Treating equine flu

30 April 2019

Interview with 

Richard Newton, Animal Health Trust

BLACK-HORSE

Black horse in field

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Keeping animals together in large numbers, moving them around the world and bringing them into close contact with humans can lead to outbreaks of infectious diseases, both in them and us. Recently the horseracing industry was temporarily brought to a standstill by an outbreak of equine flu. To explain how it happened, and why we need to be vigilant,  Chris Smith was joined in studio by, Richard Newton from the Animal Health Trust in Newmarket...

Richard - Yes, it is. All flu viruses that affect all animals originate from the same source which are wild foul, waterbirds. And some of those viruses will adapt to new hosts. So the horse flu virus that we've got that we encountered this year, not just in this country but across northern Europe originated as far as we know back from birds only in 1963 and it's been adapting and changing and circulating in horses ever since. All flu viruses in mammals require chains of transmission that have to be kept going and if we can break those chains of transmission then we can stop those viruses and we stop the evolution of them. But horse flu virus very much like human flu viruses loves environments where those horses are in close proximity to each other. The virus will cause them to cough. They will shed lots of virus and it will spread onto the next victim if you like.

Chris - So coughs and sneezes spread diseases for horses as well as humans.

Richard - Absolutely.

Chris - Some of those victims of the Newmarket outbreak and and elsewhere in the racing industry, they'd been vaccinated those horses though hadn't they? So this was an example of a virus that grew through and surmounted the vaccine.

Richard - It was. Most of the flu virus, equine influenza, that we see occurs in non vaccinated animals and unfortunately in many parts of the world whilst vaccines are used there's a sufficient proportion of the population that are not protected by vaccination. So this can circulate and occasionally that will spill over into the vaccinated population. And what we see is the flu viruses, the reason it's successful is that it adapts. It changes, it mutates and eventually it evades the protection that it gets from vaccination and that's when we see the outbreaks, such as we saw this year in vaccinated animals.

Chris - And if the horse coughs on the jockey as well as on the other horses in the race can the jockey catch it?

Richard - In theory there is a very small risk but we've never seen horse flu transmitted into humans and obviously horses are domesticated animals and they have a lot of human interaction. And so we believe the risk is very small. The flu virus has become very well adapted to the host that they're in. And so whilst they're superficially very similar they are well adapted and they don't tend to spread over into new species.

Chris - Nevertheless though, I suppose that situations where you have big groups of animals, that's an artificial situation isn't it? Because in nature, animals might live in a herd but they wouldn't be moved around the way we move animals and they wouldn't be kept on the scale that we keep animals in the modern era would they? So we are kind of creating an opportunity for diseases to come in and then create outbreaks.

Richard - Yes. If you think that the horse after humans is the most widely travelled animal and we do that on aeroplanes across the world in the same way. There are numerous examples where we have spread this infection across the world because we've travelled animals that are infected and then become infectious to other animals, and the latest example of that was back in 2007 when Australia had horse flu for the first time and despite intensive quarantine it still managed to get out, probably indirectly via humans carrying the virus, not being infected.

Chris - You mean on their feet or on something

Richard - On something, and then getting out into a completely susceptible population. And from there it could spread very very readily.

Chris - I suppose one of the challenges with flu, because you pointed this out, that it's originally a bird virus and birds don't have passports and they do have wings they can go wherever they want pretty much, and so they are the best way, if you're a virus of going anywhere around the world because birds don't observe international boundaries, do they, in quarantine or is it just going to fly down land somewhere and potentially shed the virus and if it could jump into the nearby flora and fauna it will.

Richard - Yeah absolutely right. And that's why many times in the news we will hear about avian flu and the concern when it gets into large intensively farmed flocks and it can wreak havoc in a very short time and avian flu in the wrong species can be fatal very quickly and you just have dead birds in a very short period of time.

Chris - So what sorts of measures are in place to safeguard against this sort of thing?

Richard - Well in race horses and other types of horses, where this time of year they're starting to move and mix, people use them for sport. We do rely and we recommend very strongly that they undertake vaccination and most times vaccination is highly effective and it will prevent the infection. Also it's a matter of being responsible when owners have sick animals with infections that are spreading rapidly that they call in veterinary surgeons who could take samples get the diagnosis and then keep those animals in isolation and they will get over it they will stop shedding virus and they will recover.

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