For hunter and dog owner Chris Hull, some natural enthusiasm about moving to a bird-hunter’s paradise in central South Dakota was tempered by a rude discovery—this paradise had poisonous snakes.
Coming from a place where the reptiles didn’t pack that kind of bite, Hull was nearly taken by surprise when he and his beagle, while out for a walk on the Fort Pierre National Grassland, encountered a prairie rattlesnake.
“My beagle was a foot away from being bitten,” Hull recalled.
Afterward, Hull took the only option available then and enrolled his dog in a rattlesnake-avoidance class in which trainers use a defanged rattler and shock collars to teach dogs that the sight, sound, and smell of a rattler is trouble they most definitely should avoid.
But these days, as owner of Northstream Outfitters of Pierre and Draper, South Dakota, Hull recommends his hunter clients from other states protect their dogs with a rattlesnake vaccine that can lessen the severity of a bite. The vaccine from Red Rock Biologics was approved in California in 2003, and has been in use nationwide since 2004.
“The cost of the vaccine is a pittance compared to the time and emotional and physical energy that we put into these dogs,” Hull said. As owner of three Labradors and a miniature golden doodle—all four of them hunters—Hull said he simply rolls the rattlesnake vaccine into his ongoing care for the animals. It’s as routine as annual check-ups and booster shots for rabies, for example.
Dr. Lynn Tedrow, a veterinarian with Animal Clinic of Pierre, South Dakota, where Hull takes his animals for care, said the vaccine is affordable—roughly $25 a dose. The clinic where she works has shipped the vaccine as far away as Virginia, so that hunters in other states can get their dogs started on the vaccine if they’re going to be hunting in snake country later in the year.
According to Tedrow, even if dogs have the vaccine, veterinarians recommend the owners bring in a dog if it’s been bitten. Veterinarians can give the dog intravenous fluids, pain medication, antibiotics, and sometimes antivenom, depending on the situation.
Red Rock Biologics, the company that makes the rattlesnake vaccine, said there are two formulations—one for horses, and one for dogs. Although formulated especially for the western diamondback rattlesnake (Crotalus atrox), the company says the vaccine’s best coverage also offers protection against bites of the western rattlesnake, prairie rattlesnake, Great Basin rattlesnake, northern and southern Pacific rattlesnakes, and copperheads.
The company says the vaccine also offers good coverage against the venom of the sidewinder, the timber rattlesnake, the massasauga, and the pygmy rattler. The vaccine offers limited protection against the eastern diamondback rattlesnake’s venom.
The company says the vaccine does not protect against venom from the water moccasin (Cottonmouth), the Mojave rattlesnake, or the coral snake.
Red Rock Biologics recommends that dogs weighing 25 pounds or less and 100 pounds or more get three vaccinations the first year to raise their blood titers—a measure of the level of antibodies present—but other dogs need only two vaccinations their first year. After that first year, one annual vaccination about a month before rattlesnakes become active is sufficient for most dogs. But the company cautions that because blood titers taper off after six to eight months, dog owners in areas where snakes are active longer may want to get their dogs vaccinated every six months.
Two Sides To The Opinion
Dog owners should be aware, though, that not everyone swears by the vaccine. Dr. Stephen Mackessy of the University of Northern Colorado, the editor of the “Handbook of Venoms and Toxins of Reptiles,” said research shows the vaccine’s proven effectiveness is mainly for the western diamondback.
Mackessy pointed to a 2015 study in the “American Journal of Veterinary Research” by C.C. Cates and four other researchers that exposed groups of mice to three venoms after vaccinating half the mice in each group. Half the animals in each group received only an adjuvant that enhances the body’s own immune response. The researchers concluded, “Vaccination improved survival rate and survival time after challenge exposure with WD (western diamondback) rattlesnake venom, and may offer limited protection against NP (northern Pacific) rattlesnake venom, but did not provide significant cross-protection against SP (southern Pacific) rattlesnake venom.”
Dr. Dale Wallis, on-staff veterinarian for Red Rock Biologics, said in an e-mail that there are indications the design of the study may have been flawed, given that all mice in the unvaccinated control group died. Venoms and toxins are typically measured by a reference point called “LD50,” or the lethal dose for 50 percent of animals receiving it. In the company’s studies, Wallis said, “Vaccinated animals typically survive three to five times that dose.”
According to Wallis, venoms can be divided into two broad classes: those which are hematoxic, causing bleeding, clotting, pain and swelling, for example, and those which are neurotoxic, causing progressive weakness and eventually paralysis, including of the diaphragm, resulting in asphyxia. “Western diamondback venom is largely hematoxic, with some neurotoxic components,” she said.
“The western rattlesnake (prairie, northern Pacific, Great Basin, etc.) subspecies are largely hematoxic venoms, and are broadly covered by the immunity generated by the vaccine,” Wallis said. “The southern Pacific is a subspecies of western rattlesnake, but certain populations of this snake have a great deal of neurotoxic components. The vaccine-generated immunity covers the hematoxic components of the southern Pacific fairly well, however, it does not cover the neurotoxic components.”
Regardless of whether dog owners decide to use the Red Rock Biologics vaccine, Mackessy said there are said to be new rattlesnake-vaccine products in development. If approved, those will give dog owners in rattlesnake country additional options.