Oleander (Nerium oleander) in Horses (Equis) | Vetlexicon
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Oleander (Nerium oleander)

ISSN 2398-2977

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Synonym(s): Adelfa, Rose laurel, Rosenlorbeer

Podcast: Oleander (Nerium oleander)


  • Oleander   Oleander (Nerium oleander)   is a perennial, evergreen shrub or small tree, native to southern Europe, and now widely distributed in most tropical and sub-tropical areas of the world.
  • Thrives in hot climates - used in landscaping and as potting plants.
  • Leaves are simple, lanceolate, 7.5-25.5 cm long, dark green above, leathery, with a prominent midrib and veins.
  • White, pink or red showy flowers from 2.5-7.5 cm in diameter that grow in clusters.
  • All parts of the plant are toxic, including the dried leaves.
  • Humans, livestock, dogs, cats, birds and horses are susceptible to poisoning from oleander.
  • Oleander should not be planted in or around animal pastures or enclosures. 
  • Most horses will avoid the plant unless other forage is scarce.
  • Yellow oleander, Be-still tree, Tiger apple, Lucky nut ( Thevetia thevetioides) and Thevetia peruviana, common to tropical areas, are equally toxic.


  • Contains oleandrin and neriin, cardenolides that are potent cardiac toxins.
  • Cardenolides act by interfering with the cellular membrane sodium-potassium (Na+ -K+ ATPase enzyme system) pump with resulting depletion of intracellular potassium and an increase in serum potassium. This causes irregular heart activity, and eventual complete block of cardiac conduction   →   death.
  • 40-80 mg/kg BW of dried leaves given orally causes gastrointestinal and cardiac toxicosis.
  • Signs of toxicity appear within 1-2 h of consumption.
  • Death usually results within a few hours of consumption.

Clinical signs

  • Colic   Abdomen: pain - adult  .
  • Breathing difficulty.
  • Tremors.
  • Sweating.
  • Recumbency.
  • Irregular heart rate - cardiac arrhythmias.
  • Slow or accelerated pulse.
  • Sudden death.


  • The sudden death or occurrence of cardiac arrhythmias, and evidence of the horse having access to oleander is highly suggestive.
  • Detection of cardiac glycosides in the serum, urine, tissues and stomach contents is possible using high performance liquid chromatography.



  • Guarded to poor - because of the effects of the cardiac glycosides on heart function.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Siemens L M, Galey F D, Johnson B & Thomas W P (1995) The clinical, cardiac, and pathophysiological effects of oleander toxicity in horses. J Vet Intern Med 9, 217-221.

Other sources of information

  • Knight A & Hall J (2004) The 10 Most Dangerous Plants for Horses. Equus 320, 71-81.
  • Knight A P & Walter R G (2001) A guide to plant poisoning of animals in North America. Teton New Media, USA.
  • Burrows G E & Tyrl R J (2001) Toxic Plants of North America. Iowa State University Press, USA.
  • Allison K (1999) A Guide to Plants Poisonous to Horses. J A Allen & Co Ltd. ISBN: 0851316980.
  • Cooper M R & Johnson A W (1998) Poisonous Plants and Fungi - An Illustrated Guide. The Stationery Office. ISBN: 0112429815.
  • Allison K & Day C (1997) A Guide to Plants Poisonous to Horses. British Association of Holistic Nutrition and Medicine.


  • Cornell University - Poisonous Plants Informational Database. Website: www.ansci.cornell.edu/plants.
  • Guide to Poisonous Plants. Website: www.southcampus.colostate.edu/poisonous_plants.
  • ToxicologyOnline.com. Website: www.toxonline.com.
  • Veterinary Poisons Information Service (VPIS), London Center, Medical Toxicology Unit, Avonley Road, London SE14 5ER, UK. Tel: +44 (0)20 7635 9195; Fax: +44 (0)20 7771 5309.
  • Veterinary Poisons Information Service (VPIS), Leeds Center, The General Infirmary, Great George Street, Leeds LS1 3EX, UK. Tel: +44 (0)113 245 0530; Fax: +44 (0)113 244 5849.