Toxic Plants Flashcards
Larkspur (Delphinium spp) spp susceptibility
Cattle most susceptible
Sheep and horses also affected
Larkspur (Delphinium spp) Toxic pathogenesis
Curare-like blockade of neuromuscular junctions— reversibly binding to nictonic acetylcholine receptors
Larkspur consumption can also enhance the toxicity of another range plant
Death camas (Zigadenus spp)
Larkspur (delphinium spp) clinical signs
Sudden death—3 hours post consumption
—> excitability, mm tremors, stiffness, staggerings & basewide stance or kneeling position (cattle), bloat regurge (ruminants) constipation, mmild GI irritation, venous congestion & aspiration pneumonia
Larkspur toxicosis diagnosis
Identify pieces of larkspur in the upper GI tract
Larkspur toxicosis treatment
-relieve bloat
-IV physostigmine
—> neostigmine not as effective
Larkspur ingestion/toxicosis prevention
- sheep most tolerant and can reduce plant density
- lithium chloride administration
- insect control with larkspur myrid (hoplamachus affiguratus)
Cyanogenic plants clinical signs
SUDDEN DEATH
Rarely: resp distress, rapid breathing, bloat, salivation, mm twitching, staggering, mydriasis, cardiac arrythmias, convulsions
Cyanogenic plants pathogenesis
Cyanide blocks molecular oxygen transfer in cytochrome oxidase systems in mitochondria causing tissue anoxia
Ruminants are more susceptible to cyanogenic plants because
Rumen microorganisms readily release cyanide from the cyanogenic glycosides
Cyanogenic plants post mortem findings
- cherry red venous blood
- bitter almond odor— rumen contents
- hemorrhages in multiple organs
Cyanide detection post mortem
Heart, brain, skeletal mm or rumen contents
Factors that increase the cyanogenic potential for toxicity
Wilting
Frost
Drought
Other damgage to plant
Cyanogenic plant tox treatment
- sodium thiosulfate/sodium nitrate mixture (not approved in food animals)
- vinegar orally
Examples of CROPS with the potential to accumulate nitrates
Barley (Hordeum spp) Beets (Beta vulagris) Corn (Zea mays) Flax (Linum spp.) Kale (brassica oleracea) Oats (Avena spp) Pearl millet (Pennisetum typhoides) Rape (Brassica napus) Rye (Secale cereale) Soybeans (Glycine max) Sunflower (Helianthus annuus) Turnips Triticum aestivum)
Examples of FORAGES with potential to accumulate nitrates
Alfalfa (Medicago sativa) Barnyard grass (Echinochloa spp) Buttong rass (Dactyloctenium radulans) Johnson grass (Sorghum halepense) Sudan grass (Sorghum vulgare) Sweet clover (Melilotus spp.) Tall fescue (Lolium arundinaceum)
Examples of WEEDS that can accumulate Nitrates
Canada thistle (Circsium arvense) Cheese weed, mallow (Malva spp) Dock (rumex spp.) Field bindweed (Convolvulus arvensis) Fireweed (Kochia spp.) Goldenrod (Solidago spp.) Jimsonweed (Datura stramonium) Kochia (summer cypress) *Kochia scoparia) Lambsquarters (Chenopodium spp) Nightshades (solanum spp) Pigweed (Amaranthus spp) Ragweed (ambrosia spp.) Russian thistle (salsola kali) Smart weed (Polygonum spp.)
Triggers for NITRATE accumulation in plants
— photosynthesis impaired by shade or prolonged cloudiness or excessive nitrogen applied to plants (fertilizers) Others: -drought -frost -hail -herbicide application
Characteristic clinical signs of NITRATE toxicity
Chocolate brown mucous membranes & blood
What is the cause of chocolate brown mucous membranes in nitrate toxicosis?
Ruminants— ingested nitrates converted to nitrites & ammonium in forestomaches
—>absorbed nitrites trigger oxidation of ferrous irone in hemoglobin— produces METHEMOGLOBIN
Methemoglobinemia in nitrate toxicity results in pathogenesis that leads to what clinical signs
Vasodilation & hypotension
—> hypoxia, dyspnea, exercise intolerance, death, fetal stress, subsequent abortion, stillbirths &/or weak neonates
Mares with nitrate toxicity
Produce neonates with congenital hypothyroidism
OR abortion
OR dysmature foal after prolonged gestation
(Mandibular prognathism, flexural deformities of forelimbs, secondary rupture of common digital extensor tendon just above the carpus, poorly ossified cuboidal bones, poor immune function)
Treatment of nitrate toxicity
Methylene blue (prohibited in food animals) Mineral oil/vinegar— NGT
Locoweed and milkvetch can cause 4 different toxic syndromes
- Sudden death (from methemoglobinemia)
- Respiratory syndrome w/ emphysema like signs (most commonly sheep)
- Neurologic signs
- Selenium toxicosis
The toxin swainsonine is produced by
Endophyte (Undilum oxytropis)
Swainsonine is produced in what part of the plant (seed/plant)
seeds
Swainsonine pathogenesis
Creates lysosomal storage disease
—> alpha mannosidase is inhibited resulting in swelling of axonal hillocks & grwoth of new dendrites & synapses in severe locoweed cases (nonreversible change)
Clinical neurological signs of locoweed intoxication
Depression, incoordination & progress to aberrant behavior, aggression, circling, weight loss & eventually death
Bracken fern toxic principle
Ptaquiloside
Jimsonweed thornapple toxic principle
Tropane alkaloids
Johnson grass toxic principle
Hydrocyanide
Lupines toxic principles
Piperidine, quinolizidine
Milkvetches toxic principle
Miserotoxicin
Ryegrass toxic principle
Lolitrem B
Sudan grass toxic principle
Hydrocyanide, nitrates
Milkvetch spp: Astragalus toxic pathogenesis
Beta-D-glycosides converted to 3-nitro-1-propanol (miserotoxin) nit eh rumen and subsequently changed to the toxic compound 3-nitropropionic acid in liver
Diagnosis of locoism
Based on:
- clinical signs
- swainsonine and/or alpha mannosidase in serum
- vacuolation of peripheral lymphocytes
- vacuolation of many tissues— esp. brain and liver
Day blooming jasmine (cestrum diurnum) induces what pathogenesis in ruminants/cattle
Calcinosis in horses and cattle by calcinogenic glycosides converted to vitamin D-like compounds
Cestrum diurnum location
Southeastern US & tropical countries
White snake root effects which age of cattle and why?
Does not affect adult cattle, but causes clinical signs in mild-fed calves
(C/S of msk disease)
Summer Pasture-Associated Myositis and Equine Atypical Myopathy caused by ingestion of which plant
Box elder seeds from female trees (Acer negundo)
Toxic principle in box elder seeds
Hypoglycin A
Pathogenesis of Box elder
Hypoglycin A metabolized to methylene cyclopropyl acetic acid (MCPA)— potent inhibtor of multiplle acyl-CoA dehydrogenases.
Lack of these enzymes causes:
*damages mitochondria
*impairs lipid meatbolism w/in mm cells
Cell death
4 important plants with toxins that damage the myocardium and cause mortality in large animals
- yew (Taxus spp.)
- avocado ( Persea americana)
- death camas (Zigadenus spp. )
- summer pheasant eye (Adonis spp.)
Pathogenesis of Red Maple leaf toxicosis
Oxidative damage to erythrocytes & acute Heinz body anemia or methemoglobinemia
Clinical signs of red maple leaf toxicosis
Weakness Tachycardia Tachypnea Icterus Hemoglobinuria
Plants that cause a thiamine deficiency the cause neurological signs in horses
- Thiaminase enzymes in bracken fern (Pteridium aquilinum)
* horse tail (Equisetum spp)
Plant that causes enzootic hematuria in cattle
Bracken fern (Pteridium aquilinum) ** causes cancerous the changes in urinary tract
Ptaquiloside in bracken fern through what mechanism, causes what consequently
Sesquiterpene glycoside responsible for detrimental effects on bone marrow and neoplastic changes in the bladder and upper GIT
What plant is associated with upper digestive tract squamous cell carcinoma and bovine papillomavirus type 4
Bracke fern (P. Quilinum)
Alsike clover produces what 2 syndromes in horses:
- Hepatic encephalopathy
2. Photosensitization
Examples of plants that cause damage to biliary cells leading to secondary photosensitization as the primary clinical sign
Agave (Agave lechuguilla) Bear grass or sacahuista (nolina texana) Bos asphodel (Narthecium ossifragum) Kleingrass and switch grass (Panicum spp.) Puncture vine (Tribulus terrestris)
Examples of plants that contain Pyrrolizidine alkaloids
Groundsel (Senecio spp) Heliotrope (Heliotropium spp) Houndstongue (cynoglossum officinale) Kochia (Kochia scoparia) Paterson’s cursse (Echium platnagineum) Rattlebox, rattlepod Tansy ragwort (Senecio jacobaea) Tarweed, fiddleneck (Amsinckia spp.) Viper’s bugloss (Echium vulgare)
Which spp are most susceptible to pyrrolizidine alkaloids?
Cattle
Horses
Crotolaria spp causes what in horses
Pyrrolizidine alkaloids
Liver failure & fibrosing pulmonary alveolitis
Ponderosa pine (Pinus ponderosa) needles and bark, when consumed in which term in pregnancy & cause what?
— third trimester
—abortion & premature delivery in cattle in western USA/canada
Pathogenesis of Ponderosa pine ingestion
Isocupressic acid, abortifacient compound, rapidly metabolized to agathic acid in rumen
—>vasoconstrictive ffect on uterine vessels leads to uterine inertia, abortion & freq dystocia and/or retained placenta
Examples of phytoestrogens
Alfalfa
Clovers (some types, produce coumestrol)
Soybeans (isoflavones)
Cause of crooked calf disease (problem in range cattle)
Lupine ingestion during early gestation to midgestation in ruminants
Lupine ingestion in mid to late gestation causes what musculoskeletal deformities
Arthrogryposis Kyphosis Scoliosis Roticollis Clefft palate
Teratogens identified in lupine
Anagyrine ( a quinolizidine alkaloid)
Ammondendrine (piperadine alkaloid)
Teratogenic effects of poison hemlock are greatest in which spp:
Cattle
Pigs
Ingestion of which plants in early gestation result in abortion and birth of cyclopic lambs:
False hellebore Skunk cabbage (Veratrum spp)
Goitrogenic effects may be observed from plants containing:
Excessive iodine (ie: seaweed)
Thiocyanates (white clover)
Glucosinolates (brassic spp., kale, turnips, canola seeds)
Congenital hypothyroidism in equine neonates can be caused by ingestion of
High nitrate forages
Or plants with goitrogenic effects
Many grass spp can be infected with endophytes such as
the most economically important
Fescue (lolium spp) infected with Neotyphodium coenophialum
Ergot (Claviceps spp) infected forages and grains produces what appearance of the plants:
Dark fungal sclerotia (ergot bodies) shaped like seeds readily visible in the plants seed head in pasture, hay or contaminated grains
What is the most economically important endophyte?
Fescue (Lolium spp) infected with Neotyhpodium coenophialum)
What is the most prevalent ergopeptine in endophyte infected tall fescue that is responsible for the most signs associiated with fescue toxicosis?
Ergovaline
Endophyte infection of fescue provides what advantages
Increased resistance to drought, insects, parasitic nematodes & herbivores
Species susceptibility to Ergot alkaloids
Horses (highest) Cattle Sheep Goats Camelids
Pathogenesis of Ergot alkaloids (ergovaline)
Vasoconstrictive effects (alpha 2 adrenergic agonist) &/or depress secretion of prolactin via effects on lactotropic dopamine (D2) receptrs in the adenohypophysis of the pituitary—> resulting in decreased steroid genesis= decreased progresterone production by the corpora lutea & relaxin
Ruminants are less susceptible to ergot alkaloids because:
Ruminants placenta produces relaxin (less impact on readiness for parturition)
Grasses infected with Claviceps paspali produces neurologic signs associated with
Gamma-aminobutyric acid inhibition
Clinical abnormalities attributable to ergot and endophyte infections of grasses detected in which regions of the US
Warm, wet climates of Southern US— endophytes
Cool, wet springs of NW US—- ergot
Ergot alkaloid and endophyte toxicity can result in what clinical sign in the Winter
Gangrene of distal extremities & amness
Ergot alkaloid and endophyte toxicosis can result in what clinicla signs in summer/heat
Heat stress
Hyperthermia
failure of heat dissipation in through the skin
Ergot alkaloid clinical signs in pigs
Agalactia
Abortion
Clinical signs of Ergot alkaloids/endophyte tox in mares
Faluire of udder development Agalactia Prolonged gestation Placental abnormalities Dystocia Decreased milk production Subfertility
Diagnosis of Ergot alkaloids & endophytes tox
C/s and consumption of infected feed
High performance liquid chromatography (HPLC)
Examples of plants that cause predominantly respiratory signs in large animals
Perilla mint (Perila frutescens) Sweet potatoes (Ipomoea batatas) damaged by fusarium spp molds
Pathogenesis of Perilla mint (perilla frutscens)
Perilla contains ketones & related furan compounds—> bioactivated in the lung
—> atypical interstitial pneumonia & acute respiratory distress
Toxins that cause atypical interstitial pneumonia & acute respiratory distress
Sweet potatoes ( Ipomoea batatas) damaged by Fusarium spp Perilla mint (Perilla frutescens)
Acute bovine pulmonary emphysema & edema may occur following ingestion of forages high in:
Tryptophan
—> typically immature summer grasses
Acute bovine pulmonary emphysema and edema pathogenesis
Forages high in tryptophan
—> rumen bacteria convert tryptophan to 3-methylindole—> further metabolized to a lung toxicant
Prevention of acute bovine pulmonary emphysema and edema
- gradually introduce cattle to grasses high in tryptophytan
- monensin or tetracycline in feed for a week before & 2 weeks after turnout on pasture (refer to regulations in veterinary feed directive)
Pathogenesis of photosensitization
-sunlight triggers an oxidative reaction with photoreactive, polyphenolic compounds absorbed form the digestive trac tin areas of unpigmented skin
—>leading to inflammation, cellular necrosis & sloughing of skin
Common plant sources of primary photosensitization
St. John’s Wort (Hypericum perforatum) Buckwheat (Fagopyrum esculentum) Dutchman’s breeches (Thamnosma texana) Bischops weed (Amni majus) Rain lily (Cooperia pedunculata) Spring parsley (Cymopterus watsonii) Giant hog weed (Heracleum mantegazzanium) Cow parsnup (Heracleum spp)
Plants that commonly accumulate selenium
Milkvetch (Astraglus spp)
Wood aster (Machaeranthera, section Xylorrhiza)
Goldenweed (Haplopappus, section Conopsis)
Princes plume (Stanleya pinnata)
Three syndromes of excessive selenium intake
Acute toxicosis
Blind staggers
Chronic alkali disease
Effects of oak toxicity on the urinary system
Nephritis with necrosis
Renal tubular casts
**possibly leading to acute renal failure
Common plant toxicities that are harmful to the urinary system
Bracken fern (P. Aquilinum) Cocklebur (Xanthium spp.) Inkweed (P. Octandra) Oak (Quercus spp.) Pigweed (amaranthus retrflexus)
Where are cyanobacteria found?
Suspended in water column
— easily visible or attache dot surfaces of stones & sediments along bottom of lakes or rivers
What is the most common cyanotoxin poisoning in large animals?
Acute hepatotoxicosis subsequent to microcystin exposure
Fungal sources of alfatoxins
**corn & corn-byproducts
Nuts
Cotton seed
Primary toxic effects of alfatoxins
Macromolecular binding enzymatic inhibition
DNA adducts formed—> hepatic insult/failure cancer (primary ehpatic)
Major alfatoxins found in contaminated grains include
B1, B2, G1 & G2
Conditions leading to alfatoxin production by Aspergillus spp
Drought &/or insect damage to corn or other susceptible plants followed by warm, humid (>70% humidity), ambient weather conditions
Mycotoxin: Deoxynivalenol (DON/vomitoxin) produced by:
Fusarium graminearum (formerly Fusarium roseum) -corn, wheat, barley
Primarily toxic effects of Deoxynivalenol (DON/Vomitoxin)
Decreased protein synthesis
GI irritation
INC vomiting
—>feed refusal, DEC nutrient absorption, DEC immunity
Mycotoxin Zearalenone is produced by
F. Graminearum (formerly F. Roseum)
Corn, wheat, barley
Primary toxic effects of zearlaenone
Hyperestrogenism—> productive tract changes
Pseudopregnancy
Early embryonic death
Mycotoxin Fumonisins produced by
Fusarium verticillioides (formerly Fusarium monilforme) **primary corn
Primary toxic effects of Fumonisins
Shingolipid changes—> leukoencephalomalacia *** Horses Pulmonary edema ***swine —hepatic disease in both
Zearalenone pathogenesis
Nonsteroidal xenoestrogen that binds to both alpha and beta estrogen receptors
Fumonisin toxin that is the most comon and clinically important fumonisin
FB1
What ist eh primary toxic mechanism of action proposed for fumonisins
Inhibition of conversion of sphinganine to sphingosine—> results in disruption of sphingolilpid biosyntehsis
Which spps are most susceptible to fumonisin intoxication
Horses & swine
Clinical signs of equine luekoencephalomalacia
Alterted mentation (depression— to neuroexcitation)
Head pressing
Incoordination & apparent blindness
Recumbency & death w/in 5-7 days
Equine leukoencephalomalacia pathognomonic lesion
Degeneration of white matter of the brain
** grossly visible involving one or both cerebral hemispheres
What is the primary clinical abnormalities associated with FB1 exposure in swine
Porcine pulmonary edema (PPE)
Toxic insult to liver
