Rattlesnake Poisoning in Dogs

Rattlesnakes are a common pit viper on the North American continent and possess a potent hemotoxic venom to dispatch their prey. They will also use this venom to defend themselves from anything that they may perceive as a threat. Once the venom is in the bloodstream it begins degrading the structure of the red blood cells. This can lead to blood clotting, cause degeneration of organs, and cause generalized tissue damage. If your pet is bitten by a rattlesnake it should be treated as an emergency.

Rattlesnakes are a type of pit viper with a potent hemotoxic venom. Bites from rattlesnakes can adversely affect the clotting behavior in the blood. This condition is potentially fatal if untreated and should be treated as an emergency.

Many symptoms of a rattlesnake bite are immediately apparent, however, some may be somewhat delayed depending on the size of the dog, the amount of venom injected, and the placement of the bite. 

Immediate symptoms: 

• Excessive drooling
• Panting
• Puncture wound (may or may not bleed, severely painful, swollen)
• Restlessness

Symptoms that may be delayed:

• Collapse
• Depressed respiration
• Diarrhea
• Increased swelling
• Lethargy
• Muscle tremors
• Seizures
• Weakness

Types 

To prevent rattlesnake bites from happening to your dog you should keep your pet on a four to eight foot leash when walking in rattlesnake territory, so they are close enough for you to spot potential threats and move them away. Avoid rocky areas, dense brush, and tall grasses where snakes may be obscured from view. Rattlesnakes are active anytime from March to December, and they prefer the warm weather. Their activity is more related to temperature than a particular time of day and they tend to be most energetic when temperatures are between about 70-90 degrees Fahrenheit. 

If you do encounter a rattlesnake back away as calmly, quietly, and quickly as you can manage. You will want to get at least a snake’s-length away to prevent being struck. Either leave the area or be extra alert after an encounter for other snakes. If your dog is bitten, calm quick action is vital. Keep your pet calm as calm as possible to slow the movement of the venom through the system and get your pet to the nearest veterinarian for emergency treatment. If attempting to retrieve a rattlesnake carcass use extreme caution. Not only is there the possibility that the snake is not dead, the reflex to bite in rattlesnakes can be triggered several hours after death. This behavior has been seen even in the heads of snakes that had been separated from the body for quite some time.

Snake venom is a modified type of saliva that is injected by the snake into its victim through tubular fangs which connect to the modified parotid salivary gland below and behind the eye. The toxins in snake venom are usually classified as either neurotoxins or hemotoxins. Neurotoxins are usually found in proteroglyphous elapid snakes such as sea snakes, mambas, and death adders. These toxins act on the nervous system to disable prey and predator alike. Most pit vipers such as cottonmouth snakes, copperhead snakes, and rattlesnakes employ hemotoxins to dispatch their prey and defend against predators. These toxins cause the destruction of red blood cells or induce coagulation and clotting of the blood. The toxin disbursed from the bite of the Mojave rattlesnake is of particular concern as its venom contains a very powerful neurotoxin as well as a hemotoxin.

Your veterinarian will want to get a detailed history from you regarding the symptoms you have witnessed. Any information you might have regarding the biting incident itself will also be requested at this time as well as the progression of the wound thus far. Blood will also be drawn for standard tests such as complete blood count and chemistry profile. A physical examination of the wound is likely to prompt your veterinarian to examine the blood microscopically. If the red blood cells have been exposed to a hemotoxin, they will often have a spiked appearance. If you or your veterinarian have any reason to suspect that the bite was a rattlesnake, supportive treatment is likely to start right away in order to minimize the effects of the toxin, although further testing is often necessary.  Because of the nature of the venom, bleeding disorders can develop and your veterinarian will also want to run tests to ensure that the clotting times are within normal range.

If symptoms are showing from a snakebite, supportive treatment is often begun while laboratory testing is still occurring. This can include IV fluids, pain medication, antihistamines, antibiotics and even steroids. Depending on the amount of venom that is estimated to have been injected as compared to the size of the dog and on the severity of the initial reaction, antivenin may be recommended. It is not always recommended as a first course of action because of the possibility of an allergy developing, but cases in which clotting times are being affected would warrant its use. Unless the reaction is exceptionally mild, your canine will need to stay at the hospital for several days, until the toxin has cleared his system.

Some veterinarians recommend the use of a vaccine against the toxin for dogs who have a high probability of being around rattlesnakes. The vaccine offers limited protection against the rattlesnake toxin, and although it generally won’t render your pet immune to rattlesnake venom it may reduce the intensity and length of time required to heal from a bite.

The prognosis of a rattlesnake bite is dependent on several factors. The type of rattlesnake can make a difference. Bites from the Mojave rattlesnake are far more potent than other rattlesnake bites, and the size of the snake does not always correspond with the amount of poison injected. Smaller dogs are more likely to succumb to the toxins than larger dogs and bites on the trunk of the body have a much poorer prognosis than bites positioned in other locations. 

Keeping the convalescing patient in a calm and quiet environment once they have returned home, as well as ensuring that food and water are easily accessible will speed the healing process. Your dog should be closely monitored for reoccurrence of the symptoms. Your veterinarian will want to do some follow-up tests to ensure that any blood clotting abnormalities have returned to normal and to assess how well the wound or wounds are healing.