The next topic in our canine vaccination series might seem like an odd choice, particularly if you and your dogs don’t live in rattlesnake country, but for those of us who do it’s a hot topic.

In response to the first installment in this series, “Uncle Connie” asked: “If it is convenient, perhaps you could add rattlesnake immunizations to your list of situational future installments. It's a highly touted option among vets in my area (San Diego) and, to be perfectly frank, it would be nice to have the thoughts of an expert who isn't in a position to make any money from my decision!”

The circumstances surrounding the rattlesnake vaccine (technically referred to as Crotalus atrox or the Western Diamondback rattlesnake vaccine) are somewhat atypical. According to the 2011 American Animal Hospital Association’s Canine Vaccine Guidelines:

Field efficacy and experimental challenge data in dogs are not available at this time.

  • [The vaccine is] intended to protect dogs against the venom associated with the bite of the Western Diamondback rattlesnake. Some cross-protection may exist against the venom of the Eastern Diamondback rattlesnake. There is currently no evidence of cross-protection against the venom (neurotoxin) of the Mojave rattlesnake.
  • Vaccine efficacy and dose recommendations are based on toxin neutralization studies conducted in mice. Conventional challenge studies in dogs have not been conducted. Neither experimental nor field data are currently available on this product.

It is also important to note that vaccination does not preclude the need for immediate treatment should a dog be bitten by a rattlesnake. The goal of the vaccine is to reduce the severity of the symptoms and buy the dog some time to get to the veterinary hospital.

Since we don’t have scientific proof that the vaccine works in dogs, we have to resort to anecdotal evidence. Among vets who have given it to their patients, the general consensus seems to be that it “may” help. In other words, vaccinated dogs seem to get a little less sick after being bitten than do unvaccinated ones, but they can still die after an especially severe bite. Adverse reactions seem to be in line with (perhaps a bit worse than) what is typically observed with other subcutaneous vaccines — swelling and discomfort locally, particularly in small breed dogs.

When to give the initial vaccine and how to boost it is complicated and depends upon the size of the dog and the times of the year when exposure is most likely. Average-sized dogs should initially get two vaccines approximately 30 days apart. The manufacturer recommends that dogs under 25 pounds and over 100 pounds receive an addition booster 30 days later and that all dogs be revaccinated at least annually. Any protection provided the vaccine becomes effective approximately 30-45 days after a dog receives it and lasts for about 6 months. Therefore, the manufacturer recommends that dogs with year-round exposure to rattlesnakes receive boosters every six months, while those with seasonal exposure get one vaccine per year approximately 30-45 days before rattlesnake “season” starts.

In my opinion, keeping dogs leashed and enrolling them in rattlesnake avoidance classes are still the best ways to protect them from being bitten. As long as an owner is well aware of the rattlesnake vaccine’s limitations but still wants it for their high-risk dog, I would be willing to give it at their request.

Dr. Jennifer Coates

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