Tuesday, June 7, 2016

Snakebite in Dogs

Snakebite happens. About 30,000 dogs are bitten by venomous snakes annually in the United States. Our inquisitive companions love to run through thick grass and stick their noses down holes in search of squirrels and other delights. Sometimes they frighten a rattlesnake, which may defend itself with its potent venom.   

Ghost got a painful and potentially life-threatening bite to the snout from a Northern Pacific Rattlesnake. He was treated with two vials of antivenom and made a full recovery. Photo courtesy Ashley Ventimiglia.

This photo is scary for us dog-lovers, am I right? We want the best for our canine companions, and will do everything in our power to protect them. There are important aspects to consider if you live in rattlesnake country, and that is the subject of this post.

In this post, we cover what to do if your dog is bitten by a rattlesnake, but we focus mainly on things to do (and things not to do!) to prevent snakebite in the first place.

But first, a few disclaimers. I am not a veterinarian. I am a PhD scientist and snake expert. Always check with your veterinarian when making medical decisions for your pooch.

OK, let's talk about snakebite in dogs.

TL/DR: The best way to protect your dog from snakebite is to keep him on a leash, and if he is bitten, take him to the emergency veterinarian right away for treatment with antivenom. 

Seriously, leash your dog! It keeps him with you on the trail and away from danger. Not only will your dog be more likely to avoid snakebite (and ticks, and poison oak, and foxtails up the nose... I could go on), but wildlife will also avoid being disturbed by your dog.

Now let's get into the details.

Treatment of Canine Snakebite

Dog Rattlesnake Vaccine – Is It Effective? - PetGuide

Dogs unlucky enough to be envenomated by a rattlesnake or other viper in the United States can be treated with antivenom, the only effective treatment for snakebite in dogs. Most dogs survive bites when treated rapidly with antivenom. A retrospective study on 272 rattlesnake envenomations in the Phoenix, Arizona area found that 97% of envenomated dogs survived the bite. Younger dogs were more likely to survive, and few dogs had allergic reactions to antivenom. Another study found that antivenom stabilized or terminated the effects of the venom. If your dog is bitten, get him to the emergency veterinarian right away. Don't use a tourniquet or ice, don't try to cut and suck the wound, don't do anything but take him to the vet.

OK, that's treatment. But what about prevention? Is there anything (other than the underrated, ever so valuable leash) that can help prevent snakebite?


The Rattlesnake "Vaccine"



Daleville veterinarian offers rattlesnake vaccines for dogs
Your veterinarian might tell you there is a vaccine that could help your dog if he is later bitten by a rattlesnake. This vaccine is not supposed to eliminate the need for antivenom treatment, but is marketed as a means of helping your dog survive until you can get to the veterinarian. It might even mean the dog needs less antivenom when he gets to the vet. Photo courtesy WDBJ Virginia.

The vaccine is an injection made using the venom of Western Diamond-backed Rattlesnakes, which are common in Arizona, New Mexico, and Texas, and the vaccine might provide protection against other viper species, too. The vaccine doesn't break the bank, either (prices vary, but injections are typically about $25, with most dogs needing 2-3 injections). Unfortunately, there is no evidence that the rattlesnake vaccine works. One study found no difference in outcome in snakebitten dogs who had the vaccine and those that did not, a result that was later echoed in another studyA third study showed that mice vaccinated with the drug had some protection against venom from Western Diamond-backs, but little protection against venoms from Northern and Southern Pacific rattlesnakes (the ones that most commonly bite dogs in California). Of course, dogs are not mice, but this is the closest thing to an experimental study that can be done because injecting dogs with the vaccine or placebo, and later injecting them with snake venom to see which survives, would be considered unethical.

The rattlesnake vaccine might actually be dangerous for your pooch. First off, if your vaccinated dog gets bitten, take him to the veterinarian! The vaccine is not a substitute for antivenom treatment, and I worry about complacent owners thinking the dog will be fine. The vaccine could be dangerous in another way, too. A recent study reported that two dogs who had received the vaccine exhibited anaphylaxis (a life-threatening allergic reaction) when they were later bitten by rattlesnakes. Anaphylaxis occurs when the body's immune system overreacts to the allergen (proteins in the venom in this case). Anaphylaxis almost never occurs at first exposure, but rather at subsequent exposures when all the immune cells initially activated during the first exposure explode in activity. The researchers suspected that the vaccine was the "first exposure" that sensitized the dogs to venom proteins, later resulting in anaphylaxis when the dogs were bitten. In other words, it is highly likely that the dogs went into anaphylaxis because of the vaccine.


Rattlesnake Aversion Training


Snake-aversion training for dogs can be done humanely and ...
Dogs safely learn to avoid rattlesnakes at aversion training. Photo courtesy Eric Briggs, in Lewiston Tribune. 

You might have heard of rattlesnake aversion training, where dogs learn to avoid rattlesnakes. I have never seen data showing that aversion trained dogs are less likely to be bitten by rattlesnakes, but there is little harm in doing the training. Given how efficacious dog training can be, it seems that rattlesnake avoidance training could work very well in some cases. We know pooches belonging to biologists who know to stay away from snakes when joining their masters for field work. However, aversion-trained dogs could still be bitten accidentally (e.g., when running through tall grass), even if they have been trained to avoid the scent and/or warning defensive behavior of a rattlesnake. One paper mentions that this training is “overall unreliable and may provide a false security for snakebite prevention but may be efficacious in a well-trained dog. The only preventative measures are leash walking and avoiding possible snake habitats that have poor visibility." Take home? The training will likely help for many dogs, but you should still take care to avoid accidents when out on the trail.


Rattlesnake-Proof Yard Fencing

This rattlesnake-proof fence keeps rattlesnakes out. Yard-lizard approved!

We've been mainly talking about keeping your doggo safe if you go out hiking. But what about if a rattlesnake enters your yard? While the aversion training might help in that scenario, the bottom line is that your dog is at an increased risk of being bitten if a rattlesnake hangs out in your yard. Solutions that seem easy, like snake repellant sold at home improvement stores, do not work at all. Simply getting rid of a snake (whether by relocating it or killing it) doesn't solve the problem because other snakes will likely also visit at some point. However, there are many things you can do to make your yard less attractive to rattlesnakes. For people who frequently get rattler visitors and are very concerned about pets' and kids' safety in the yard, rattlesnake-proof fencing is available in Arizona and Central California and is an excellent option for keeping your loved beasties safe in the yard.


Grand take home? Keep your dog on a leash, and go forth and enjoy the beautiful outdoors! Thanks for reading. 

Pet Series: 10 Dog-Friendly Hikes in San Diego | ScrippsAMG
Leashing your dog when out and about is the best way to protect him from snakebite.


Note: This blog was originally published in 2016, but was updated in 2020 based on additional published studies.