Pioneering therapies trialled overseas could mean an important step forward in the treatment of laminitis. Thomas O’Keeffe MRCVS investigates
Laminitis can be devastating, whether it affects a field-kept pony or an elite athlete.
The recent plight of triple Coronation Cup winner St Nicholas Abbey highlighted the indiscriminate nature of the disease. Following surgical repair of a horrific fracture of a foreleg, the 7-year-old then faced the further challenge of overcoming laminitis that developed in the supporting limb.
Despite much research and study, our understanding of laminitis remains far from clear. It is universally agreed, however, that the disease stems from a diverse set of processes including sepsis — the body’s inflammatory response to infection — endocrine disorders, excessive weightbearing and concussion.
The subsequent inflammation of the leaf-like laminae, which anchor the pedal bone within the hoof, can result in a tearing of this vital support structure. The pedal bone can then drop or rotate, causing permanent damage.
An international conference in Florida last November brought together leading minds in the field of equine laminitis to discuss current research and scientific evidence, share successful case studies and take steps towards preventing this life-threatening disease. Alongside therapies that have recently been trialled, this new knowledge could soon be helping horse owners in the UK.
Feeling the chill
A scientific study published in the Equine Veterinary Journal last year confirmed that the application of ice, known as cryotherapy, can be an effective aid in the prevention of laminitis in severely toxic animals.
Laminitis is a common consequence in horses that are clinically compromised, such as those suffering from colitis — a colon disorder that can lead to a sepsis associated form of the disease. In this study, performed at Michigan State University, USA, it was demonstrated that horses whose limbs were iced preventatively were 10 times less likely to develop laminitis.
Ice is one of the oldest forms of medical therapy, known for its anti-inflammatory and analgesic (painkilling) effects. Ice boots are probably the most useful tool in applying ice to the lower limbs safely without causing skin irritation, but the ice must be changed as frequently as every 3hr to maintain its frozen state.
To prevent laminitis, the study author and her fellow clinicians now make it standard practice to ice all four feet of horses diagnosed with colitis — as well as those recovering from colic surgery — for 24hr after clinical signs of sepsis have resolved.
Rood and Riddle Equine Hospital in Kentucky, USA, has been experimenting with stem cells as a treatment for laminitis.
Mesenchymal stem cells (MSC) are unique in that they are pluripotent, meaning they can differentiate into multiple types of cells, including those that make up bone and connective tissue.
Previous research has shown that stem cell therapy helps improve the quality of healing in some tendon lesions, but vets are optimistic that it can also help repair laminar damage and stabilise the pedal bone within the hoof capsule.
Stem cells have also been shown to have an antiinfl ammatory action, which is an additional benefit.
The study looked at 30 chronic (long-lasting) laminitis sufferers admitted to the hospital between 2010 and 2012. Each horse received 20-30million MSC per affected foot at 1 month intervals, averaging 3 to 4 treatments in total.
The stem cells are injected into blood vessels in the lower limb by a technique known as regional limb perfusion. A tourniquet is applied above the injection site for 20min in a bid to retain the cells in the area where they are needed. Alternatively, they can be injected directly under the skin at the coronary band.
The treatment was successful in 70% of the cases, but it is important to point out that it was used as part of a multimodal approach, along with traditional laminitis therapies.
Stem cells are available for equine use in the UK, but therapy is currently costly. This study demonstrated the importance of using stem cells in the first 30 days following the onset of laminitis for the best results.
Various drugs have been studied around the world in the war against laminitis.
One recent possible breakthrough involves the drug t-TUCB, which belongs to a group of anti-inflammatory compounds that were discovered more than 40 years ago.
In a promising study published last year at UC Davis, USA, 4 laminitis sufferers who had previously been unresponsive to all other modes of treatment were treated with t-TUCB.
According to initial reports, 1 horse experienced a complete remission that has lasted for more than a year. The 3 others have shown improvement.
This particular treatment is not available in the UK, but these early results merit further investigation on a much larger pool of horses.
Other treatments, including painkillers such as paracetamol have also been investigated.
Frustratingly the nature of laminitis means it is difficult to obtain clear proof of what helps sufferers most.
Maggot therapy, pioneered at Rood and Riddle, aims to use the healing properties of maggot larvae to help with cases of chronic laminitis with sepsis and necrosis (dead tissue) in the foot.
Sterile maggots are bred in a laboratory for this non-invasive medical therapy. The continuous debridement (removal of damaged tissue) and healing properties of the larvae are thought to produce enzymes that destroy and consume the dead tissue and bacteria and stimulate the growth of new blood vessels. New maggots are introduced to gorge themselves on the dead tissue and the maggots also excrete anti-bacterial saliva.
It may be early days, yet each of these innovative treatments provides a further piece of the laminitis puzzle. Recent research developments give us a greater understanding of this truly global disease, enabling us to improve the welfare of our horses now and in the future.
‘The change was remarkable’
The high-profile case of St Nicholas Abbey publicised the use of maggot therapy as a treatment for laminitis.
The racehorse underwent surgical repair of a fractured pastern last July. This was a complex procedure involving metal implants and a bone graft from his hip.
Complications ensued when the weight-bearing pin in his cannon bone broke. He then developed colic that required surgery.
In October, X-rays revealed that the stallion had developed laminitis in his support limb and that the pedal bone was beginning to move.
“This type of laminitis is a recognised complication of such a surgery,” said Tom O’Brien of Fethard Equine Hospital in Co Tipperary.
“We enclosed medical-grade maggots in the cast on the laminitic foot to eat the dead tissue. The change was quite remarkable and we started to see new hoof growth at the coronet band and on the sole.”
Sadly, despite showing promising signs of recovery, St Nicholas Abbey died in January after suffering another bout of colic.
Laminitis recovery: a UK perspective
What are the chances of recovery from pasture-related laminitis?
A UK study looked at 107 laminitis sufferers of all sizes and types, 43 of whom had previously suffered from the disease. Two-thirds of the horses and ponies were deemed to be mildly to moderately affected, while the remaining third were classified as severe.
In the opinion of the vets involved in the study, 77 of the cases showed good initial response. 8 weeks after the onset of laminitis, 102 of the 107 were doing well. But only 48 of the 88 riding horses were able to return to ridden exercise — and those who had never previously suffered from the disease were 2.6 times more likely to return to ridden exercise.
The degree and stage of the disease were thought significant in recovery. Lower bodyweight and optimal body condition were also associated with successful management of laminitic horses.
How you can help
As part of an ongoing study funded by the British Veterinary Association, the University of Liverpool is seeking horse owners’ views on the prevention and management of laminitis.
If you would like to take part — regardless of whether or not you have direct experience of the condition — visit www.liv.ac.uk/equine/owners/horsehealthstudy