Included are some newsletters and reviews on toxicology issues that Tennessee health professionals might find useful. The topic for March is Venomous Snakes in Tennessee:
Venomous Snakes of Tennessee
Death from a snake envenomation in North America is quite rare. In the year 2005, only 6 deaths from snakebites were reported to the American Association of Poison Control Centers and at least one of these was an anaphylactic type reaction in a patient who had previous envenomations.
All viperids have hinged fangs that are solenoglyphous (hollow). These fangs can rotate back and forth. When the mouth is closed, the fangs fold back against the roof of the mouth and are enclosed in a membranous sheath. The left and right fang can be rotated together or independently. If a tooth is lost, it is replaced, similar to a shark’s mouth.
When a snake strikes, the speed is lightening fast. The mouth of the snake is nearly at an 180o angle as the target is approached. The generally accepted distance for striking is half the length of the snake. Most bites are defensive due to the snake trying to defend itself or being startled. Snakes have no interest in striking humans. Many times a warning rattle is not heard since the snake was startled. The Agkistrodon species do not even possess a rattle. Up to 20-25% of snakebites are “dry” bites, meaning that no venom is actually injected.
Venomous snake species in Tennessee
A. contortrix, photo courtesy of Dr. Ian Jones
The most common envenomation in Tennessee is from the copperhead snake (Agkistrodon contortrix
Fortunately, these envenomations tend to be limited to tissue toxicity and most of these envenomations do not require antivenom. Tennessee is also home to the cottonmouth (Agkistrodon piscivorus
) whose name is derived from the behavior of opening its mouth to show the snowy white buccal mucosa. Tennessee is also the territory of the Timber rattlesnake, Crotalus horridus.
Envenomations from the Timber rattlesnake can be quite severe and present with cytotoxicity, hematotoxicity, and neurotoxicity. In addition, there is a Western Pigmy rattlesnake (Sistrurus miliarius
) that resides in Tennessee but this species is rarely involved in envenomations. The Eastern Diamondback Rattlesnake (Crotalus adamanteus
) is not usually found in Tennessee. Their range is along the coastal areas of southeastern North Carolina extending to Florida and Louisiana.
Initial measures after snakebite
- Remove victim from the vicinity of the snake
- Immediately remove any jewelry, watches, or rings from the affected extremity
- If the bite is on an extremity, immobilize it.
- Transport to the hospital.
C. adamanteous, photo courtesy of Dr. Ian Jones
What to avoid doing in the setting of a North American snakebite
- No ice
- No electrical shock
- No ligatures or tourniquets
- No cutting or sucking on the wound
At the hospital
- If there is a bite to the face with swelling, secure the airway immediately
- Assure that all jewelry, watches, rings are removed from the affected extremity
- Assess degree of cytotoxicity, hematoxicity, and neurotoxicity
- Elevate affected area
- Contact the Tennessee Poison Center regarding indications for antivenom (1-800-222-1222)