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.

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.

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).

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.

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).

Strategies to prevent bacterial cellulitis include:

• Close observation and care of the skin and coat, especially on the feet and legs
• Disinfection of any wound on the legs or feet
• Exercise and turnout
• Provision of dry, clean shelters
• Careful, thorough grooming and bathing with regularly sterilized equipment

Bacterial cellulitis is common in horses.

• Antibiotics
• Nonsteroidal antiinflammatory medications
• Cold water therapy/cold hosing
• Sweat wraps
• Bandaging or booting for compression
• Steroids
• Topical medications
• Physical therapy