VET 406 Toxic Plants Flashcards
When are grazing animals more likely to eat toxic plants?
When stressed e.g. driven through pastures with poisonous plants, thirsty, hungry, handled
How to diagnose plant poisonings?
History, evidence of ingestion, identifying plant on farm visit, clinical signs, consistent gross and histologic findings, response to therapy, confirmation in the analytical toxicology lab
-diagnosis can be difficult bc signs can be non-specific or plant may be gone when signs manifest
Plants affecting the nervous system
poison hemlock, lupine, tobacco, yellow star thistle (1st 3 are neurotoxic and teratogenic), cyanide containing plants
Poison hemlock scientific name
Conium maculatum
Lupine scientific name
Lupinus spp.
Tobacco scientific name
nicotiana spp.
Yellow Star Thistle scientific name
Centaurea spp
Poison Hemlock Characteristics
4-6 ft tall, hollow stems with purple spots, root is like a carrot, leaves are coarsely toothed with a fernlike appearance, flowers in compound umbels small and white, strong odor (like mouse urine)
Tobacco characteristics
N. gluaca= tree tobacco: tubular/yellow flowers, shrub/small tree, bluish green alternate leaves, leaves/stems have white powder that rubs off easily,
Lupine Characteristics
many species, 3 feet tall, white or purplish flowers around main axis, fruit is multi-seeded pod, palmately compounded leaves
Neurotoxic/teratogenic toxic principle (poison hemlock, tree tobacco, lupine)
-Alkaloids act on autonomic nervous system by mimicking the action of acetylcholine
Neurotoxic/teratogenic symptoms (poison hemlock, tree tobacco, lupine)
-neurotoxic: shaking, twitching, staggering, paralysis, convulsion, heavy breathing, coma, death
-teratogenic: immobilization of fetus, cleft palate, scoliosis, other congenital defects
Poison hemlock toxin, toxicity, species affected
coniine (alkaloid)
-toxic in fresh plant, hay and seeds
-cattle and pigs mainly (and other grazing animals)
Nicotiana spp. toxin, toxicity and species affected
anabasine (alkaloid)
-toxic when dried or fresh
- cattle, sheep, goats, pigs
Lupinus spp. toxin, toxicity, and species affected
ammodendrine
-dried and fresh toxic, seeds are most toxic
-cattle (teratogenesis), sheep (acute poisoning)
What is the lab diagnosis for poison hemolock, nicotiana spp., and lupinus spp.?
alkaloids in urine or GI contents
When are teratogenic effects seen in gestating animals for poison hemlock, tree tobacco, lupine?
Varies based on species in what gestation period (ex pigs 30-60 are very susceptible to poison hemlock)
Poison Hemlock, Tree Tobacco, Lupine Treatment
- no specific treatment
- in acute poisoning: activated charcoal, cathartics, careful monitoring
- if survive acute poisoning full recovery is possible
- prevent by removing these plants from pastures
Heteromeles asbutifolia (Toyon, tollon, christmas holly, christmas berry) type of toxin
Cyanide
Cyanide containing plants
-sorghum species: sudan grass, etc
-prunus spp.: chocke cherries
- triglochin spp.: arrow grass
- malus spp.: crab apple leaves
- eucalyptus cladocalyx: sugar gum
- amelanchier alinifolia: service berry
Where are cyanogenic glycosides found (glycosides)?
- leaves, fruit, seeds of mature fruit
- newly developing leaves
Cyanogenic glycosides (cyanide) mechanisms
-hydrolysis of beta-glucosidase yields hydrogen cyanide
- this happens in the GI tract and can happen in plant when stress (frost, wilting, etc)
- free hydrogen cyanide is highly poisonous to all animals
- absorbed free cyanide binds to iron in cytochrome oxidase preventing normal enzymatic action and inactivates cellular respiration
- oxygen saturated hemoglobin can’t release oxygen so get cherry red blood
Cyanide clinical signs and diagnosis
-death within 1-2 hours after lethal dose
- labored breathing, frothing, ataxia, muscle tremors, convulsions
- bright red MM initially then turn blue terminally
-Diagnose: check color of blood, test blood/tissue for cyanide (protect sample from heat because cyanide can volatize)
Cyanide treatment
-Antidote available: sodium nitrate and sodium thiosulfate
- traps cyanide before can make methemoglobin
Yellow Star Thistle (Centaurea solstitialis) and Russian Knapweed (Centaurea repens) toxicity
- both only affect horses and require large intakes over weeks to months
-fresh and dried plants are toxic - toxins are not definitely determined (lactones)
-destroys dopaminergic neurons resulting in “Equine nigropallidal encephalomalacia” (ENE)
Yellow Star Thistle (Centaurea solstitialis) and Russian Knapweed (Centaurea repens) clinical signs
- “chewing disease”: continuous chewing, frothing, difficulty swallowing food
-open mouth, frequent yawning
-drinking dip whole head in bucket and then tip head back
-ulceration of mouth - dies of starvation
- diagnosed by MRI
Plants affecting the Cardiovascular System
-Nerium oleander: oleander (top toxicant of large animals in California)
- rhododendron spp.: Azalea
- persea americana: avocado
- taxus spp.: Yews
(similar to Oleander: Foxglove, summer pheasant’s eye, cardiotoxic milkweed, Lilly of the valley)
Diagnosis of Oleander Poisoning
- identification of leaves in ingesta (often mistaken for eucalyptus)
- test for oleandrin
Oleander Toxicity and Clinical Signs
-toxic in pretty much all animals
-all parts dried and fresh are toxic
-minimum lethal dose about 5 leaves
- clinical signs happen with a few hours: diarrhea, depression, anorexia, excess salivation, bradycardia, tachycardia, arrhythmias, sudden death, kidney failure (necrosis in kidneys)
Oleander Treatment
-No specific treatment
- active charcoal
- maybe atropine or other meds for the arrhythmias (depends on type of arrhythmia)
-avoid calcium and potassium containing fluids
- guarded prognosis
Mechanisms of cardiac glycosides
- many different types but generally inhibits sodium- potassium pumps in the heart and skeletal muscle, and as sodium accumulates fail to pump out calcium and get mineralization in the heart
- toads have similar mechanisms
Grayanotoxins (cardiovascular toxin) are found in
- the heath family (ex rhododendron, azalea, rosebay and many more)
-highest concentrations in the leaves but also in flowers, nectar and stems