Tetanus

By Jennifer Kunz, AnimalForum.com staff

The mortality rate for horses infected with tetanus has been reported as high as 50 percent. Half the animals die. All horses are susceptible regardless of age, gender, or location. It is a horrible disease, painful to observe and expensive to treat. But tetanus can be prevented. Vaccinating your horses against this deadly disease is essential in preventing their loss.

Tetanus is caused by the bacteria Clostridium tetani. Most commonly the bacteria enters the body through a deep puncture wound where an anaerobic environment is created. After a wound has been incurred, the bacteria germinates in the damaged muscle tissue. The bacteria begins to produce toxins, two of which are the most potent toxins currently known; a quantity the size of a pin head easily can cause disease and death.

The toxins travel through the blood stream toward the spinal cord where they bind to the relay area that helps to control the nervous system. The toxin deactivates the ability to inhibit excitatory signals and with that delicate balance disrupted, the excitatory signals predominate and cause intense muscle contractions. It is important to note that once the toxin is bound to the cells in the spinal cord, there is no therapeutic intervention to dislodge it.

Often the first obvious clinical sign of tetanus is colic, followed quickly by a vague stiffness. Some of the other early signs are a slight retraction of the lips and flaring of the nostrils, a pulled downward and back position to the ears, difficulty in opening the jaws, and a slight elevation of the tail. Usually within 24 hours of the initial signs, there is a generalized spastic activity of the large muscles required for standing; the legs are extended tightly in a ridged fashion, and horses adopt a sawhorse stance. Retraction of the eyeball into the socket and spasms of the third eyelid over the eye can also occur. All of the muscle spasms can be evoked by sudden sound, movement, or touch. Horses often will lie on their sides with their legs extended in rigid extension and their neck extended in an upward manner.

The muscles of breathing, the diaphragm and those located between the ribs, also are affected and respiratory distress can occur. Respiratory failure is the most common eventual cause of death for horses infected with tetanus.

Sedatives and muscle relaxants can give some relief from the muscle spasms and placing cotton in the ears can help with respect to sound-induced spasms. Stabling or hospitalization in a dark, quiet stall with as little handling and disturbance as possible is desirable. Good footing is also important. If an affected horse manages to lie down, it can have difficulty getting back up; slippery footing can result in needless trauma. A commercially manufactured antitoxin can be administered if the diagnosis is made early, but once the toxin is bound to the nervous system, the antitoxin will have no effect. The antitoxin will neutralize any toxin that is still circulating in the bloodstream. Another important aspect is to maintain the horse’s nutritional needs, possibly with an intravenous tube if necessary.

The tetanus vaccine is not perfect, but it is of significant assistance in preventing this horrible disease from infecting your horse. Horses with unknown vaccination histories should be vaccinated and boosted on a veterinarian’s instructions. Pregnant mares in their last month can be boosted to ensure both her protection and the development of the foal's immunity. A newborn foal is usually given a dose of antitoxin and vaccinated at the same time shortly after birth if the mare’s vaccination status is not known. A booster vaccination is generally recommended prior to any surgical procedure or after injuries if vaccination status is not current.

Speak to your veterinarian today about protecting your horse from tetanus!