Rattlesnake Bites: Avoidance training and treatment

Background:
Rattlesnakes are a common issue across most of the western states and Arizona is certainly no exception. Every year we are plagued by snake bites to dogs and cats as well as our other 4-legged friends.

Reactions to snake bites varies on the location the animal was bitten, the type of rattlesnake and even on the amount of venom injected. As many as 20 – 25% of snake bites are “dry” bites, meaning no venom has been injected; 30% of bites are mild, meaning they cause local pain and swelling in the bite area and no systemic symptoms; 40% of bites are severe with approximately 5% being fatal. The 3 most common rattlesnakes in Arizona are the Western Diamondback, the Sidewinder and the Mojave.

Rattlesnakes in Arizona have a long season – first bites are often reported as early as February and as late as November. There have been reports of rattlesnake activity in every month of the year. Snakes are most active in cooler weather during the day but for most of the season they are active primarily at dawn and dusk, hiding during the heat of the day.

The venom from most rattlesnakes is the hemotoxic type of venom that destroys tissues, can lead to organ destruction and causes a coagulopathy (inability to clot blood.) The Mojave rattlesnake is considered one of the most toxic snakes in North America. Their venom is primarily neurotoxic venom which can also lead to muscle weakness, difficulty breathing and respiratory failure. The faster the bite is recognized, the more effective treatment will be. Treatment of snake bites generally includes IV fluid therapy to prevent circulatory collapse, Antivenin (an IV injection of antibodies toward the venom collected from horses) and pain control. Animals are closely monitored for at least 24 hours after the snake bite.

To Shock or to Stick:

Now comes the most important and controversial subject in regards to rattlesnakes. How to prevent snake bites in the first place and how to protect animals from the severity of the bites.

Aversion Training:

Rattlesnake aversion training has been a well-accepted means of deterring dogs from the lure of snakes. When done well it can help dogs associate the snakes with a painful, unpleasant experience. When not done well it may only make your pet afraid of the parking lot or park where they were trained. I cannot stress enough the importance of researching the trainer – this should be someone trained in handing snakes (live, FANGED snakes must be used – if they have been de-fanged they will die.) and the must be well trained or certified as a dog trainer. There is an art to “reading” your dog and to be able to deliver the shock when the dog is focused on the snake. I spoke to a client just this morning who told me that her dog is now terrified of this specific park, but yesterday went after a snake in the back yard. Clearly this was not an appropriate training. For some dogs (terriers and hunting dogs come to mind) training may not be effective or will need to be reinforced a few times before they understand. Terriers have such strong drive to kill a snake that they get bit multiple times (at least once on the tongue as they try to swallow the snake!) Hunting dogs tend more to be so focused on their job they just step on or over the snake and get a bite on a leg.

Rattlesnake Vaccine:

This is where the controversy comes in. If you have read previous posts you know that we selectively vaccinate our dogs and cats, choosing only the most important core vaccines and vaccine intervals. To date, there have been no studies performed that show a benefit to the vaccination. Dr. Ahna Brutlag, DVM from the Pet Poison Helpline, Bloomington, MN, reported at the Western States Veterinary Conference in 2010 that “… to date there is little published evidence regarding the efficacy of this vaccine and many in the toxicological community remain skeptical. No scientific literature about the product could be found in a Pub Med literature search and repeated requests by the author to speak with a technical services representative from Red Rocks Biologics went unanswered.”

The idea behind the vaccination is good and theoretically could minimize the reaction to a snake bite. You can read anecdotal accounts on-line that state that the pets have reduced reaction if vaccinated or that you don’t have to give antivenin thereby making cost of treatment less. The current recommendation, however, is to still give antivenin whether the dog was vaccinated or not. So, considering that 25% of bites are dry and 30% of bites are mild, how do we truly assess the efficacy of the vaccination? I can tell you from my own experience that most dogs given appropriate treatment do well. In fact I can only remember one patient that died from snake bite and that one was suspected to be a Mojave.

Our doctors have 2 main reservations with the vaccination. The first is that researchers tell us that the venom of snakes is so complex and variable even within a single species of snake that there is no realistic way to create a vaccine that will cover all of the proteins. Additionally we see significant local reactions to the vaccine itself. This includes sterile abscesses or even sloughing large patches skin in the site of the vaccination. Since we don’t give the vaccination, I can’t report on incidence however at our practice we have seen 5 reactions that all required medical intervention. All cases were for a second opinion.

In short – yes there may be benefit for some dogs in high risk situations. This risk must be weighed individually by owners and their veterinarian. I personally feel there are too many unanswered questions to ever give this to one of my dogs.