Equine Snakebite Management
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Antivenom is always indicated for equine envenomation
Written by Dr. Claire TK
The best treatment for snake bite is antivenom. Period. Venom can cause damage to cardiac muscle, which can result in heart failure months or years down the road. I always recommend antivenom for horses.
Pain management for equine snakebite envenomation
Written by Dr. Claire TK
Horses are frequently treated with banamine or dexamethasone, and it does not seem to have the same contraindications that are applied to other species. I am not aware of a position statement on equine treatment at the moment regarding things like NSAIDs, steroids, DMSO, antibiotics, etc. We don't have a ton of normally utilized pain management options for horses compared to small animal species (where I routinely use methadone, fentanyl CRIs or patches, etc).
Keep feed and water elevated to minimize the effects of gravity.
Prevail (Banamine) is an NSAID and should never be given IM. For reading material on that topic, Google clostridial myositis and banamine. You can give it orally or IV, but should never give it IM.
Dexamethasone is a steroid.
We never want to give steroids and NSAIDs at the same time in horses as that is definitely a recipe to fry kidneys. We never want to give multiple NSAIDs to horses as that can cause gastric ulceration or can trash their kidneys. Especially in cases where the horse isn't drinking enough because of swelling/facial pain and is dehydrated, those meds can cause kidney damage much more easily than in a normal horse.
Antibiotics are likely indicated for equine snakebite management
Written by Dr. Becky Legere
Important considerations with horses are the tetanus vaccine status, and whether to treat with antimicrobials. While the use of antimicrobials in small animal medicine is controversial, it is commonplace in equine medicine because of the risk of contamination in the wound with dirt from the environment. This dirt contains several types of bacteria that result in secondary infections in horses and can have very serious consequences, including gram negative bacteria and clostridial bacteria. Horses are highly susceptible to these infections, and especially their secondary consequences that can be severe and even fatal. This is why many DVM's treat horses with antimicrobials following snake bites to treat presumptive infection, ensuring that the antibiotic therapy is targetting the most likely contaminants.
It's also important to remember that tetanus is caused by a clostridial bacteria, and another important component of post-bite treatment to ensure the horse is maximally protected against tetanus.
That being said, antimicrobial therapy should ONLY occur under the advisement/recommendation of YOUR veterinarian, because there are potential severe consequences to antimicrobial therapy in horses, including gut dysbiosis and colitis, so blanket therapy without advising a DVM on your specific horse/scenario is NOT advised.
Mojave rattlesnake neurotoxic effects following equine snakebite
Written by Dr. Becky Legere
Mojave rattlesnakes have a neurotoxin that can cause irreparable damage to the nervous system. The only documented treatment we have to help with this is antivenin, which is costly. It is good to hear that his airway is OK, and that he is eating and drinking. It sounds like you are doing quite a bit of supportive care, which is half the battle. There isn't a good documentation in literature for how long these neurologic signs will take to recover, if they will. There is evidence of progression of neurologic signs to the diaphragm, causing respiratory failure, but there are also cases of recovery after prolonged supportive care (weeks).
It sounds like your veterinarian has been proactive in terms of anti-inflammatory treatments. These can be helpful, but must be used wisely in regards to potential secondary effects on the kidneys and gastrointestinal tract. Other important considerations are his tetanus vaccine status, and whether to treat with antimicrobials (up to your veterinarian, based on the physical examination and other concurrent issues in your pony). Supplementation with a bioavailable vitamin E supplement may also help. General nursing care measures such as ensuring where he is laying is well-padded can help minimize risk of pressure sores. Monitoring his water intake and fecal output will be important as lack of mobility can contribute to slow GI motility and colic. Monitoring him for secondary complications such as arrythmias or decreased function of the heart, laminitis in the feet, and pneumonia from prolonged recumbency will be important as well. If your veterinarian has further questions, they can and should reach out to us here.
NSAIDs and equine snakebite management
Written by Dr. Becky Legere
It may be helpful to offer anti-inflammatory treatment during recovery, but these must be used wisely in regard to potential secondary effects on the kidneys and gastrointestinal tract.
Airway support for equine snakebite management
Written by Dr. Becky Legere
Lastly, horses are obligate nasal breathers; if their nasal passages swell, they will not be able to breathe through their mouths. It’s a good idea to speak to your vet to learn how and when to provide airway support in the event of a bite.
Venom Vet Antivenom for equine snakebite management
Written by Dr. Gena Broussard
Definitely okay to use Venom Vet in horses - has been on the market for 10 years, used off-label safely and effectively in horses and multiple other species. You can dilute each vial in as little as 100 to 150 ml of saline. Infuse slowly at first to watch for any adverse reaction, then can finish infusion within 30-60 minutes. It will be rare for a horse to need more than 1-2 vials. And it’s fine to use LRS in place of saline.
Side note, for Colorado equine DVMs, it’s a good idea to treat all confirmed cases of (Prairie) rattlesnake envenomation with antivenom. We’ve done clinical trials with the CSU veterinary school equine department, and there’s been evidence that the venom can cause delayed cardiac damage in horses. Troponin levels can peak at about 10 days post-envenomation.