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Horse & Hound’s definitive guide to equine vaccinations *H&H Plus*


  • A white check mark
    This article has been edited and approved by Karen Coumbe MRCVS, H&H’s veterinary advisor since 1991.
  • 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

    There are a number of equine vaccinations available to help protect your horse’s health. These include equine flu, tetanus, equine herpes virus and equine rotavirus, while a new vaccine against strangles is expected to become available in 2o21. Unfortunately a recent field trial of a vaccine to protect against grass sickness proved inconclusive.

    The 2019 equine flu outbreak in the UK highlighted the need for more horses to have protection and a number of governing bodies of equestrian sports have updated their rules around the frequency of vaccination as a result, with many moving from annual to six-monthly requirements. All vaccination records should be kept up to date in the horse’s passport document.

    During the first 2020 coronavirus pandemic lockdown in the UK, vets were told to stop giving six-monthly flu vaccinations, so they could prioritise emergency care for their patients. Any competition horses that missed their annual vaccinations as a result of this would need to restart the course.

    Equine vaccinations: Vet’s view | Equine flu | Tetanus | Equine herpes virus | Equine rotavirus | Reactions | Strangles

    Only healthy horses should be vaccinated. If your horse is showing any signs of being unwell, discuss this with your vet prior to any vaccine being given. It is recommended that a horse is given a couple of quiet days after being vaccinated, with only light work and turnout. A horse should not be worked hard or made to sweat as they may be feeling below par or a little sore at the site of the injection.

    A small percentage of horses experience a reaction after being vaccinated. If your horse appears unwell then speak to your vet for advice. If your horse has previously had a reaction then discuss it with the vet prior to any future vaccinations being given.

    A vet’s view

    “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 a 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 and other viruses. 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. 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 that can take a considerable amount of time for horses to recover from. A major outbreak occurred in the UK during 2019 mainly affected unvaccinated animals, although some vaccinated horses also showed clinical signs.

    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. Many governing bodies that previously required annual vaccinations moved to six-monthly following the 2019 outbreak – the latest details are available here – although some of these rules changed in 2020 due to the human coronavirus pandemic.

    How often? First one at around five months old, second one about four weeks later (21-92 days), then again around six months (150- 215 days) and then annually or more frequently depending on the rules of individual disciplines, e.g. British Eventing requires a booster within six months of competition. If the horse misses its regular booster then the course may need to be started again for the horse to be compliant with affiliated competition rules in the UK (check the rules of your governing body).

    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 virus (EHV)

    What is equine herpes virus? There are five types of equine herpes virus, but EHV-1 and EHV-4 are the most clinically important and they are the only types which can be vaccinated against. EHV-1 and EHV-4 can cause a flu-like respiratory infection in horses, but may also cause abortion in pregnant mares and severe neurological disease. The effectiveness of the EHV vaccine against the neurological form of the disease is unclear.

    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 EHV-1 and EHV-4 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: equine rotavirus

    Pregnant mares are vaccinated against equine rotavirus to protect their foals from suffering diarrhoea or illness caused by the virus. Vaccines are given in the eighth, ninth, and 10th months of pregnancy in order that the antibodies can be transferred to the foal via the mare’s colostrum (first milk). Please contact your vet for more information.

    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.”

    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 2021. Please contact your vet for more information.

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