The lymphatic system is essential because it helps balance your horse’s fluids and supports the skin’s defense mechanisms. Chronic progressive lymphedema (CPL), also called milk leg, happens when this system doesn’t work correctly in the lower legs.

With CPL in horses, they get swelling and redness in their lower legs, leading to skin sores and nasty infections caused by bacteria and parasites. This can make life challenging for them, interfering with movement and their overall well-being. How bad it gets varies; some might only have a little trouble, while others could end up severely disabled or even disfigured.

 

What is Chronic Progressive Lymphedema (CPL), Also Called Milk Leg, in Horses?

 

• Chronic Progressive Lymphedema is a severe issue that interferes with the lymphatic system of horses, especially in larger draft breeds. As this disease progresses, the skin can suffer from secondary infections of parasites and microbes.

The equine lymphatic system

 

• The lymphatic system has four primary roles: balancing fluid, assisting the immune response, fat absorption during digestion, and removing wastes from the body.

Fluid balance

• Blood vessels will leak blood into the surrounding tissues, and the lymphatic system returns this fluid to the blood. Without this, fluid levels in tissues increase and create swelling in lower limbs and lungs while lowering blood pressure.

Immune response

• The organs of the lymphatic system, the spleen and thymus primarily, keep tabs on the blood and respond to invaders. Within the lymph nodes are lymphocytes, a white blood cell, and these specialized cells deploy to attack microbes, viruses, cancers, and damaged cells.

Absorption of fat

• The lymphatic system also helps a horse remove fats from the intestine as part of digestion.

Waste removal

• Lymph fluid takes the body’s trash, like broken bacteria, and sends it back into the blood, running through the liver and kidneys for removal through urine or manure.

 

 

CPL damages the lymph system

 

• CPL disrupts this system, leading to swelling, skin changes, and discomfort for affected horses. The lower legs end up with poor lymphatic drainage, causing thickening of the legs. Many horses also develop skin nodules and scars.

 

• This malfunction creates skin that is stretched and sometimes folds onto itself. This is the perfect home for bacterial, parasitic, and fungal infections, which create another set of issues.

  

Complications of CPL and secondary infections

 

• The swollen lower legs are painful and susceptible to equine pastern dermatitis and mites. As the lymph fluid can’t clear waste from your horse, the lower legs roll out the welcome mat for recurrent infections.

 

Bacterial infections

 

• The bacteria invaders such as Staphylococcus and Dermatophilus congolensis are frequent fliers that create open sores, pus, and more inflammation. This can be painful for your horse and creates a never-ending cycle of skin infections. Fungi often link to join in and create further problems and complicate treatment.

Mites and mange

 

• Horses with feathers also create a home for feather mites. These tiny parasites are Chorioptes bovis mites and cause chorioptic mange. These mites can chew on parts of your horse to survive. They feed on dandruff and dead skin, fatty tissue, lymphatic fluid, and your horse’s skin lesions.

 

• These tiny freeloaders thrive and usually infect the thickened skin that comes with CPL, although they can spread on the horse’s body, damaging both the skin and the superficial lymph vessels underneath.

 

• This mange infection can be terribly itchy and needs topical and oral medications to clear. Unfortunately, they, too, are a recurrent problem with chronic progressive lymphedema.

 

Hoof health

 

• The coronary band is the birthplace of hoof growth. CPL interferes with this, often compromising a healthy hoof. Hoof growth is negatively affected, and hoof diseases like thrush and white line are more likely.

 

• The pain and swelling also affect how well your horse can manage the trimming and shoeing during a farrier visit. First, it’s uncomfortable to be handled on the lower legs. Secondly, shoeing may help or hinder your horse’s hoof growth because of the constant stomping that CPL triggers.

 

The Impact of CPL on Horse Health and Mobility

 

• Horses become less mobile over time, and chronic progressive lymphedema is a debilitating condition. Many horses eventually lose a tolerable quality of life as they continuously fight pain, hoof problems, secondary infections, and lameness. While diligent management can offer comfort and some longevity, CPL frequently causes premature death.

This scientific paper discusses many aspects of this disease. 

 

 

 

Causes of CPL in horses

 

• There are two primary factors contributing to CPL. Genetics and lifestyle are the primary considerations, and the understood development mechanism includes elastin in the skin.

 

Equine genetics

 

• The most susceptible breeds are the Belgian draft horses, Clydesdales, Friesians, Shires, and other large, feathered draft horse breeds. This hints at a large genetic predisposition.

 

• No specific genes responsible for CPL have been pinpointed yet, but mounting evidence shows that genetics play a significant role. Belgian draft horses are one example where generations of selective breeding aimed at producing horses with heavier legs and excessive leg feathers also triggered more CPL in these horses. Friesians are another breed with genetic links worth exploring. A group of Friesian horses with CPL also showed a longer gaskin length. While inconclusive, this shows a possible genetic link to other equine traits.

Read more about the genetics of CPL in horses here in this fascinating scientific study. 

This study researched the Friesian horses and gaskin length.

 

Environmental and lifestyle factors

 

• A horse’s living arrangements hugely impact their health. Just as dusty environments with little ventilation affect lung health, a horse’s lower legs are affected by mud, moisture, bedding, and grooming.

 

• We understand the mechanisms behind mud fever, photosensitivity, and how mites and lice damage the lower legs. These multiple causes of lower leg skin problems fall under the umbrella of equine pastern dermatitis (EPD) and involve poor care, bacteria, moisture, fungus, parasites, and thicker leg hair, trapping all that against the skin.

 

• When chronic progressive lymphedema begins, the skin changes and is more likely to support EPD development. So, we need to factor in the paddock and pasture moisture and mud, the cleanliness of bedding and shavings, how wet the legs remain, and how much feathering a horse has.

 

• Also, consider our diligence in noticing the early stages, clipping feathers, calling the vet, mitigating mud, and staying ahead of secondary infections.

 

Read more about EPD here.

 

 

The mechanism that creates lymphatic problems – the role of elastin

 

• Elastin is a protein that strengthens and supports many structures in the body – including the skin and the lymph system. Elastin helps the lymphatic fluid circulate in the lymphatic system and acts like a sponge.

 

• In horses with CPL, researchers find that elastin levels in the legs and neck are much higher in affected horses. One would think this is good, but the elastin’s structure needs to be more cohesive and organized. It’s theorized that horses create more elastin to compensate for the poor structure and support.

 

• Another protein-related compound, desmosine, plays a role, too. Desmosine is an amino acid, a precursor to proteins, and it is reduced in the leg and neck skin of affected horses. Desmosine increases when secondary infection sores and lesions develop.

Read some science about elastin here. 

 

Recognizing the Signs of CPL

 

• Spotting the early signs of CPL in horses is key to stepping in quickly and managing this issue. At first, you might notice their lower legs swelling, which feels soft if you press it. As things get worse, this swelling gets stiffer, and skin folds can appear because of tissue damage.

 

• With CPL, other things to watch out for are lesions, fibrosis (which means parts of the body get stiffer), poor hoof growth, scaly skin, pus coming out from those areas, and skin folds not just on their legs but also around their neck and trunk. It’s essential to monitor any changes happening with your horse’s legs – like how they look or feel – and call a vet immediately if you think something’s off.

 

Early Indicators of CPL in Horses

 

• When horses start showing signs of CPL, you might notice a few things early on. Their lower legs might swell up a bit. This swelling can be hard to spot, especially with horses with lots of hair or heavy feathering around their legs. If you press on the swollen area, it might feel soft and squishy because of something called edema.

 

• As time goes by and the disease gets worse, other symptoms begin to show up more clearly. One common issue is pastern dermatitis – also known as scratches – which shows up as redness and scaly skin near the horse’s hooves; this part is uncomfortable for them. Horses that belong to draft breeds often have extra thick hair around their legs (that’s what we mean by “heavy feathering”), which unfortunately makes spotting these problems harder and contributes to issues like pastern dermatitis sticking around longer.

 

• Keeping an eye on your horse’s lower legs is crucial for catching any weird changes in how they look or feel – think swelling or changes in skin condition – pretty early on. Catching these signs sooner rather than later means you can do something about it quickly, helping your horse improve faster.

 

 

Progression of Symptoms in Affected Horses

 

• As CPL in horses progresses, pain and complications increase while mobility and quality of life decrease.

 

• Early stages of the disease show the legs swelling slightly, and there may be some pitting edema, where you press the swollen area and the dent remains.

 

• As things progress, the skin thickens, creases, and folds. These pockets trap moisture, hair, microbes, and parasites to fester. Then the sores happen.

 

• As CPL moves along, the hoof quality decreases, hoof growth may slow, and infections like thrush take hold. The hoof will receive less blood flow, too.

 

• Lameness occurs, and moving in general can become agonizing in later stages. Harder nodules of skin and tissue and sores make moving even harder and more painful.

 

• At this point, a horse’s quality of life is quite poor, and there is a severe disability. Euthanasia is often the kindest decision.

 

What is the prognosis for chronic progressive lymphedema?

 

• The nature of any progressive disease is an overall decline. Our job is to encourage a comfortable life, doing what we can for a horse’s lifestyle and providing timely veterinary care to keep a higher quality of life.

 

• There are many things we can do to help alleviate discomfort and give our horses the best life while supporting their health and slowing the progression of the disease.

 

Diagnosing CPL in Horses

 

• CPL doesn’t have a specific test that pinpoints it or can test for the cause of CPL. A thorough exam is the starting point, followed by monitoring any signs of progression. It’s often best to clip feathers during this process so your vet can see what’s happening. Genetic factors will also come into play, as will ruling out other possible causes of the swelling.

 

• It’s important to note that mud fever and scratches can clear up and associated swelling goes away, but with CPL, the swelling is persistent regardless of sores, mites, scabs, or other skin infections.

 

• The clinical presentation of this disease resembles cellulitis, lymphangitis, and chronic pastern dermatitis. Your vet is the best source of information and diagnosis if your horse shows signs.

 

Advanced diagnostics – lymphoscintigraphy and ELISA tests

 

• Some vets may suggest lymphoscintigraphy, which uses nuclear imaging (nuke scan) to map the lymphatic system. This shows us if lymphedema and lymphatic disease is an underlying cause of swelling.

 

• Another method is to run an ELISA test looking for antibodies to elastin. A positive test would signal that a horse’s elastin is abnormal, and their body is making antibodies against it.

 

This scientific paper talks about lymphoscintigraphy in horses. 

 

 

 

Innovative Treatments for CPL

 

• You can approach CPL treatment in a few ways – improving lymph flow, medications, and environmental changes.

Fancy massage therapy

 

• Combined Decongestive Therapy (CDT) is one treatment that mixes manual lymph drainage and special support bandages. The goal is to physically help a horse move lymphatic fluid up the leg. This massage may also help loosen the hardened tissue. The support bandages serve to mimic this action, too, and not let the fluid come back down.

 

Pharmacological Interventions and Their Efficacy

 

• Topical and oral medications help treat CPL in horses.

 

• If mites are the issue, treating these parasitic infections requires topical antiparasitic treatments and oral meds. This can eliminate the mites and help the swelling brought on by those little jerks.

 

• Sulfur shampoos may support gently cleaning affected limbs and help soothe irritated skin.

 

• Oral and topical antibiotics or antifungals help heal the mud fever-esque sores.

 

• It’s essential to have your vet involved so you get the proper treatment for the exact cause. There’s no use treating only for fungus when it’s a mite.

 

Environmental changes and daily habits

 

• Daily attention to a horse with chronic progressive lymphedema is the best way to support a better life.

 

• Grooming is more than brushing – it’s noticing the small changes so your horse can have earlier vet care. It’s noticing when your horse isn’t doing great and when they are. Grooming is health care, and it starts with your observations.

 

• Then, attend to daily exercise, hoof care, and feather management.

 

Grooming and hoof care practices for managing chronic progressive lymphedema

 

• Here are some things to remember when helping a horse with CPL:

 

• Your eyes and hands should track changes to the legs.

 

• Do daily care to ensure the legs are clean and dry.

 

• Treat any sores with topical treatments and medications.

 

• Look for evidence of mites. Sometimes, the skin becomes oily, and your horse may feel extra itchy.

 

• Find yourself picking hooves like it’s an Olympic sport. You’ll notice thrush earlier and any changes to hoof growth so your farrier can intervene earlier.

 

 

 

Clip the feathers

 

• Feathers on horses with CPL do many things:

 

• Hide the skin so progress is hard to measure

 

• Trap moisture to encourage microbe growth

 

• Create a fairy land for mites to enjoy life

 

• Hide the hooves so it’s harder to register hoof and coronary band health

 

• Make cleaning and drying the lower legs more complex and less thorough

 

• Finding and measuring your horse’s digital pulse is much easier when there are no feathers. This helps you monitor hoof health.

 

• It’s a tough pill to swallow, but removing the feathers will help your horse.

 

Movement for the win

 

• As the saying goes, move it or lose it. Exercise and free movement help blood flow, lymphatic drainage, and your horse’s mental health. And, they won’t be standing in bedding, which is bound to get gross no matter how often we pick stalls.

 

• Movement also benefits hooves! There is a link between sedentary horses and thrush. And while any horse can get thrush, even in the most pristine environments, thrush thrives without movement. Also, horses can get thrush and skin infections in a dry environment.

 

• Movement also improves metabolism, making weight management more effortless.

 

Dietary Considerations and Supplements

 

• Feed your horse’s skin from the inside out. The more we know about equine nutrition, the more obvious it becomes that a low-sugar and low-starch diet is best for horses. Here are the basics of how to assemble an anti-inflammatory diet that supports healthy skin and a healthy weight:

• Forage first. Choose low-sugar hay.

 

• Use ration balancers or vitamin and mineral supplements to supply missing ingredients without added calories. Draft breeds are already susceptible to being overweight, so we don’t need to add to this when they are less mobile.

 

• Add Omega-3 fatty acids. These fats are anti-inflammatory and must outnumber the Omega-6s in a diet. Corn oil is NOT it; it is loaded with Omega-6s and promotes inflammation. Stick to flax, chia, or fish oils.

 

• Add collagen and antioxidants. Incidentally, these are in a vitamin and mineral mix. Avoid overlapping things and end up with too much of an ingredient.

 

• Reduce the overall NSC value of the diet to 10% or lower. This includes pasture!

 

Use grazing muzzles.

• Pasture is sometimes too rich for horses that need a lower NSC diet. But, CPL in horses means movement is necessary. Using grazing muzzles reduces the volume and speed of grass traveling to their hindgut, making grazing safer.

• Using a wearable hay net, they can still move, eat, and interact with their friends.

 

Read this for tons of great info on diets to manage CPL in horses. 

 

 

Preventing CPL in Your Horse

 

• You may not be able to prevent CPL entirely, but you can do your best to ensure a nice quality of life for your equine partner. Besides your eyes and hands, you should loop your vet and farrier into the plan as soon as you notice anything about keeping your horse comfortable.

 

• To help end the genetic cycle, avoid breeding your horse.

Frequently Asked Questions

 

Why is chronic progressive lymphedema called milk leg in horses?

 

Milk leg is the old term for this disease process and traces back to the phrase “phlegmasia alba dolens,“ translating to white leg or milk leg. From the limited information about this in horses, except that it’s a common term to describe CPL, phlegmasia alba dolens refers to a mother with swollen legs during pregnancy. It was also thought to involve the metastasis (cancer-like growth) of the mother’s milk. Wild, right?

What is the life expectancy of a horse with CPL?

 

There is no correct answer to this, although horses can be comfortable with careful management, veterinary care, and regular farrier visits. Once movement becomes painful and challenging, the quality of life diminishes. Unfortunately, there is no cure for CPL in horses.

Do you have a horse that may be at risk of developing CPL?

 

A draft breed or draft cross is more likely to develop chronic progressive lymphedema or show early signs of the condition. Managing the feathers, noticing any swelling in the legs early, and regular skin infections like mud fever are symptoms of CPL. 

How does CPL in horses differ from other equine leg conditions like cellulitis or lymphangitis?

 

Chronic Progressive Lymphedema is a long-term issue with the lymphatic system that leads to ongoing swelling, skin getting inflamed and full of sores, nodules with skin crusts, and inadequate lymphatic drainage on affected legs. Cellulitis and lymphangitis also affect the legs similarly but result from skin infections of the skin or lymph tissues, usually due to bacteria entering through a minor wound.