The rattlesnake is the most common poisonous snake in the United States, but in some regions, copperheads and cottonmouths (also called water moccasins) are a concern. The rattlesnake usually gives warning, but copperheads may just try to hide — and then bite if you get too close. The severity of a bite usually depends on the amount of venom injected and the type of toxin, which can vary depending on the snake.

Jen Haugland, veterinarian at Sorensen Veterinary Hospital in Belgrade, Mont., has treated many snakebitten animals.

“Most of the bites in the Intermountain West are from the prairie rattler, and there are several subspecies.” — Jen Haugland 

“Most of the bites in the Intermountain West are from the prairie rattler, and there are several subspecies. The vaccine commercially available for horses or dogs is not for this type of snake,” she says. “It is more specific against effects of western diamondback venom — a snake more common in Texas and the Southwest — but it may have some cross-protection.”

If a snake is startled by the sudden approach of a large animal, it may strike reactively. If the animal gets too close after the snake rattles as a warning, the snake strikes and bites. A large animal won’t be as adversely affected by the toxin as a smaller animal like a cat, dog or small child. However, the bite wound often becomes infected.

“A cow bitten on the leg may not have much effect from venom, but may develop secondary infection,” Haugland says, explaining the wound may abscess, or infection may travel up the leg and cause the skin to slough. “If infection goes systemic, the animal has septicemia and fever.”

If the animal is pregnant, high fever may kill the fetus, Haugland warns. “If you know a cow was bitten, treat her with antibiotics. If she seems sick, take her temperature and give medications to reduce the fever.”

Haugland recommends consulting your veterinarian for a treatment protocol.

“Our choice of antibiotics includes oxytetracycline or a ceftiofur product,” she says. “You can use penicillin if you administer it daily or twice a day. Most people choose something longer-lasting.”

Dexamethasone works as an anti-inflammatory and is typically the first drug of choice, Haugland says, noting it is a steroid and good at calming down the entire system. Banamine, a non-steroidal anti-inflammatory, can also be used. Dexamethasone works well for non-pregnant animals, but if given during the latter half of pregnancy, it may cause abortion. For a pregnant cow, Banamine may be the better option.