This a great question and very timely as we are definetly starting to see these snakes emerge from their dens this time of year. Rattlesnake bites are frightening and can be challenging to treat. Unfortunately there is currently no equine rattlesnake vaccine like they have for dogs. Rattlesnakes present several unique challenges in the horse.
Horses may also need supportive treatment such as IV fluid or a liquid diet for a few days if facial swelling prevents them from being able to easily eat and drink. In addition to the immediate life threatening facial swelling rattlesnake venom has several other slower onset complications. The two most significant is the venom’s ability to effect blood clotting and its effect on the heart. Horses can develop dangerous cardiac arrhythmias or they can sustain damage to the heart muscle itself causing heart attack like results. These side effects often don’t occur until several days(and in some cases up to months) after the snake bite. Antivenin can be used to treat horses but there are several draw backs to its use. First, in Texas where I practice we have several different types of venomous snakes in our area including the Coral snake for which rattlesnake antivenin is not effective and more often than not, the type of snake is unknown. Second, very little research has been done looking at antivenin in the horse. For that reason, the most effective dose is really not known. Lastly, like you noted it is extremely expensive. The cost for antivenin is about $2,000 per vial, the average human patient is usually given at least five vials. For this reason most veterinary practices don’t keep it on the shelf but it can sometimes be obtained from nearby human hospitals.
Although rattle snake bites are painful and frightening, most horses survive them. A recent study from the UC Davis School of Veterinary Medicine found that 91% of horses survived rattlesnake bites. The most important aspect of successful treatment of rattlesnake bites is rapid treatment. My condolences for the lost of your Mule, and I hope this information helps prevent future tragedies from snake bites.
~ Rachel Wilson, DVM
If you have a question you would like to ASK A VET, please email email@example.com with the subject: ‘ask a vet’