Introduction

• Cause: septicemic cutaneous ulcerative disease (SCUD), occurs in aquatic and semi-aquatic chelonians, particularly in soft-shelled turtles. This syndrome covers ulcerative skin and shell diseases in these species. It is caused by systemic, usually Gram negative, bacterial infections. Citrobacter freundii, Beneckea chitinovora, Aeromonas hydrophila, Pseudomonas spp and Serratia spp are commonly implicated, but other bacteria may be involved. Infection is usually via a wound or abrasion and is often associated with poor husbandry and immunosuppression.
• Signs: ulceration of the plastron, carapace and skin (typically irregular, caseated and crater-like ulcers often with a rim of hyperpigmentation) alongside systemic signs such as anorexia and lethargy. Petechiae and ecchymoses are often seen in chelonians with bacterial septicemia.
• Diagnosis: consistent history and clinical signs. Cytology or histopathology showing heterophils and bacterial rods is suggestive and bacterial culture will help to show the infective organism. Blood culture can be performed when bacterial septicemia is suspected. Radiography can help assess the depth of lesions on initial assessment to guide prognosis.
• Treatment: surgical debridement, antibiotics (based on culture and sensitivity) and supportive care. Shell support/reconstruction may be required if the damage is very extensive. Correction of suboptimal husbandry is extremely important.
• Prognosis: often guarded but may have success with intensive treatment. Welfare is paramount and euthanasia may need to be considered in some cases.

Pathogenesis

Etiology

• Infection usually via a wound with Gram-negative bacteria, leading to septicemia and ulcerative dermatitis of the shell in aquatic and semi-aquatic chelonian species:
  • Citrobacter freundii, Beneckea chitinovora, Aeromonas hydrophila, Escherichia coli, Klebsiella spp, Pseudomonas spp and Serratia spp are commonly implicated, but other bacteria may be involved.
  • Indeed, it has been suggested that infections with Citrobacter freundii or Beneckea chitinovora may be the primary etiology of SCUD in aquatic turtles and pig-nosed turtles. Whether the other bacteria are the cause of the disease or simply co-infections is currently unclear.
  • Beneckea chitinovora ingestion via contaminated shellfish may be another source of infection.

Predisposing factors

General

• Affects water-dwelling chelonian species, ie exposure to bacteria in the water. Predisposition if high levels of environmental bacterial contamination, eg due to feeding the turtle in its daytime tank.
• Immunosuppression, eg due to concurrent illness or suboptimal husbandry (in particular, low temperature provision/inadequate POTZ, overcrowding and poor water quality).
• Stress.
• Abrasions on the skin and shell, eg due to inappropriate substrates or continuous soaking of the skin and shell. The latter is often caused by lack of an appropriate ‘haul-out’ basking area out of the water.

Specific

• Systemic infection, eg via a wound with specific Gram-negative bacteria.

Pathophysiology

• Trauma damages the blood supply of osteoscutes, leading to tissue damage or death allowing secondary infection.
• If untreated, septicemia, hepatic necrosis and death may ensue.

Timecourse

• Days to weeks depending on the severity of infection, environmental stressors and individual immune competence.

Epidemiology

• Often an individual issue but can be seen in groups of chelonians, eg kept in the same suboptimal conditions.

Diagnosis

Treatment

Prevention

Outcomes