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| Credit UK AHT |
#14,158
While H3N8 equine influenza (EI) is not currently considered a zoonotic threat, the history of H3N8 in humans (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?) - and its species jump to dogs in 2004 - make it a virus well worth our attention.
In 2016, in Epizootics, Host Ranges, and Conventional Wisdom, we looked at the (admittedly, limited) scientific and historical evidence suggesting that equine influenza may have infected humans in the past, and could possibly do so again someday.This is a scenario we looked at again in 2018 in Equine H3N8: Looking At A long-shot In The Pandemic Sweepstakes. Both Canine and equine flu are of particular interest because the H3N8 and H3N2 subtypes they carry are similar to pandemic strains of the past (see chart below).
Earlier this year, we followed the start of an equine influenza outbreak in the UK (see UK BHA: All Horse Racing Halted After Equine Flu Reported In Vaccinated Horses) which somewhat surprisingly, turned out to be due to the “Florida Clade 1” strain, which is endemic to North and South America.
The Clade 2 strain is endemic to Europe.Since January, Nigeria has reported ongoing, widely scattered outbreaks of equine influenza to the OIE (see update #9), and in April we saw reports of a Large Equine Influenza Epizootic In Senegal.
In April of 2019, the OIE summarized outbreaks in South America, Africa, Europe, North America, and Asia and concluded there has been an increase in
global equine influenza activity over the past year.
Although the UK has been hardest hit outside of West Africa, a number of other Western European nations have reported outbreakssince the start of the year, with the AHT and Equiflunet.org.uk reporting on July 1st:
Outbreaks of EI in Europe
There has been an increase in equine influenza activity reported in Europe. Multiple outbreaks were reported in Northern France at the end of December, whilst positive diagnoses have been made since the beginning of 2019 in France, Belgium, Germany, Ireland, Italy the Netherlands, Denmark and Sweden.
Of the 155 outbreaks reported in the UK this year, more than 1/3rd were reported in June (n=53) - a monthly total nearly double what was reported the previous month (n=27).
Yesterday the UK's Animal Health Trust (AHT) issued the following update:
Statement on equine influenza outbreaks
1 July 2019
The number of confirmed outbreaks of equine influenza (EI) has now exceeded 150 in 2019, which means we have seen more outbreaks in the second quarter of 2019 than the first quarter. Equine Influenza has definitely not gone away. We strongly believe it is gathering pace; with the recent resurgence in activity undoubtedly related to the increased movement and mixing of horses and ponies attending events at this time of year.
We urge all horse owners to remain extremely vigilant and recommend vaccination of entire premises and quarantining of new or returning animals to help limit the spread of the disease. On premises where EI is confirmed we urge horse and yard owners to implement voluntary movement restrictions and not send animals to events, even if they appear outwardly healthy.
While the threat to humans from equine influenza is currently small, it isn't zero, as the following EID Journal Article (June 2019) explains:
Volume 25, Number 6—June 2019
Historical Review
Equine Influenza Virus—A Neglected, Reemergent Disease Threat Metric Details
Alexandra Sack, Ann Cullinane, Ulziimaa Daramragchaa, Maitsetseg Chuluunbaatar, Battsetseg Gonchigoo, and Gregory C. Gray
.C. Gray)
Abstract
Equine influenza virus (EIV) is a common, highly contagious equid respiratory disease. Historically, EIV outbreaks have caused high levels of equine illness and economic damage. Outbreaks have occurred worldwide in the past decade. The risk for EIV infection is not limited to equids; dogs, cats, and humans are susceptible.
(SNIP)
Although the role of humans in EIV evolution is unknown, historical and serologic evidence suggest EIV has zoonotic potential and is known to infect other nonhuman species (26,28,30). Historical review suggests the 1889 human influenza pandemic might have been of equine origin, with equids playing the role that swine play in modern outbreaks (12). With all this in mind, we posit that EIV should be recognized as a potential epidemic, if not pandemic, threat.(Continue . . .)
And lastly, for a particularly fascinating account of the 1972 equine epizootic, and its possible spillover into poultry, and humans, you may wish to revisit 2010's Morens and Taubenberger: A New Look At The Panzootic Of 1872.
Highly recommended.
