You feel tired, you can barely crawl out of bed, your head hurts, your nose is blocked, your throat is sore and your appetite has vanished. You probably have the flu. It makes you feel lousy and the same condition in horses — although it cannot be transmitted from humans or vice versa — can make our four-legged friends feel pretty sick too.
Horses with horse flu or equine influenza (EI) share many of the same classic symptoms as humans, such as high temperature, dry cough and clear or white nasal discharge. All these can be accompanied by enlarged lymph nodes in the throat, general weakness, lack of appetite and depression. The cause is damage to the upper respiratory tract (nose, throat and windpipe) sparked by a viral infection.
According to the BHS, less than half of the UK’s 1 million horses are vaccinated against EI, which leaves a large proportion of the population at risk of developing this highly contagious disease. It is recommended, therefore, that your horse is vaccinated regularly. Generally this should be once a year, but the FEI, the governing body of international equestrian sport, recommends that sport horses are vaccinated every six months.
Because EI spreads through the air, any gathering of horses — such as a show — can lead to an outbreak. One case of flu on a yard can spread like proverbial wildfire, too, hence the need to vaccinate horses who live in close proximity, but also to have an isolation strategy in place should an outbreak occur. Because EI is such a contagious disease, you should ensure that you isolate new horses coming into the yard for about four weeks.
To confirm whether your horse has EI, your vet may want to take a nasal swab which will be sent off for analysis.
Very young foals, as well as horses with compromised immune systems, older horses and those who are over-exercised while suffering from EI can go on to develop a secondary bacterial infection. Just as it happens among humans, a horse with a secondary infection is likely to be unwell for a lot longer than one just suffering from EI. They are also likely to need antibiotics from a vet. In very severe cases of secondary infection, the horse may develop pneumonia, which can prove fatal. Horses who go on to recover from secondary infections should not be exercised too soon as this can seriously damage their health.
Healthy adult horses with no secondary complications should recover from EI within a few weeks, although in some cases returning to full health and fitness can take months. Bear in mind that it takes between 50-100 days for the lining of the respiratory track to fully recover. As a result, it is recommended that for every day the horse has had a fever he should be given a week’s rest to allow him to fully recover. To avoid complications, consult your vet on when to recommence exercise and how much you should do.
There is no magic cure for EI. You should ensure that your horse receives enough fluids, while anti-inflammatory drugs can help to reduce the fever.
The good news is that once a horse has had a certain strain of EI, he will have built up an immunity to it, but that doesn’t mean that he won’t succumb to a different one as various strains exist — plus the virus can also mutate. Because of mutations, vaccines can lose their effectiveness, but scientists at Newmarket’s Animal Health Trust are constantly monitoring the disease through their surveillance scheme and vaccines are updated when necessary.