For gun dog owners, there are few moments more gut wrenching than those following a snake bite. Sideways encounters with one of the most feared and respected serpents in the uplands are wrought with fear and chaos as hunters rush to triage a dog in pain and face the prospect of a more sinister, potentially life-threatening reaction to the bite.

Traditionally, dog owners have relied on avoidance training to keep their hunting partner safe. In these scenarios, dogs learn to avoid snakes by pairing the sound and smell of an angry buzztail with a stout (but far from lethal) negative stimulus. This technique works great for discouraging those dogs who readily plunge headfirst towards anything that wiggles, but in my field and clinical experience, many snake bites occur without the dog ever knowing that danger lurks around them.

As added protection against a bite, my clients routinely inquire about whether the rattlesnake vaccine provides them with any appreciable benefit in the unfortunate event that snake avoidance fails. The answer is complicated, and the subject of debate among dog owners and veterinarians alike.

Snake venom is universally regarded as fairly nasty stuff. It’s a dangerous cocktail of anticoagulants, histamine-releasing factors, and cytotoxic compounds that work in unison to impart massive tissue destruction, pain, and swelling, while slowing the rate of healing. These traits are certainly undesirable and contribute to much of the localized pain and inflammation of a bite, but most gun dog owners fret over the less predictable and potentially life-threatening anaphylaxis that may occur. The immune reaction to a bite can be swift and severe, leaving hunters with precious few minutes to seek help, and even fewer options to treat in the field.

What is the Difference Between Snake Vaccines and Antivenom?

It’s worth a quick mention that my clients often confuse the rattlesnake vaccine with antivenin (also referred to as antivenom), as they’re both discussed in the aftermath of a bite. Antivenin is an intravenous solution of concentrated antibodies designed to bind up and neutralize snake venom in the body, after a snakebite has occurred. It’s expensive and has a relatively short shelf life, so it’s usually only available in clinics that see heavy caseloads of snakebites.

Conversely, the vaccine is a micro dose of rattlesnake venom toxoid, a benign venom compound that has been chemically altered so that it is recognized by the immune system in exactly the same way as real venom, without the same harmful side effects.

The idea behind the rattlesnake venom toxoid vaccine (and many vaccines like it) is that it introduces the body to a small volume of the inactive toxoid before a bite has occurred. This gives the immune system the opportunity to develop and mount a larger, more directly targeted, immune response during a real bite. As a practical application, the vaccine should help reduce the risk of—or at least delay— the scorched earth approach that a naive and overzealous immune system may employ after a strike.

That’s the idea, anyway. The reality is that first-hand experiences with the vaccine remain highly variable.

Real World Veterinary Experience with Snake Vaccines

Whether or not your veterinarian recommends the vaccine likely depends far more on their personal experience with it than their familiarity with the research behind its development.

Dr. Rachel Shutter, who encounters prairie rattlers routinely on foot and horseback where she practices in Rapid City, SD, often recommends the vaccine as an added insurance policy—even if it doesn’t perform equally in every patient. “There are some cases where I’ve definitely seen vaccinated dogs benefit,” she said. “My philosophy is that even if it buys the patient some time, it’s worth the minimal expense.”

“They all end up at the hospital anyway,” Shutter said, “but in my experience, the vaccinated patients spend less time in the hospital, and their symptoms are slower to crop up and less severe overall.”

Shutter recommends an annual booster prior to snake season (early spring) or in late summer for bird dogs hitting the field for early season upland hunts in snake country.

Understanding the Data (or Lack Thereof) Surrounding Rattlesnake Vaccines

The problem inhibiting any hard data around the rattlesnake vaccine is that it’s impossible to create an authentic controlled study. No two dogs—nor two snakebites—are exactly alike.

Every dog creates antibodies to immunizations differently, and each unique individual has an immune system that is genetically programmed to respond differently in the face of venom or other elements of the snakebite. The location of the bite seems to play a major role in the severity of the symptoms, with the face, limbs, and ears being highly sensitive. The amount of venom released is dependent upon highly variable circumstances, ranging from the age and size of the snake, to his particular mood that day. It’s hard to replicate an experimental bite when the amount of toxin varies with each encounter. It’s also entirely possible—although just as difficult to prove—that in a few cases, the snake's oral bacteria or saliva could play a role in a bad reaction, rendering a venom-focused vaccine useless.

“There are so many variables in each snake encounter,” Shutter said. “The species of snake, the location of the bite, and the amount of venom released in each bite.” Couple those variations with each dog’s individual immune response to the toxin, and it’s clear that your hunting partner’s reaction to the bite is highly individualized.”

“The vaccine itself is not entirely benign,” Shutter admits. About 10 percent of the dogs she vaccinates experience a localized reaction, ranging from mild sensitivity at the injection site, to a sterile abscess that requires draining.

“With dogs that react to the vaccine,” Shutter said, “we evaluate their bite risk each year and adjust our vaccine schedule accordingly.”

With the risk of a reaction in mind, Shutter adds that she’s never lost a vaccinated patient to a snakebite, so she continues to push for immunization.

Like many research projects in veterinary medicine, the vaccine does not boast a strong body of peer-reviewed evidence as to how well it works. The sample size of dogs in the original study was small—a shortcoming which, in all fairness, is fairly common in industry funded experiments. Without boring you with details, the research was more theoretical than borne of real-world applications, and understandably so. As you can imagine, there would be very little public appetite for studies that involved exposing vaccinated dogs to the perils of live rattlers.

Naysayers often reference a 2014 retrospective study that determined the vaccine offered little to no support in curbing the morbidity or severity of a snakebite. As a specialty referral center in the heart of rattlesnake country, they had access to years of snakebite records that they reviewed for this study. Their data demonstrated that the size of the dog had more to do with the severity of the snake bite reaction, regardless of whether the dog had received a vaccine against the venom.

While it’s undeniable that their data (obtained from analyzing past medical records) showed no correlation between vaccination status and severity of symptoms, this conclusion is far from the final word on the matter. Most people, veterinarians included, fail to read the entire article. Like many other published research papers, it’s lengthy, dry, and loaded with statistical jargon.

The authors are completely transparent that their study did not include any dog that was bitten by a snake and had symptoms mild enough to not warrant a trip to the specialty hospital. Either the reaction in those cases was mild, or at least not severe enough to seek medical help beyond the scope and expertise of a home remedy or their local veterinarian. In the unknown number of cases not in the authors’ medical records, the vaccine may or may not have helped them avoid a trip to a referral center altogether.

Potential Drawbacks of Snake Vaccines for Dogs

With so much ambiguity, veterinarians who practice in snake country typically recommend or avoid the rattlesnake vaccine based solely on their own experience with it in the clinic.

Amber Mabee, DVM, whose resume includes emergency medicine from Phoenix to the viper pit of Arizona’s San Tan Valley, offers a hefty dose of skepticism about the vaccine. In her opinion, the reactions between vaccinated and unvaccinated patients are similar, and the risks associated with the immunization outweigh any perceived benefits.

“I used to recommend (the vaccine) quite a bit,” Mabee said, “but once I started seeing more and more snakebite cases, I really couldn’t tell any notable differences between the vaccinated and unvaccinated cases.”

“There are so many variables,” Mabee added, “that I feel like the vaccine gives owners a false sense of security.”

In her professional experience, which includes hundreds of bite cases, the risk of vaccine reactions are significant enough that she has since rescinded her recommendation.

“Anecdotally, my worst vaccine reactions have come from the rattlesnake vaccine,” Mabee admits. She cited new, but admittedly controversial, research that indicated vaccinated dogs may have an increased risk for anaphylaxis (a life threatening, severe immune reaction) to the actual venom.

In her experience, the risk is so great that she doesn’t vaccinate her own dog, and the two of them spend plenty of time outdoors in snake-infested habitat. “He would definitely get (the rattlesnake vaccine) if I felt like it was worth it,” Mabee added.

When I personally practiced in snake country, our team felt as if the vaccine kept symptoms from being life-threatening in many instances. We saw an occasional mild reaction to the injection, but we believed that for dogs in high-risk situations, it was a side effect worth enduring.

What is Best for Your Dog?

A trip to the veterinarian is still strongly recommended following any snakebite, but some veterinarians—myself included— believe the vaccine may buy some time to get professional help. Keep in mind that this claim is neither advertised by the manufacturer, nor supported by evidence, but it nonetheless remains a common justification for its use. I, too, used this anecdote when talking with clients about rattlesnake vaccination. The vast majority of dogs I treated in practice encountered the snake at least a couple hours’ drive from our clinic. Any treatment that could help prevent—or at least delay—a severe reaction for that long seemed like prudent medicine, even if there is no hard evidence to support the claim.

While we can’t prove beyond a reasonable doubt that the vaccine works, I'll be the first to admit that the inability to prove it doesn’t is far from a defensible endorsement. I advise an in-depth conversation with your dog’s veterinarian. Ask them what their personal experience has been, and how that has shaped their recommendation. Depending on your particular dog and your assessment of their snake bite risk, they may recommend, as I have often done in practice, the vaccine as an insurance policy against a disaster.