Tuesday, June 7, 2016

Snakebite in Dogs


Snakebite happens. Our inquisitive canine friends love to run through thick grass and stick their noses down holes in search of squirrels and other delights.   

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: Ashley Ventimiglia

I’m giving a presentation on local rattlesnakes to SLO Search & Rescue today, so I thought I’d look up some info on snakebite in dogs. I found four relevant and recent (within the past five years) scientific publications on snakebite prevention and treatment. I found some of the information really interesting, so I am posting to share.

1. Most dogs survive snakebite, but most of these dogs treated were with antivenom.
A retrospective study (4) on 272 rattlesnake envenomations in the Phoenix, Arizona area found that 97% of envenomated dogs survived the bite, but most had been treated with antivenom, so it is hard to determine how much the antivenom improves outcomes. Younger dogs were more likely to survive, and few dogs had allergic reactions to antivenom. Another study (3) found that antivenom stabilized or terminated the effects of the venom.

2. There is little evidence that the “rattlesnake vaccine” works.
A vaccine made against Western Diamondback rattlesnake venom can be obtained from a veterinarian. Although the manufacturer states that it has evidence that the vaccine works, no experimental studies on its efficacy in dogs have been performed. One study (4) found no difference in outcome in dogs who had the vaccines and those that did not. Another study (2) vaccinated mice with the vaccine and found some protection against venom from Western Diamondbacks but little protection against venoms from Northern and Southern Pacific rattlesnakes.

3. No data are available on the efficacy of rattlesnake avoidance training.
Given how efficacious dog training can be, it seems that rattlesnake avoidance training could work very well. However, 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. There have not been any studies on this (admittedly, this would be very logistically difficult). 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” (1).  

Summary: Outcomes for envenomated dogs are good if dogs are brought to the veterinarian for antivenom treatment right away. If possible, try to prevent your dog from exercising, which could speed up dispersal of venom through the body. Vaccines may work against Western Diamondback bites, but we do not have any data on this. Rattlesnake avoidance training could help, but keeping dogs on leash is the best way to prevent bites.

Disclaimer: I am not a veterinarian. Always seek medical advice from your veterinarian.

Sources:

(1) Armentano and Schaer. 2011. Overview and controversies in the medical management of pit viper envenomation in the dog. Journal of Veterinary Emergency and Critical Care 21:461-470.

(2) Cates et al. 2015. Comparison of the protective effect of a commercially available western diamondback rattlesnake toxoid vaccine for dogs against envenomation of mice with western diamondback rattlesnake (Crotalus atrox), northern Pacific rattlesnake (Crotalus oreganus oreganus), and southern Pacific rattlesnake (Crotalus oreganus helleri) venom. American Journal of Veterinary Research 76:272-279.

(3) Peterson et al. 2011. A randomized multicenter trial of Crotalidae polyvalent immune Fab antivenom for the treatment of rattlesnake envenomation in dogs. Journal of Veterinary Emergency and Critical Care 21:335-345.

(4) Witsil et al. 2015. 272 cases of rattlesnake envenomation in dogs: Demographics and treatment including safety of F(ab’)2 antivenom use in 236 patients. Toxicon 105:19-26.

1 comment:

Moreninha76 said...

It sad when dogs get bitten by some venomous snake like the massasauga rattlesnake