PET DOCS: Knowledge is key to treating snake bites
Let's face it. We live in snake country. South Carolina has every type of venomous snake that exists in the United States. These, as well as nonvenomous species, play a vital role in our ecosystem. Most of the snakes you see are not venomous.
I (Dr. Henri Bianucci) believe that we must learn about snakes and learn to live with them instead of feeling the need to kill them.
I used to think that in the unlikely event that a person or animal was bitten, the nearest emergency room would have the correct treatment, including antivenin. We have learned that this assumption probably is incorrect.
On a recent early morning, on rural Wadmalaw Island, a bird feeder had attracted its usual patrons.
As is the natural order of things, these herbivores will catch the attention of carnivores. Otis, a 1-year-old mixed breed dog, is one such carnivore.
He was poised by the back door, which may as well have been the starting gate at the Kentucky Derby. When the door popped open, he launched into pursuit of the squirrel that was nervously feeding.
But the squirrel also had attracted the attention of another predator, a 5-foot canebrake rattlesnake. The snake poised patiently to strike, his venom glands primed to deliver a lethal dose.
The squirrel had no idea that luck was on his side that morning, because these equally deadly predators canceled each other out.
Otis plowed in and surprised the snake, that defensively struck, delivering the venom intended for the squirrel into Otis' hind leg.
Otis was rushed to our emergency hospital in Mount Pleasant, and the venom was already taking hold. His leg was slightly swollen and his urine was turning red, signaling that muscles were already beginning to die. Antivenin was administered and Otis began to respond.
By midafternoon, it appeared that the medicine was doing its job to prevent necrosis of the muscles, blood, liver and heart. But Otis took a turn for the worse that evening.
Otis began to develop neurologic symptoms. He lost all facial muscle control, including the ability to blink. His breathing became shallow, just enough to survive with supplemental oxygen. His prognosis was now very guarded, and he was facing the need to be kept alive on a ventilator.
Snakes and venom
The canebrake rattlesnake is the most common rattler in our area. The Eastern diamondback is equally dangerous but is very rare, and the pygmy rattler is not as venomous as either of these.
The venom of all rattlers contains cytotoxins. These are toxic to cells and are responsible for tissue death. There are other biotoxins that are damaging to the liver, heart, kidneys, etc. But all rattlesnakes also have some neurotoxin in their venom.
Canebrake rattlesnakes vary widely in the composition of their venom, and some can be strongly neurotoxic. This is a problem for treating these bites in humans and dogs.
Antivenin is made by injecting a horse or a sheep with the venom of various snakes. Not enough is given to kill them, but just enough so they will form antibodies to the venom.The antibodies then are collected from their blood and stored as a powder. When someone is bitten by a snake, the antibodies are given to intercept the venom before it can cause harm.
Antivenin for humans is made from Eastern and Western diamondback rattlesnakes, Mojave rattlesnakes and cottonmouth snakes. Antivenin for dogs is made from diamondback rattlesnakes, South American rattlesnakes and the fer-de-lance snake.
According to Dr. Jason Madey, a neurology resident at the Medical University of South Carolina who recently treated a Goose Creek boy for a nearly fatal bite from a canebrake rattler, this neurotoxin is complex and the treatments in our arsenal might have little effect on them.
He explained that the human-approved antivenin does not have antibodies to the canebrake venom, and the antibodies to other snake venoms might not offer protection to the neurotoxic component of canebrake venom.
This is what was nearly fatal for Otis and for the Summerville boy.
Madey said that the human antivenin worked beautifully against the tissue-destructive elements of the venom but did not seem to affect the neurotoxin.
That was our experience as well. Otis had minimal tissue damage, but the neurologic signs developed despite aggressive therapy with both human and veterinary approved products.
Madey's opinion, which we share, is that there should be an antivenin developed specifically to include the most prevalent rattlesnake in our area, the canebrake.
Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC.