The veterinarians at VCA are committed to providing the most effective, most efficient care for pets. Part of their investment in that cause is research that helps them learn how well specific approaches work in specific types of cases. In fact, VCA runs a Clinical Studies group, overseen by Dr. Philip Bergman, a specialist in veterinary cancer care, to coordinate studies that leverage the cutting-edge care veterinarians provide every day in the VCA network.
For one recent study, led by Dr. Sarah Carotenuto, a board-certified veterinary specialist, researchers reviewed meticulously captured case documentation from a high-volume emergency veterinary hospital in Tucson, Arizona. They studied the cases of 282 dogs who were treated for rattlesnake bites to learn whether any of the available antivenoms worked better and which elements of treatment were most critical to survival. The results of the study were published in September 2021 in the Journal of the American Veterinary Medical Association—a publication that veterinarians around the world turn to for new insights on caring for their patients.
“We see two to three dogs with snake bites every day at Valley Animal Hospital. As more antivenoms became available, I was curious if any worked better or had lower reaction rates,” says Dr. Carotenuto. “Antivenom is expensive, so I was also curious if less expensive options were equally effective. The research is really all about what’s best for our clients and patients—and what will work the fastest.”
To answer those questions, the researchers reviewed the records for a complete description of the patients and their treatment including the location of the snakebite or bites, number of strikes, the number of antivenom units the hospital team administered, the total cost of antivenom administered, and survival to hospital discharge.
The dogs in the study all arrived at the hospital with characteristic signs of a rattlesnake bite: two small puncture wounds that ooze a clear bloody fluid; pain, swelling and bruising at the site; and impaired blood clot formation. The snakes that bit dogs in the study included representatives of these local-to-Arizona venomous pit vipers: Western diamondback, Mojave, black-tailed, Arizona black, sidewinder and tiger rattlesnakes. Of these, the Western diamondback was the most common rattlesnake species.
The name pit viper comes from heat-sensing glands on either side of the triangle-shaped head that let snakes detect their prey and accurately strike even in complete darkness. And rattlesnakes are everywhere in Arizona. “I’ve found rattlesnakes on my doorstep and next to my trashcans,” says Dr. Carotenuto. “We’re choosing to live in their home, and we’re more prone to injury the more we inch into their space.”
Of course, dogs aren’t the only creatures a snake will bite. Cats, children and adults are also at risk.
The researchers categorized the dogs by the predominant breed identified by the pet owner on hospital admission forms. The 282 dogs included 76 breed categories. The most common were pit bull mixes, Labrador Retrievers, Chihuahuas, and Dachshunds.
Dr. Carotenuto says pets most often get rattlesnake bites in the early morning or late at night, because those are snakes’ prime times to be out hunting mice and rabbits. In Arizona, snakes only hibernate December through March, so for the rest of the year rattlesnakes are an ever-present threat.
Most dogs in the study suffered only one snakebite, but 10 had multiple strike sites. Strike locations included the muzzle, forelimb, hind limb, neck, chest, and globe of the eye. Ninety-six percent of dogs survived to discharge.
The research showed that none of the evaluated antivenom products had a survival rate significantly superior to another. Instead, what appeared to be important to survival were the age and body weight of the dogs, number and location of snakebites, and whether the dog suffered a reaction to the antivenom.
“The study confirms that small dogs tend to do worse with rattlesnake bites, because of the concentration of venom in the body,” says Dr. Carotenuto. “We also confirmed that if a pet is struck more than once, it’s in more danger because it received more venom. And then there are some strike sites that are more problematic, including the eye, tongue, and right over the chest.”
Here’s some good news: If your dog does get bit by a snake, no matter which antivenom your veterinarian chooses, it will be effective. However, clearly it’s better to avoid snake bites if you can. Beyond the risk to your pet, the treatment is expensive—often more than $2,500. Beyond the normal costs of emergency care, the average vial of antivenom costs $600 to $1000, and your pet may need more than one. “The antivenom is so expensive, we only give as much as we have to,” says Dr. Carotenuto.
The key to keeping pets safe is to keep a close eye on them. Dogs that are left outside by themselves or walked off leash are most likely to get bitten. “Dogs think the rattle sounds like a toy,” says Dr. Carotenuto. “And they often don’t associate the pain of a bite with the snake. So they don’t learn their lesson, even if they do get bitten. Last night we treated a dog for its second rattlesnake bite in two days.”
If a rattlesnake bites your pet, the key is to get to a veterinary hospital as soon as possible so it can receive antivenom. “Don’t try to administer any care. Don’t try to suck out the venom. Don’t apply a tourniquet,” Dr. Carotenuto says. “These strategies really don’t work, and any delay makes the odds worse for your pet.”
Dr. Sarah Carotenuto is a board-certified veterinary specialist in dog and cat care at VCA Valley Animal Hospital and Emergency Center in Tucson, Arizona and an assistant professor at the University of Arizona College of Veterinary Medicine. Her professional interests include emergency medicine, critical care, surgery, and ultrasound. After graduating from Duke University in 1999, Dr. Carotenuto worked in strategic business consulting in New York City, using creative thinking to clarify challenging business situations. She then realized she was having more fun in her volunteer work as a docent at the Central Park Zoo and walking dogs at an animal shelter. So she returned to school to pursue a career in veterinary medicine and graduated from North Carolina State University College of Veterinary Medicine in 2007.
In her spare time, Dr. Carotenuto enjoys hiking, biking, swimming, kayaking and all the great outdoor time in Arizona—which puts her at risk for snakebites. She’s currently training for a triathlon. (And playing with a new pasta maker.)
“If your dog does get bit by a snake, no matter which antivenom your veterinarian chooses, it will be effective.”