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By T.J. Dunn, Jr., DVM
We are all familiar with situations where a dog happens to bite another dog or even a human. These occurrences are always scary. For me, the most heart-stimulating bite cases are the ones where the headline might read "Dog Bites Vet." Snakes, however, react quickly and don't care what's on the menu! So no matter who you are -- man or animal -- the effects of a venomous snake bite can be extremely painful and disfiguring. Venomous snakes kill many dogs, cats and people every year.
Did you know that each year in the United States, over one million animal-bite wounds are reported? Dogs and cats inflict the vast majority. On occasion the tables get turned on our canine friends though, and without warning they are recoiling from the pain inflicted by sharp, poison-injecting fangs. Caught off guard, it is a moment you will never forget if you and your dog encounter a poisonous snake while simply taking a pleasant walk in the outdoors.
Snakebites are a fact of life for dogs and humans in a wide area of North America. Venomous snakes bite about 8,000 people annually in the United States, but according to most estimates, no more than 12 of these bites are fatal each year.
You won’t find details on the numbers of dogs bitten, or killed, by venomous snakes, though. I asked Michael Schaer, DVM, Professor of Veterinary Internal Medicine at the University of Florida, College of Veterinary Medicine, about the numbers of dogs bitten or killed by snakes in the U.S.
"I don't believe we have a valid source of information on the actual numbers of dogs bitten or killed by snakes annually in the United States," he explained, "because there is no central data resource for this."
In his twenty-two years as the lead clinician handling snake bites at the veterinary school, Dr. Schaer estimates about a 20 percent fatality rate for dogs bitten by the Eastern Diamondback and the Eastern Coral snakes.
Although there surely are isolated areas of the United States where venomous snakes are not plentiful, their range spreads all across the country with only Alaska and Hawaii reporting no species of the poisonous kind. Many cases of snakebite occur in dogs that are "just visiting" a part of the country where poisonous snakes are plentiful. It has happened that dog owners who reside in an area devoid of poisonous snakes are shocked into reality when visiting an area where venomous snakes reside!
The Unites States has fifteen species of rattlesnakes; two kinds of water moccasins, the copperhead and cottonmouth; and two kinds of coral snakes. The six types described here make a good representation of the venomous snakes present in the United States.
Average adult size is 22-36 inches; has been reported to reach up to 53 inches long.
Range: Northern Florida up to Massachusetts, west to Texas and southeastern Nebraska.
Cottonmouth (Water Moccasin)
Average adult size is 20-48 inches but over 70 inches has been reported.
Range: From Florida all the way north to Virginia and west to Illinois, Missouri, Oklahoma, and Texas.
Eastern Diamondback Rattlesnake
Average adult size is 36-72 inches; the longest reported was 96 inches.
Range: All through Florida and several offshore islands and keys, north to southeastern North Carolina and west to southern Mississippi and parts of Louisiana.
Average adult size is 36-60 inches; timber rattlesnakes over 70 inches have been reported.
Range: This is an endangered specie; its range is limited to small areas of the eastern U.S.
Dusky Pygmy Rattlesnake
Average adult size is 12-24 inches; the longest was recorded at 31 inches.
Range: Throughout Florida, eastern North Carolina and west to parts of Missouri and Texas.
Eastern Coral Snake
Average adult size is 20-30 inches; some exceed 40 inches.
Range: All of Florida and north to parts of North Carolina and west to eastern Texas and northeastern Mexico.
Fortunately, if your dog happens to be bitten by a poisonous snake the odds are in favor of a complete recovery. The degree of damage inflicted by a venomous snake is determined by a wide variety of variables. The age and species of snake, the intensity and depth of the fang penetration, the amount of venom injected, the location of the bite, and the size of the dog are just a few of the variables.
In general, snakes want to be left alone. But along comes an inquisitive dog probing every mysterious hole in the ground, sniffing under downed logs, slogging along the riverbank, and digging up leafy patches on the forest floor -- a lightening strike of the serpentine kind may be the result!
First, let me tell you what not to do. Do not take out your pocketknife and cut Xs over the fang marks! Do not attempt to suck venom through those X marks. Do not grab the snake in a fit of anger and attempt to choke it to death. You may be bitten yourself.
Instead, you should:
Venom is a toxic fluid created in specialized oral glands related to salivary glands, and the toxic component is composed of an array of complex proteins. Every snake’s venom contains more than one toxin, and in combination the toxins have a more potent effect than the sum of their individual effects. Most of the toxic effects are due to the enzymes in the venom and there have been about twenty-five enzymes discovered so far.
Venoms are of two types: neurotoxic (affecting the nervous system) or hemotoxic (affecting the blood and vessels). The venom of many snakes contain both neurotoxic and hemotoxic components.
Venomous snakebites cause severe pain, cell death, numbness, diminished function and, occasionally, loss of a limb. Snake venoms inflict local effects such as inflammation, damage to blood vessel lining, clotting defects and localized tissue destruction. Some venom can also cause neurotoxicity and interfere with nerve transmission resulting in paralysis.
Antivenin is a serum that is commercially produced to neutralize the effects of the injected venom. At special laboratories healthy horses are injected with increasing amounts of selected snake venom (non-fatal, of course), gradually challenging the horse to make more antibodies. To obtain these antibodies, a small amount of blood is later removed from the horse and the protein antibodies are separated out and purified.
A specific antibody is produced for each type of snake. According the Dr. Schaer the newer antivenins are ovine derived and very expensive at $1500 per 2 vials. Severe envenomations might require as many as 10 vials.
Should dog owners carry antivenin kits with them routinely while outside with their dogs? Probably not, says Dr. Schaer.
"An antivenin kit probably wouldn't be that practical because of expense, routes of administration and other important reasons."
Most antivenin products are targeted for a particular species of snake and may have no effect on the snake that bites your dog. Antivenin may not have a long shelf life and due to expense, most animal hospitals so not keep a supply on hand.
Above all, be vigilant when walking with your dog in areas inhabited by poisonous snakes. It’s not a bad idea to memorize your veterinarian’s emergency phone number, too!
Image: Greg Schecter / via Flickr