Venomous snakes poisonous to pets: Part I

Pet owners should keep their pets on a leash while hiking or during other outdoor activities to prevent an accidental envenomation from encounter with a venomous snake. If the pet is bitten, pet owners should take care to protect themselves and not risk being bitten. Keep in mind that approximately 25 percent of pit viper snakebites may be “dry” bites, where venom was not actually released. That said, immediate veterinary attention is still warranted, and when in doubt, call Pet Poison Helpline for further assistance.

When it comes to venomous snakes, there are two families represented by several different genera and species throughout most of North America. These include the Elapidae family (coral snakes), and the Viperidae family (rattlesnakes, copperheads, and water moccasins). All have a mixture of different pharmacologically active components in their venoms, and varying clinical signs may result following a venomous snakebite. Owners, team members, and veterinarians should have basic knowledge of what venomous species are native to the geographic region they live in.

Elapidae (coral snakes)

Two medically and clinically important species of the Elapidae family-commonly known as coral snakes) in North America to be aware of are:

• The eastern coral snake (Micrurus fulvius), which is typically found in southern North Carolina, down through southern Florida, and westward to southeastern Arkansas just east of the Mississippi River.

• The Texas coral snake (Micrurus tener, formerly Micrurus fulvius tener), which is found west of the Mississippi; in southwestern Arkansas, western Louisiana, and the eastern half of Texas.

How to identify a coral snake

These species have a relatively small head, black snout (having the appearance of a black sock over it), and round pupils. Their color pattern of red, yellow, and black bands (in this order-red touching yellow: kills a fellow, red touching black: venom lack) fully encircle the body with the red and yellow colors touching each other.

Assess the threat to pets

Coral snakes are typically nocturnal, timid, reclusive, semi-fossorial (may burrow underground), and generally non-aggressive. Bites to animals are relatively uncommon and usually occur because the animal is harassing the snake (hence, the importance of keeping your dog on a leash). These snakes have fixed front fangs, a relatively small mouth, and they chew to inject their venom. Bite wounds most often occur to an animal's lips, tongue, mouth, and webbing of the paws and may appear as scratches rather than the classic two-fang punctures associated with pit viper bites. Envenomation (the injection of venom by sting, spine, bite, or other similar means) by coral snakes is usually associated with a prolonged contact bite and puncture of the skin. Their venom is a primarily neurotoxic (venom complex composed of small basic proteins that act on the nervous system) causing a descending paralysis and CNS depression. The major systems affected with Coral snake envenomation include the neuromuscular, respiratory, and cardiovascular systems.

What to do if a pet is bitten

Clinical signs of coral snake envenomation may be delayed up to 18 hours after envenomation, and may take seven to 10 days before initial clinical signs resolve. Full recovery may take months. Evenomations from the Eastern coral snake are clinically more severe than those from the Texas coral snake. However, evenomation from the Texas coral snake can be extremely painful. Dogs and cats are equally affected, although cats may have a more difficult time surviving if prolonged respiratory support is necessary. Clinical signs include:

• Central nervous system signs: staggering, drooling, disoriented, acting drunk, lethargy, inability to walk, abnormal pupil size (aniscoria), bulbar paralysis (loss or impairment of motor function) affecting the cranial motor nerves, abnormal vocalization, and acute flaccid quadriplegia (the weakening or the loss of muscle tone)

• Cardiorespiratory signs: hypotension, respiratory depression, secondary hypothermia, elevated heart rate, difficulty breathing, respiratory paralysis, and secondary aspiration pneumonia

How to treat it

Pet owners should avoid performing any first aid measures at home. The most effective treatment is rapid transportation of the pet to the clinic/facility. If the snake is available, an accurate identification (i.e. cell phone picture) is useful; however, clients shouldn't put themselves at risk. As it is often difficult to determine if a bite has actually occurred due to the small fang size of these snakes, use of a magnifying glass and good lighting to examine the pet can aid in determining if skin penetration has occurred. In general, early treatment is most beneficial. If definite skin puncture from fangs has occurred, do not wait for the onset of clinical signs to initiate antivenom administration and supportive care. However, supportive care is all that can be offered in most cases as coral snake antivenom is very difficult to acquire.

If the antivenom is not available, provide respiratory support at a 24/7 emergency critical care facility, and hospitalize for a minimum of 48 hours. Other ancillary treatment includes wound management, monitoring of the patient hematologically, monitoring respiratory and neurologic function (including ECG, blood pressure, pulse oximetry, end-tidal carbon dioxide, etc.), analgesic therapy, and symptomatic supportive care. Full blood work, including a complete blood count (CBC), serum chemistry, urinalysis (UA), and coagulation panel should be performed. Abnormalities found on blood work include elevated ALP, CK, and presence of pigmenturia. Treatment includes intravenous fluid therapy, frequent vital signs checks and good wound care if there is local tissue damage (which is extremely rare with coral snake envenomation). Broad-spectrum antibiotics may be needed if infection has occurred. Provide symptomatic and supportive care as signs develop.

Prognosis

Prognosis is fairly good with early intervention. Severe envenomation in small animals bitten by a large coral snake requires intense monitoring, and support. Antivenom given late after envenomation may not reverse toxic symptoms. Aspiration pneumonia worsens prognosis.