Should I be worried about my horse getting ill or dying from botulism?  

Well, yes, and no.  Botulism is RARE in horses - but it does happen, it’s horrible, it can kill horse horse in a horrible manner, and it does have a vaccine.  But how do you know if you horse needs to be vaccinated, or if he’s at risk of botulism?


These microscopic jerks can kill your horse.  Easily. 

Backing up a few steps, let’s chat about Botulism.  It’s a bacteria - Clostridium Botulinum.  You may recognize Clostridium Tetani, which causes tetanus.  So this particular bacteria has the ability to produce 7 different toxins - aptly named A to G. The toxic spores live in areas with no oxygen, some moisture and a specific pH.  While we think botulism mostly lives in decaying animal matter, it’s really more likely to be found in decaying vegetation.  


It’s the B version to be really worried about - it’s the most toxic to horses.  The B strain of C. Botulinum is commonly found in the North East US and Appalachia, but it could be anywhere. Type C of the toxin is usually found in association with decaying animals and bird droppings (hello birds in the barn….).  You also have Type A, which likes to live in the Northwest US, but it typically not a problem with horses. 



Prevent with vaccines.  Treat with antitoxin if possible. 


So what happens if your horse is infected?  Well - the botulism toxin will interfere with your horse’s neurological system by not letting the muscles respond to the nerves.  You will likely see problems eating, swallowing, moving ears, blinking.  Your horse might also lose function in his tail, and in some cases your horse must lay down because of paralysis.  The amount to toxin influences how sick he becomes.  Some horses have mild cases, other horses die within days from the lungs and heart stopping as the pulmonary and cardiac muscles are paralyzed.  The signs of botulism also mimic those of rabies, EEE, WEE (more on those here) and other neurological diseases. 


There is an antitoxin that can be administered.  It will help with the spread of the toxin, but it can’t repair damage already done to the nerves. Very often in a horse that is down, there is nothing more to do.  There is also a test to detect the botulism toxin, but it can take up to 10 days, in which case it is likely too late. 


Anytime your horse has neurological signs, call the Vet.  Immediate intervention is key.  


So how does your horse end up with botulism toxicity?  Well, it’s everywhere in the soil - but remembering that it really enjoys anaerobic and wet conditions, hay is a common location.  Round hay bales are recipes for botulism salad.  Round bales often rest on the ground, are rained on, and can be a very tempting hotel for C. Botulinum.  There’s also the risk that an animal has died in the hay making process, but that’s typically Type C.  You can also find risky amounts of botulism in hay bales that are improperly stored (read this enlightening article), hay thrown on the ground and silage for cows (DUDE don’t feed this to your horse ever).  Hay tossed on wet/damp/muddy creates that moist environment that C. Botulinum loves.  Also remember about grass clippings!  (More on that here!)


There’s also the very rare possibly that botulism finds it’s way into a would that scabs over quickly.  Punctures are notorious for doing this, and the depth of the wound has that anaerobic factor.  Even a tiny wound can be trouble, which is why clipping, cleaning, and a quick photo to your Vet is a good idea.  For any size wound.  


The horse world is very lucky that there are vaccines for C. Botulinum, types A and B.  Depending on the type of vaccine, your horse might need an initial series and yearly boosters.  These are a must for the horse that eats from a round bale or has hay tossed into a paddock.  Using deep trough like feeders for outside feedings is best.  

If you have a broodmare, in some parts of the country she should be vaccinated.  Foals can develop (and die from) the botulism related Shaker Foal Syndrome.  A broodmare properly vaccinated can pass along necessary antibodies. 


Again - botulism is rare in horses, but it’s also deadly.  If you horse has any risk factors, talk to your Vet about vaccinations against botulism.