Vaccinations are an effective and cost efficient way of protecting your horse from common preventable diseases. This in turn assists in the prevention of the spread of these diseases should an outbreak occur. They are an important part of your horse’s annual routine to maintain health.

What can you vaccinate against?

The most common diseases to vaccinate horses against are equine influenza, tetanus, strangles and for respiratory infection and abortion caused by equine herpes viruses 1 and 4 (EHV 1, 4). Under certain circumstances horses can also be vaccinated against equine viral arteritis (EVA).

The principle of vaccination is to administer an initial course and then follow this up with booster doses at varying intervals, depending on the nature of the vaccine and the immune response.

Equine Influenza ('flu)

This is a highly infectious disease associated with high fever and a dry cough, there may also be a discharge from the nostrils. Equine influenza may spread very rapidly through a yard if individuals are unvaccinated. Influenza may affect the horse for several weeks and necessitate the horse being rested from work but the symptoms are easily prevented or lessened by vaccination.

The recommended initial course for the vaccinations comprises three injections at the following intervals:

- 1st vaccination
- 2nd vaccination 4-6 weeks after the 1st
- 3rd vaccination 6 months after the 2nd

After this initial course a booster vaccination is required annually except for horses competing under FEI rules which require boosters every 6 months.

It is important that these dates are adhered to in order to hold a valid vaccination card. It is important that each vaccination is entered onto the card, dated and signed by the veterinary surgeon as this card is the only proof that your horse has been vaccinated correctly. You may be asked to produce it at competitions. In order to be valid the card must be completed by a veterinary surgeon clearly showing the horse's identification markings. The usual competition rules regarding timing of vaccinations are that the initial 2 vaccinations should be between 21 and 92 days apart and that the 3rd vaccination should be 150-215 days after the 2nd. Thereafter no more than 365 day intervals (or no more than 6 months plus 21 days for FEI) should separate booster vaccinations. Horses are not usually allowed to compete for 7 days following vaccination.

NB. The vaccination card is a very important document and should remain with the horse for life, passed on with the horse if it is sold or put on loan.

The responsibility for ensuring that the horse’s history complies with the relevant regulations is entirely that of the owner (including the I.D.). Do not forget the annual boosters - even a day late is too late!!

The foal should start its own vaccinations against 'flu when it is five to six months old.

Tetanus (lockjaw)

This is a frequently fatal infectious disease that affects all domestic animals but horses are the most susceptible species. It is caused by toxins from a bacterium, which is present in the soil – Clostridium tetani. The bacterium usually enters the animal through puncture wounds particularly in the foot but cases are also seen in the absence of a known wound where toxin is presumably absorbed through the intestine.

The symptoms of tetanus are progressive muscle stiffness and a hypersensitivity to noise or touch, provoking painful (tetanic) muscular spasms. Third eyelid prolapse is most notable in horses.

Tetanus is seldom seen nowadays, due to the fact that most owners now keep their horses currently vaccinated.

The initial course comprises of two injections – the first vaccination is followed four to six weeks later by a second vaccination. (These time scales fit in with the requirements for the influenza vaccination and we will usually amalgamate the two injections.) The initial course is followed by a third injection within a year of the second. Thereafter a booster will be required every other year. This is commonly administered in alternate years with the annual influenza vaccinations.

If the history is unknown and the horse sustains a wound then a tetanus antitoxin injection should be given to ensure immediate but temporary protection.

It is important that a brood mare is given a booster vaccination during pregnancy in order to provide the foal with a degree of protection from birth. This booster is best given 4 – 6 weeks before foaling. The foal should start its own vaccinations against tetanus when it is five to six months old.

Equine Herpes Virus (EHV 1,4)

EHV comes in nine sub-types each with a variety of symptoms - the most important being respiratory disease, abortion and occasionally, neurological signs.
These vaccinations are required for brood mares to guard against abortion and also in healthy horses as prevention against respiratory disease (the vaccine does not protect against neurologic disease).

The primary course will vary depending on the reason the vaccine is being administered:

- For protection against respiratory disease an initial injection should be given to foals from five months of age (and adult horses at any time) followed by a second injection after 4 – 6 weeks. Following this primary course a booster needs to be administered every 6 months.

- As an aid in the prevention of abortion pregnant mares should be vaccinated during the 5th, 7th and 9th months of pregnancy with a single dose being administered on each occasion.

Strangles

A new strangles vaccine (called "Equilis Strep E") became available in the UK in 2004. In order to gain a UK license this vaccine has been proven to be more effective than previous types and far safer also. A very small amount (0.2ml) of vaccine is actually introduced into the horse's upper lip rather than an intramuscular injection as in other vaccine types - although this sounds painful, horses rarely seem to object to this. A small painless local swelling and pustule usually develops for a few days but there is no need to interupt exercise programmes and the horse can be ridden as normal. Trials have shown that the vaccine typically protects about 75% of horses against strangles infection - the remaining 25% may show some signs of strangles but are far less ill than unvaccinated horses. The vaccine is unnecessary and not recommended for widespread use in all horses and ponies. Rather a targeted approach is advised and use is recommended in yards that may be at an increased risk of strangles due to a history of previous cases on the yard or due to frequent movements on and off the yard, especially youngsters and newcomers from sales or dealers. The vaccine can be used in adults or in foals from 4 months of age. Two initial doses are required, 4 weeks apart, followed by boosters every 3-6 months depending on the height of the estimated risk on the yard. Vaccination in the face of a strangles outbreak is unlikely to be helpful unless horses have been vaccinated previously as a good response to initial vaccination does take several weeks.

Equine Viral Arteritis (EVA)

This virus may cause abortion in brood mares and respiratory disease in any horse. The vaccination may be used in breeding stallions.

Suspected Adverse Reactions

Short term and temporary problems can and do occur rarely; these take the form of either local reactions (bruising, muscle hardness, and occasional formation of an abscess) or systemic reactions (depression and raised temperatures). Consult your veterinary surgeon as soon as possible if you think your horse may be showing an adverse reaction, as early treatment can be a great help.

Long term consequences are extremely rare.

Exercise

As a general rule try to vaccinate your horse during a quiet or rest period and do not exercise strenuously afterwards for at least a few days although this might not be strictly necessary nowadays

These notes are designed as a guide only. Your own veterinary surgeon will be happy to answer any other queries you may have regarding vaccinations.

Copyright The Liphook Equine Hospital 2005