Horse vaccinations and disease control

Horses are susceptible to many diseases and infections. These can cause health problems for the individual animal and may also spread to others. Therefore, routine hygiene procedures form an essential part of horse management by preventing disease and minimising the potential spread of infection. Additional protection against common infections can be provided by routine vaccination.

Common infections in horses

Horses can suffer numerous health problems as a result of bacterial, viral or fungal infections. The healthier the horse and the higher the standards of horse care, the greater the chance of fighting and minimising the effects of an infection. It is vital that veterinary advice is sought as soon as a horse shows signs of a possible infection.


Caused by the bacterium Clostridium tetani, commonly found in the soil and often present in horse dung. Horses are particularly at risk, being prone to small puncture wounds (eg from thorns or nails), through which infection can enter the body and then thrive. The infection takes three weeks to have an obvious effect, with the first signs (muscle stiffness, spasms and a reluctance to move) often becoming apparent some time after the wound has healed.

An affected horse may have a high fever and move with a stiff-legged gait. Other signs include flared nostrils, a startled expression (with eyes wide and ears pricked) and the tail held out stiffly. Spasms of the head and neck muscles cause difficulty in chewing (hence the common name, lockjaw). The reaction of the animal to sudden noise or movement is heightened, causing violent, uncontrollable body spasms.

The risk of infection varies from area to area and from horse to horse, with younger horses (and those with impaired health) at greater risk. Unvaccinated horses usually die shortly after contracting tetanus, with fewer than ten per cent surviving. Recovery requires extensive veterinary treatment and nursing throughout the long period of convalescence. Vaccination provides simple and effective protection against tetanus. If an unvaccinated animal is wounded, the veterinary surgeon should be called immediately.


Strangles is a highly contagious respiratory infection, caused by the bacterium Streptococcus equi. A horse contracts the infection though direct contact with an infected horse or indirectly through contamination in the surrounding area. The disease is characterised by swelling of the lymph glands below the horse’s throat, which subsequently develop into abscesses. Other symptoms are a thick nasal discharge, often accompanied by a weak cough, a high fever and a generally unwell appearance.

A veterinary surgeon must be contacted immediately if strangles is suspected as early diagnosis and treatment are essential for the individual animal and to prevent the spread of infection. Following veterinary advice, together with careful nursing, strict isolation and scrupulous hygiene is of vital importance. All horses that have been in contact with an infected horse should be monitored twice daily for signs of fever and the onset of infection.

Vaccination against strangles has only recently been made available in the UK, consequently few horses are currently vaccinated. Therefore, prevention through effective hygiene measures and strict control is essential. No infected horses should be taken to public events, and no new or visiting horses should be permitted into the yard until a month after the last abscess has healed.

Equine influenza

Equine influenza is a highly contagious viral disease of the respiratory tract. Infection can occur following inhalation of the airborne virus from other infected horses or by indirect transmission via, for example, the stable, equipment or grooms.

Veterinary diagnosis and treatment is essential. Signs of infection, which begin to develop a few days after exposure to the virus, include a husky cough and nasal discharge (which changes over a period of four to five days from thin to thick mucus), combined with general signs of ill health. Influenza debilitates the animal, leaving a horse susceptible to secondary infections. It may also develop into a more serious respiratory disorder.

Every effort should be made to isolate an infected horse. Strict hygiene measures should be adopted, to minimise the risk of infection spreading to other horses. The veterinary surgeon will advise on suitable convalescent care. Recovery may take several weeks and the horse may take even longer to return to full health. Prevention is better than cure and horses should be vaccinated routinely against the most common strains of equine influenza. Vaccination is compulsory for horses competing in most equestrian sports.


Ringworm is a contagious fungal infection of the skin. The disease is spread by both direct and indirect contact, so infected horses should be isolated wherever possible, with strict hygiene measures adopted and veterinary advice sought. Infection shows initially as tufts of raised hair which eventually fall off leaving weeping lesions. Often circular in shape, these lesions may vary in size and density, and usually occur around the head, neck, saddle and girth regions. The horse’s immediate environment also becomes infected, so bedding material should be destroyed and the stable, tack and all equipment should be washed thoroughly with a fungicidal disinfectant.

Equine herpes

Equine herpes is a serious viral infection that can cause abortion and respiratory disease. All horses are susceptible to the respiratory form, especially foals and yearlings, and it also poses a particular risk to studs. As with other respiratory infections, the horse will appear generally unwell and have a high fever, nasal discharge and a slight cough. A veterinary surgeon should be contacted as soon as a horse shows any of the signs of ill health, so that the type of infection may be identified and treated promptly.

Horse vaccination intervals and records

Vaccination maximises protection against a specific disease by stimulating the natural immune response, boosting the ability of the animal’s body to fight subsequent infection. Veterinary care should be sought to ensure that all horses are vaccinated against tetanus and equine influenza, and continual cover maintained.

A tetanus vaccination course consists of two primary doses of vaccine, given by injection approximately four weeks apart, followed by a booster at twelve months and thereafter at intervals of two to five years. The course can be started from the age of three months onwards. Pregnant mares may require an additional booster to provide initial protection to the newborn foal.

The influenza vaccination is given annually and is often combined with a tetanus booster every other year. Influenza vaccination is compulsory for most equestrian competitions and horse racing. In addition, nowadays, many livery yards and training establishments will accept only those horses that have an up to date vaccination record.

If a vaccination is compulsory, the vaccination record (which can be included in the horse passport) must show that the horse has received an initial course and a continual annual vaccination thereafter. The initial course comprises two primary injections given at an interval of at least 21 days (and no more than 92 days apart), followed by a first booster at 150 days (and no later than 215 days) after the second primary injection. Booster injections must be given at intervals of less than one year.

Horses should not be exercised strenuously for 24 to 48 hours after vaccination. Occasionally, there may be a slight reaction to vaccination, evident as a small lump under the skin. However, the risk of side effects is minimal and greatly outweighed by the benefits of protection.

Horse hygiene and disease control

Routine hygiene measures should form an essential part of stable management for all horse keepers. Keeping stables, yards and equipment clean should be routine, combined with daily observations of the health of all horses in care.

Flies and vermin can spread disease and have an adverse effect on the health of horses. Feed should be stored in vermin-proof containers and measures taken to reduce the available food sources for vermin, thus eliminating breeding sites.

Stagnant water, manure and effluent from muck heaps provide ideal breeding grounds for flies and midges. Manure should not be allowed to accumulate in or around stables and shelters. During the summer months it is important to reduce the fly problem by collecting and disposing of muck regularly, in combination with chemical control and provision of physical protection for the horses (fly sheets, fringes and shelter).

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— Page last updated 10/02/2023