Equine flu: how experts decided six-month boosters are the way forwards

  • An expert in the spread of diseases has explained what was learnt during the 2019 equine flu outbreak

    The reasons the UK veterinary industry acted as it did in this year’s equine flu (EI) outbreak and the decision-making behind six-month booster requirements have been explained by an expert.

    Dr Richard Newton, director of epidemiology and disease surveillance at the Animal Health Trust (AHT), spoke about what UK vets have learnt from the 2019 outbreak at an event at the British Racing School on 19 November.

    The take-home messages were that despite advice, some horse owners are not either believing in or complying with the six-month booster recommendation.

    Dr Newton said the strain responsible for the outbreaks this year, and the way it moved across Europe, were behind the decision to shut down racing in February.

    “We were seeing a different picture emerging in Europe,” he said, explaining that the decision was not based on the situation in the UK alone and that vets were seeing clinical signs in vaccinated horses in Europe. “This is when the alarm bells rang.”

    The strain was also different to the flu usually seen in the UK and Europe — this was Florida clade 1, as opposed to Florida clade 2.

    “In 2019, we witnessed the largest epidemic in Britain and Europe in 30 years,” he said.

    “What we hadn’t counted on, was the second wave taking off in April through May, which peaked in the last week of June. This made headlines and events started to take stock and were cancelled.

    “A large proportion of the UK has had flu diagnoses at some point this year. There were also reports of airborne spread, which is the first in my time at the AHT.

    “If we were being self-critical, we did fail to raise adequate awareness at the crucial time. Some of our messages were missed or ignored, despite our urgings or reminders.”

    He added factors that facilitated spread of the disease included low vaccine coverage, certain events not requiring vaccination, a lack of preventative measures (such as isolation) for arrivals or horses returning from events, and the spread of anti-vaccine rhetoric on social media.

    He said there was also confusion “even among vets, let alone owners” as to why there were so many variations of the flu vaccination rules between the sporting governing bodies.

    The European Horserace Scientific Liason Committee has proposed new harmonised vaccine rules in European racing from 2021. The British Horseracing Authority (BHA) and other individual racing organisations will liaise on these in 2020, while the British Equestrian Federation and its associated disciplines are looking to follow the BHA’s lead.

    Dr Newton also went through studies that informed the six-month recommendation, and explained how maths helped experts come to this conclusion.

    This is because statisticians are able to run many variations of outbreak scenarios against the immunity levels of the vaccine given at different intervals to find out when the most effective time is for a booster.

    “What we repeatedly saw is that when you vaccinate at six months, rather than 12, you see smaller outbreaks and sometimes no outbreaks at all,” he said. “We are trying to look forwards and prevent future happenings.

    “We need to get smart as to how we use these vaccinations at the moment if we are going to protect our horses from flu.”

    Dr Newton added temperature monitoring is vital in early diagnosis and urged owners to get into the habit of this. He also stressed that as flu is a non-notifiable disease, it is up to the industry, including individual owners, “to protect itself”.

    “Temperature, with many infectious diseases, is the first indicator that you have a problem,” he said. “If you get into good habits and routines and know what normal is for a horse, then if you do see that spike, that is the earliest sign you can get.

    “If you start to see a spike in [healthy horses], that’s when alarm bells should start ringing. I think it is good basic biosecurity, health monitoring. If horse owners all regularly monitor their horses twice a day, record it in a diary or on a spreadsheet, then you can see a pattern. That will pay dividends as it will indicate when a horse has a problem.”

    Knowing your horse’s temperature was a major theme of the event and leading US vet Dr Alan Dorton explained how valuable this is.

    He spoke about how he uses the new EquiTrace app that works with a microchip to take and record temperature and other details crucial to a horse’s health.

    “The beauty of the chip is it records the temperature in about three seconds,” said Dr Dorton, who specialises in youngstock.

    “The app has been a wonderful addition for me, in identifying horses, keeping them separate, and it will also tell you where the horse was the last time he was scanned.”

    They microchip the foal the day he is born, before he leaves the foaling stall, and from then on, any treatment or observations are added instantly to his records which can be accessed via the app by scanning his microchip.

    Vaccinations, de-worming, and any signs that he is under the weather can all be quickly added and emailed as a record to whoever might need to see them.

    The horse’s temperature can also be seen as a list or a graph, so any abnormalities are instantly visible.

    “Everything is scanned before I get to the farm and that means I can see as soon as I arrive whether anything is abnormal,” said Dr Dorton, giving the example that one stud farm was able to take the temperature of 60 yearlings in four barns in 20 minutes.

    “It is going to be an amazing tool for me next spring. Everything I need for the next breeding season is right here without me having to call the stud farm manager to ask questions.”

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