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Horse Vaccinations - Which ones do you need and why?

Horse Vaccinations - Which ones do you need and why?

Aug 24, 2023


Tetanus is a bacterial disease caused by Clostridium tetani which is commonly found in soil and droppings all across the world. The bacteria spores are capable of surviving in the soil for long periods of time however if your horse has any wound (even gastrointestinal ulcers) this means the bacteria can penetrate the body and cause disease. The bacteria causes death in about 80% of cases as it produces a powerful nerve toxin which results in the muscles of the body
spasming uncontrollably. Signs of infection may be delayed for 1-3 weeks following infection but most commonly seen 9-10 days following infection.

In an infected horse we see:
- Progressive muscle stiffness
- The tail becomes ‘flagged’ and stiff
- The ears are erect
- An anxious facial expression
- Trouble eating
- The third eyelid protrudes across the eye
- Stiff limbs
- Respiratory failure

The only way to prevent tetanus is with vaccination. It is important your horse receives this vaccination at 3 months of age with 2 doses 4 weeks apart required and a 12 monthly booster given every year. It is important to also vaccinate mares in foal before having a foal as foal’s receive immunity from maternal antibodies in their mother’s milk however this immunity fades at 3 months of age when they will require their own vaccinations. The vaccination is given by intramuscular injection which horse owners can do themselves or contact their veterinarian to
administer this vaccine for them.


Strangles is a bacterial respiratory disease which is highly contagious and has a worldwide distribution. It is caused by the bacteria Streptococcus equi. Signs of infection are generally seen 3-8 days following infection. This bacteria is spread horse to horse via pus or respiratory discharge from an infected horses nostrils, cough or draining lymph nodes. Flies are also able to spread the infection from horse to horse. Infected horses are able to shed the bacteria for weeks to even years following recovery. Contaminated grooming equipment and tack, human
clothing or shared feed and water points can also facilitate spread of disease.

In an infected horse we see:
- Nasal discharge that is green/cream/yellow and thick
- Fever
- Trouble swallowing and not wanting to eat
- Cough
- Depressed demeanour
- Swollen submandibular lymph nodes (at the base of the head behind the jaw)
- Impaired breathing

Vaccination is strongly recommended to aid in preventing serious infection. The vaccination protocol involves 3 doses 2 weeks or less apart from 3 months of age with booster doses required every 6-12 months for life.

Herpes Virus

There are a multitude of strains of equine herpes virus however the most common are types 1 and 4 (EHV-1 and EHV-4). EHV-1 can cause respiratory disease, neurological disease and abortion and is most commonly seen as respiratory disease in young horses. EHV-4 causes respiratory disease and abortion also. The virus can remain within the horse and become reactivated during times of stress. The respiratory disease usually lasts around 7-10 days however can linger for longer and is mainly spread horse to horse via respiratory secretions or
poor hygiene. Mares can also shed the virus in in the placenta, foetus and foetal fluids. Foals affected in utero born alive will typically only live a few days.

In an infected horse we see:
- Fever
- Nasal discharge
- Coughing
- Abortion usually in late pregnancy
- For neurological cases we see ataxia, urine retention incontinence and on occasion an inability to stand disease prevention is via good hygiene and management practices as well as vaccination. Vaccination is from 5 months of age (although can be given from 3 months in a high risk setting) and 2 doses are required 4-6 weeks apart. A 6 monthly booster is then required. Breeding
mares should be vaccinated at 5, 7 and 9 months of pregnancy.

Hendra Virus

Hendra is a deadly virus which is shed by bats and can spread from horses to humans. Flying foxes (fruit bats) shed the virus in their urine, faeces and bodily fluids generally via contaminating feed. The virus can also spread from horse to horse. The virus is deadly and has only been detected in Australia in QLD and NSW however with the growing population of flying foxes in Adelaide the risk of Hendra is increasing in SA.

In an infected horse we see:
- A rapid onset of illness
- Fever
- Increased heart rate
- Rapid respiratory and/or neurological deterioration

Whilst there is no treatment for Hendra currently vaccination is available. The vaccination protocol is 2 doses 3-6 weeks apart followed by a dose 6 months later and then an annual booster is required every 12 months. In South Australia we routinely vaccinated for tetanus and strangles using a 2in1 vaccination however we can certainly provide Herpes and Hendra vaccinations upon request. If you are
unsure of which vaccination program will suit your horse, your vet will be able to help you conduct a risk assessment for your individual horse and help you come up with a unique vaccination protocol to suit.

If you have any further questions please don’t hesitate to contact our clinic on 08 8318 1801.