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Distal limb necrosis

obovis
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Synonym(s): Dry gangrene, Ergotism, Fescue foot, Septicemia, Salmonellosis, Necrosis of extremities


Introduction

  • Cause: a deficit in local circulation. Most common causes are ergotism, poisoning by tall fescue grass or septicemia (particularly salmonella).
  • Signs: cold, dry, discolored skin in distal limbs +/- tail and ear tips.
  • Diagnosis: clinical examination.
  • Treatment: removal of causal agent, antibiotics if infective cause, supportive therapy until necrotic skin sloughs off and is replaced by healthy tissue.
  • Prognosis: guarded, slow recovery, often need euthanasia on welfare grounds.

Pathogenesis

Etiology

  • Caused by agents that damage or occlude arterioles leading to local damage to the skin in the distal extremities.

Fungal toxins

  • Parasitic fungus Claviceps purpurea (ergotism) Ergotism .
  • Fungal endophytes (ergovaline) in tall fescue; ‘fescue foot’.
  • Less commonly, Aspergillus spp Aspergillus spp and mushroom poisoning.

Secondary to general septicemia

Predisposing factors

General

  • Not common due to the improvement in modern management systems.
  • Although rye grass is widespread in distribution, it is rare that sufficient quantities are eaten in large amounts during the toxic stage to induce poisoning.

Specific

  • Grazing high risk pastures during periods of cooler weather conditions.

Pathophysiology

  • Distal limb necrosis is DRY gangrene; it is unrelated to WET gangrene:
    • Dry gangrene: arterioles damaged/occluded, venous drainage intact, sterile.
    • Wet gangrene: lymphatic/venous vessels obstructed, no drainage, putrefaction +/- infection.
  • Distal limb necrosis is caused by interference with local blood supply, namely arterioles – either damaged by trauma, pressure or toxins or obstruction by microemboli or spasm.
  • Lymphatic drainage and venous return vessels remain patent.
  • Lack of oxygen and nutrients to tissue results in necrosis of the dermis, epidermis and sub-cutaneous tissue.
  • Dead tissue then sloughs away. Underlying tissue is granulation tissue.
  • If prolonged, epiphyseal osteomyelitis, polysynovitis and arthritis may occur.
  • In extreme cases, the digit may slough off.

Timecourse

  • Distal limb necrosis is a chronic disease; skin sloughing may take several days/weeks.
  • Treatment will necessarily be prolonged.

Epidemiology

  • May affect several animals if all are exposed to a common causal agent, but generally single animals in a group are affected.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Loeb E, Toussaint J M, Rutten P M G & Koeman J P (2006) Dry gangrene of the extremities in calves associated with Salmonella dublin; a possible immune-mediated reaction. J Comp Pathol 134 (4), 366-369 PubMed.
  • Baker I (1995) Ergotism. In Pract 17 (7), 317.
  • Holliman A & Barnes J (1990) Ergotism in young cattle. Vet Rec 127 (15), 388 PubMed.

Other sources of information

  • Osweiler G D (2014) Fescue Poisoning. In: MSD Manual - Veterinary Manual. Website: www.msdvetmanual.com.
  • Radostits O M, Gay C C, Hinchcliffe K W & Constable P D (2006) Veterinary Medicine. 10th edn. Saunders Elsevier, USA. pp 666, 909, 1902-1903.
  • Science Direct (online) Festuca Search Results. Website: www.sciencedirect.com.

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