Horse & Hound’s definitive guide to equine vaccinations: all you need to know

If you aren’t sure about what vaccinations your horse needs, when they should be given and how often, then Horse & Hound’s definitive guide contains everything you need to know

“Equine vaccinations are important to prevent your horse from contracting nasty diseases, particularly contagious diseases such as equine flu,” explains Wolverhampton vet Sue Taylor.

“Horse owners often say that their horse doesn’t go anywhere and so doesn’t need to be vaccinated, but if your horse is on a stable yard alongside horses who do compete, there is a chance that those competition horses could bring back the flu virus.

“Herd immunity is a concept that owners should be aware of too. If there is a yard full of vaccinated horses, it provides a kind of ‘wall’ to flu. It can’t pass on very successfully as vaccinated horses limit the amount of virus that is shed. Whereas if your horse is unvaccinated, they’ll catch it and snot virulent virus all over the place, making it more likely to be caught by other horses — even vaccinated horses can present with mild symptoms of flu. The higher the vaccination percentage in the overall population, the less opportunities there are to infect horses.

“Also, owners of competition horses should be aware that an up-to-date vaccination record is a requirement of many sporting governing bodies for horses competing under their rules.”

Equine vaccinations: equine flu (Influenza)

What is equine flu? Influenza is a viral infection that affects the respiratory system resulting in a high fever, runny nose and coughing. Though rarely fatal, it can be a very debilitating disease. A number of outbreaks have occurred among unvaccinated animals in the UK over recent years.
Which horses need the vaccination? Every horse should be vaccinated against equine flu. It is a requirement for competition horses to have up to date protection under the rules of most governing bodies. If competing under FEI rules, horses must have been vaccinated within six months, plus up to 21 days, of a competition, but cannot have been vaccinated within seven days of arriving at a competition venue.
How often? First one at around five months old, second one six weeks later, then again at six months and then annually. If the horse misses its annual booster then the course must be started again for the horse to be compliant with affiliated competition rules in the UK.
Any other relevant info: Only healthy horses should be vaccinated for flu. If your horse has a temperature, cough or is unwell in any way, make your vet aware before he vaccinates your horse with flu, as the vaccine could make him more ill.

Equine vaccinations: Tetanus

What is tetanus? Tetanus is caused by the production of endotoxins by the bacteria Clostridium tetani and is often fatal in horses. The spores of the bacteria are found in soil and enters the tissues via wounds. Deep puncture wounds are particularly dangerous as they provide an ideal site for infection.
Which horses need the vaccination? Every horse is susceptible to tetanus due to the nature of the disease.
How often? A primary course of two vaccinations given four to six weeks apart, followed by a booster 12 months later. Subsequent vaccinations can be given at two yearly intervals. Foals will receive antibodies from their mother’s colostrum, but many are also given tetanus anti-toxin shortly after birth too. Vaccination for tetanus is usually started at five months old and is often given as a combination vaccine with equine flu.
Any other relevant info: You can get lumps or unwell horses occasionally after vaccination, but it is usually from a combined flu/tetanus vaccination rather than a sole tetanus injection.

Equine vaccinations: Equine herpes (EHV)

What is Equine Herpes? There are five types of Equine Herpes virus, but EHV1 and EHV4 are the most clinically important and they are the only types which can be vaccinated against. EHV1 and EHV4 can cause a flu-like respiratory infection in horses, but may also cause abortion in pregnant mares and severe neurological disease.
Which horses need it? Any horse can have the herpes vaccine, but it is particularly important for breeding mares — many big studs will insist a mare is vaccinated before being allowed to foal there.
How often? The first vaccine can be given at five months old with the second vaccine at four to six weeks later, followed by a booster every six months. To provide effective immunity against abortion caused by EHV1 and EHV4 a course of three vaccinations should be given to a mare during her fifth, seventh and ninth months of pregnancy.
Any other relevant info: There is a lot of virus shed in the aborted foetus’s fluid so surrounding mares can potentially catch the disease from breathing in the virus. The vaccine doesn’t always prevent the mare from aborting, but it can limit the amount of the virus that she passes when giving birth.

Equine vaccinations: reactions

“Some horses can have a reaction to their vaccination,” says Sue Taylor. “In some cases it is the injection itself that causes the reaction, not the vaccine. Vets shouldn’t swab the area of the vaccine injection because there is a risk that the antiseptic can deactivate the virus. If you have a very dirty horse, there is the risk that the needle will take bacteria in with it, causing an infection and abscess.

“I usually inject vaccines into the brisket (chest) which is often a cleaner part of the horse and if they do react, it drains well. A lot of people inject in the neck but if the horse reacts, it is a difficult area for the fluid to drain from, and the horse can find it difficult to put its neck down to eat and drink, and certainly can’t be ridden.

“If you have a very hairy horse, it might be advisable to clip a patch of hair with clippers or scissors to minimise the risk of dirt being taken in with the needle, or ensure the horse is clean in the area he is being injected.

“If they have a history of reactions, speak to your vet about placing the injection in his chest, and discuss the vaccine itself. In some cases, it is the carrier of the vaccine that causes a reaction, although this is much less likely now with modern vaccine technology. If you know that your horse is prone to reacting to a certain vaccine, tell your vet so that he can organise an alternative next time.”

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New strangles vaccine

In 2004, a strangles vaccine called Equilis StrepE was launched, but unfortunately, three years later, it was withdrawn due to ‘quality control issues’.

Over a decade later, and a new protein-based strangles vaccine Strangvac is being developed by a group of scientists from the Animal Health Trust (AHT), the Swedish University of Agricultural Sciences, the Karolinska Institute and Intervacc AB, to prevent equines from contracting the highly contagious disease.

Trials have been carried out on 16 horses, 13 of which were protected from strangles after being given the vaccine, and none showed signs of adverse reactions.

Strangles is caused by a bacteria called streptococcus equi, which causes large pus-filled abscesses in a horse’s throat and neck. An estimated 600 outbreaks of strangles occur each year in the UK alone, so the development of a vaccine will benefit horse health world-wide. The vaccine is anticipated to be available for use in 2020.

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