Equis ISSN 2398-2977

Toxicity: cantharidin

Contributor(s): Karyn Bischoff, Birgit Puschner

Introduction

  • Cause: cantharidin, produced by beetles in the genera Epicauta spp, Lytta spp, Tegrodera spp, and others, often present in alfalfa hay.
  • Signs: colic, oral ulceration, polyuria.
  • Diagnosis: presence of beetles in hay, cantharidin in urine or stomach contents.
  • Treatment: activated charcoal, pain control, and fluid therapy.
  • Prognosis: guarded.

Pathogenesis

Etiology

  • Cantharidin is produced by Epicauta, Lytta and Tegrodera spp:
    • Produced by male beetles.
    • Transferred to females during copulation.
  • Beetles feed on plants and larvae feed on grasshopper eggs.
  • Beetle swarm in alfalfa fields:
    • When cut alfalfa is crimped, the insects are killed and trapped in the hay.
    • Beetle distribution in the hay is not homogenous.
    • The swarms can be trapped in a few flakes or throughout.
    • Beetles often not found in remaining hay of clinically affected horses.
  • Cantharidin is very stable and may persist in hay for long periods.

Predisposing factors

General

  • Alfalfa hay in the diet.

Specific

  • More common in South Central and Southwestern US.
  • Consider pelleted rations containing alfalfa.

Pathophysiology

  • Cantharidin is a potent vesicant.

Timecourse

  • Abrupt onset:
    • Sometimes colic progresses over a few days.
    • Some animals found dead unexpectedly.

Epidemiology

  • Associated with alfalfa hay:
    • Beetles feed on flowering foliage, especially blooming alfalfa.
    • Beetles proliferate after years with high grasshopper populations.
    • Larvae feed on grasshopper eggs.

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.
  • Qualls H J et al (2013) Evaluation of efficacy of mineral oil, charcoal, and spectate in a rat model of equine cantharidin toxicosis. J Vet Intern Med 27 (5), 1175-1184 PubMed.
  • Helman R G & Edwards W C (1997) Clinical features of blister beetle poisoning in equids: 70 cases (1983-1996). JAVMA 211 (8), 1018-1021 PubMed.
  • Schmitz D G (1989) Cantharidin toxicosis in horses. J Vet Intern Med 3 (4), 208-215 PubMed.


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