If it isn't one thing, it's certainly another-that sure is true around my house, what with all the critters we have. From pulling Stella out from under the bed to give her asthma medications, to making sure Verbal gets her arthritis drugs and supplements every day, and more recently chasing a ticked-off rooster so I can dose him with some pain meds-gee, what more do I need to medicate? I shouldn't have asked that question. Can anyone say limping donkey?
Yep, Jesse, my very furry, long-eared donkey is very lame, barely putting any weight on his left hind leg. I am pretty sure it is due to an abscess in his hoof-he seems to get one every year. Donkeys or burros are supposed to have really tough, hardy feet. Well, I don't know if it is all the mud we have (really not too bad considering all the rain here) or the rocks, his particular conformation or what, but Jesse's feet are just prone to these infections that occur within the hoof.
A hoof abscess can be defined as a localized accumulation of purulent exudates (pus) located between the germinal and keratinized layers of the epithelium (hoof capsule), most commonly subsolar or submural. I have seen these occur in horses secondary to nails from shoeing, but Jesse has never had shoes on his feet, and the last trimming he had done was over a month ago. Of course, the same thing can happen if a horse is punctures by a nail or other sharp object. Other abscesses occur after a deep bruise to the sole, usually from a stone wedged in the sulcus or groove adjacent to the frog tissue. The frog is the softer triangular wedge of tissue that acts as a pump in an equine leg. Often referred to as an additional heart, the 4 frogs (one in each foot) help the circulatory system, literally pumping blood back up those long legs to the lungs so it will get oxygenated again. Breakdown at the junction between the sole and wall as happens in white line disease or a simple crack in a hoof wall can predispose a foot to abscessation.
Understanding how an abscess forms can help in the understanding of how to best treat the often very painful condition. Bacteria will enter at the puncture, bruise, nail hole or white line defect, usually at the sole-wall junction at any point around the foot. As the horse walks and puts weight on the foot, dirt and other foreign matter push into the tract made by the bacteria. Once inside the hoof, the body's defense mechanism sets off a reaction called inflammation-this is ultimately what causes the heat, swelling and pain. The bacteria continue to grow in this environment, and white blood cells migrate to the area to help fight the infection.
Enzymes are released from the bacteria and this causes the hoof tissue to melt or liquify, turning into the blackish/gray "goo" associated with abscesses. The body tries to wall this off with a thin capsule, forming the abscess capsule. It can get very tight as the bacteria continue to reproduce within, resulting in more inflammation and thus more pain. It usually only takes about 3 to 5 days from the initial "insult" for clinical signs to occur, so if your farrier accidentally misplaces a nail or your horse (or donkey) gets a puncture from some other cause, treating with an antiseptic for a few days might ward this off. Of course, we often never know about the puncture or bruise that caused the abscess, as in Jesse's case. If I had, I would have loved to have prevented this apparent excruciating pain-and my need to fight with yet another of my own own butthead patients.
Jesse lets me know he has an abscess by showing up extremely lame in the affected foot. The lameness can be pretty sudden as his tend to be, and can vary from subtle early on to non-weight bearing as the condition progresses. It is often possible to palpate a digital pulse near the fetlock, stronger on the side of the foot where the abscess is located. Overall, the affected foot is usually warmer due to the inflammation, and if long-standing, the entire pastern or fetlock may become swollen from the disease or from disuse. We often use hoof testers to locate exactly where the abscess is, although some horses are sensitive in the entire foot making you need to rule out laminitis or founder, a severe bruise or even a fracture of P-3, the coffin bone itself.
Treating hoof abscesses requires first and foremost good drainage. An opening should be made that is big enough to allow good drainage and won't heal closed too quickly, but also won't be so big that it causes more problems. Under no circumstances should an abscess be approached through the sole. Dirt and manure and other foreign matter will just pack into a solar drainage hole, making it ineffective or even worsen the condition.
When an abscess is localized with the hoof testers, a small tract is often found in the sole-wall (white line) junction. If it is not visible or has closed up already, a poultice can be applied in an attempt to soften the area and break it open again. Animalintex, available at feed stores or veterinary supply stores, is a great product, as are epsom salt soaked sponges. Full foot soaks, once the norm for so many foot conditions, are now discouraged as they can really soften and weaken the integrity of the hoof wall.
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The drainage tract is followed within the white line using a thin small loop knife, a 2 mm bone curette or other suitable probe. Gray/black pus is the reached when the "belly" of the abscess is reached and this area is cored out carefully.
A small opening is all that is necessary to obtain proper drainage. This can be determined by placing thumb pressure on the solar side of the tract and observing more drainage being expressed or a bubble at the opening when pressure is applied. Care should be taken to avoid exposing any corium, as it will invariably prolapse through the opening, prevent closure of the tract and create an ongoing source of pain.
The draining tract should be kept soft and drainage promoted. The application of an Animalintex or epsom salt poultice that has been soaked in hot water can be applied for the first 24 to 48 hours. The whole foot, including the coronet band, should be incorporated into the poultice for best results.
The relief is usually pretty immediate. Once the pressure is relieved, most animals will bear weight again, and if the infection is controlled, all lameness should be resolved in just a few days. It is often best to keep the foot bandaged to prevent the introduction of more bacteria and debris into the newly opened drainage site, and antibacterial dressings can be applied to help speed up the healing. Betadine or iodine solutions are effective and inexpensive.
I rarely put these patients on systemic antibiotics as it was mentioned above that these infections are usually walled off from the body and therefore inaccessible to the bloodstream. Pain relief medication such as phenylbutazone is very welcome, however. Jesse, of course, hates his bute, even the apple-flavored paste, and isn't making this process very easy. Be sure tetanus vaccinations are up to date as the tetanus organism thrives in soil and would love this type of wound.
So, today after work, my terrific horse shoer, Fred, came over and helped me wrestle with my problem child. Jesse really does love most people, but he and Fred have always had a bit of a love/hate relationship. Fred doesn't take any of Jesse's shenanigans, one time even trimming his feet laying down when Jesse threw a fit and decided to fall down to the ground in protest. He has since learned it doesn't do a darned bit of good; Fred will win every time, darn it!
Jesse was in fine form tonight, though, and oh so quick with that sore hind foot. While Fred got ready with the hoof knife and nippers, I got out the drugs. It was no fun finding a vein in which to give his drug through all that winter hair of his, and he proved just as stubborn metabolically-his drug dose probably would have stopped an elephant but Jesse barely hung his head. It was enough for Fred to quickly cut into that hoof, find the abscess and provide some good drainage before Jesse decided he had enough and found his aim again. He could barely walk-he looked like quite the drunk donkey-but I wouldn't have trusted that back foot one iota. I snuck some bute between his lips much to his chagrin and let him stagger off to commiserate with Raquel. He's going to be just fine.
Prevention of hoof abscesses is achieved through proper hoof care and centers on promoting a strong, solid sole-wall junction (white line) that resists penetration by debris. Hoof abscesses are less likely to occur when a solid sole-wall junction (white line) is maintained.
Excessive toe length increases the bending force exerted on the toe, leading to a widening and weakening of the white line. Other conditions that cause mechanical breaks or weakness in the continuity of the white line are hoof capsule distortions (long toe-under run heels, excessive toe length, heels too high or a club foot, sheared heels), hoof wall separations (white line disease, seedy toe) and chronic laminitis. Excessive moisture or dryness, and the extreme back and forth from one season to the next, may also contribute to weakness in the white line. I really think this is Jesse's problem, as we do a pretty good job keeping his feet trimmed and he has never had white line disease, laminitis or any of the other hoof pathologies mentioned.So, thanks to Fred, Jesse is all doctored up for the evening. I chased down Viggo and pulled off that last straggling bandaid from his surgical site. It is healing well and he is crowing and herding his ladies in the yard-I think he is doing well, too. Verbal got her dinner with her medications for arthritis mixed in. And I just popped Stella her prednisolone tablet to help calm her inflammed airways until her inhaler arrives later this week. Whew! It feels like a vet hospital around here. It's a darned good thing that Bill the emu is healthy-I better knock on wood!
Peace,
DrReneigh
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