Viral respiratory disease is a major cause of poor performance in horses. Most equine coughs and colds in New Zealand are caused by viral respiratory infections, of which the most common is equine herpes virus.
Outbreaks are common in groups of young horses that are kept in close proximity and the infection can spread rapidly by nose-to-nose contact, aerosols (coughing) or recently contaminated feed/water troughs etc. The common signs of infection are loss of appetite, being a bit off-colour, or dull, a clear-cloudy runny nose and sometimes a cough.
There is no specific cure for viral respiratory infections and early recovery depends on good supportive care while the horse’s own immune system takes control. Infected horses should be isolated if possible, and careful hygiene practices employed following handling, to prevent the spread of infection to others. Total rest is the best approach as the stress of training may prolong the course of the disease. Anti-inflammatories can help relieve inflammation and irritation and make the horse feel more comfortable. A course of immune stimulant injections may be of benefit in some cases – please talk to your vet about these.
Some horses may develop a secondary bacterial infection, usually characterised by a thick yellow nasal discharge. This is the result of the virus compromising respiratory defences, making it easier for bacteria to invade and set up an infection. In these cases, the horse may require a course of antibiotics. Although most recover from viral respiratory infections uneventfully, some, especially the very young, old or debilitated, can develop more serious complications such as bacterial pneumonia.
The herpes virus can lie dormant in the body after recovery and may re-emerge during times of stress such as a sudden change in exercise or long-distance transport. This can be why some horses seem to have frequently recurring colds.
The best method for prevention of equine herpes virus is vaccination. The vaccine does not give complete protection but lessens the chance of infection, decreases the severity of disease, and recovery occurs a lot faster. Unvaccinated horses require two vaccines, four weeks apart. A yearly booster is then used to maintain immunity. Horses at a high risk of exposure to others at shows, races, or in a stud/stable situation benefit from booster vaccination every six months.
It is important to remember that coughs and runny noses can also be a symptom of many other conditions, minor or serious, including allergies, strangles or equine influenza. Please contact us if you have any concerns or would like to have your horse vaccinated against equine herpes virus.