Laminitis Update, May 2016

Laminitis in horses continues to be a significant health problem that can often lead to chronic lameness or premature death. Reported incidence varies from 7-34% of horses, and it has been identified as a top research priority among national research funding organizations and the American Association of Equine Practitioners. Consider that the laminae tissues are truly responsible for suspending the horse within the hoof capsule. They require a constant delivery of blood, oxygen and nutrients to support the physical load, and anything that disrupts that process causes the laminae to weaken and potentially fail. Failure leads to swelling and rotation- both of which are extremely painful within the hoof capsule. The pain laminitic horses feel is thought to be analogous to a splinter under the human fingernail. The hoof capsule cannot expand to accommodate the swelling.

Laminitis is a syndrome in horses, with several underlying causes. This makes it difficult to study as there are likely different mechanisms of laminar damage. In addition, many horses suffer from sub-clinical laminitis, which goes undiagnosed over time and adds chronicity to the disease. Finally, transport is contraindicated in acute laminitis, which limits caseload to a tertiary care facility. Causes of Laminitis include:

1) Sepsis or Endotoxemia: This is a primarily inflammatory response often associated with grain overload, retained placenta, pleuropneumonia, kidney failure, carbohydrate overload and Black Walnut exposure. It is thought that in these cases, increased blood flow to the hoof delivers damaging inflammatory products that weaken the strength of the laminae.

2) Endocrine Associated Laminitis: associated with Equine Cushing’s disease, Equine Metabolic Syndrome, and sometimes iatrogenic administration of steroids in a susceptible horse. It is thought that insulin regulation is affected in these cases and that this inhibits the metabolic activity of the laminae.

3) Trauma associated laminitis: often due to concussion or excessive weight bearing. This can manifest as “road founder” where the hoof wall is pulled away from the bone, or support limb laminitis, where a non-weight bearing lameness in the opposite limb prevents the horse from resting the affected limb. Blood supply and oxygen delivery are affected and the laminae fail.

The UC Davis School of Veterinary Medicine is actively working on research to advance the prevention, early diagnosis and treatment of laminitis in horses. Currently funded projects include:

  • Identification of Biomarkers indicative of laminitis, and response of those Biomarkers to Mesenchymal Stem Cell Administration Intra -arterially. This work holds great promise for improving diagnosis and treatment of laminitis and validating the use of MSCs.
  • Role of Neutrophils (a type of white blood cell) and the formation of extra cellular traps within the laminar circulation as an underlying mechanism of laminitis in the horse. This work is looking at the molecular level to better understand inflammatory laminitis. It will likely inform new treatment options and acute interventions.
  • Mesenchymal Stem Cell (MSC) tracking using Positron Emission Tomography (PET) in horses suffering from laminitis. The Equine PET scanner is an exciting new tool that UCD has acquired that has already demonstrated new information regarding the metabolic response of laminae in chronic laminitis. Read more about PET technology at CEH...
  • Use of PET to image acute and chronic laminitis. This will be the first study of its kind to use PET to establish baseline images of laminitis.

UCD continues to work on ways to enhance early diagnosis of Insulin Resistance and Cushing’s disease, as these conditions predispose horses to laminitis. UCD has published testing protocols for both conditions which are used nationally.

Much of the research on laminitis has been funded by CEH donors who have identified laminitis as an area of concern. For further information about laminitis and the work we are doing to improve outcomes for horses, please call Dr. Claudia Sonder DVM, Director of the Center for Equine Health.