Vitamin K Deficiency

Introduction

The absolute or relative deficiency of vitamin K can give rise to defective coagulation. Anticoagulant rodenticide toxiticy is one of the most common causes of acquired coagulopathy in small animals. Warfarin itself has a short half-life and a fairly low toxicity in non-rodent species, so unless large or repeated doses are consumed clinical bleeding is rare. However, the second generation anticoagulant rodenticides are far more potent, and it is possible for a domestic animal to acquire secondary poisoning by ingesting a poisoned rodent¹. Dogs are most commonly effected, but predator species such as cats and owls do occasionally suffer from secondary poisonings.

The clotting factors - factor VII, factor XI and factors II and X in the extrinsic, intrinsic and common pathways respectively are dependent on Vitamin K when activated by the coagulation cascade.

Other Causes of Vitamin K deficiencies

Malabsorption syndromes and sterilisation of the gastrointestinal tract by prolonged antibiotic usage will also result in the depletion of vitamin K-dependent clotting factors². In herbivores, fungi growing on poorly prepared hay or silage containing sweet vernal grass or sweet clover may break down natural coumarins in the plants to form dicoumarol and cause poisoning.

Replacement of Vitamin K

Vitamin K₁ is available as a subcutaneous treatment for cases of rodenticide poisoning. Alternatively, whole blood or plasma transfusion provides vitamin K dependent clotting factors, which can control symptoms in severe acute cases.

References

1. Campbell, A (1999) Common causes of poisoning in small animals. In Practice, 21(5), 244-249.
2. Tilley, L P and Smith, W K (2007) Blackwell's Five Minute Veterinary Consult: Canine and Feline (Fourth Edition), Blackwell.