Lymphangitis in Horses

In horses, lymphangitis usually affects the lower part of the rear legs, although any leg can have this condition. It is an infection of the lower limbs caused by a bacterial (sporadic) or fungal (epizootic) infection or from an infected wound (ulcerative). In some cases, it has been known to affect the neck, but this is uncommon. In epizootic lymphangitis, the lesions can spread to other areas including the eyes, nostrils, lungs, and other organs.

Lymphangitis in horses is the swelling and inflammation of the lymph nodes, most often one or both of the rear legs. This is usually caused by a bacterial infection although a fungal infection is sometimes the culprit. This condition has been referred to as fat leg disease to some horse owners due to the inflammation of the leg. In fact, the leg can get up to three times its normal size. There are three types of lymphangitis; sporadic, epizootic, and ulcerative.

Most often, the first thing you will notice is the swollen limb. Some other common signs are:

Sporadic Lymphangitis

• Extremely swollen leg or legs (usually the rear)
• Severe pain in the affected leg or legs
• Lack of appetite
• Depression
• Increased body temperature
• Lameness
• Muscle contractions
• Abnormally high blood pressure
• Rapid heart rate and breathing

Epizootic Lymphangitis

• Skin nodules most common on legs but can also be on the neck or head
• Extremely swollen glands (visible)
• Nodules turn into abscesses with thick yellow pus

Ulcerative Lymphangitis

• High body temperature
• Sweating more than usual
• Extreme pain in affected areas
• Leg will swell and burst, leaking fluid

Types

• Sporadic lymphangitis is the most common and causes extreme problems, causing lameness due to the swelling of a leg, which is usually one or both of the back legs
• Epizootic lymphangitis is a contagious form of lymphangitis caused by a fungal infection
• Ulcerative lymphangitis is similar to sporadic lymphangitis but is caused by an infected wound; this form is severely painful and the leg or legs get so swollen they will burst and leak fluid

Causes can be different depending on which type of lymphangitis your horse has. 

• Sporadic may be caused by many different bacteria such as staph aureus, strep zooepidemicus, e. coli, or corynebacterium pseudotuberculosis
• Epizootic is caused by the fungi, histoplasma farciminosum
• Ulcerative is caused by an infected wound

Taking your horse to see an equine veterinarian is recommended, but any veterinary professional should be able to make the diagnosis. First, you need to give the veterinarian your horse’s medical history, immunizations, abnormal behavior, recent illnesses or injury, and what symptoms you have noticed in your horse. After, the veterinarian will do a complete thorough physical examination. This usually consists of watching your horse from a distance to assess behavior, stature, conformity, and overall body condition. The veterinarian will then have you walk, run, and trot your horse to see muscle and joint function. However, if your horse’s legs are too swollen, this part may be skipped. The veterinarian usually palpates the abdomen and listens with a stethoscope for any abnormalities. 

Finally, the veterinary caregiver will assess your horse’s body temperature, blood pressure, height, weight, reflexes, heart rate, respirations, and body condition score. Radiography images (x-rays) are necessary to rule out other diagnoses such as tendonitis or a broken leg. In addition to x-rays, your veterinarian will probably perform an MRI, CT scan, and maybe a bone scan. Additionally, an ultrasound will be used to find the pockets of abscesses as a guide in getting a sample of fluid for microscopic analysis. Other tests will include a bacterial and fungal culture, complete blood count (CBC), blood urea nitrogen (BUN), serum chemical panel, insulin and glucose levels, packed cell volume (PCV), and urinalysis.

The treatment for your horse depends on which kind of lymphangitis it is.

Sporadic Lymphangitis

This type of lymphangitis should be treated with nonsteroidal anti-inflammatory drugs (NSAIDS) and, if necessary, steroids may be given for pain and inflammation. Hydrotherapy and physiotherapy can help in treating this type of lymphangitis as well. Other medications that may be used for pain and swelling are flunixin meglumine (Banamine) and phenylbutazone (Bute).

Epizootic Lymphangitis

This type is treated with surgical excision of the lesions and antifungal medication such as amphotericin B. However, the infection just has to run its course. In addition, ice packs and hydrotherapy may be used.

Ulcerative Lymphangitis

Aggressive therapy is important here, with antimicrobial medication and an anti-inflammatory such as corticosteroids or NSAIDS. Any external abscesses will be treated by lancing and draining when they are ready. If your horse has internal abscesses, it will be harder to treat and may include hospitalization.

Prognosis is good for all three types of lymphangitis. However, if your horse gets internal abscesses, the prognosis is fair to guarded because even with treatment, an average of 35% of horses die. Be sure to keep in touch with your veterinarian and follow instructions exactly.