ISSN 2398-2977      

Toxicity: anticoagulant rodenticide

pequis

Synonym(s): Anticoagulant rodenticide poisoning


Introduction

  • Cause:  commercial anticoagulant rodenticide products.
  • Signs:  increased coagulation times, hemorrhage.
  • Diagnosis: history of exposure, clinical hemorrhage, elevated coagulation times, detection of anticoagulant rodenticide in plasma or tissues.
  • Treatment: vitamin K1 administration.
  • Prognosis: excellent with early treatment; poor with delayed treatment in the presence of severe clinical signs.

Pathogenesis

Etiology

  • Commercial anticoagulant rodenticide products:
    • Short-acting anticoagulant rodenticides:
    • Long-acting anticoagulant rodenticides:
      • Brodifacoum.
      • Bromadiolone.
      • Chlorophacinone.
      • Difenacoum.
      • Difethialone.
      • Diphacinone.
      • Others.

Predisposing factors

General

  • Most anticoagulant rodenticide baits are grain-based.
  • Access to stored anticoagulant rodenticide:
    • Large storage containers of rodenticide bait left in horse access areas.
    • Routine use of small amounts of bait unlikely to be associated with poisoning.

Specific

Pathophysiology

  • Vitamin K1 needed for production of vitamin K-depending clotting coagulation factors in the liver.
    • Factor II (prothrombin).
    • Factor VII.
    • Factor IX.
    • Factor X.
  • Prevent vitamin K1 recycling:
    • Inhibit vitamin K1 epoxide reductase. 
      • Vitamin K1 converted to vitamin K1 epoxide during synthesis of coagulation factors. 
      • Enzyme reduces vitamin K1 epoxide to usable vitamin K1.
  • When coagulation factors become depleted, hemorrhage occurs.
    • Intrinsic pathway (factor IX).
    • Extrinsic pathway (factor VII).
    • Common pathway (factor II and X).

Timecourse

  • Increased PTT 12-24 h post-ingestion:
    • Factor IX VII has the shortest half-life in horses (Factor VII is all other species).
    • Clinical evidence of hemorrhage 24-96 h post-ingestion.

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.
  • Carvallo F R et al (2016) Cluster of cases of massive haemorrhage associated with anticoagulant detection in race horses. J Vet Diag Invest 27 (1), 112-116 PubMed.
  • Ayala I et al (2007) Fatal brodifacoum poisoning in a pony. Can Vet J 48 (6), 627-629 PubMed.
  • McConnico R S, Copedge K & Bischoff K L (1997) Brodifacoum toxicosis in two horses. JAVMA 211 (7), 882-886 PubMed.
  • Boermans H J, Johnstone I, Black W D & Murphy M (1990) Clinical signs, laboratory changes, and toxicokinetics of brodifacoum in the horse. Can J Vet Res 55 (1), 21-27 PubMed.
  • Byars T D, Greene C E & Kemp D T (1986) Antidotal effect of vitamin K1 against warfarin-induced anticoagulation in horses. Am J Vet Res 47 (10), 2309-2312 PubMed.

Other sources of information

  • • Plumb D C (2015) Veterinary Drug Handbook 8th Edition. Wiley Blackwell. ISBN: 978-0-4709-5964-0.

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