Horses, ponies and donkeys are susceptible to a number of diseases which thankfully we can vaccinate against.
What is a vaccination?
A vaccination is a way of producing an immune response against a specific disease. It primes the immune system so that an appropriate immune response can be stimulated if your horse comes in to contact with the disease. Initially a primary vaccination course will be required when vaccinating against a specific disease. This involves two or three vaccinations fairly close together. Regular booster vaccines at set time intervals depending on the disease you are vaccinating against.
Is vaccinating compulsory?
Vaccinating your horse is not compulsory. It is not cheap but the cost of treatment will be considerably more if your horse does contract one of these diseases that can be protected against. With some diseases such as tetanus, there is little treatment that can be administered and many horses will die. However, if you wish to enter your horse into any competitions, if it’s entering a racing yard then vaccination against equine influenza (flu) is compulsory. If you are putting your horse into livery then some yard owners will also insist on vaccination before allowing your horse onto the premises.
Is it dangerous to vaccinate my horse?
All vaccines are tested extensively by the drug companies to ensure they are safe and there are no adverse reactions before being put on the market. Some adverse reactions have been seen but these are incredibly rare when you consider the number of horses routinely vaccinated against flu and tetanus. Of these reactions, most are either a local soft tissue reaction to some of the components of the vaccine or mild muscle stiffness. The risk of your horse contracting flu or tetanus is much greater and can even be fatal compared with the risk of your horse developing a reaction to a vaccine.
Following vaccination how long before I can ride again?
It is advisable that for the first 24 – 48 hours following vaccination of your horse or pony stress is minimised. This will reduce the risk of adverse reactions developing. After this time period you ride your horse as normal. If you vaccinate against influenza then you are not allowed to compete until seven days after the vaccine has been given.
Equine Herpes Virus (EHV)
This is a common virus in the worldwide horse population. The most common strains to infect horses are EHV1 and EHV4. EHV4 is most commonly associated with respiratory disease whilst EHV1 is more commonly associated with neurological disease and abortion.
Abortions generally occur in late gestation at about seven months and pregnant mares don’t always show signs of infection prior to abortion. Following infection, abortion occurs from two weeks to several months later. Foals can become infected whilst still in the mare’s uterus, which can lead to premature birth, birth of weakly foals or foals that initially appear healthy but become progressively weak and lethargic within the first week of life. Ideally pregnant mares should be kept in small groups and kept separate from any other horses that come on to the premises.
Respiratory disease due to EHV is most commonly seen in weaned foals and yearlings in the autumn and winter. Following infection with the virus, it is likely that they will develop a secondary bacterial infection.
Horses that have recovered can become latently infected with the virus; that is they don’t appear unwell but the virus is still within the body. When the horse becomes stressed the virus can then be reactivated and re-infection can occur.
Vaccinated horses can still become infected with the virus, shedding it in the environment and infecting other horses but the severity and length of disease will be reduced. Horses can be vaccinated from five months of age. The primary course involves two injections four to six weeks apart. Foals with insufficient colostrum intake can be vaccinated with a single dose at three months then again at five months, then four to six weeks after. It is advisable that all animals on a stud farm are vaccinated against EHV, whether they are pregnant or not, although pregnant mares can still abort following vaccination. It is not advisable to vaccinate in the face of an outbreak of EHV on a yard since it can exacerbate clinical disease.
Vaccination of pregnant mares
Pregnant mares that have had the primary course of vaccination should then also be vaccinated in months five, seven and nine of pregnancy. Boosters are required every six months.
Equine influenza virus
This is a highly contagious viral disease of the upper and lower respiratory tracts. There are many different strains of the flu virus but the most common ones seen in this country are H7N7 and H3N8. Whilst equine flu is now endemic within the horse population the virus strains continually mutate and therefore epidemics or outbreaks of disease can be seen. Vaccine companies regularly update the vaccine to protect your horse against the strains that are currently circulating in this country.
Equine influenza can be spread rapidly through a group of horses either via direct contact with an infected horse or indirectly via virus particles in the environment. It is therefore important to isolate any horse you suspect of having flu.
Clinical signs of flu
Clinical signs are generally seen one to five days after infection and can last for two to three weeks or longer if complications occur. Signs to look out for are:
- Harsh dry cough that can last for two to three weeks
- High temperature 43⁰C (106⁰F)
- Clear moist nasal discharge that progresses to become thick and creamy yellowy-brown
- Depressed and lethargic
- Decreased appetite
Infection with the flu virus can make the horse more susceptible to bacterial infections and bronchitis or bacterial pneumonia can subsequently develop. This can prolong recovery time and increased treatment will be required.
Vaccinating against flu is highly recommended and is in fact mandatory if your horse is going on to any race courses. The Jockey Club, international equestrian federation and many show societies produce vaccination protocols to follow for equine influenza. These all vary and it is therefore important that you check the requirements for your particular society. Different vaccination companies also have different vaccination protocols so it can get very confusing to work out when each vaccination is required.
The most common vaccination protocol is
- Initial primary vaccination course which involves two injections no less than 21 days and not more than 92 days apart.
- First booster is then required at not less than 150 days and not more than 215 days after the second injection of the primary course.
- Subsequent boosters are then required at intervals of not more than 365 days apart.
- Each horse must have a valid vaccination certificate which is completed, signed and stamped by a veterinary surgeon.
- You must be able to show that your horse has had a primary vaccination course against equine influenza as stated above.
- No vaccination should be given in the seven days leading up to a competition or entry into a competition stables.
- Check with the competition organisers/society as to what the protocol is for vaccinating against flu.