An epidemiological overview of the equine influenza epidemic in Great Britain during 2019

Abstract

Background: During 2019, an epidemic of equine influenza (EI) occurred in Europe.Objectives: To describe the epidemiology of the 2019 EI epidemic within Great Britain (GB).Study design: Retrospective descriptive study of laboratory confirmed EI cases.Methods: Epidemiological data were obtained from veterinary surgeons referring samples for EI virus testing. Where available, data on confirmed cases and their wider resident population on EI-infected premises were collated and described. On a national level, spatial and temporal representations, consisting of choropleth maps and epidemic curves, described the spread of EI. EI-infected premises-level factors associated with the first of two epidemic phases were investigated using ordinary logistic regression analysis.Results: There were 412 confirmed cases and 234 EI-infected premises, with the first of two epidemic phases occurring between January and April, followed by a second phase through to August. The median age of confirmed cases was 5 years and Sports horses (24%) and Cobs (16%) made up the highest proportions by general horse type and breed. Among confirmed cases 72% were unvaccinated and 18% were vaccinated against EI. New horses arriving within 2 weeks of a confirmed case were reported by 42% of EI-infected premises. Investigation of EI-infected premises biosecurity measures indicated that 23% quarantined new arrivals, 37% had isolation facilities and 57% of resident horses were vaccinated. EI-infected premises were more likely in the first than second epidemic phase to be classified as professional, have a vaccinated confirmed case and EI confirmed in a newly arrived animal.Main limitations: Data were collected at a single time point for each EI-infected premises with no follow ups performed.Conclusions: During 2019, EI-infected premises generally had low levels of population vaccine coverage and implemented limited preventive biosecurity measures, particularly linked to horse movements. Without substantial improvements in infectious disease prevention and control, the GB equine population remains at risk of future EI epidemics.

Equine influenza vaccination catches an autumn cold! But must get over it as soon as it can

“…In the recent overview of the 2019 equine influenza (EI) epidemic in Great Britain (GB), it was concluded that the British horse population remains at risk to a lesser or greater extent from EI, whether in its current but ever‐evolving H3N8 incarnation or a novel subtype that is yet to make itself known 1 . It is logical therefore that collectively the UK's equine and equestrian industry needs to maintain its awareness and be prepared to react deftly to gauge threat levels and mitigate appropriately to the perceived risks.…”

“…When racing in GB was temporarily halted for 6 days due to EI in February 2019, this was largely a pre‐emptive measure as clinical EI had suddenly emerged in a small number of vaccinated racehorses attending race meetings as well as in vaccinated young Thoroughbreds in pretraining 1 . Also, there had been a marked increase in EI being diagnosed across Europe in early 2019 compared with extremely low levels throughout 2018 and some early indications from France confirmed clinical EI appearing in vaccinated horses there 2 …”

“…Temporal and spatial representation of the two phases of the 2019 UK equine influenza epidemic (from Whitlock et al 1 ) Reproduced with permission from The Editor, Equine Veterinary Journal…”

Highlights of recent clinically relevant papers

“…An epidemic of equine influenza (EI) occurred in Europe in 2019. This retrospective study by Fleur Whitlock and co‐workers in the UK and South Africa described the epidemiology of this epidemic within Great Britain .…”

Equine influenza bi‐annual boosters: What does the evidence tell us?

“…However, disease events such as those experienced in the United Kingdom in 1989, 2 2003 3,4 (Figure 1), and most recently in 2019 5 are portents of EI's epidemic potential, even in vaccinated horse populations.Across Europe during early 2019, an EI epidemic started to emerge with sufficient speed, magnitude and apparent potential for disruption that UK racing was pre-emptively cancelled for 6 days in February, to allow the industry to take stock but thereby incurring significant costs on itself. 1,[5][6][7] Even before racing's shutdown, the British Horseracing Authority (BHA) had already in 2019 recommended booster vaccination of any racehorses that had not been administered EI vaccine in the preceding 6 months. The BHA subsequently increased the frequency of EI booster…”