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ACVPM Board Review

ACVPM Board Review. Plant -Related Toxicoses. Introduction. Osweiler, GD. Toxicology. National Veterinary Medical Series. Williams and Wilkins, 1996 Fowler, M. Poisonous Plants: A Veterinary Guide to Toxic Syndromes. Iowa State University Press, 1998 (CD ROM). Plant Toxins.

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ACVPM Board Review

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  1. ACVPM Board Review Plant -Related Toxicoses

  2. Introduction • Osweiler, GD. Toxicology. National Veterinary Medical Series. Williams and Wilkins, 1996 • Fowler, M. Poisonous Plants: A Veterinary Guide to Toxic Syndromes. Iowa State University Press, 1998 (CD ROM)

  3. Plant Toxins • 2 products of plant metabolism • adjunct mechanism for plant survival • vary widely in chemical properties

  4. Factors favoring toxicoses • adverse climatic conditions • agricultural practices • animal management practices • nutrient deficiencies  pica • overgrazing inadequate forage,  weeds • thirsty or hungry animals in new location • confinement  boredom, curiosity

  5. Recognition depends on • familiarity with indigenous toxic plants • knowledge of seasonal variations in concentration of toxins • access to other resources

  6. Diagnosis • Were toxic plants consumed? • History • Examination of environment, ingesta • Compatible signs and lesions • Laboratory diagnostics • I.D. of toxic plants

  7. History • geography - range and habitat of plant • time of year - are toxic parts of the plant available? • recent changes in pasture or forage? • recent melting of snow cover, or plant growth following flooding? • overgrazing?

  8. ID of Toxic Plants • collect entire plant, including flowering parts • provide detailed location information • preserve green plants • seal in plastic bag and refrigerate • dry in press for 1-3 days

  9. General Treatment • Reduce exposure • prevent access • give adequate water and alternative feed • Detoxification • emesis or gastric lavage • activated charcoal • osmotic cathartics (unless specifically contraindicated)

  10. Prevention • allow acclimation to new pasture and provide alternative feed initially • avoid overgrazing or withholding water • don’t feed chopped or ground forages containing toxic plants • don’t allow access to areas recently sprayed with herbicides • minimize close confinement of pets

  11. Toxic Principles • Alkaloids • contain nitrogen • most bitter • Diterpene (phorbol) esters • Grayanotoxins are diterpenoid • Rhododendron, Kalmia

  12. Toxic Principles - Glycosides • toxin aka glycone linked to sugar • often not toxic until sugar hydrolyzed off • bitter, colorless, noncrystalline • 6 groups

  13. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  14. Cyanogenic Glycosides • yield hydrogen cyanide upon hydrolysis • ruminants highly susceptible • rumen contains large amounts of -glycosidase • -glycosidase hydolyzes the glycoside

  15. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  16. Cardiac Glycosides • aka cardioactive glycosides • interfere with Na+/K+ ATPase • decrease intracellular K+ • high-grade heart block • increased vagal tone • cardiac arrthymias

  17. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  18. Goitrogenic Glycosides • prevent the accumulation of organic iodide •  formation of thyroid hormones •  TSH release •  size thyroid gland (goiter was endemic in the U.S. until the advent of iodized salt)

  19. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  20. Isothiocyanate Glycosides • irritant oils • allyl isothiocyanate most common • found primarily in Cruciferae (mustard family)

  21. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  22. Protoanemonin • glycoside ranunculin  protoanemonin upon hydrolysis • volatile yellow oil • combines with sulfhydryl • strong vesicant and irritant action on skin and mucous membranes

  23. Toxic Principles - Glycosides • cyanogenic • cardiac • goitrogens • isothiocyanates • protoanemonin • saponins

  24. Saponins • produce soapy froth when shaken with water • irritant to skin and mucous membranes • nausea and vomiting if swallowed

  25. Toxic Principles • Nitrates • Oxalates • Gallotannins • Toxalbumins (phytotoxins)

  26. Oxalates • calcium oxalate • insoluble needle-like crystals • especially indoor houseplants • soluble oxalates • Na or K salts • Nitrates

  27. Toxic Principles • Nitrates • Oxalates • Gallotannins • Toxalbumins (phytotoxins)

  28. Toxalbumins • glycoproteins • highly toxic but not well absorbed from the gi tract • many animal cells contain receptors for certain toxalbumins • e.g., ricin, abrin • seeds are most concentrated source

  29. Neurotoxicants Increased CNS activity, seizures

  30. Asclepias (milkweed) • Narrow-leafed species more toxic • resinoid- galitoxin • digitalis-like cardenolides • all veg parts • cattle, sheep, horses • Dx - clinical • profuse salivation, incoordination, violent seizures, bloating/colic • arrythmias, hypotension, hypothermia, death

  31. Cicuta maculata, C. douglasii (water hemlock) • hollow purple-streaked stems, roots like cluster of small sweet potatoes • resinoid- cicutoxin, extremely toxic! • mainly in roots and base • Dx - clinical • acute onset of violent tetanic seizures like strychnine poisoning • salivation, muscle twitching, seizures, champing of jaws, coma, death

  32. Corydalis (fitweed) • hilly or mountainous W. or Appalachian states, rocky/sandy soils high pH • isoquinolone alkaloid • all plant parts • ruminants, esp. sheep • Dx - clinical • acute onset of polypnea, tremors, ataxia • periodic seizures, facial twitching, champing of the jaws • death or recovery in 24 hrs

  33. Gelsemium sempervirens (yellow jessamine) • evergreen vine, fragrant yellow, trumpet-shaped flowers, SE U.S. • gelsemine, gelseminine, and related indole alkaloids • all plant parts, honey • Dx - clinical • abdominal pain, slow respiration, muscle weakness, convulsions, hyperthermia, signs of colic • may die in 24-48 hrs.

  34. Neurotoxicants Incoordination, depression, bizarre behavior, agitation

  35. Aesculus sp. (buckeye, horsechestnut) • Aesculin - mixture of saponin glycosides • nuts, bark, leaves, twigs, pollen, nectar • cattle and horses most susceptible • Dx - clinical • incoordination, staggering, hypermetria, weakness, falling • severe gastroenteritis • nonspecific hepatic and renal congestion

  36. Astragalus (locoweed) -1 • many species • Great Plains to Rockies in dry, alkaline soil • 3 toxic fractions • fresh plants are toxic, loses toxicity as dries except for Se • cattle and horses may become habituated to locoweed and seek it out, even when good forages are available • reserpine may reduce severity in horses, may not be safe to ride

  37. Astragalus (locoweed) -2 • 3 toxic principles: • glycoside - miserotoxin, hydrolyzed in ruminants to 3-nitropropanol, releases nitrite • alkaloid - swainsonine, inhibits -mannosidase  neuronal swelling; after 2 weeks or more of ingestion, passes in milk • selenium (some sp. accumulate)

  38. Astragalus (locoweed) -3 • Clinical - miserotoxin • demyelination of posterior spinal cord  incoordination, hypermetria, ataxia, clicking of dewclaws “cracker heels” • emphysema (sheep), dyspnea, cyanosis, sudden collapse, death may occur 4-24 hrs with large doses • methemoglobinemia

  39. Astragalus (locoweed) -4 • Clinical - swainsonine • ataxia, emaciation, staggering, proprioceptive deficits • horses may become belligerent or startle violently from small stimuli • vision may be impaired • decreased lacrimation, retinal degeneration • immunosuppression • abortions mid-late pregnancy, teratogenic effects (contracted tendons) • male infertility d.t.  spermatogenesis

  40. Astragalus (locoweed) -5 • Dx. clinical plus lesions • emaciation, congestive right heart failure, pulmonary emphysema, congestion of liver and lungs • myelin degeneration and neuronal vacuolation

  41. Centaurea solstitialis, C. repens(yellow star thistle, Russian knapweed) -1 • C. solstitialis w. of Rockies • C. repens w. of Missouri R. • toxic principle unknown • all parts, dried plants toxic • toxicosis after 30d consumption • horses most susceptible, also donkeys and mules • neurologic lesions permanent • treatment is ineffective

  42. Centaurea solstitialis, C. repens(yellow star thistle, Russian knapweed) -2 • Dx - clinical signs and lesions • hypertonicity of facial muscles (may be unilateral), partial to complete paralysis of tongue, chewing motions without swallowing, inability to eat or drink normally  emaciation • nigropallidal encephalomalacia • ischemia and necrosis of globus pallidus and substantia nigra

  43. Ipomea (morning glory) • heart-shaped leaves, trumpet flowers, vining • lysergic acid and other indole alkaloids (lysergic acid diethylamide = LSD) • seeds major source, but whole plant toxic • Dx - clinical • nausea, mydriasis, hallucinations, decreased reflexes, diarrhea, hypotension • bizarre behavior, barking, disorientation

  44. Neurotoxicants CNS depression

  45. Eupatorium rugosum (white snakeroot) • flowers Sept.-Oct. • east central and northeast US forests • true toxic principal not identified (formerly trematol or trematone) • veg parts toxic • toxin passed in milk and may poison nursing animals or babies - early settlers died of “milk sickness” • toxin readily detectable

  46. Eupatorium rugosum(white snakeroot) -2 • Dx - clinical, lesions, lab • horses • depression, weakness, congestive heart failure, tremors, posterior weakness within several days of ingesting plant • CHF, myocardial degeneration, necrosis, fibrosis • hepatic necrosis and lipidosis possible • cattle • depression, ataxia, muscle tremors about face, neck, flank, hind quarters, coma and death • constipation, salivation, ketone or acetone on breath • hepatic congestion, lipidosis, NO myocardial necrosis

  47. Isocoma wrightii (rayless goldenrod) • formerly known as Haplopappus heterophyllus • low moist areas, SW U.S. • trematol or trematone • clinical signs like white snakeroot, except myocardial lesions in horses not described

  48. Stipa robusta (sleepy grass) • perennial with distinctive twisted awn on flowers and seeds • SW U.S. • toxic principle unknown • neurologic depression main effect • mainly horses affected, cattle resistant • moderate to severe CNS depression may progress to recumbency

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