Info and Advice

Immunisation

The first vaccine used was back in 1796 to help prevent the disease cow pox. Vaccines have now become an important part of preventing a large number of diseases in many animals especially the horse. The vaccine consists of a part of the biological agent and this is created into a preparation that won’t cause the disease. Therefore it is inactive. This preparation is usually injected into the body of the individual to stimulate the immune system to recognise and hence attack the disease if it were to ever enter the body unannounced.

A common vaccine used in the horse is tetnus which is caused by a bacterium called Clostridium tetani. It is a bacterial disease that affects all animals. The horse is extremely sensitive to it. The bacteria infect wounds that have an environment that is low in oxygen such as deep and necrotic wounds. Once infection is established the bacteria release a neurotoxin that prevents the muscle from relaxing once they are contracted. Initial clinical signs generally are a protruded third eye lid and a stiff gait. The disease rapidly progresses and death occurs in 80 percent of cases. The bacteria is abundant in soils contaminated with faeces and can persist for years.

To vaccinate against this disease there are two vaccines. Long term protection is given in the form of a tetanus toxoid. The protocol is to give an initial vaccine followed by a second shot in 4 weeks and then a booster in a year. To ensure protection boosters are recommend at 5 year intervals. Short term protection if the horse requires a surgery or is injuried is obtained by a tetnus antitoxin. Pregnant mares are recommended to be vaccinated before giving birth to give immunity to the foals. Foals can be vaccinated from 3 months of age.

The second common vaccinated disease is strangles. Strangles is caused by Streptococcus equi subspecies equi. Clinical signs can include loss of appetite, depression, nasal discharge, elevated temperature above 38.5 degrees, painful swelling under the jaw and a cough. It generally affects young horses where the disease is more severe, but can occur in older horses. The disease is extremely contagious but it generally doesn’t have a high mortality. To provide protection the horse should be vaccinated from 3 months of age. The initial vaccination is followed by a second and third injection approximately 2 weeks apart. Yearly boosters are recommended.  

There is a vaccine called 2in1 that combines tetanus and strangles vaccines together. The protocol to follow is to give the 2in1 followed by a strangles or 2in1 followed by another 2in1 approximately 2 weeks apart. A booster is given in 6 months and then the vaccine can be given yearly to ensure protection.

Adverse effects are rare. Horses should not be vaccinated when the horse is sick especially with a fever. If the horse has strangles vaccinating with the strangles vaccine may cause a more serious form of the disease.

Hendra as most people are aware is a serious disease carried by flying foxes that has affected horses predominately in the more tropical areas of Australia along the eastern coast. This disease has an extremely high level of mortality for both the horse and owner and is being diagnosed more frequently. A vaccine has been developed to provide the horse immunity from the disease. The vaccine is still being clinically trailed but results so far have shown that horse didn’t develop the disease when vaccinated and exposed to high levels of the disease. Currently the protocol for vaccination includes the giving the initial vaccine, followed up by a booster 21 to 42 days later with a booster in 6 months. A yearly booster will then be required. Vaccination against Hendra virus is highly advised as it has been shown to have no adverse effects and protects both the horse and people from the serious disease. Even through Hendra has not been identified in Victoria yet, it does not mean the disease will not occur. Where there a bats that carry the virus no horse is absolutely safe.
For more information about the diseases mentioned above and for other vaccines available for horses please call the Kilmore Equine Clinic on 03 5781 0163.