Bovis ISSN 2398-2993

Rhododendron poisoning

Synonym(s): Rhododendron toxicity

Contributor(s): Nicola Bates , Ben Dustan

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Introduction

  • Cause: ingestion of rhododendron nectar, leaves or stems.
  • Signs: gastrointestinal signs (regurgitation, vomiting, signs of abdominal pain), bradycardia and weakness.
  • Diagnosis: based on history of exposure, clinical signs and post-mortem findings.
  • Treatment: supportive.
  • Prognosis: guarded, particularly if aspiration pneumonia has occurred.

Pathogenesis

Etiology

  • Circumstances of poisoning include:
    • Access to pasture bordered by rhododendron plants.
    • Accidentally fed rhododendron cuttings.
    • Ingestion of rhododendron when other forage is not available.

Pathophysiology

  • Rhododendron contains several grayanotoxins in the nectar, leaves and stems  .
  • The main toxin is grayanotoxin I (also known as rhodotoxin, acetylandromedol or andromedotoxin).
  • Grayanotoxins are partial agonists that act on sodium channels of cell membranes.
  • The sodium-channel effects of grayanotoxins have positive inotropic effects and cause severe weakness and hypotension.

Timecourse

  • Signs generally start within 6 hours. 
  • Recovery usually occurs over 1-3 days, but in more severe cases recovery may take 1-2 weeks.

Epidemiology

  • Most cases of grayanotoxin poisoning occur in goats and sheep, rather than cattle but occasional cases are reported.
  • Ruminants readily eat rhododendron.

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.
  • Vargas S F Jnr, Marcolongo-Pereria, Halinksi-Silveira D, Borelli Grecco F, Buss Raffi M, Schild A L & Viegas Sallis E S (2014) Rhododendron simsii poisoning in goats in Southern Brazil. Ciencia Rural Santa Maria 44 (7), 1249-1252 VetMedResource.
  • Holstege D M, Puschner B & Le T (2001) Determination of grayanotoxins in biological samples by LC-MS/MS. Journal of agricultural and food chemistry 49 (3), 1648-51 PubMed.
  • Puschner B, Holstege D M & Lamberski N (2001) Grayanotoxin poisoning in three goats. JAVMA 218 (4), 573-5, 527-8 PubMed.
  • Tokarnia C H, Armien A G, Peixoto P V, Barbosa J D, De Farias Brito M & Döbereiner (1996) Estudo experimental sobrea toxidez de algumasplantas ornamentais em bovinos. Pesquisa Veterinária Brasileira 16, 5-20.
  • Casteel S & Wagstaff J (1989) Rhododendron macrophyllum poisoning in a group of goats and sheep. Veterinary and Human Toxicology 31, 176-177 PubMed.

Other sources of information

  • Burrows G E & Tyrl R J (2013) Toxic Plants of North America. 2nd edn. Wiley Blackwell, Ames, Iowa.
  • Kernfarm BV (2016) Buscopan Compositum Solution for Injection Summary of Product Characteristics. Available at: https://www.vmd.defra.gov.uk.

Organisation(s)


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