Horses are generally thought of as being extremely hardy and robust animals. Despite their size and strength however, horses’ legs can be subject to a variety of problems. It is not uncommon for a horse owner or manager to suddenly discover significant lower leg swelling in a horse that was put in its stall in seemingly perfect condition the night before.

A horse’s lower legs can swell for any number of reasons, although there are several that are more common. Stall confinement following intense exercise can lead to a buildup of fluid in a lower leg or legs, as can a general lack of exercise, obesity or a diet too high in protein. In some instances, a localized allergic reaction can lead to swelling in one or more legs. These types of swelling are often—but not always—temporary. Usually, they cause little discomfort other than minor stiffness, and often improve or vanish following exercise.  In some cases, both hind legs or all four legs will be affected. 

Cellulitis and Lymphangitis in the Horse

Cellulitis and lymphangitis in horses are more serious problems. Cellulitis is an inflammation of the skin and the soft tissues directly underneath. Lymphangitis develops when the inflammation spreads to deeper tissues and vessels that move lymph through the body.¹ Lymph is a clear, yellowish fluid produced by the lymph glands; it contains white blood cells which help the body regulate fluid balance and fight infection.

Cellulitis and lymphangitis are typically caused by bacteria that have entered the horse’s body through a break in the skin. Horses are unusually susceptible to infections from puncture wounds and even insect bites; quite often, these can be very difficult to see until an infection is evident. Other causes of cellulitis and lymphangitis include softening of the skin due to excessive moisture, stocking up or bruising.^1,2

In a leg, cellulitis often will start in the lower leg, around the heels, pastern, or fetlock. If a horse develops a case of cellulitis, whatever the cause, it should be fairly easy to detect. The swelling will be considerable, hot, and often painful to the horse. The leg may have a “stovepipe” appearance; the skin may also crack and/or develop an abscess. In some cases, the horse will also present with a fever.¹ The literature suggests that anything above 102 degrees Fahrenheit could be indicative of an active systemic inflammatory process.

Lymphangitis usually presents more dramatically, with a horse experiencing acute onset of a severely swollen leg, extreme pain and an elevated temperature (between 102-105 degrees F). In many cases, the horse will go off his or her feed, probably due to the fever and discomfort. Some horses will tremble, breathe rapidly and sweat.²

Circling back to how susceptible horses tend to be to puncture wound infections, it is generally thought that varieties of Staphylococcus, Streptococcus, or Escherichia coli bacteria opportunistically infect such wounds, leading to lymphangitis.³ These bacteria reproduce rapidly, causing and inflammatory reaction as the body attempts to repel the invaders. “The lymphatic system drains fluid from the leg, filtering it through lymph nodes that try to remove foreign pathogens (disease-causing organisms). The lymph nodes are overwhelmed and can, themselves, become infected. Lymph ducts and blood vessels become damaged and swollen and lose elasticity, with blood and lymph pooling on top of the one-way valves. The heart continues to pump fluid in, but the exits are blocked.”²

Within hours, the fluid seeps through the most damaged areas of the tightly stretched skin. This can damage the epidermis, or dry into a yellow crust. Abscesses can develop under the skin as the body walls off the bacteria.² In some cases, the veterinarian will lance and drain these.

Heaves, RAO and COPD in the Horse

Heaves is a chronic, non-infectious airway condition of horses that is sometimes labeled as recurrent airway obstruction (RAO), and was formerly known as chronic obstructive pulmonary disease (COPD). This usually occurs in horses more than six years of age and is the result of an allergic reaction to inhaled particles.⁴ The allergens that cause heaves are primarily found in hay and straw. Once inhaled, an allergic reaction causes the small airways in lung tissue to narrow and become obstructed. 

Typically, one of the first symptoms observed by an owner or manager is an occasional cough. As the disease progresses, the clinical signs become more apparent and can include:

• Exercise intolerance
• An increased respiratory rate
• Nasal discharge
• Wheezing and flaring of the nostrils  

As a result of obstruction of the small airways, a horse with heaves works harder to pull air into and expel air from the lungs. The increased labor forces the horse to use its abdominal muscles during exhalation. Ultimately, the additional work results in the visible enlargement of the abdominal muscles and the formation of what is called the “heave line.”⁴ As the condition progresses, it becomes increasingly difficult for the affected horse to expel the air from the lungs at the end of exhalation and the lungs may remain over-inflated (emphysema). If left untreated, non-reversible damage to lung tissue may occur resulting in a permanent loss of lung function.

There is no cure for heaves, but protocols focused on eliminating the allergens from an affected horse’s environment can reduce or even eliminate clinical signs. When horses suffering from heaves evidence respiratory difficulties, medical treatment is recommended. It is important to realize however, that administering medication without minimizing environmental exposures usually does not provide prolonged benefits. The usual treatment for heaves is the administration of anti-inflammatory medicines such as corticosteroids and bronchodilators. These drugs are typically administered either by mouth or by injection.⁴ More recently, aerosolized corticosteroids and bronchodilators administered via aerosol have also become available for the treatment of heaves. These aerosolized drug preparations are generally more expensive than oral or injectable formulations, but the inhaled drugs are highly effective and carry a reduced risk of adverse effects.

Dexamethasone is typically used in the management of various rheumatic, dermatologic, allergic and other diseases known to be responsive to anti-inflammatory corticosteroids. Dexamethasone Solution may be used intravenously as supportive therapy when immediate hormonal response is required.

Where to buy Dexamethasone + Trichlormethiazide

Dexamethasone + Trichlormethiazide is available in the U.S. through several pharmaceutical manufacturers and through veterinary custom compounding companies. 

Please consult your veterinarian prior to beginning any treatment regimen.

FOR RX ONLY: A valid prescription from a licensed veterinarian is required for dispensing this medication.

¹Adam, E., et. al. Primary and secondary limb cellulitis in horses: 44 cases (2000–2006). Journal of the American Veterinary Medical Association. December 1, 2007, Vol. 231, No. 11, Pages 1696-1703.  

²Gobena Ameni, G. Preliminary trial on the reproducibility of epizootic lymphangitis through experimental infection of two horses. The Veterinary Journal, Volume 172, Issue 3, 2006, Pages 553-555.

³aaep.org.

⁴Tesarowski DB, Viel L, McDonell WN. Pulmonary function measurements during repeated environmental challenge of horses with recurrent airway obstruction (heaves). Am J Vet Res. 1996 Aug;57(8) 1214-1219. PMID: 8836377.