What is a vaccination?
A vaccination is an injection which stimulates an immune response against a specific disease. A vaccination programme will insure that your horse has maximum protection against these serious (and sometimes fatal) diseases. It will usually mean two injections at the start of the course followed by yearly boosters. To provide your horse with full and continuing protection against these diseases it is essential that the course of vaccinations is completed.
Do I have to have my horse vaccinated?
Some owners give the excuse that vaccination is too expensive as the reason for not vaccinating their horse. Although courses of vaccinations and annual boosters may not be cheap, if your horse contracted one of these illnesses the cost of treatment would be considerably more expensive!
If you wish to show, race or enter your horse in competitions it must be vaccinated against influenza according to the regulations of the event committee or organisation. This usually involves the presentation of an up-to-date vaccination certificate signed by a veterinary surgeon.
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 us if you are considering breeding from your mare. Vaccination is the only proven means of helping protect horses against potentially fatal diseases which can severely affect a horse’s health and performance.
Tetanus - 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. 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 occur resulting in difficulty chewing, nostril flaring and a wide-eyed expression. The corners of the mouth are drawn back tightly and the ears are erect. Trembling progresses 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 vet treatment and nursing care is required for around 6 weeks.
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 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.
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 quickly.
The symptoms include a rise in temperature up to 41oc for 1-3 days and a harsh, dry cough of sudden onset that persists for 2-3 weeks or more. Clear nasal discharge progresses to thick, greeny yellow discharge and the horse will be lethargic with no appetite. The disease can develop into life-threatening bronchitis or pneumonia.
Outbreaks of influenza are most common when large numbers of young horses are brought together in stressful conditions, i.e. sales or shows.
Equine Herpes Virus (EHV) - Equine Herpes Virus (EHV) is classified into 4 types but EHV 1 and 4 are the major causes of disease in this group. EHV 1 causes abortion, respiratory disease and occasionally paralysis; whereas EHV 4 is an important respiratory virus and a more common cause of respiratory disease in young horses than EHV 1. EHV 1 causes abortion usually during the last 3 months of pregnancy. The horse may have a mild high temperature, watery nasal discharge, and an intermittent cough. The neurological form starts as varying degrees of ataxia (unsteadyness) ranging from mild swaying to collapse. EHV 4 causes a mild high temperature, watery nasal discharge, and an intermittent cough.
It’s estimated that a staggering 75% of horses become ‘silent’ carriers, able to pass it on to others without displaying any signs. The disease can also remain dormant in previously infected horses and can be reactivated by ‘stress’ factors such as transport, competing, a change in environment and - in the case of youngsters - weaning, sales and breaking-in.
The primary vaccination course is two vaccinations 4-6 weeks apart, then a booster is required every 6 months. Pregnant mares are vaccinated at 5,7 and 9 months of pregnancy.
Strangles - Strangles is a highly contagious disease caused by the bacterium, Streptococcus equi. Whilst the incubation period of strangles is approximately two weeks, infected horses can release the bacterium for long periods, so new outbreaks can occur up to three weeks after the initial outbreak. Once strangles is established in a horse population, it can spread rapidly. Outbreaks may last for months, effectively closing down the affected premises. About 10% of horses can carry the disease after an infection of strangles up to a year previously. Strangles is transmitted by direct and indirect contact and particularly through shared water sources, where the bacterium lives for longer periods. It can affect all ages and types, but those most at risk are youngsters; those kept in large numbers that mix with others and horses that travel a lot to competitions and riding club events.
With onset, the horse appears depressed, dull, and stops eating. Typically, the temperature rises to 41°C. After a few days lymph nodes around the throat swell, forming abscesses. The horse can have difficulty breathing and swallowing (hence the name ‘strangles’). A nasal discharge is at first clear and then becomes thick with signs of pus, after the abscesses have ruptured in the nasal passages. Abscesses that rupture shed highly infective pus into the environment, which can infect other horses. In some outbreaks and in a small percentage of cases, these abscesses spread to other parts of the body (a condition known as ‘bastard’ strangles) which is nearly always fatal.
Atypical strangles presents as ‘flu-like symptoms, which is a complication that can become persistent on a yard.
A horse's vaccination programme should be based on the risk of an outbreak. The basic vaccination schedule is two submucosal (inside of the lip) vaccinations four weeks apart. Revaccination interval will be determined by the risk of disease for the horse and yard as well as the economic consequences of an outbreak and can be every 3 or 6 months as appropriate. In general, the more a horse is in contact with other horses the greater its risk of contracting strangles.
Is vaccination dangerous?
No, it is not dangerous. Millions of horses have been vaccinated against tetanus and influenza over many years and the number of adverse reactions reported from these vaccines is insignificant. Of these reported adverse reactions, most are only local injection site reactions or mild muscle stiffness.
How effective is vaccination?
As in humans, vaccination is never a 100% guarantee since it relies on the ability of each horse to individually mount a satisfactory immune response. As a result, you should never vaccinate a horse that is unhealthy or stressed. A combination of having a complete vaccination programme and enough of the population vaccinated (herd immunity) is how viruses and bacteria are kept at bay. The gold standard is to have a whole yard vaccinated and follow good stable management and hygiene procedures. This will reduce the amount of infective organism in the horse’s environment.
What should I do if my horse appears sick following vaccination?
Just as humans sometimes feel unwell following immunisation, horses also can appear off colour after being vaccinated. This is not usually a cause for concern, but if you are worried you should talk to your vet.
Rules and regulations
It is advisable to vaccinate all horses that regularly encounter large groups of unfamiliar horses, for example hunters and horses that take part in Riding Club and Pony Club activities.
Riders or trainers who compete under the International Equestrian Federation (FEI) or Jockey Club rules, have to ensure their horses vaccinations are up-to-date to enable them to compete. Most competitions do not permit vaccination within seven days of the event.
Jockey Club Rules - The Jockey Club rules stipulate that a horse must have two primary vaccinations against equine influenza given 21-92 days apart. The horse must receive a booster vaccination given 150-215 days after the second component of the primary vaccination, and receive booster vaccinations at intervals of not more than a year apart or such lesser time as the Stewards of the Jockey Club may, in an emergency, decide.
FEI rules - Horses competing in FEI competitions require a primary course, in accordance with Jockey Club guidelines, then boosters annually.