Introduction

• Cause: a form of localized streptococcal infection with systemic toxemia.
• The infection can progress from a small skin lesion to a large region of necrosis and ulceration within several hours, often with systemic signs of shock (Streptococcal Septic Shock Syndrome).
• Blunt trauma can also initiate the problem.
• Signs: characterized by rapidly advancing infection of skin and subcutaneous tissues including muscle and fat with severe local pain and high mortality.
• Progression to systemic shock syndrome can be rapid.
• DIC and multiple organic failure - respiratory, hepatic and renal occur terminally.
• Diagnosis: clinical presentation, imaging, cytology and, definitively - histopathology and bacterial culture.
• Treatment: because definitive diagnosis is based on histopathology and bacterial culture, treatment cannot be delayed - lifesaving treatment must be initiated based on a clinical diagnosis.
• Prognosis: guarded-poor.

Pathogenesis

Etiology

• Local Streptococcal infection in the skin and, especially, in the local subcutaneous fat, fascia and muscle.
• Streptococcus canis Streptococcus canis (B-haemolytic Lancefield group G) is the usual cause.Streptococcus zooepidemicus Streptococcus equi andStaphylococcus intermedius(nowpseudintermedius) have also been reported and Gram negative bacteria are possible causes.
• It is possible for spread to skin and fascia to come from a respiratory or urinary tract infection.
• Severe local tissue damage comes from bacterial toxins and tissue-damaging enzymes, especially proteases. Thrombosis of vessels can result in extensive areas of necrosis.
• Prior treatment with enrofloxacin may predispose to Streptococcal infection or bacteriophage-induced lysis of Streptococci and induction of superantigens that cause T-cell proliferation and peracute release of cytokines.
• Toxemia and cytokine stimulation cause systemic shock.
• The overlying skin may show relatively mild erythema early in the disease process.

Predisposing factors

• No controlled studies have been performed to show predispositions.

Specific

• Minor wounds from animal bites, minor trauma and veterinary intervention such as dentistry or injections, including vaccinations, have been associated with cases. These probably are more likely in younger dogs which predisposes to younger dogs having necrotizing fasciitis. Immature immunity may also be a factor.
• Prior irradiation is a recognized predisposition in humans and at least one case has been seen in a dog.
• Treatment with enrofloxacin Enrofloxacin may predispose to severe Streptococcal disease.

Pathophysiology

• An initiating traumatic event is expected but may not be found on taking the history. This may be a trivial episode, a blunt trauma or a veterinary intervention.

Timecourse

• Hours to a few days.

Epidemiology

• It seems more common in young dogs, perhaps due to minor traumas being more common.

Diagnosis

Treatment

Prevention

Outcomes