Copperhead Snakes: Envenomation Risk for Animals

Renee DiPietro, CVT
Associate Veterinary Information Specialist
Pet Poison Helpline

If you and your dog tend to ramble wooded edges, creeks, deserts, rocky outcrops, and meadows, or like to hike wooded areas in a large geographic swath that runs from Southern New England to Texas, you may one day encounter the North American Copperhead Snake (Agkistrodon contortrix).

Photo provided by Daniel Keyler, PharmD, FAACT

These venomous snakes in the Crotiladae (Pit Viper) sub- family, account for a large percentage of snake vs animal encounters in the southeastern and southcentral United States and Mexico every year. Unlike other pit viper species, these snakes are more likely to bite without warning if disturbed.

They are valuable rodent eradicators, and when left alone are effective at reducing rodent damage and disease transmission.

The snake is 2-3 feet long with a wedge or triangular shaped head. The top of the head is distinctly copper in color and the body has hour- glass shaped “saddles” that are reddish tan in color down its length. Copperheads also have vertical slits in their eyes and as indicated by their family name, heat sensing “pits” between their eyes and nostrils. To observe these latter characteristics, you would need to get dangerously close to the snake. This is not recommended.

Juvenile Copperheads have bright yellow/green tipped tail.

This reptile is comfortable in a wide variety of habitats and is fond of transition areas between terrain zones. They are adaptable and can also set up comfortably in suburban areas.

In the cooler seasons (spring and fall) these reptiles are diurnal but as the heat of summer moves in they become more nocturnally active.

The snake bites to kill prey and to defend itself when a threat is perceived. During a bite, venom travels through hollow curved fangs into the puncture wounds it has inflicted on its victim (rodent or other small mammal) or the animal or person it perceives as a threat.

Copperhead venom is considered less potent than many other Pit Viper Species, but a bite from these snakes is still a serious health issue. Hemotoxic, necrotizing, and anticoagulant effects are possible but fatalities in humans, larger dogs, and other larger animals are rare. Small dogs, cats, or other small mammals can be more severely affected. Local tissue damage is related to enzymatic proteins and coagulopathy (blood clotting issue) is rare with Copperhead bites. Severe local swelling, pain, redness, and bruising are commonly seen. Hyperthermia is also a possible clinical sign.

Dogs (off-leash) and other animals that roam and investigate curiously are prone to bites to the head and face. This can cause serious swelling that at times can compromise breathing, potentially causing a life-threatening situation.  Goats, sheep, horses, and other livestock are also reported snake-bite victims.

Twenty five percent of bites from Copperheads are dry, meaning no venom is injected into the victim during the bite. It is not possible to know if for many hours after the bite whether the animal has been injected with venom or received a dry bite and swift medical attention is imperative.

If your pet sustains a bite from a snake you may not see the offender. In some areas, other venomous snakes with more potent venom may be present.  If you can get a picture of the snake without getting close enough to endanger yourself, this may help your veterinarian focus their treatment plan on a particular species’ venom.  Copper head bites rarely need treatment with antivenin (antidote) but this may be a very important therapy if your dog was bitten by a different venomous snake.

As soon as you are aware your pet has been bitten by a snake it is important to get them immediately to a veterinary clinic, or if this is a large animal/livestock, have a veterinarian out to your farm immediately.  The time to veterinary care can directly correlate with the success level of the outcome. Underlying health issues may complicate successful treatment.

Before transporting your pet to your veterinarian remove any collars/halters or other devices that could become restrictive as swelling occurs. If waiting for your large animal veterinarian to arrive you can wash the area of the bite gently with water and mild soap to remove any additional venom on the skin.

Photo provided by Daniel Keyler, PharmD, FAACT

Do not:

Incise and suction the wound.

Apply a tourniquet or hot or cold compresses.

Administer any medications of any type

Keep your pet as calm and comfortable as possible during transport or while waiting for your large animal veterinarian. Your veterinarian will assess the situation and treat any emergent symptoms such as difficulty breathing or excessive bleeding.  Other treatments may include sedation, clipping and cleaning the bite wound, pain control, antibiotics, antihistamines, blood work, monitoring vitals, and monitoring coagulation and other hematological parameters.  A stay in the hospital for intensive care is common after venomous snake bites.

As with many outdoor potential toxic exposures, the best way to protect your pet is to keep them on leash when exploring and safely fenced in a yard close to the house when at home.  These measures minimize the potential for exposure to dangerous animals such as snakes, who when in their own habitat are only protecting themselves.  Large Animal/Livestock vs snake encounters may be harder to prevent.  If you live in area that Copperheads also inhabit, have a plan for yourself and your animals in case of snake bite. Keep your veterinarian’s phone # and Pet Poison Helpline’s contact information on hand. Know where your local Emergency Room is in case of human exposure.

Let the snake be.