Everyone worries about strangles and the risk of that infection spreading to their horse, but many forget equine ‘flu, which is another major equine respiratory disease that has recently reappeared:

A recent letter to the Veterinary Record (June 16, 2007) from staff at the Animal Health Trust (AHT) reports several concurrent positive diagnoses of equine influenza virus infection that have been made lately among horses in different parts of England. “Four foci of infection in the Midlands, Kent and Hampshire have been identified since the end of May by the laboratories of the AHT” according to this letter, which also highlights that “in all four outbreaks to date the index cases have been animals that have been recently imported into the country, having been bought at a horse sale in County Kilkenny in the Republic of Ireland. All these horses were reported to be either non-vaccinated or of unknown vaccination status, and there is some evidence emerging of onward transmission to non-vaccinated contacts on some of the affected premises”.

 

Every now and then an outbreak of equine influenza like this occurs. It is a greater risk as horses travel internationally more , but there have frequently been seasonal flare ups with increased mixing at shows in the summer months and sales in all times of year. It highlights the need for regular vigilance and flu vaccination. Vaccinated horses may show signs but these are usually milder than those experienced by unvaccinated horses. The reason that vaccines do not always provide 100% protection is due to the fact that the virus can change slightly with time and different strains develop. The vaccines are regularly updated in order to provide maximum protection.

FACTS ABOUT EQUINE FLU
Equine Influenza (‘flu) is a disease that affects the upper and lower respiratory tract of horses, donkeys and mules. It is caused by several strains of the equine influenza virus. The disease is very infectious and spreads rapidly through groups of horses. The incubation period is 1 – 3 days.

Clinical Signs
The horses in the recent outbreak are reported to have showed signs that included:
• a very high temperature of 39-41˚C (103-106˚F) which lasted for 1-3 days
• a frequent harsh, dry cough that can last for several weeks
• a clear, watery nasal discharge that may become thick and yellow or green
• enlarged glands under the lower jaw
• clear discharge from the eyes
• depression and loss of appetite
• filling of the lower limbs.

What to do:
As soon as a horse shows any suspect signs, strict hygiene and isolation procedures should be applied. Any horses that have been in contact with the affected horse should be carefully monitored and ideally should not attend shows or any other competitions as they may be incubating the disease. Exposure to the virus combined with the stress of travelling will make infection more likely, which is presumably was a part of the problem in the cases affecting horses that have recently travelled from Ireland.
The disease is spread by inhalation of virus released into the atmosphere as an aerosol by coughing and blowing, essentially one horse coughing over another. For this reason equine ‘flu is highly contagious within a group of horses, but thankfully it is not airborne over long distances like some other viruses such as foot and mouth disease virus.
If you suspect your horse has equine influenza you should contact your vet. Steps can then be taken to stop the spread of the disease. One of the most crucial is identifying the infection accurately; if you know what you are dealing with, then you can control it.

Diagnosis:
An accurate diagnosis can be made by
• recognising the clinical signs and the rapid spread between horses
• isolation of the virus from nasopharyngeal swabs
• a number of other laboratory tests which identify the virus
• rising antibody levels in blood (serum) samples taken early in the course of the disease and 2-3 weeks later
• history of recent contact with a confirmed case of the disease

What causes the illness?
Equine ‘flu is caused by a virus. Viruses are tiny infectious particles that can produce disease, although they can only replicate inside another cell.
Once a horse has breathed in the virus, it invades the lining epithelium of the airway, which becomes swollen and inflamed producing a very sore throat and a nasty cough. The viral damage causes of patches of the membranes lining the airways to ulcerate and these changes disrupt the clearance of mucus and other debris from the airways. In turn these damaged areas end up being invaded by bacteria and further infections ensue. Antibiotics have no effect against a virus, but they can be useful to control secondary bacterial invasion. This is a particular risk in foals that can succumb to a fatal pneumonia.

What to do about it
All horses with respiratory infections should be given complete rest. Ideally, they should not recommence any strenuous exercise until two weeks after the signs have gone. Frequently the advice is given that they should have a week off for every day that they have had a fever ( raised temperature) , but many riders will find the their horses are below par for longer, in the same way the people can feel run down after ‘flu.
Good stable ventilation and management is essential. Exposure to dust and spores should be minimized as horses with respiratory infections are susceptible to developing recurrent airway obstruction (RAO). If hay is fed, it should be of good quality and soaked. If weather conditions permit, affected horses benefit from being turned out into a small paddock for at least part of the day once their temperatures have returned to normal. This is especially important in the recovery stages.
Some of the new antioxidant feed supplements market to help respiratory function may well be of benefit as well as some other medications to help breathing. It is best to consult your own vet for the appropriate treatment of individual cases

Prevention
Regular vaccination is the key to the prevention of outbreaks of equine influenza. When the disease occurs locally, it may advisable to give a booster to any horse that has not been vaccinated in the previous 6 months. Maximum immunity is not reached until about 2 weeks after the vaccination.

Facts about flu
• Equine flu in not a worldwide disease. Some countries ( for example Japan, Australia and New Zealand) are free of the disease due to strict quarantine measures
• The equine flu virus has been scientifically shown to be transmitted from horses to dogs The virus has caused outbreaks of the disease in racing greyhounds and in pet dogs, and is suspected to have affected some hound packs.
• Efforts have been made to pre-empt an equine flu epidemic by vets investigating and identifying acute respiratory disease in horses. If your vet suggests taking a few blood tests or swabs, it may be very useful to help prevent further cases of respiratory illness.
• Since vaccination of racehorses became mandatory in 1980 there has been no need to cancel racing because of influenza.
• A vast number of horses and ponies are not vaccinated and are at risk.