Treatment of rattlesnake bites with antivenin

Antivenin is produced by repeatedly injecting horses with rattlesnake venom, gradually building up their immunity.  Rattlesnake antivenin is concentrated  immune serum from horses.

The first time a dog receives this serum, no matter how much is given, it is unlikely there will be any serious reaction.  However some dogs become hypersensitized to horse serum after receiving even a single dose.  If a dog is bitten again and receives a second dose of antivenin, he could die from a hypersensitivity reaction.

Placerville Veterinary Clinic was once the only small animal practice between Sacramento and Tahoe.  We saw a lot of  rattlesnake bites, sometimes several over a long holiday weekend.  Most dogs did not receive antivenin.  In all those years, we had only two deaths associated with rattlesnake bites.  One was a little old dachshund.  She had been bitten on her chest and nobody realized this until it was too late.  The other was a big German Shepherd who had been bitten previously and treated with antivenin.  She received a second dose of antivenin and died approximately thirty seconds later.

Rattlesnake bites are much more serious when small dogs are bitten, or when the tongue, lip, or eyelid areas are involved.  Cases such as these should be treated aggressively and treatment should include antivenin. 

Moral of the story:

The vast majority of snakebite cases can be treated without the use of antivenin.  A dog that has received antivenin in the past, (and is probably not in mortal danger from a rattlesnake bite anyway) should, in our opinion,  never again receive antivenin unless bitten in the tongue, lip, or eyelid areas.

Cats are much more resistant to rattlesnake bite than dogs.  Cats need supportive care, but we do not administer antivenin.  We have not seen fatalities or permanent damage from snakebite in cats.