Information on Chronic Progressive Lymphoedema (CPL) / Lymphedema, feather mites and associated conditions
Chronic Progressive Lymphoedema
Welcome to the world’s first comprehensive guide to CPL for owners, veterinary professionals and complimentary therapists in the equine industry.
What is CPL?
Chronic Progressive Lymphoedema or CPL is a lifelong disease that affects draft horses with feather. There is no cure. It is noted in Belgian drafts/Brabants at an estimated 96% prevalence and is becoming increasingly common in other breeds:- Shires, Clydesdales, gypsy vanners, cobs, Percheron, Boulonnais and Friesians are all affected. Some correlations have been noted between the incidence of CPL and bone and hair thickness.
Essentially CPL is a failing of the lymphatics in the lower legs. We know in part this is caused by the fact that equines don’t have muscles below the knee and hock that contract against the lymph vessels to aid the flow of lymph. Therefore they rely on the movement of the fetlock joint and natural hoof function instead of muscular contraction, making them very prone to lymphatic incompetence when standing still. This is why horses that are stabled are far more likely to develop CPL – when standing still for long periods the natural lymphatic retraction is removed. But why does CPL affect feathered horses specifically?
Researchers suspect that CPL is a complex disease consisting of a multifactorial process involving an underlying genetic cause and triggers from the horse’s environment and husbandry. There seem to be differences in the sexes – stallions can develop CPL later but more severely compared to mares who develop it earlier. The exact gene or mutation is yet to be identified. In one study horses with CPL were shown to lack a protein called elastin which normally acts as a sort of compression bandage to stimulate the lymph back into circulation. Indeed several studies have noted altered elastin metabolism in CPL horses. This elastic squeezing action is what is replicated in lymphoedema care by way of Combined Decongestive Therapy.
The trapped waste and fluid (lymphoedema) kickstarts the body’s natural inflammation process, causing the blood capillaries to open up so more lymph is produced – this is why mites and bacterial infections causing inflammation also logically worsen the oedema. The body then tries to fix the resulting oedema and waste itself by making a lot of collagen fibres in a process called fibrosis. Fibrosis creates scar tissue through which lymph can not travel and makes up the nodules and folds that are so unique to the presentation of the disease.
“C.bovis infestation may affect the progression of chronic pastern dermatitis (also known as chronic proliferative pastern dermatitis, chronic progressive lymphoedema and dermatitis verrucosa) in draft horses, manifesting with oedema, lichenification and excessive skin folds that can progress to verruciform lesions.”
In yellow is a crease caused by hyperkeratosis. It is essentially “mallenders“, just further down the leg. Once the area has been allowed to scar like that it can create problems for the superficial drainage as the lymph can not pass through scar tissue thicker than 4mm.
Creasing like this can be prevented to some degree by applying an emollient regularly and using something like Sebolytic® shampoo to remove the keratin build up and restore the natural balance of the skin.
We will see oedema start to develop around crease and gravity will bring that further down around the joint – see the minor folds developing, highlighted in red. Regardless of whether we think the horse will develop actual CPL, the best course of action is to treat as though it is, while also remembering to apply emollient to the area to prevent any further keratin build up and scarring. The area directly around the ergot may become puffy.
Below we can see two more unfortunate examples of this hyperkeratosis creasing and the subsequent oedema and loss of definition, as the leg starts to develop the familiar “traffic cone” shape and folds.
Thanks to the members of the CPL Facebook Group for submitting the above images.