All horses, ponies and donkeys should be vaccinated against tetanus, a condition that equine species are very susceptible to. Sadly, most cases die, very few live and a huge amount of time, money and effort is required to keep them alive if they do survive. Vaccination against tetanus is very effective.
Tetanus is caused by a bacteria called Clostridium tetani that lives in the soil, the horse's digestive tract and the environment. This bug likes to propagate itself in places that do not have much oxygen, an anaerobic bacteria. Usually horses become infected after a puncture type wound becomes contaminated with the Clostridium bug, a deep wound is an ideal oxygen free site for the bacteria to multiply. Other types of injury that can lead to problems with tetanus would include puncture wounds to the foot and wounds within the mouth.
It is important to keep a close eye on wounds that are quite small externally that may have punctured deeper into the tissues than first thought. It is particularly important to check horses out in the field with thick coats or wearing rugs in winter.
The spores from the Clostridium bacteria produce a series of neurotoxins that are circulated around the body in the blood stream and enter the central nervous system. The main neurotoxin is neurospasmic and it is these neurotoxins that cause the problem and the clinical picture that we see with horses with tetanus. The neurotoxins cause a spasm of muscles, without really any twitching. This is a tetanic type of contraction, hence the name “tetanus”.
The classic symptoms of tetanus are initially a stiff legged gait and almost a saw-horse type stance, the ears will be very erect and immobile, flared nostrils, the third eye lids may protrude, the jaw will not open, hence the old name of “Lock Jaw”, and the tail will often be held straight out behind the patient. The affected individual may be hypersensitive to noise, with its muscles going into spasm at a loud sound. As the disease progresses the patient ends up lying down and eventually the respiratory muscles become paralysed which results in death.
The signs of tetanus can occur 7-21 days after the penetrating wound. Death usually follows within 7-10 days.
Foals are particularly susceptible to tetanus, the navel is a site at which contamination with the Clostridium bug can occur. This is why it is important to have a foaling box that is as clean and hygienic as possible prior to foaling, the navel should quickly be treated with a topical antibiotic spray and a tetanus antitoxin should be given within the first 24 hours of life. Mares around the time of foaling may also be injured internally and may become affected by tetanus. Simply vaccinating the mare a month prior to foaling will boost her own antibodies and will also boost the level of antibodies within the colostrum that the foal should receive from its mother in the first 12 to 24 hours of life.
If a wound is detected on a horse it is always important to clean it thoroughly, even clip any long hair away from the edges so that the nature of the wound can be investigated properly. A cold hose is a good way of rinsing contamination out of wounds. Hoof wounds can be lavaged with a hydrogen peroxide solution. If there is any doubt about the character of a wound and the vaccination status of the patient, then veterinary attention should be sought.
If a horse, pony or donkey is thought to have tetanus, treatment can be attempted - the wound in question would be surgically debrided, opened up to allow oxygen in and lavaged to remove contamination. A tetanus antitoxin can be administered in massive doses to neutralise the neurotoxins and antibiotics such as penicillin will be used to kill the bacteria. Other than this it is a case of nursing the patient in a cool, dark, quiet space; usually intravenous fluids are given to maintain hydration status. Sedatives and muscle relaxants can be used to control the muscle spasm. Often the bladder and rectum do not work properly so it may be necessary to catheterise the bladder so it can be emptied and also to empty the rectum manually. Some patients may survive, but sadly very few.
Vaccination is a very effective way of preventing tetanus. Ideally the first vaccine for tetanus should be given to foals at about 3 months of age, when the antibodies that the foal has acquired from its mother in the colostrum have diminished. However, mostly foals are first vaccinated for tetanus in combination with influenza vaccine at about 7 months of age, when the maternal antibodies for flu have gone. A second vaccine is then given approximately a month later (21-92 days later in combination with the second flu vaccine). Once a horse has had 2 vaccines it should really be adequately protected within 2 or 3 weeks of the second vaccine.
Vaccination is then usually repeated with the third flu vaccine of the course within the period 150 to 215 days after the second vaccine of the primary course. The vaccine can then be repeated at the first annual booster for flu (within 365 days of the third vaccine), thereafter vaccination is only necessary for tetanus every 2 years. The exception to this is mares that are in foal and these are usually vaccinated every year prior to foaling for both flu and tetanus.
Any horse (including foals) that has not had a correct course of tetanus vaccine should be given a dose of tetanus antitoxin if a wound or foot abscess is identified.
Dr Ed Lyall, BVetMed, CertEM (StudMed), MRCVS