Page 10 - 28 September 2012

It is reported that roughly 80-90% of horses recover from cellulitis.
by Bonnie Barr VMD, Dipl. ACVIM
Cellulitis is diffuse inflammation and infec- tion of the subcutaneous tissues. In horses cellulitis most commonly involves the limbs,
although it may occur in other areas of the body. Commonly the dermal and subcutaneous layers of the tissue are affected although deeper more severe cellulitis can occur. Lesions can spread rapidly and dissect along tissue planes with devitalization and loss of skin. The initial symptoms include acute swell-
ing and lameness that involves one or more limbs. The entire limb rapidly becomes two to three times the normal size and becomes hot and painful to the touch. Cellulitis occurs more often in the hind limbs than the front limbs. Accompanying systemic signs include increased rectal temperature and heart rate.
Bloodwork often will reveal an increased white blood cell count and fibrinogen. An ultrasound of the limb may identify a localized fluid pocket that can be aspirated for culture, although sometimes the ultra- sound just confirms the diagnosis of cellulitis. If there is a deep wound, a specimen can be obtained for cul- ture. Radiographs may be performed to rule out bony related causes for the lameness and swelling. Cellulitis is usually caused by bacteria entering into the con- nective tissue. A majority of the time an underlying cause is not determined or the wound may be small and superficial. Cellulitis often occurs where the skin has previously been broken from cuts, scrapes, bruises or insect bites resulting in inoculation of normal skin bacteria or exogenous bacteria. Normally the skin has many types of bacteria living on it, but where there is a break in the skin, bacteria can enter the body and cause infection and inflammation. Cellulitis can also be secondary to recent injections of the limb, surgery or trauma. The most common bacteria isolated are Staphylcoccus aureus and Streptococcus species. Other bacteria occasionally isolated include E. coli, Actinobacillus sp, Enterococcus sp and Pseudomonas sp. It is often not possible to isolate a causative agent.
Treatment involves broad-spectrum antimicrobials such as penicillin and gentamicin or trimethoprim- sulfadiazine. Once the culture results are available, antimicrobials might be switched based on the susceptibility pattern of the bacteria isolated. Non- steroidal anti-inflammatory agents, such as Bute or Banamine, are administered for pain and inflamma- tion. Hydrotherapy, bandages and hand-walking can also help to reduce the swelling. Horses with deep seeded infections, devitalized skin or poor response to
medical treatment may require surgical debridement or drainage. Possible secondary complications include laminitis in the opposite limb, thrombosis of vessels in the affected limb, extensive tissue necrosis with loss of skin or lymphangitis.
In the literature it is reported that roughly 80-90% recover. Horses that recover rarely regain the original contour of the limb and seem to be predis- posed to re-occurrence. Prevention includes such measures as carefully clipping long hair on the legs and keeping them clean and dry. Avoid abrading the skin when cleaning the legs thus use soft brushes and sponges. Frequent bathing may predispose the skin to drying and chapping, thus frequent bathing should be avoided or the limbs should be carefully dried afterwards. Because bathing equipment may act as a fomite for the causative bacteria, it is best to clean the equipment on a daily basis and, if the horse is prone to cellulitis, have separate bathing equipment for that horse. Finally wounds should be properly treated by a veterinarian.
Hind limb swollen from cellulitis.
CELLULITIS
Sudden swelling and pain could be cellulitis.
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SPEEDHORSE, September 28, 2012
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