Rattlesnake Envenomation

There are 7 species of venomous snakes in Utah. They are the sidewinder, speckled rattlesnake, Mojave rattlesnake, Hopi rattlesnake, midget-faced rattlesnake and the Great Basin rattlesnake. The Green Prairie Rattler has been seen in far eastern Utah but it is not considered a native species. The venom of these snakes is hemotoxic, meaning that it destroys red blood cells,  disrupts the blood’s ability to clot, and can cause organ degeneration and generalized tissue damage. In northern Utah the most likely culprit of envenomation in domestic species is the Great Basin rattler. This rattler is common to northern Utah and is commonly found in the foothills and benches. 

Signs of envenomation are typically noticed within 30 minutes of a bite, but they may be delayed up to 24 hours. Initial signs are typically localized swelling, swelling with bloody discharge and extreme pain at the location of the bite. 

Diagnosis of a rattlesnake bite is based on evidence of a bite, proximity to a rattlesnake or being in an area known to have snakes. As well as certain laboratory findings. Any pet that is suspected of being bitten by a rattlesnake should have a complete blood count with microscopic analysis, complete serum chemistry, urinalysis and blood clotting times run. The majority of these tests can be performed in the hospital. In the majority of cases a pet that has been envenomated will have a low platelet count, elevated blood clotting times as well as tell tale changes to the appearance of red blood cells when looked at under a microscope.

Treatment for envenomation is the administration of antivenom. Antivenom is most effective when administered within 4 hours of envenomation, but has been shown to be beneficial in cases when administered later.  Most antivenoms come from sheep or horses that have been vaccinated against snake envenomation. Antivenoms are administered intravenously over 30 minutes to one hour. A pet that has been bitten by a rattlesnake is usually hospitalized not only for antivenom treatment as well as further fluid therapy as well as pain control. 

In the United States, 99% of all venomous snake bites are from Crotalids. In canines, 70% to 80% of snakebites occur on the face and head and 20% to 30% occur on the legs. Crotalidae venom is composed of enzymes, myotoxins, cytotoxins, hemorrhagic toxins, cardiotoxins and neurotoxins that have a toxic effect on a canine’s physiological systems. The only proven therapy against Crotalidae envenomations is antivenin. In general, antivenin if given early after an envenomation can be effective at reversing the neurological, coagulopathic, cardiovascular and necrotizing effects of venom.

The prognosis for envenomation cases is generally good with appropriate therapy. 

Previous administration of the rattlesnake vaccine has also not shown to improve the pet’s outcome, it may however delay the onset of and decrease the severity of symptoms.