Bacterial Cellulitis in Horses

Key Takeaways

Bacterial cellulitis in horses is a dangerous infection and inflammation of the tissues beneath the skin.

Bacterial cellulitis is an emergency that requires immediate veterinary attention

• Characterized by sudden, dramatic swelling that arises in less than twelve hours, typically affecting one leg

• The affected limb is warm to the touch and extremely painful. Fever is often present. Lameness can be mild or severe. When firm pressure is applied to the swelling, the indent remains on the surface for some time (pitting)

• Diagnostic tools include physical examination, bloodwork, culture swabs, and diagnostic imaging. 

• Treatment includes intravenous antibiotics and anti-inflammatory medications

• Survival rates range between 55 and 89%

• In some cases, life-threatening complications such as laminitis or skin sloughing occur

• Chronic bacterial cellulitis requires ongoing treatment and therapy

A Closer Look: What is Bacterial Cellulitis in Horses?

Bacterial cellulitis is an emergency. Prompt, aggressive treatment within 24 hours of onset is crucial for a good prognosis. Immediate veterinary attention is required. Left untreated, bacterial cellulitis can cause permanent damage or death. In some cases, despite prompt treatment, bacterial cellulitis becomes chronic and requires ongoing treatment and therapy.

Bacterial cellulitis is classified into two categories: primary or secondary. Primary infection is diagnosed where no penetrating trauma to the limb is detectable. Approximately half of cellulitis cases fall under this category. Secondary infection is diagnosed when the initiating cause of the infection is known, for example penetrating injuries, injections, or surgery.

Risk Factors

In some cases, horses suffer from chronic bacterial cellulitis. Recurring bouts of cellulitis occur, requiring ongoing treatment. Careful management of these horses is required to prevent flare-ups. Some cases develop life-threatening complications, such as opposing limb laminitis, or thrombosis leading to skin or tissue necrosis. Some infections become severe and deep enough to require surgical drainage and debridement. In some cases, the infection involves underlying structures including bone synovial tissue and the lymphatic system, requiring long-term, intensive care. In some cases, systemic infections such as sepsis occur.

Possible Causes

Bacterial cellulitis occurs when common bacteria such as Staphylococcus spp. or Streptococcus spp. that usually inhabit the upper layers of the skin cross the barrier to deeper tissues, leading to infection. The associated inflammation causes edema (the accumulation of fluid between the layers of the skin).

Main Symptoms

The main symptoms of cellulitis include:

• Sudden, dramatic swelling • Severe pain • Lameness • Hot to the touch • Fever

• Oozing on the skin’s surface • Pitting (indent left after firm pressure is applied)

Testing and Diagnosis

In cases of suspected bacterial cellulitis, emergency veterinary care is required. Physical examination, ultrasound and other diagnostic imaging, bloodwork, and culture swab confirm diagnosis of bacterial cellulitis.

Steps to Recovery

Treatments to fight the infection include aggressive antibiotic therapy and nonsteroidal anti-inflammatory medications. In some cases, hospitalization is required to manage the infection.  Once the infection is under control, horses benefit from therapies to promote healing and reduce swelling. These include:

• Cold water therapy/cold hosing • Sweat wraps • Bandaging or booting for compression

• Steroids • Topical medications • Physical therapy

Horses with chronic bacterial cellulitis require close monitoring of all breaks in the skin. Regular exercise encourages circulation to the affected areas. Bandaging can limit swelling. Protection for the legs during transport, exercise, and competition prevent injury. In some cases, proactive antibiotic treatment is recommended when a break in the skin is identified. In cases where detection and treatment are prompt, survival rates are good (55 to 89%). Recovery occurs within a few days. In more severe cases, or cases where treatment is delayed, survival rates are lower. Horses that develop fever, are left untreated, or develop laminitis or sloughed skin are more likely to be euthanized. Horses that develop chronic bacterial cellulitis require ongoing treatment and monitoring, and in some cases suffer disfigurement (unrelievable swelling) or disability (lameness).

Prevention

Strategies to prevent bacterial cellulitis include:

• Close observation and care of the skin and coat, especially on the feet and legs • Exercise and turnout

• Disinfection of any wound on the legs or feet • Provision of dry, clean shelters 

• Careful, thorough grooming and bathing with regularly sterilized equipment

Is Bacterial Cellulitis Common in Horses?

Bacterial cellulitis is common in horses.

Typical Treatment

• Antibiotics • Nonsteroidal antiinflammatory medications • Sweat wraps • Steroids • Topical medications

• Cold water therapy/cold hosing • Bandaging or booting for compression • Physical therapy

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