Equine Cellulitis and Lymphangitis

By Garret Metcalf, DVM

If you’re a horse owner and have never experienced a horse with cellulitis or lymphangitis you need to consider yourself lucky. This common condition that affects the lower limbs of horses is a frustrating and rarely a life threatening condition for horses. Cellulitis is a term used to describe when a bacterial infection is migrating and spreading under the skin throughout tissue planes. Lymphangitis is when the bacterial infection spreads deeper into the lymphatic vessels. There are technical differences between these two diagnoses but for the sake of this article they will be considered synonymous because the treatment is essentially the same.

Cellulitis is a term used to describe when a bacterial infection is migrating and spreading under the skin throughout tissue planes.

One part of the frustration about these conditions is that we really don’t know why or exactly how it starts. The best educated guess of how this occurs is by some small injury or injuries to the lower limb that allow bacteria into and under the skin. These injuries can be small puncture wounds that are hardly noticeable, nicks in the skin or lacerations. I personally witnessed a horse that had hundreds of seed ticks on its lower limbs develop very significant cellulitis. Once the bacterium that is commonly on the skin of a horse is introduced into the tissue planes below the skin it begins to quickly spread causing lots of pain, swelling and lameness.

Horses that develop cellulitis or lymphangitis often will only have one limb affected at a time compared to just generalized “stocking up” of the legs which will involve the hind limbs or all four at a time. The way to differentiate between stocking up and cellulitis is lameness, heat and pain occurs with cellulitis vs. stocked up limbs will be cool to the touch and non-painful when squeezed. Other symptoms of cellulitis are elevated body temperature, breathing more rapidly, lameness, sweating, extreme swelling of the lower limb that develops quickly, swelling continues to spread up the leg and palpation of the limb is rather painful. Horses with swollen limbs from a serious case of cellulitis will have legs referred to as tree trucks or stovepipe limbs because they are so significantly swollen from the ground up to the stifle or shoulder.

Horses that develop recurring cellulitis often have experienced some form of injury to the limb that may have damaged venous blood flow or lymphatic drainage in that particular limb. Horses don’t have the best mechanism of removing venous blood from their lower extremities already and when injury has occurred leading to further stagnation of lymphatic and venous blood further perpetuating the risk of cellulitis. Recommendations to lower the risk of recurring cellulitis in horses more prone to this condition is to maintain good limb hygiene in these horses by washing and groom their limbs routinely to reduce dirt and bacteria on the skin. Allowing free exercise by means of regular turn out or routine forced work is also beneficial for horses with recurring issues of cellulitis.

Treatment of the cellulitis entails pain management, anti-inflammatory drugs, antibiotics and management of the swelling. The typically cause of cellulitis is from staphylococcus or streptococcus bacteria on the skin. When choosing an antibiotic to treat cellulitis typically a veterinarian will choose injectable antibiotics for faster results that have good antimicrobial coverage against these common bacterial culprits. A rather effective way to administer higher concentrations of the antibiotics into the affected limb is to use IVRLP or intravenous regional limb perfusion. This is a technique that has been utilized in horses for many years to deliver much higher concentrations of antimicrobial drugs into horse’s limbs where it is often needed the most. This is commonly used to treat serious wound, joint, bone or tendon sheath infections in the lower limb of the horse and is rather great a treating difficult cellulitis cases.

Pain management and anti-inflammatory drugs are also very important in order to manage these cases and resolve the massive swelling that develops. Phenylbutazone (Bute) and flunixin meglumine (Banamine) are the most commonly used non-steroidal anti-inflammatory drugs to control inflammation and pain at the same time. In more extreme cases opioids and anticonvulsant drugs are used to help control pain as well. Many times steroids like dexamethasone are needed to help further reduce swelling and inflammation but can be contraindicated in cases that may be more prone to laminitis or other complications from cellulitis.

Hydrotherapy or icing of the affected limb can be rather helpful in controlling the swelling and pain, but can be rather challenging in a hind limb of a horse. There are specially made ice boots, ice gel packs or machines that will circulate ice water to sleeves that can be attached for the horse’s limbs to accomplish this task. Limb compression with stack bandaging and sweat wrapping the limb is critical in helping reduce the swelling as well. My experience is that if you do not apply good compression wrapping on the limb it takes much longer period of time if at all to get the swelling out of a horse’s leg with cellulitis.

Read more in the August 2021 issue of Oklahoma Farm & Ranch.