Horses with sepsis—a systemic inflammatory response to a suspected or diagnosed bacterial infection, such as colitis, endometritis, or pneumonia—are already in a precarious position. However, they’re also at risk of developing sepsis-related laminitis, a serious complication that can quickly prove fatal.
Fortunately, researchers have made strides in understanding how to prevent laminitis and are learning what treatment options can help if it does develop. Andrew van Eps, BVSc, PhD, MACVSc, Dipl. ACVIM, associate professor of equine musculoskeletal research at the University of Pennsylvania’s School of Veterinary Medicine, in Kennett Square, reviewed these techniques at the 2017 American Association of Equine Practitioners Convention, held Nov. 17-21 in San Antonio, Texas.
“Sepsis is differentiated from simple infection by the presence of a … dysregulated host response—inflammatory, coagulopathic (blood-clotting), and metabolic derangements—and organ dysfunction,” van Eps said. Laminitis, defined as inflammation of and damage to the lamellae, which suspend the coffin bone inside the horse’s hoof, “seems to be a form of end-organ dysfunction/failure that is ultimately most important in terms of recovery for the adult horse with sepsis.”
Unfortunately, he added, “the pathway from the systemic inflammation of sepsis in horses to lamellar structural failure remains unclear.”
Changes associated with sepsis-related laminitis typically happen suddenly, van Eps said. The dermal lamellae—located closest to the coffin bone inside the hoof—that connect to the epidermal lamellae—found on the inner hoof wall—first become inflamed before separating completely in severe cases.
“Progression tends to depend on the severity of the initial insult,” van Eps said. “Once established, laminitis causes derangements of lamellar structure that are largely irreversible. Therefore, efforts should be aimed at prevention, and this begins with identifying at-risk horses.”
Some septic conditions appear to be associated with a higher risk of laminitis, including colitis (inflammation of the colon), enteritis (intestinal inflammation), complicated intestinal obstructions, metritis (toxic uterine inflammation that develops following a retained placenta), pneumonia, and carbohydrate overload. Treating the underlying cause of the sepsis is the first step in preventing laminitis development. This entails:
- Providing circulatory support via intravenous (IV) fluids;
- Administering hyperimmune plasma (which contains high levels of antibodies) and the antibiotic polymyxin B to bind and remove endotoxin from the system; and
- Using non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine, phenylbutazone, or pentoxifylline, which van Eps said probably won’t eliminate pain completely, but could help control it.
Another key, he said, is to implement digital hypothermia, or cryotherapy, as soon as possible. Researchers have shown that cooling the hoof consistently to below 10°C (50°F) from the mid-cannon down inhibits the inflammatory effects that cause lamellar failure. Researchers have learned that horses with colitis that undergo cryotherapy are 10 times less likely to develop laminitis than those that don’t.
However, “there’s not a particularly good way to do it,” van Eps admitted.
The best way he’s found to apply cryotherapy is to keep the horse’s hooves submerged in boots, empty IV fluid bags secured to the horse’s legs, or a receptacle filled with an ice and water slurry. Ice packs applied to the hoof tend to warm quickly, he said, and he’s found in studies that ice boots that contact the lower limb, but not the hoof, just don’t do the job as well.
“But at the end of the day, even the less effective methods are probably still better than nothing,” he added.
Adverse effects are rare, but some horses experience frostbite, he said, especially when ice contacts the skin directly without a water interface.
Van Eps said it’s best to implement cryotherapy before signs of laminitis develop and maintain it continuously until the sepsis resolves. If lameness has already developed, he said, studies have shown that cooling the hooves can still help keep the lamellae nearly normal when compared to uncooled hooves.
Post-cryotherapy, it’s important to limit further lamellar damage in the acute laminitis case by administering NSAIDs, keeping the horse on stall rest (one week for every day of lameness, he said), and providing frog and sole support with therapeutic shoeing. Van Eps said soft bedding or footing is essential to reduce mechanical forces on the hooves; sand is ideal, he said, but can be difficult to maintain. Additionally, it’s important to keep the horse quiet to limit stress on the lamellae, even if it means administering mild sedation. He advised practitioners to use serial radiographs to monitor the internal structures for changes.
Above all, he said, be patient. Laminitic changes can occur rapidly in sepsis cases, whereas resolution can take a significant amount of time.
Veterinarians and researchers are still working to fully understand sepsis-related laminitis and predict when it will occur in septic patients. But they’ve made headway in producing positive outcomes.
“Advances in the way we manage primary diseases and concurrent sepsis, as well as the incorporation of specific preventive strategies for laminitis, are leading to improved outcomes for horses with acute septic diseases,” van Eps said.