Why should horses be vaccinated?

Veterinarians generally recommend that all horses should be vaccinated at regular intervals in order to protect them from certain diseases. Fortunately many responsible horse owners do vaccinate their animals thus reducing any possible risks of infection. Vaccines consist of weakened or dead forms of a type of pathogen and are administered into the animal’s body usually via injection. The result is for the animal’s immune system to be triggered into learning how to fight off the infection and create certain memory cells. Therefore, in the future, if that type of pathogen does enter the body then the animal’s immune system should be able to recognise and destroy it. Vaccinations are an example of preventative medicine and allow the horse to survive what could have otherwise have been a fatal or seriously damaging disease. Sometimes, the act of vaccination does not prevent the disease completely but it does ensure that it results in noticeably milder symptoms.  

Vaccinations are vital in the prevention of the spread of contagious diseases, some of which generally cannot be cured. Horses are vaccinated against diseases which adversely affect health in ways which could reduce performance levels or even result in death. Horses in particular transfer pathogens easily between them due to their need for close companionship such as grooming, the sharing of grazing areas and their susceptibility to certain diseases. It is then safer for the horse to socialise with other horses and this is important since, as herd animals, they require the company of others. 

When buying or acquiring a new animal, vaccination records should be checked with the previous owners. If unvaccinated it is advised that a vaccination course, especially those of equine tetanus and equine influenza, is be started as soon as possible. If vaccinated then annual boosters should be given to provide long term protection or immunity against the disease. Vaccination can reduce the stress and expense when owning a horse in comparison to if the horse has actually become infected.  Medicinal treatment can be costly and working horses lose money as they have to take time off work or, in the most severe cases, have to be euthanized.

When should horses be vaccinated?

Young foals can be vaccinated starting from the age of four months old. Prior to this, they receive the necessary antibodies and protection from their mother’s milk for a short period of time. In addition the mother’s milk might actually reduce the effectiveness of the vaccine. Pregnant mares are usually vaccinated to provide their unborn foals with adequate immune systems.

Boosters are given at different intervals depending on the vaccine used. They should also be given before a horse travels to a show or a similar event. This is because travelling can increase stress, thus making the horse more susceptible to any infection. Additionally, some events might require proof of vaccinations and refuse unvaccinated animals to enter. Some vets may sent reminders in the post for boosters although owners should take care to note in their calendars the dates that the vaccines are due.  

Which vaccines are most commonly used?

The main diseases vaccinated against are the more infectious and serious types. The incidence of certain diseases has shown a marked decrease following correct vaccination in those areas. It is important however to continue vaccinating here since the disease can easily begin to spread once again.  

A brief overview of the main diseases is as follows:

Equine Tetanus

For most unvaccinated horses, equine tetanus is a fatal disease which affects the central nervous system. It is transmitted when open wounds or sole punctures are exposed to contaminated soil. Most owners vaccinated their horses once every two years to provide long term protection against the bacteria which cause it.

Equine Influenza

The disease is very contagious and is transmitted via aerosol droplets during respiration. Symptoms include coughing, nasal discharge, a high temperature, and a loss of appetite. If the disease progresses to pneumonia, death can occur. Vaccination is strongly recommended for all horse owners.

Equine Rhinopneumonitis

Equine rhinopneumonitis is caused by the herpes virus (EHV-1 and EHV-4) and is highly infectious. The disease is transmitted by aerosol droplets and contaminated surfaces. Symptoms include nasal discharge, loss of appetite and a high temperature. Although rare, death can occur in certain situations and environments. Vaccines are available to help protect against this disease.

Equine Rotavirus

This disease is contagious and the virus is transmitted into the mouth from infected faeces. Equine Rotavirus is familiarly known for the symptom of sever diarrhoea in foals. Without careful monitoring, rotaviral diarrhoea can cause fatal dehydration. It has been suggested that vaccinating pregnant mares reduces the incidence of the disease in their foals.

Equine Viral Arteritis

Equine Viral Arteritis is a contagious viral infection and can be transmitted via aerosol droplets during coughing or during intercourse. When symptoms do arise they include fever, nasal discharge, lethargy, depression, and abortion in pregnant mares. Vaccines do exist to prevent the spread of this disease.


Strangles is a highly contagious disease and infected animals should be kept in quarantine. The disease can be transmitted via both direct and indirect contact. The most well-known symptoms are swelling around the lymph nodes and the emergence of abscesses. Fatality can result of an occurrence of the disease progressing to “bastard strangles”. Vaccinations are available but usually own administered to horses in areas where there the disease is present.


Although uncommon, horses can become infected by rabies. If bitten by an infected animal, the virus can be transmitted into the bloodstream. The infected horse shows symptoms including behavioural changes, lameness, paralysis, and usually death. Vaccination is recommended for horses in high risk areas.


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