Your Guide to Equine Health Care

Equine Tetanus: Signs and Treatment

Tetanus is an often deadly but preventable disease. Here’s what you need to know.

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tetanus in horses
A classic sign of tetanus is prolapse of the third eyelid. | Photo: Courtesy Dr. Dana Zimmel

It’s a beautiful sunny day and being that nothing exciting is happening in the pasture today, you decide to lie down and roll a bit. In the midst of an extremely satisfying roll, there is a sudden sharp pain in your rump area, but it goes away as fast as your initial perception of it—no big deal. Unbeknownst to you, that sharp pain was a small piece of old and dirty wire coated with a plethora of bacteria that violated your skin and about two inches of muscle tissue. The skin wound quickly seals over and heals, but a small population of bacterial spores germinates and starts to proliferate in the damaged muscle tissue. As this family of bacteria begins to flourish in the muscle tissue, a small protein that is manufactured by the bacteria is released and eventually enters the bloodstream. During the elapsed time, you hardly notice a thing wrong; you go about the daily routine of eating and whatnot. The protein now has made its way to the spinal cord and is starting, ever so slightly at first, to wreak havoc on your nervous system’s control over your muscular system. You start to feel stiff and cannot see well as your third eyelid protrudes up and obscures vision. The slightest noise startles you and makes all the muscles in your body contract and spasm; you want to flee in panic, but the more you panic, the more your muscles spasm. It becomes impossible to move or even eat, and you stand with a wad of half-chewed grass clenched between your teeth. Eventually when startled, you fall, unable to rise again. In the end you fearfully suffocate from an inability of your muscles to allow you to breathe, and you die—the grass still clenched between your teeth.

This is my visualization of what a horse dying from tetanus experiences. Some might feel that this is an over-dramatized rendition, but having personally observed five horses die from tetanus, I believe this horror to be real. The saddest part is that it could have been prevented.

Tetanus is caused by the bacteria Clostridium tetani that when viewed under the microscope have a characteristic rod-like shape that often is reported to look like a “tennis racket” or “drumstick.” The bacteria stain darkly purple with the Gram method of staining. The round bulging end of the organism, the shape likened to a tennis racket or drum stick, is called the terminal spore. Like all the Clostridium species of bacteria, Clostridium tetani is considered an anaerobic organism (the absence of oxygen is necessary for it to live). But, despite the fact that oxygen is not needed for life, the organism can survive in the spore state. The spore can be viewed as a seed that, when the environmental conditions are right, can “germinate” into a viable bacterium capable of replication and spore

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Written by:

Michael A. Ball, DVM, completed an internship in medicine and surgery and an internship in anesthesia at the University of Georgia in 1994, a residency in internal medicine, and graduate work in pharmacology at Cornell University in 1997, and was on staff at Cornell before starting Early Winter Equine Medicine & Surgery located in Ithaca, New York. He was an FEI veterinarian and worked internationally with the United States Equestrian Team. He died in 2014.

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