When Rattlesnakes Strike

Q. I live in an area where rattlesnakes are just part of life. What should I expect if one of my horses does get bit?

A. When I first started into practice fresh out of vet school, I was working near Reno, Nev., where rattlesnakes are the norm. One of my first Sundays on call, I got an early morning phone call from a rancher whose horses had been out in the back 5,000 acres. In a slow drawl, the rancher told me that one of those horses, a young Quarter Horse gelding, wasn’t right.

I can hear the rancher’s words clearly to this day: “I just didn’t remember him as being that ugly!” The rancher trailered into my clinic and, sure enough, the horse was ugly, indeed. The animal’s face was swollen bigger than would fit any available halter, even draft size, and his head resembled more an elephant than a horse.

Usually a horse will get bitten on the muzzle while grazing as he inadvertently sticks his nose on top of a resting snake. This is pretty obvious when you see blood spots that are fang marks. The most likely initial effect is that the horse feels crummy and is depressed. Typically, the bitten area swells quite rapidly. In severe cases, the airway can swell shut, necessitating emergency measures to insert a garden hose, syringe case, or flexible tube into the nostrils to permit breathing. Most importantly, the bite has the potential to become infected with anaerobic bacteria, like Clostridal spp., that can cause tetanus or sepsis. 

If a horse is bitten on the lower leg, there is great concern because there isn’t much room for swelling, plus there is danger of severe injury to the blood supply. Any lower limb bite has the potential to be life threatening because of wound complications.

In about 20 percent of rattlesnake bites, no venom is injected into the wound. Even if it is, an adult horse usually survives this, but veterinary treatment is aggressive and proactive, requiring anti-inflammatory medications, antibiotics, and continuous monitoring to make sure the horse can eat, drink and get around. In addition, the horse needs to be kept out of the sun. Snakebite can alter liver function, making a horse more sensitive to ultraviolet rays from the sun.

Expert: Nancy S. Loving, DVM, is a performance horse veterinarian based in Boulder, Colo. She is also the author of All Horse Systems Go.