ISSN 2398-2969      

Cardiotoxic plant poisoning

icanis
Contributor(s):

Nicola Bates


Introduction

  • Rare.
  • More common in young dogs and puppies.
  • Cause: ingesting of toxic plants Poisonous plants: overview.
  • Signs: arrhythmias and gastrointestinal signs.
  • Diagnosis: history and signs.
  • Treatment: controlling arrhythmias and activated charcoal to prevent further absorption.

Pathogenesis

Etiology

Common plants include
  • Foxglove (Digitalis purpureaFoxglove (Digitalis pupurea).
  • Lily of the valley (Convallaria majalisLily of the valley (Convallaria majalis) - 3 cardiac glycosides of which convallotoxin is the most important.
  • Spindle tree (Euonymus europaeus).
  • Oleander (Nerium oleanderOleander (Nerium oleander).
  • Rhododendronspecies Rhododendron including azaleas - contains grayanotoxins,
  • Pierisspecies - contains grayanotoxins.
  • White Bryony (Bryonia dioicaWhite bryony (Bryonia dioica).
  • Bluebell (Hyacinthoides non-scripta).
  • Solomon's seal (Polygonatum multiflorum) - contains convallamarin.
  • Hellebore species Stinking hellebore (Helleborus foetidus).
  • Privet (Ligustrum species) Privet (Ligustrum spp) - especially in berries.
  • Laburnum (Laburnum anagyroidesLaburnum anagyroides contains a quinolizidine alkaloid called cytisine which causes a reduction in intracellular potassium and hence high atrioventricular block:
    • All parts of the tree contain the toxin especially the bark and seeds.
    • Some alkaloids have actions on the heart.
  • Yew (Taxus baccataYew (Taxus baccata) contains taxine alkaloids which cause a rapid, weak pulse.
  • Monkshood, Wolf's bane (Aconitum napellusMonk's-hood (Aconitum napellus) is initially stimulatory then depressive causing a slow irregular pulse:
    • Poisoning by monkshood can occur through ingestion with the lethal dose being about 5 g/dog, or by absorption through the skin.
  • Toxic fungi Mushroom poisoning :
    • Muscarine-containing fungi can cause a perspiration, salivation and lacrimation syndrome:
  • Blood pressure and heart rate are decreased.
  • Ergot poisoning in the chronic form causes gangrene of the extremities due to peripheral vasoconstriction.

Pathophysiology

  • Over 400 cardiac glycosides have been identified.
    • A cardiac glycoside consists of one or more monosaccharides and a glycone.
    • The sugar enhances cardiac activity by affecting lipid solubility and hence cell penetrability.
    • Hydrolysis releases the glycone which slows the heart and increases the force of contractility.
  • Grayantoxocins bind to sodium channels of cell membranes resulting in activated cells maintained in a persistent state of excitation and depolarisation.
  • Other toxic compounds in plants can also have effects on the heart.

Timecourse

  • Signs occur within 4-12 h of ingestion and can last for 2-3 days.
  • If lethal doses are absorbed, death occurs in 12-24 h.

Diagnosis

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Treatment

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Atkinson K J, Fine D M, Evans T J, Khan S (2008) Suspected lily-of-the-valley toxicosis in a dog. J Vet Emerg Crit Care 18 (4), 399-403 VetMedResource.
  • Milewski L M, Khan S A (2006) An overview of potentially life-threatening poisonous plants in dogs and cats. J Vet Emerg Crit Care 16 (1), 25-33 VetMedResource.
  • Gwaltney-Brant S M, Rumbeiha W K (2002) Newer antidotal therapies. Vet Clin North Am Small Anim Pract 32 (2), 323-339 PubMed.
  • Cooper M R & Johnson A W (1998) Poisonous plants and fungi in Britain - animal and human poisoning. The Stationery Office 2nd edn, pp xviii + 398 pp VetMedResource.
  • Clark R F, Selden B S, Curry S C (1991) Digoxin-specific Fab fragments in the treatment of oleander toxicity in a canine model. Ann Emerg Med 20 (10), 1073-1077 PubMed.
  • Evans K L, Cook J R (1991) Japanese yew poisoning in a dog. JAAHA 27 (3), 300-302 VetMedResource.
  • Moxley R A, Schneider N R, Steinegger D H, Carslon M P (1989) Apparent toxicosis associated with lily-of-the-valley (Convallaria majalis) ingestion in a dog. JAVMA 195 (4), 485-487 PubMed.
  • Carmichael M A (1987) Suspected foxglove poisoning. Vet Rec 120 (15), 375 PubMed.
  • Leyland A (1981) Laburnum (Cytisus laburnum) poisoning in two dogs. Vet Rec 109 (13), 287 PubMed.
  • Clarke M L, Clarke E G, King T (1971) Fatal laburnum poisoning in a dog. Vet Rec 88 (7), 199-200 PubMed.
  • Trautvetter E, Kasbohm C, Werner J (1969) Oleander poisoning with respiratory AV-block in a dog. Berliner und Munchener tierarztliche Wochenschrift 82 (16), 306-308 PubMed.

Other sources of information

  • Burrows G E & Tyrl R J (2013)Toxic Plants of North America. 2nd edn. Ames, Iowa, John Wiley and Son.
  • Osweiler G, Hovda L R, Brutlag A G, Lee J A (eds) (2011)Blackwell's Five Minute Veterinary Consult Clinical Companion. Small Animal Toxicology.Ames, Iowa.
  • Mukai M, Russell N, Boyd R, Doescher B, Poppenga R H (2009)Unusual cases ofNerium oleandertoxicosis: A dog and sea lion.American Association of Veterinary Laboratory Diagnosticians (AAVLD), 52nd Annual Conference Proceedings, San Diego, California.

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