Lymphangitis in Horses

OK – if you thought cellulitis was gross and bad, wait till you learn about lymphangitis. It’s cellulitis, but worse. The nitty gritty is that lymphangitis is the swelling of your horse’s lymph vessels, which is one way that your horse’s body rids itself of metabolites and wastes.

***** There are some pretty gross photos on this page, but I put them all at the very bottom so you can skip them if you like. *****

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Let’s zoom out and talk about the lymphatic system.

The cardiovascular system is closely linked to the lymphatic system. As blood vessels become smaller and smaller, the capillaries emerge. These tiny vessels allow water to diffuse through the blood vessel walls, both in and out of the vessels. This creates fluid loss from the cardiovascular system.

Now – this fluid needs to get back! This is what the lymphatic system does. Lymph vessels gather this lost fluid from the body and return it to the cardiovascular system. The lymph vessels are one way – meaning fluid can only flow into the cardiovascular system in a series of vessels that start as lymph capillaries, then become bigger and even bigger vessels. A series of one-way valves direct the fluid.

The lymphatic system is critical as it’s also the most direct route from the skin to the lymph nodes, which are basically filters for the fluids running through them. There is a collection of immune cells in the lymph nodes ready to attack and devour anything that shouldn’t be there.

Here’s something cool and also uncool about the lymphatic system. It relies on a horse’s muscles and movement to transport the fluids. This is great, but horses don’t have muscles below the knees and hocks. There’s also gravity to contend with! And, a horse that isn’t moving a lot isn’t pumping lymphatic fluids a lot.

During a bout of lymphangitis, these lymph vessels are blocked and the surrounding tissues cannot drain.

Cellulitis and lymphangitis look the same, usually! Thanks for the photo, Bree

What are the types of lymphangitis in horses?

There are three types of lymphangitis, and all three are things to avoid if at all possible.

Sporadic lymphangitis is the most common in horses. It’s the swelling of the lymph vessels, usually in the hind legs of horses.

Epizootic lymphangitis is caused by a fungal infection and doesn’t seem to be a big threat to sport horses. It’s most common in donkeys, mules, and other working horses. It’s highly contagious, causing sores around the legs and face.

Ulcerative lymphangitis occurs when pockets of infection, an abscess if you will, start to form under the skin. Blech.

How lymphangitis happens.

As with cellulitis, lymphangitis can happen with a wound, even a tiny one. This opening in the skin can let infection in. Equine pastern dermatitis (EPD) is one case in which there are lots of openings for bacteria to enter the horse’s leg.

Staph, Strept, or E.coli are common bacteria linked to lymphangitis, and are everywhere, including your horse’s skin. Upon entering the leg, the bacteria set up shop (the jerks) and your horse will start to respond with inflammation and heat to kill the jerks. This swelling is drained by lymph vessels, and things can get backed up as the volume needing to be drained gets out of hand. Even lymph nodes can become infected and damaged.

Initially, the lymph vessels thicken. As things progress, which can be much slower than with cellulitis, the swelling expands outward and upward. The “stovepipe” leg is common.

As with cellulitis, there is pain, and possible lameness, and the leg joints seem to be gone. Serum can leak from the leg, as well. Fevers are common with lymphangitis as well, and some horses are visibly depressed and will stop eating.

Because of the pain and restricted movement from the swelling, laminitis is a real possibility.

Here’s where things get bad. The one-way valves in the lymph vessels can become damaged, unable to help keep fluid on its upward track. Permanent leg swelling is a real possibility, as is impaired movement.

There’s a whole lot going on in this stovepipe of a leg!

It’s rather difficult to separate cellulitis from lymphangitis in some cases, as they can both present in such a similar manner. Lymphangitis is also a case in which it can be the primary problem or a secondary problem associated with a wound or injury.

Some horses develop lymphangitis associated with strangles or other diseases, or it might just appear from the ether.

Some horses decide that this isn’t enough, and start transforming into the ulcerative version of things on more than one leg. Pockets of infection collect, which must be drained somehow. Some pop, and some are lanced by a vet. They can sometimes be visible to the naked eye, other abscesses need to be found with an ultrasound.

Interestingly enough, cases of ulcerative lymphangitis seem to be endemic to certain areas, in that many creatures on the same farm can have the same problem. The more sporadic cases seem to affect a single limb on a single horse. Some horses have pairs of legs affected. There’s also the case in which a horse develops a type of lymphangitis that is not the result of an infection, it’s just pooling of normal fluids in the legs.

How do you recognize lymphangitis?

AH! Leg swelling is the first clue. It’s always a good idea to pop in a thermometer to check for fever as well, which also has an unwelcome relationship to laminitis. Horses with lymphangitis may also seem colicky, lame, and very painful when the leg is touched.

Please call the vet!

Take your horse’s temperature, and start noting a few things for your vet. Is the leg hot, how high is the swelling? How fat is the leg? You want baselines so that you can track the progression of things.

Sometimes things erupt. Rose sent over this photo to share, and adds that early intervention is key!

What you can do to help the horse with lymphangitis.

You and your vet will come up with a healing plan! It’s a marathon, not a sprint. Antibiotics are KEY, as are pain medications and diuretics to help the fluid drain.

Some horses might respond to steroids, immune support, or topical treatments. There are no hard and fast rules about this, each case will be different.

If a horse can move, even if it’s uncomfortable, it should be encouraged to help the fluid drain from the leg. Against gravity. Some horses also respond to massage.

Cold, warm, or alternating therapies may help. Each horse will have his own reaction to these!

It’s the consensus that lymphangitis-affected legs should not be wrapped, as the fluid just sits higher on the leg. There’s also a wonderful article here that talks more about that.

https://soxforhorses.com/pdf/EquiManagement-FEI-Vet-Dr.-Stephen-Soule-Cites-Circulation-Not-Compression-etal.pdf

When a horse has such swelling and edema in the legs, any compression can effectively reduce the amount of fluid movement and affect the oxygen levels in the area. This hampers healing! And, there’s the chance that pressure sores can happen.

Some horses will need to be wrapped. It all depends.

Sometimes, the skin will seep, crack, and scar. This can hamper movement in the present and down the road. Folds of skin can thicken, and these weird warty growths can start to appear on the lower legs. They may look like scratches, but they are not.

The long-term care.

Lymphangitis is often a recurrent battle to be fought. The damage to the lymph vessels is often permanent, and the associated lameness can also be permanent.

Sometimes, standing wraps in between lymphangitis episodes can help. So can plenty of exercise, proper paddock and stable hygiene, and lots of turn out.

Silver Whinny’s can help keep a lower leg clean. This is especially important if any lower leg swelling has created sores and open areas.

How is lymphangitis different from cellulitis?

The primary difference between the two -itises is the location of the affected tissues. Cellulitis occurs under the skin in the soft tissues, and the blood vessels are primarily affected. Lymphangitis is within the vessels of the lymphatic system. For more on cellulitis, this article has you covered.

Because blood vessels have the knack to heal, re-route, and make the best of things, there’s a chance that cellulitis can be a “one and done” event. With lymphangitis, the scarring and damage to the one-way valves and the lymph vessels are permanent, creating a lifelong problem.

Nip this in the bud! Get your vet involved quickly and help your horse recover.