A Bite of Another Kind (Fangs a Lot!)

by Christopher Forsythe, DVM

They say you can´t teach an old dog new tricks, so when Molly Margaret came into the hospital for her second rattlesnake bite, I realized that the little tenacious and completely adorable Scottish Terrier had been running with the BIG DOGS. Let´s just say that the ebullient terrier with a joie de vivre that you´ve got to see to believe, treats all other living creatures as potential buddies, even the deadly rattlesnake. Thankfully, her human raced her down to the hospital for critical care, and she is now safely back at her winery, cruising among her vines.

In this issue, I am going to focus on some toxic, venomous animals that can harm your pet, and provide some practical (and possibly life-saving) information which may help you keep your pets out of danger this fall.

Shake, rattle, and roll over

Rattlesnake bites result in serious injury or death to thousands of dogs each year. Rattlesnake venom is a complex mixture of venoms, enzymes, and proteins that spread through a dog´s body following a bite. This "pit viper" toxin causes local tissue damage, blood vessel injury, red blood cell changes, coagulation defects and shock. The effects are so dreadful that eating maggots on Fear Factor would be pleasurable by comparison. The severity of a rattlesnake bite depends on the location and amount of venom injected and the size of the animal. Most dogs (80%) are bitten on the face, so an owner of a bitten dog often first sees a large, painfully- swollen nose resembling Karl Malden´s proboscis!

In the North Bay, you and your dog live in an area heavily populated with the Western Rattlesnake, Crotalus viridis. The Northern Pacific rattlesnake grows between 3-5 feet, can swim well, and can even climb into bushes and trees to forage! Dogs and cats who are allowed to venture outside could encounter one of these serpents at any time. Rattlesnakes are most active in the warmer seasons, from spring to autumn; they have fangs as long as 9mm (almost 4 inches). The average amount of venom secreted in a bite has been reported to be 65-90 mg. Since the lethal dose for a human adult is 70-160 mg, people do die, and have died, from untreated or poorly-treated bites. Like people, dogs may stumble upon a snake by accident when curiosity or a protective instinct takes over. The bite happens lickity-split. Then, your pet´s life is on the line.

Snake-bit! What now?

From the moment your pet is bitten, venom causes a cascade of destruction starting at the bite site then extending systemically. You usually have no more than 45 minutes to get treatment; otherwise, death can be imminent.

If you think your dog has been bitten by a poisonous snake, but you are not positive, your veterinarian can check your pet´s blood for something called acanthocytes, or red blood cells with surfaces compromised by rattlesnake venom. If this test is positive your vet will want to treat your pet with IV fluids to prevent cardiovascular collapse caused by low blood pressure and shock, often the cause of death from rattlesnake bites. (I have often had clients ask me to treat them for shock too, especially after they ask how much the antivenin costs.)

After immediate stabilization, antivenin is carefully infused into the patient to slow down the cascade of life-threatening events: tissue destruction and blood pooling. Depending on the size of the pet, one to three vials of antivenin might be needed, each costing several hundreds of dollars. So, you can see that one poisonous snake bite can ruin your pet´s day and level your bank account at the same time. The bite wound will also need to be cleaned and flushed thoroughly, and antibiotics are necessary to prevent infection. Veterinarians may also give tetanus antitoxin to prevent the growth of dangerous anaerobic germs caused by deep puncture wounds.

Why wait for a bite?

Red Rock Biologics offers a vaccine for dogs that provides rattlesnake bite immunity. Once injected under your dog´s skin, the vaccine coaxes your dog´s body into making protective antibodies that neutralize venom from a future rattlesnake bite. Initially, your veterinarian will administer two vaccine doses one month apart, followed by an annual booster administered about a month before you plan on taking your dog into rattlesnake territory. On average, antibody levels in recently-vaccinated dogs are comparable to treatment with three vials of antivenin.

What does this mean? Your vaccinated dog will experience much less pain and a reduced risk of permanent injury from a rattlesnake bite. However, all pets, vaccinated or not, who are bitten by a rattlesnake still need professional veterinary evaluation and care. Vaccinated dogs will only need some supportive care, while unvaccinated pets will most likely need life-saving care.

What about a bite from a non-venomous snake? Even bites by non-venomous snakes can lead to serious infections, so do see your veterinarian for appropriate treatment.

Welcome to the Widow´s den

Black Widow Spiders are found throughout the North Bay and love to hang out on their funnelshaped webs in dry, dimly lit, secluded places. The web is irregularly shaped, has a tattered "cobwebbed" appearance, and is usually found in corners. Black Widows are commonly found around houses where outside lights help to attract prey insects. If a resident spider disappears, its web is usually re-inhabited by another spider at a rate faster than a Sonoma fixer-upper at below-market price.

Male Black Widows are of little medical concern because they are unable to penetrate human skin due to small jaws. Alas, like we male humans, they are of limited value!

Female Black Widows can be 20 times larger than males, up to 2.5 cm long. Oh, and they can kill. Also known as shoe button and hourglass spiders, the female can be identified by an hourglass pattern, red or orange in color, right on her shiny black tummy. The hourglass becomes more prominent as she ages. The young "ingénue" female has a colorful pattern of red, brown, and beige on the top surface of her abdomen.

Both dogs and cats are extremely sensitive to Black Widow spider venom. Cats are very sensitive to the venom, and deaths are common. In the dog, the toxin provokes severe clinical signs, including localized numbness, muscle pain, twitching of the affected area, and cramping of large muscle areas, leading to paralysis. Death is usually due to respiratory or cardiovascular collapse. If you didn´t have arachnophobia before, do you have it now?

If you don´t bug me, I won´t bite you

The Brown Recluse is a dangerous spider recognized by the violin-shaped marking on the dorsal surface of its upper thorax. These arachnids are nocturnal and are generally active from spring through fall. They are obviously reclusive and live in dark, secluded locations, under stationary objects, in sheds, closets, and basements, and in old shoes. They like warm, undisturbed locations as well, such as behind clothes washers and dryers. Their webs have a bluish hue.

Brown Recluses are non-aggressive, biting only when threatened. Dogs and cats are usually bitten when they lie down and trap the spider between bedding and themselves. Several hours after a bite, the wound will turn red, and then blister. It will then evolve into a bulls-eye or "target" lesion, which ulcerates about a week later. Since there is no treatment for this wound, the veterinarian usually will need to excise the dying flesh. As you can see, this is a dangerous spider and a serious problem for pets.

Meanwhile, little Molly Margaret has so much to look forward to in her vineyard. I just hope she can manage to fill her days with her chardonnay vines and leave all the nasty critters alone. I, on the other hand, am planning on renting and watching "When Harry Bit Sally."