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Poisonous Plants June 9, 2010 Beth McEvoy DVM
DISCLAIMER---I’m a vet, a farmer, no plant specialist How I managed to be asked to speak on poisonous plants
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Poisoning by plants Plant poisonings in the Northeast uncommon; usually pasture growth is lush, adequate graze Sheep and goats will naturally avoid less palatable toxic plants Dozens of potentially toxic plant species grow in our pastures, meadows, roadsides and are incorporated in our hay Sometimes conditions occur where our animals chose to eat plants they wouldn’t ordinarily eat
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Conditions contributing to plant poisonings
Low forage supplies Early spring, summer drought, fall frosts Small shoots of toxic plants easily consumed by mistake Overgrazing forces hungry animals to eat plants they normally would avoid Confinement, lack of access to browse/graze Sudden access to a single shrub or tree is tempting even if it is not very palatable Hurried grazing/browsing increases risk of ingesting poisonous plants
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Conditions contributing to plant poisonings
Poisonous plants incorporated in hay harvest Some plants are toxic only when wilted, dried or improperly stored yellow and white sweetclover Run-out fields- grasses cannot compete with weeds and unwanted species of weeds may invade Bracken fern
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Conditions contributing to plant poisonings
Curious animals Animals standing on their hind legs Escaped animals Unsanctioned access to gardens or planted fields Unavoidable bad luck happens!
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If we’re surrounded by poisonous plants, why don’t we see more poisonings?
Plant factors Condition and stage of maturity of the plant Parts of the plant that are eaten Environmental conditions where the plant is growing Chemical nature of the toxin How fast does it act? Does it accumulate in the animal over time? Availability of alternative forage
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If we’re surrounded by poisonous plants, why don’t we see more poisonings?
Animal factors: The species of animal The age, sex and general conditions of the animal How hungry How curious
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Avoiding plant toxicities
“ In general, most plant toxicities can be avoided by supplying hay and grain in times of drought, not overstocking pastures, not turning hungry animals out to forage, and preventing access of goats and sheep to ornamental plants (including trees and shrubs) and their clippings.” MC Smith DVM
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Diversity of Substances
Plants have a diverse array of specialized chemical protection against insects and herbivores The broad categories in which these chemical defenses may be placed include: Alkaloids (basic with nitrogen bound ring structure) Amino Acids Proteins Glycosides (includes cyanide linked to sugars) Acids (Oxalic Acid) Terpenes (substances contain branched 5-carbon skeleton of isoprene) Phenolics and Tannins Essential Oils Oxalic Acid Terpene Glycoside
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Diagnosis of Plant Poisoning
Diagnosis is difficult due to the lack of specificity in clinical signs and lack of characteristic post mortem lesions Few laboratory tests are available to detect plant toxins Therefore, the best way to diagnose plant poisoning is to: Identify the suspect plant in the animal’s environment, Confirm that the animal has ingested the plant, Correlate symptoms with those known to be associated with the suspected plant.
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Treatment of Plant Poisoning
Decontamination procedures Emesis Administration of activated charcoal and cathartic hastens elimination of plant from GI tract Supportive and symptomatic care Removal of plant from the animal’s habitat Specific antidotes are available for the treatment of cyanide or nitrate intoxicated animals Cyanide causes death in 15 min, tx not often possible IV sodium nitrite, sodium thiosulfate ? Nitrate converted in rumen to nitrite, changes hemoglobin, blood turns dark chocolate brown Methylene blue IV therapy reverses methemoglobin
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Plant Identification To submit plants for identification, collect the entire specimen (including roots!) Wrap wet newspaper around roots, keep in a plastic bag in a cool place Plants may be alternatively dried and pressed, although this form will take longer to process Walk your pastures and hedgerows, learn and recognize common plants
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Common pasture plants in Maine
buckwheat Alsike clover buttercup
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Common pasture plants in Maine
milkweed lupine Lambs quarters Curly dock
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Common pasture plants in Maine
Common or purple vetch St. Johnswort Rhubarb
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Common pasture plants in Maine
Plantain Queen Anne’s Lace Goldenrod
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Prunus species:Chokecherry, wild black cherry, Pin cherry
High toxicity rating Damaged leaves contain cyanide, disrupts oxygen release, cells asphyxiate Venus blood is bright red Bitter almond smell reported
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Conium spp. Poison Hemlock
Parsnip family Moderate to high toxicity rating Smooth purple spotted stem, all parts contain toxic alkaloids Signs w/in 2 hrs. CNS excitement, then depression, death
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Datura stramonium: Jimsonweed
Nightshade family High toxicity rating All parts of plant toxic esp. seeds, which may contaminate prepared feeds CNS, autonomic system effects
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Chenopodium album: Lambsquarters
Nitrate accumulator: toxicity depends on soil nitrate levels Moderate to high toxicity rating
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Solanum nigrum: Nightshades
Moderate to high toxicity rating All plant parts toxic esp. berries contain alkaloids, glycosides, atropine Poisoning signs are GI irritation, CNS depression
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Amaranthus retroflexus: Pigweed or Redroot
HIGH toxicity rating Nephrotoxin, oxylates, nitrate accumulator Requires significant consumption over several days
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Taxus spp: Japanese Yew
Very high toxicity rating Alkaloid mix taxine Quick cardiac death Yew Balsam fir spruce
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Rhodendron and Azalea also Kalmia spp.
Moderate to high toxicity rating Perennial shrubs, all parts toxic, contain grayanotoxin. GI and cardiac signs 0.2% of body weight in leaves must be ingested for signs
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Eupatorium rugosum: White Snakeroot
High toxicity rating Late summer and fall Trematol toxin
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White and Yellow Sweetclover: Mellilotus
Low to moderate toxicity rating when present in moldy hay OK to eat fresh Dicoumerol anticoagulant
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Cicuta spp. Water hemlock
Parsnip Family Cowbane One of the most poisonous plants in the eastern US Toxicity of leaves, stem decreases through the growing season, but root is always highly toxic Alkaloid cicutoxin affects CNS
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Acer rubrum: red maple ONLY HORSES affected
High toxicity rating for equines Wilted or frosted leaves toxic
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Thank you for listening.
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