Venomous snake bite in dogs

Most venomous snakebites in North America are due to Pit Vipers. These include rattlesnakes, pygmy rattlesnakes, Massasauga, Cottonmouths and Copperhead snakes.

Brown Snake envenomation is the most common envenomation in pets in Australia. The exceptions are in Victoria, where Tiger Snake envenomations are more common, and Tasmania where there are no Brown Snakes and Tiger snake bites predominate.

Generally pets are bitten during the warmer summer months. Rattlesnakes are cold-blooded animals and so they prefer hot arid environments such as the desert, sand hills, grassy planes or rocky hillsides.

Timber rattlesnake ©Lyndi L Gilliam

Bites are most common in dogs, typically on the head, neck and legs. Young dogs are more likely to receive multiple snakebites and suffer severe envenomation.

The effects of snake bite include:

• Extensive local swelling at the bite site which may be painful
• Puncture wounds (fang marks) may be visible
• If the bite is on the muzzle and there is marked swelling this may prevent your pet from drinking/eating and may lead to difficulty breathing
• Lethargy
• Distress
• Vomiting and diarrhea, drooling
• Lameness (if bitten on the leg)
• Bruising
• There may also be effects on the heart, kidneys, liver and some venoms cause uncontrollable bleeding
• Seizures if the snake possesses a neurotoxin

The clinical signs associated with envenomation may appear immediately (bleeding from the fang marks) or the signs may be delayed for up to one hour.

It is now fairly rare for dogs promptly treated with antivenom to die from a snakebite. They will make a good recovery if specific anti-venom is given within the first 1-4 hours after envenomation.

If walking your dog in an area where venomous snakes are known to occur keep your dog to paths and under control (preferably on a leash) when snakes are most active (March to October in Northern America, October to March in Australia and South America).

Do not attempt to handle or harm the snake. If possible, take a photo of the snake so that it can be correctly identified.

Leave the bite alone. Do not attempt to suck out the venom, cut the wound open or apply a tourniquet, as these interventions are ineffective and may introduce infection, aggravate bleeding and restrict circulation of blood.

Ideally you should try and keep your pet quiet. If possible, depending on the size of your pet, carry them home, back to your vehicle or to the veterinary practice. This can help reduce the spread of venom around the body.

All pets bitten by a snake should be taken to a veterinary practice.

On arrival at the veterinary surgery someone will assess your pet immediately and make sure that its condition is stable before any other treatments are instigated. Your veterinarian will want to know:

• What happened (where the incident occurred, how your pet behaved). Remember you may not have seen the snake bite your pet or even the snake itself
• Describe the snake if you have seen it, or take a photo so it can be identified
• How long ago the incident happened
• If your pet is showing any signs of being unwell
• If your pet is receiving any medication or has any pre-existing medical conditions.

Because dogs often receive the snakebite in the head or neck region, its airway may become obstructed by any swelling. If necessary, your dog may be intubated to help it breathe or an emergency tracheostomy may be carried out.

Blood samples may be taken and intravenous fluids given. Antihistamines and analgesic drugs may be given to control any pain that your pet may be in. Your pet may be treated with antivenom products depending on availability and cost. If clotting of the blood is affected, your dog may require blood product transfusions.

Available snake antivenins in Australia include those for the venoms of Brown snake, Tiger snake, Taipan, Death Adder, and Black snake. There is also a polyvalent snake antivenin available.

The pets should be monitored for a minimum of 8 hours, even if the rattlesnake bite is suspected to be a dry bite. If antivenom is given, your pet will be monitored for any allergic reactions.

Avoid walking your dog (especially off-leash) in an area known to be high-risk for venomous snakes.

You could also ask your veterinarian about a rattlesnake vaccine which is available and could protect your pet.