Vaccinations

Vaccination is a vital part of horse ownership. As vets we are faced with an increasing number of vaccinations on the market, and as owners you are faced with more choices when it comes to the vaccination of your horses. What follows are some brief reminders as well as some new information.

Tetanus

An essential - unlike other diseases which we vaccinate against, tetanus does not require contact with other horses. In fact, the bacterium (Clostridium tetani) which causes tetanus, lives in the soil - especially where there is a lot of manure. As such, most horses are exposed. The organism gains entry when the skin barrier is breached, most commonly in puncture wounds, but sometimes the point of entry can be more subtle than an obvious wound. I am sure that you are all aware of the classic ‘lock jaw’ appearance of a horse with tetanus and of the limited success and large expense of treatment. We would all like to believe that tetanus is a disease confined to historical vet books, but three horses in our practice have died of tetanus over the past year. It should also be noted that insurance companies do not pay out for the treatment of tetanus because they view it as part of normal management.
VACCINE PROTOCOL: Initial course - 2 injections 21 - 92 days apart, then a booster every 2 years.

Influenza

Influenza infection results in a cough, fever, nasal discharge, lethargy and unwillingness to eat. Spread occurs through the aerosol produced by coughing individuals. All ages are susceptible to this virus although it is most common in young (2-3 years) unvaccinated horses. Vaccination against ‘flu is often a requirement for entry into livery yards and competitions. The FEI, which is the regulatory body for many equestrian sports, has some strict guidelines for the vaccination against ’flu (these are outlined below). It is also thought that the FEI is soon to reduce the booster time from one year to six months.
VACCINE PROTOCOL: Initial course - 2 injections 21 - 92 days apart and the third 150 - 210 days later. Booster injections are then given within 365 days. Therefore it is not necessary to give this just before 365 days, i.e. the date can be bought forward to allow it to fit in with other horses to be vaccinated on the same day.

Herpes

The herpes virus is responsible for three syndromes in the horse:

1. Abortion in pregnant mares.
2. Upper respiratory tract infection
3. Neurological disease.

The virus is spread via aerosol inhalation i.e. in the air. Protection is available in the form of a vaccination, the timing of which is determined by the syndrome being guarded against. Where the concern is mainly respiratory, there is a vaccination which combines ‘flu and herpes (Equillus Resequin) which is both effective and economic. It has been shown that the maximal protection against herpes abortion has been to vaccinate in mid to late pregnancy.
VACCINE PROTOCOL:
General protection against upper respiratory/neurological syndromes either in the form of herpes only vaccine or Equillus Resequin (Flu and Herpes). Initial course - 2 vaccinations 3 - 6 weeks apart then boosters every 6 months.
Pregnant mares and abortion prevention: Given during pregnancy at 5, 7 and 9 months of gestation.

Strangles

A disease caused by the bacteria Streptococcus equi equi strangles (unlike herpes and ‘flu) requires direct contact. It is highly contagious, with high morbidity (those succumbing to the disease) although the number of deaths is low, about 1%. Horses affected have a high fever, nasal discharge, swollen and possibly draining lymph nodes of the head, dullness, lack of appetite, respiratory noise. There are also complications which come with recovery, some horses may develop generalised abscesses (‘Bastard Strangles’) generalised vasculitis (Purpura haemorrhagica) or become carriers of the disease and therefore capable of transmission
The exciting news is that there is now a vaccination available to protect against this disease which is undoubtedly common, debilitating and of vast economic importance. The vaccination is administered in the mucosa of the upper lip where it causes a local immune response in the head. Strangles was one of the subjects of our client night last month. We have recently started using the vaccination and have found no adverse reactions in either the administration of or reactions after.
VACCINE PROTOCOL: Initial course - 2 vaccinations 3-4 weeks apart then boosters given 3 -6 months apart (depending on risk/exposure).

Grass sickness

There is increasing evidence that grass sickness is caused by a strain of botulism bacteria. To prove this conclusively it would involve giving horses live botulism toxin. No country in the world will obviously approve of this. To prove that grass sickness is caused by botulism it is proposed that a large number of horses (possibly over 1,000) be vaccinated against the suspect strain and then monitored for several years to determine if they are protected against the disease. It is thought the horses chosen will come from areas where grass sickness has occurred before. At the moment safety trials are being conducted on the vaccine. If it proves to be safe then the vaccine may be tried on horses in Scotland in approx 3-4 years. If the use of the vaccine stop horses developing grass sickness then it may become generally available.

Mares and Foals

The greatest immunity is passed on to a foal from a mare if she is vaccinated 1-3 months before foaling. Herpes, flu and tetanus are all licensed for use in the pregnant mare. Then the foal can begin the primary course of vaccinations at 5-6 months.

If the mare has not been vaccinated, the mare and foal should receive a tetanus antitoxin injection within 24hrs of foaling . The foal can begin its tetanus vaccine course at 6 weeks of age and its ‘flu course from 3 months.