance indicator for predicting UK equine influenza outbreaks and timing of control interventions
Key Findings
- •52% of equine influenza outbreaks in the UK occurred in Q4 (October-December) with a 3.25-fold higher monthly rate than other quarters
- •Over 75% of premises with confirmed EI cases reported a new arrival within ≤2 weeks, with 56% of index cases originating from Ireland
- •Q4 incidence was 6.9-fold higher than Q1 (p<0.001) and 2021-2024 incidence was 4.5-5.6 fold higher than 2020
- •Trade in non-pure-bred horses imported from Ireland significantly predicted outbreak timing, with higher import quartiles showing IRRs of 3.7-4.5