Equine Vaccinations

What conditions can be vaccinated against?

Vaccinations are available for a number of diseases but some are only appropriate for horses that travel overseas for racing and competitions. The two most important vaccinations that every horse should receive are influenza and tetanus.

There is also a vaccination against Equine herpesvirus, which can cause abortion in pregnant mares. Contact your vet to discuss this if you are considering breeding from your mare.

Tetanus ('lock jaw')

Tetanus is caused by a bacterium, Clostridium tetani, which is found in soil and enters the horse's bloodstream via an open wound. Even small wounds can allow Clostridium tetani contamination and, because the incubation period is 7-21 days, the wound has usually healed by the time the first signs of the disease are apparent. Often owners are not even aware that their horse has received a wound, or thought it minor and of no importance and yet their horse develops tetanus.

The signs of tetanus are:

• Vague stiffness in the head and limbs progressing to reluctance to move.
• Spasms in the muscles of the head and neck resulting in difficulty chewing, nostril flaring and a wide-eyed expression.
• Trembling progressing to violent, whole body spasms in response to sudden movements or noise.

Approximately 90% of unvaccinated horses that develop tetanus die. In the small number of horses that do recover, intensive veterinary treatment and nursing care is required for a period of about 6 weeks.

Equine influenza ('flu')

This is a highly contagious, viral disease of the respiratory system caused by different strains of influenza virus. A horse contracts the virus either through contact with an infected horse, or indirectly by contaminated environments/air. Infected horses incubate the disease for 1-3 days before displaying any symptoms, which is why outbreaks of equine influenza spread so rapidly.

The symptoms of influenza include:

• A rise in temperature up to 41^oC (106^oF) for 1-3 days (often undetected).
• A harsh, dry cough of sudden onset that persists for 2-3 weeks or more.
• Clear nasal discharge progressing to thick, green-yellow discharge.
• Lethargy.
• Loss of appetite.

The disease can develop into life-threatening bronchitis or pneumonia. When horses recover from influenza, they can be left in a debilitated state making them more susceptible to secondary infections.

Outbreaks of influenza are most common when large numbers of young horses are brought together in stressful conditions, i.e. sales or shows.

Equine Vaccination Regime

Influenza vaccination

Approved vaccination schedules for the influenza vaccine are published by the Jockey Club, International Equestrian Federation (FEI) and various show societies and committees and these form part of the entry requirements for horses competing or racing in their events.

Unfortunately, these schedules differ between organisations and it is confusing for the owner to determine which they should follow. To complicate matters further, the manufacturers' of each vaccine recommend a different schedule again, based on the efficiency of their vaccines determined by clinical trials.

The manufacturers' recommendations provide your horse with the most protection against influenza and will satisfy Jockey Club, FEI and most racecourse, show committee regulations.

Manufacturers' protocol:

Tetanus vaccination

Most influenza vaccinations also contain the tetanus vaccine and if you follow the above vaccination schedule using the combined Prevac T Pro vaccine, your horse will also be protected against tetanus.

When using separate tetanus vaccine, the schedule for vaccination is:

Pregnant mares should be given a tetanus booster in the last 4-6 weeks of pregnancy which will provide the foal with some protection through the milk for the first 6-12 weeks of life.

Foals can also be given an injection of tetanus antitoxin (an 'antidote' to the tetanus infection) as soon as possible after birth to provide temporary cover for 3-4 weeks. This should be followed by another dose after 4 weeks. Regular tetanus vaccination can be started at 3 months old.

You should try and reduce stress (e.g. heavy exercise) on your horse for the 24-48 hours after vaccination. This will further reduce the very small chance of any adverse reaction.