Rattlesnake Envenomation (Snakebite)
Why are snakebites dangerous?
In North America the most common snakes associated with snakebite include the Crotalidae family (rattlesnakes, copperheads, and cottonmouths) and the Elapidae family (coral snakes and cobras).
In Colorado the prairie rattlesnake (crotalus viridis viridis) is the most common cause of snakebites.
Rattlesnake venom is designed to immobilize, kill, and digest its prey. The venom can cause shock, severe tissue swelling and damage, hemorrhage, infection, and clotting disorders.
The snake may not inject venom every time it bites (dry bites), but it is impossible to determine this simply by examining the bite. Therefore, it is important that you seek veterinary attention immediately if you suspect your pet has been bitten by a rattlesnake.
What should you do if you and your pet encounter a rattlesnake?
In general, rattlesnakes are fearful of people and pets and so will avoid encounters if at all possible. If you come across a rattlesnake, immediately put your pet on a leash and quickly and quietly leave the area. Keep them at your side and do not allow your pet to sniff, play with, or harass the snake. Even dead snakes are potentially dangerous as post-mortem muscle contractions can result in envenomations. If your pet is bitten, seek veterinary attention IMMEDIATELY. Do not attempt to ice the wound, apply tourniquets, or suck the venom from the wound. Snakebites are extremely painful and cause a state of shock in the patient. Therefore, the sooner you can get them to the veterinary hospital, the better off your pet will be.
What are the clinical signs?
Often one, two, or more several small puncture wounds may be observed, but occasionally no wounds will be found. The most common areas for dogs and cats to be bit are on the face and lower limbs. Some pets are bitten on the chest, neck, or rear end.
Most common signs include severe swelling and pain at the bite site. There are often signs of shock, weakness, and excessive bleeding or bruising.
It can take as little as 30 minutes before signs develop, and the symptoms will likely worsen over the next 24 hours.
How are snakebites confirmed and the severity determined?
Various blood tests will be run to check the platelet count (cells involved in clotting), electrolytes, and the ability of the blood to clot normally. These tests will likely need to be rechecked while your pet is hospitalized in order to assess their progress.
A blood sample will be taken to look for microscopic changes in red blood cell shape that the venom may cause.
Initially, a blood pressure and ECG will be checked to determine the severity of shock as well as check for cardiac arrhythmias. Some pets may require continuous blood pressure and EKG monitoring while in the hospital.
How are snakebites treated?
For mild to moderate bites, the standard treatment includes hospitalization on IV fluids, pain medication, anti-inflammtories, and antibiotics. Antivenin can be administered to help neutralize the effects of the venom. Ideally, the antivenin should be given as soon as possible to maximize effectiveness; however its effects can be helpful even 24 to 48 hours after the bite occurs. While medium and large breed dogs generally survive rattlesnake envenomation without receiving antivenin therapy, there is evidence that antivenin treatment helps to more rapidly decrease swelling, pain, and length of hospital stay.
If your pet is bit on the face or neck, there is a risk that the airway may swell shut. If that occurs, the doctor will need to anesthetize the patient and place a tube into the trachea (windpipe) to provide a clear way for them to breathe until the swelling resolves.
Pets presenting in shock or with severe clotting disorders require very aggressive treatment and monitoring.
Generally, hospital stays for rattlesnake envenomation last 2-3 days, depending on the progress of your pet’s condition. When the veterinarian feels your pet is ready for discharge from the hospital, your pet will likely be sent home on antibiotics and pain medication. It will be important during this time to watch your pet closely for loss of appetite, lethargy, excessive bruising, continued or worsening swelling, pus and/or pain around the wound. If any of these symptoms occur, contact a veterinarian right away.
Prognosis
The prognosis will vary with the location of the bite, how much venom is injected, and length of time before treatment.
In general, cats and small dogs have a more guarded prognosis than medium and large breed dogs simply due to smaller body mass. Also, cats will often hide after a bite causing more time to pass before treatment.
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