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EQUINE HEALTH
DEALING WITH
SNAKEBITE
IN HORSES
by Heather Smith Thomas
The rattlesnake is the most common poisonous snake in the U.S. and part of a larger family called pit vipers, which include the water moccasin and copperhead. All of these can be dangerous to pets, livestock, horses and humans.
The danger/potency of a bite depends on
the amount of venom injected by the snake, the types of toxins in the venom, and size of the animal bitten. Very small animals like rodents and birds generally die quickly; this is how the snake kills its prey. Larger animals are less at risk for immediate death, but the bite can still be dangerous—especially for a small child or pet. Large animals like horses or cattle are less likely to be killed by the venom itself but, complica- tions such as swelling or infection from the bite wound can sometimes be serious.
Cattle generally recover without treatment, even when bitten on the nose or face. Swelling around the nose tends to shut off the airways, but cattle can breathe through their mouths. Horses are more likely to suffocate. Snakebite on a horse’s face or muzzle can be an emergency, and if you don’t find the horse in time you may lose the horse.
A large snake that hasn’t bitten/eaten for several days, with a full pouch of venom, is more deadly than a small snake or any snake that has recently bitten and killed prey. Venom contains several types of toxin, and the pri- mary toxin may depend on the type of snake, according to Dr. Ginger Elliot, veterinar-
ian in Guthrie, Texas, who has seen a lot of snakebites in large animals during her many years of ranch practice. “Of the 21 species of rattlesnakes found in the western U.S., the Prairie Rattlesnake is the most numerous and the Western Diamondback is the largest snake. The rare Mojave Rattlesnake inhabits southern California, Nevada, Arizona, New Mexico, and southwestern Texas,” she says.
Toxins in rattlesnake venom immobilize and kill prey (small rodents) and break down their body tissues to start the digestive process. “The main toxins are myotoxins (the primary toxins in Western Diamondback venom), which create rapid swelling, pain and bleeding at the bite site, and hemotoxins (the main toxin found in Prairie Rattler venom) that damage the blood vessels.
The toxins create inflammation, tissue destruc- tion and blood vessel leakage—allowing the venom to spread,” explains Elliot.
Dr. A. Jacques Fuselier has spent a lot of time in Louisiana and had a lot of experience with livestock bitten by water moccasins as well as rattlesnakes. “Most bites from the water moc- casin are on the lower limb or muzzle, especially if horses or cattle encounter the snake at a pond,” he says. They may be curious and get bitten on the face or muzzle, or on the leg if they walk past the snake on their way to water.
“On hot days the animals may go into the water to cool off and may get bitten on the body or muzzle. Bites on the muzzle are the ones I’m most concerned about because the rapid swelling can make it difficult to breathe,” he says.
If you find an animal that’s been snake- bitten, try to give emergency treatment without moving that animal very much--since increased activity and blood circulation will spread the toxins farther; exertion may make it more dif- ficult for the animal to breathe if the face or muzzle is swelling.
The rattlesnake is part of a large family of snakes called pit vipers, which also includes:
Water Moccasin Copperhead
64 SPEEDHORSE August 2020