Distal limb necrosis
Synonym(s): leg necrotic septicaemia septicemia lameness lame salmonella fescue foot mould mold fungal toxin toxic toxicology poison poisonous poisoning ergotism salmonellosis
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.
Presenting signs
- Animal may be bright and well.
- Swelling of lower limb for example, pastern-hock area, in 1 or more limbs.
- Hindlimbs more commonly affected than forelimbs.
- Lameness with or without pain.
- Dry, leathery, discolored, sunken, cold skin in affected area.
- May see a line of sharp demarcation of healthy and diseased skin between coronet and fetlock
.
- Ear tips or tail may also be affected
.
Acute presentation
- Necrotic skin eventually sloughs but this may take a long time.
- If prolonged, may lead to joint involvement with separation of phalanges from metatarsal/metacarpal.
- In extreme cases, the digit may even slough off.
Geographic incidence
- Worldwide.
Age predisposition
- Calves and young animals are more susceptible to Salmonella septicemia Salmonellosis; therefore, distal limb necrosis is more commonly seen in the young.
Seasonal predisposition
- Incidence of ergotism Ergotism is more common in wet, humid, warm climates.
- Fescue foot is more likely to occur in autumn - grass toxins (Festuca arundinacea) are higher in autumn and it is more readily seen 7-10 days after turnout to affected pasture in cooler weather Plants associated with nitrate poisoning.
- The cold weather causes low blood flow to the feet and distal extremities, which exacerbates the problem.
Breed/Species predisposition
- Cattle showing Bos indicus ancestry are more likely to lose their tails if affected.
Cost considerations
- Veterinary costs: drugs and supportive treatment.
- Possible death/euthanasia of the affected animal(s).
- Lowers conception rate in breeding animals.
- Cost of treating affected pasture (see Prevention below).
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
- Especially with Salmonella spp, particularly Salmonella dublin Salmonellosis. Pressure
- Constriction by wire or other foreign body impingement Constricting foreign body: distal limb.
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.