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Can a Cat Survive Being Bitten by a Rattlesnake?

Rattlesnake venom acts as a neurotoxin in cats; the success of treatment can depend on timing.

Dr. Eric Barchas  |  Sep 20th 2016


About 20 years ago, my father and I took a road trip to check out a ghost town in Idaho. We found ourselves on a windy dirt road in the foothills. As we rounded a curve, I saw a snake in the middle of the road in a spot where it was very likely to be hit by the next car that came along. I pulled up next to it. It was a rattlesnake.

Determined to help it, I picked up some pebbles and started tossing them in its direction. Eventually it shook its rattle a few times and moved off the road.

I was lucky. A rattlesnake expert later informed me that trying to help rattlesnakes is one of the most common ways people are bitten. Rattlesnakes aren’t very grateful creatures.

In fact, they strike first and don’t bother to ask questions later. Dogs bump into them all the time, and canine rattlesnake bites are pretty easy to identify. The dog usually will have two fang marks somewhere on his face. The area will start to swell, and it will be painful. Very painful. Extreme pain is one of the most consistent features of rattlesnake bites in dogs. Also, the owner usually will have seen or heard the snake.

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But how about cats? Do rattlesnake bites cause the same symptoms in them?

I recently treated a three-year-old Domestic Shorthair cat. He had escaped from his owner’s friends’ house in the California foothills about 200 miles from San Francisco two nights before. He was found, of all places, on the roof the next morning. His right front limb was swollen, and he was paralyzed.

He was taken to a local veterinarian, who identified necrotic (black, dead) skin on the right forelimb. The cat was essentially comatose, and was laterally recumbent — he could do nothing but lie on his side. He could not even lift his head. IV fluids, pain killers, and antibiotics were started. Blood tests showed significant blood clotting abnormalities. The other vet suspected a rattlesnake bite. He spent a night in that hospital, and then the owner moved the cat to a hospital near his hometown, which happened to be on the San Francisco Peninsula. The cat came to me.

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My patient was moribund. He was breathing and his heart was beating, but those were the only signs of life when he was left at rest. His right front limb was moderately swollen with a large black area of dead skin near the elbow. His remaining limbs were swollen. And his back legs were painful — when I touched them he wailed in agony. That was the only thing that roused him from his stupor.

Incredibly, his blood pressure was normal. This gave us leeway to double down on the pain killers. After an injection of Dilaudid he was much more comfortable.

The symptoms, indeed, were compatible with a rattlesnake bite. Cats tend to be bitten on their forelimbs, because they defend themselves with their front feet. They will suffer swelling and pain at the site of the bite, but rattlesnake venom acts largely as a neurotoxin in cats. They might become paralyzed, and their mental status often deteriorates. They might suffer significant abnormalities with blood coagulation, and vasculitis (inflammation of blood vessels) can cause generalized swelling in the body and limbs. Unfortunately, the prognosis for cats struck by rattlesnakes usually is not good.

I spoke with the owner. The cat’s only hope would be antivenin, but there was a chance that it was too late. Antivenin, in general, works better the sooner it is administered. Some experts claim that it is useless when administered more than six hours after a rattlesnake bite.

This cat was at least 36 hours out.

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The antivenin available in my hospital is made of horse proteins. Cats’ bodies sometimes react to the foreign proteins, triggering anaphylaxis. It’s expensive — the price has lately gone down and it’s still $1,000 a pop. Finally, the antivenin might be useless. I suspected the cat had been bitten by a rattlesnake, but I couldn’t prove it.

The owner elected to try the antivenin. Administering the stuff is not simple. It must be reconstituted in a specific manner, diluted appropriately, and administered by a dedicated, experienced technician. The process took an hour and a half.

After the first vial of antivenin had been administered, I became confident of two things. First, antivenin can be beneficial when administered more than six hours post-bite. Second, unless one of the history’s greatest coincidences had occurred, the cat had indeed been struck by a rattlesnake. By the time the whole vial had been given, the cat could sit up and he was no longer comatose.

The owner was ecstatic. We administered a second vial of antivenin. By the time it was complete the cat was ambulatory, vocalizing, and eating. His blood clotting parameters had normalized. His prognosis was upgraded from poor to fair.

In northern California the most common rattlesnake is the northern pacific rattlesnake. They are relatively wimpy snakes compared with eastern diamondbacks and mojave rattlesnakes. But over the years I have gained a healthy respect for all rattlesnakes. Wimpy is a relative term, and even a wimpy rattlesnake can pack a nasty punch.