Bovis ISSN 2398-2993

Foxglove toxicity

Synonym(s): Digitalis purpurea (common foxglove)

Contributor(s): Louise Cox-O’Shea, Paul Wood

Introduction

  • Cause: ingestion of any part of the foxglove plant.
  • Signs: diarrhea, cardiac arrhythmias, rapid, weak, irregular pulse, increased respiratory rate, abdominal pain or sudden death
  • Diagnosis: clinical signs and blood sample for detection of digitalis glycosides.
  • Treatment: unlikely to be cost effective, but suggestions are listed below.
  • Prognosis: dependent on quantity consumed and size of animal.

Pathogenesis

Etiology

  • Livestock are infrequently poisoned, due to the unpalatable nature of the plant, but may ingest the plant either fresh or dried in hay.
  • Some animals have been reported to actively seek the plant to graze on it.
  • Foxgloves remain toxic when dried.

Predisposing factors

General

  • Access to plants.
  • Lack of or inability to access other forage.

Pathophysiology

  • All parts of the plant are toxic, including the dried leaves.
  • The plant contains several cardiac glycosides (digoxin Digoxin, digitoxin and their genins).
  • Cardiac glycosides are negative chronotropes and positive inotropes; that is, they cause decreased frequency and increased force of contraction of heart muscle.
  • Cardiac glycosides also interfere with the cellular membrane sodium-potassium (Na+ -K+ ATPase enzyme system) pump resulting in depletion of intracellular potassium and an increase in serum potassium. This causes irregular heart activity, and eventual complete block of cardiac conduction.
  • They also have irritant effects on the gastrointestinal tract.
  • Cardiac glycosides can result in cardiac arrhythmias Dysrhythmias including first- and second-degree heart block and ventricular tachycardia. Pulse may be rapid, weak and irregular.

Timecourse

  • Clinical signs usually occur within 6 h of ingestion.
  • When poisoning occurs, the clinical signs may be severe and dramatic.
  • Death may occur rapidly or up to 36-48 h after 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.
  • Falciola C, Davanzo F, Rivolta M, Molino L & Colombo M L (2015) Nerium oleander: case report of a severe poisoning case involving numerous cows [abstract]. Clin Toxicol 53 (7), 753.
  • Wijnberg I D, van der Kolk J H & Hiddink E G (1999) Use of phenytoin to treat digitalis-induced cardiac arrhythmias in a miniature Shetland pony. Vet Rec 144 (10), 259-261 PubMed.
  • Rezakhani A & Maham M (1992) Oleander poisoning in cattle of the Fars Province, Iran. Vet Human Toxicol 34 (6), 549 PubMed.
  • Thomas D L, Quick M P & Morgan R P (1987) Suspected foxglove (Digitalis purpurea) poisoning in a dairy cow. Vet Rec 120 (13), 300-301 PubMed.
  • Mahin L, Marzou A & Huart A (1984) A case report of Nerium oleander poisoning in cattle. Vet Hum Toxicol 26 (4), 303-304 PubMed.
  • Corrigall W, Moody R R & Forbes J C (1978) Foxglove (Digitalis purpurea) poisoning in farmed red deer (Cervus elaphus). Vet Rec 102 (6), 119-122 PubMed.
  • Maclean A (1966) Suspected foxglove poisoning in sheep. Vet Rec 79 (25), 817-818 PubMed.

Other sources of information

  • James L Voss (2019) Guide to Poisonous Plants. Colorado State University. Website: https://csuvth.colostate.edu.
  • Burrows G E & Tyrl R J (2013) Toxic Plants of North America. 2nd edn. Wiley Blackwell, USA.
  • Frohne D & Pfänder H J (2004) A Colour Atlas of Poisonous Plants: A Handbook for Pharmacists, Doctors, Toxicologists, and Biologists. Timber Press: UK.
  • Cornell University Poisonous Plants Informational Database. Website: www.ansci.cornell.edu/plants.
  • Cooper M R & Johnson A W (1998) Poisonous Plants and Fungi in Britain. 2nd edn. The Stationery Office, UK.
  • Rezakhani A & Maham M (1994) Cardiac Manifestations of Oleander Poisoning in Cattle and Donkeys. In: Plant-associated Toxins: Agricultural, Phytochemical and Ecological Aspects. Eds: Colegate S M, Dorling P R, Allen J G, Huxtable C R & Panter K E. CAB International, UK. pp 534-537.

Organisation(s)


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