The Vet Is In: Rattlesnakes

Dr. Marvin Ordway
By Dr. Marvin Ordway June 15, 2011 13:00

By Dr. Marv Ordway

The western rattlesnake is the only venomous snake in our area that can inflict a painful and rarely fatal bite.

In the foothills, rattlesnakes come out of dormancy in March when the temperature is above 70 degrees. They breed within a few weeks. Rattlesnakes hatch inside the mother snake in the fall and are born alive, ready to care for themselves. Just 10 to 12 inches long, they have fully developed fangs but are without functional rattles, which form after each of two to three skin sheds yearly.

Baby snakes cannot control the amount of venom they inject, and thus may inject more than an older snake. The venom apparatus consists of two sharp hollow fangs on the roof of the mouth, connected to poison glands (think hypodermic needle). The snake will strike to protect itself or to kill prey. Snakes are good swimmers and can strike in the water.

Dogs and cats are usually bitten on their face or extremities. In Twain Harte, we treat anywhere from three to 12 rattlesnake bite victims a year, while vet hospitals at lower elevations may see twice that number.

An estimated 25 percent of rattlesnake bites are “dry,” meaning little or no venom is injected. Another 25 percent involve mild “envenomation,” and in 45 percent the level is moderate to severe. Fewer than five percent of bites are fatal.

Bites to the face can lead to suffocation if swelling is severe. Limbs may die due to massive tissue destruction if envenomation is severe. Bite severity depends on the snake’s size, the victim’s size, amount of venom injected, and the body’s response to the toxin.

If venom has been injected, symptoms usually appear within 30 minutes. They include rapid swelling, bruising, and pain as the venom destroys tissue and causes blood vessels to leak blood and plasma into the bite area. This results in decreased blood volume and thus hypovolemic shock, in which the heart is unable to pump enough blood through the body. Clotting problems, pulmonary edema, cardiac arrhythmias and, rarely, kidney failure may result.

The sooner treatment begins the better. Initially, we give intravenous fluids to replace the blood that is pooled at the bite site. After giving strong pain medication (rattlesnake bites are extremely painful) the bite site is gently cleaned, and antibiotics given to prevent infection.

If the animal shows systemic problems – weakness, rapid respiration, rapid and/or arrhythmic heart rate, depression, vomiting, diarrhea, or rapid swelling at the bite site –antivenom (also called antivenin) should be administered.

If in doubt, we give the antivenom, which binds to the rattlesnake venom and neutralizes it. It is best to administer this within four hours of the bite, but there is still some benefit up to 24 hours after the bite. Antivenom is expensive – $650 a vial, and up to five vials may be needed. Fortunately, many snake bites are dry or result in minimal exposure, and antivenom is not needed.

To minimize exposure to snakes, hike during the day when the temperature is above 70 degrees. Avoid hiking in the early morning, late afternoon and evening. Snakes cannot tolerate heat well, and will hide in cooler places until the temperature drops. In some heavy snake areas it might be best to hike only during the dormant snake season (October through February in our area).

To make the area around your home safer, keep debris and wood piles away from the house and barn where dogs and cats roam. Also, minimize vegetation that might allow hiding places for rattlesnakes.

A rattlesnake vaccine is available and affordable only for dogs, not cats. Initially, two doses of vaccine are given three to six weeks apart. Then an annual booster is given one month prior to rattlesnake season (usually March in our area). If your dog is at risk, talk to your veterinarian about the pros and cons of vaccinating.

© 2011 Friends and Neighbors

Dr. Marvin Ordway
By Dr. Marvin Ordway June 15, 2011 13:00