Vaccinations

Equine influenza is a viral disease caused byviruses that are closely related to those that cause ‘flu in humans.

The virus affects the upper and lower respiratory tract of horses and donkeys. There are many different strains but the clinical signs are usually similar.

Affected horses have a high temperature, inappetance, a frequent cough, an initially clear discharge from the nostrils (and sometimes eyes) which may turn a thick yellow/green and an enlargement of the lymph nodes of the head, seen as swellings below and behind the jaw. The incubation period for equine influenza is between 1 and 5 days and it is extremely infectious spreading through groups of susceptible horses very quickly. These horses usually recover over 2 to 3 weeks.

Any horse that has had a bout of 'flu should be rested for about 6 weeks.

As with any disease isolation of possibly infected horses is a priority coupled with strict hygiene to try and limit the spread. Transmission is via respiratory secretions in aerosolised droplets whilst coughing but also possibly on hands, tack, clothes etc. Usually 100% of horses that have not been vaccinated against ‘flu or had it before will become infected.

Diagnosis is on the basis of the clinical signs, i.e. a rapidly spreading respiratory infection in a group of horses characterised by a fast onset, high fever, depression and widespread coughing. As there are many possible causes of respiratory infection in horses isolating the virus on swabs of nasal secretions or observing rising antibody levels in the blood to the virus gives a definitive diagnosis.

There is no effective drug treatment for equine influenza and good nursing whilst the horse recovers is all that can usually be done. Sometimes the lining of the respiratory system will be damaged by the ‘flu virus and will be susceptible to a secondary bacterial infection causing pneumonia. For this reason antibiotics are sometimes prescribed to prevent this, although they have no affect on the ‘flu virus itself.

The best way to limit the spread of equine influenza is to keep your horse's vaccines up to date. Although this is not guaranteed to stop the disease completely it will decrease the chances of contracting it and decrease it’s severity.
 
If you are competing your horse then there is usually a fixed protocol for when the vaccines should be administered. Our practice protocol is outlined below, however certain clubs and associations may require different vaccination schedules:

• 1st vaccination: (Day 0)

• 2nd vaccination: 4 weeks after the first injection

• 3rd vaccination:  5 months after the second vaccination. After this 3rd vaccination the horse needs to be vaccinated yearly.

• Annual vaccination: Can be given six months early, can be given on anniversary of previous vaccination but not one day over.



Tetanus

Horses are the most susceptable to this disease of all domestic animals. A very serious, normally fatal disease, tetanus carries a very guarded prognosis.

The disease is caused by a group of potent toxins produced by the bacterium Clostridium tetanii, the spores of which are very resistant in soil and droppings for many years. These toxins target the nerves that supply the horse’s muscles. In the majority of cases the bacterium proliferates in wounds, particulalry puncture wounds, though foals may be infected via the naval. Puncture wounds of the foot are a particularly well recognised route of entry.

Clinical signs may take weeks to manifest, and can often be distressing to both horse and owner, particularly in the latter stages. They are characterised in the early stages by a stiff gait and an ‘over-response’ to external stimuli. Spasm of the jaw muscles results in characterisitc ‘lockjaw’, but spasm of the muscles of the neck, body and limbs, with increasing severity soon develops. Other signs include a ‘hyper-alert’ expression, nostril dilation, salivation, difficulty eating, prolapse of the third eyelid (a membrane that can easily be seen at the inner corner of the eye), and an elevated tail head. Once recumbent, with continuous generalised severe muscle spasms, affected horses usually die from respiratory paralysis and exhaustion over a period of days.

Treatment can be attempted in a selection of early cases and revolves around eliminating the bacterium, e.g. debriding and flushing the wound (which is not always readily obvious) and reduction of external stimuli (cotton wool in ears, kept in a dark box). This is supplemented by intravenous antibiotics (requiring hospitalisation preferably, but transport often not possible due to the nature of the disease), antitoxin, sedation, and intensive nursing. This is obviously expensive and unfortunately not often successful.

Prevention as many will know is through routine vaccination. This is often combined with the horses’ flu vaccine.

Vaccination for tetanus alone is possible for those who choose not to vaccinate for flu in, for example, older horses not mixing with the general horse population. The vaccine is given as two doses 4-6 weeks apart, with a booster 1 year later, then every other year thereafter.

Normally foals simply receive tetanus antitoxin rather than the vaccine itself, as they cannot respond to the vaccine. Once the foal is old enough it will receive the tetanus vaccine in conjunction with its flu vaccination. Newborn foals will receive some antibodies in the mare’s milk. The foal's immunity to tetanus can be further improved by vaccinating the mare with a booster dose 4-6 weeks prior to foaling.