Poisonous Plants

Cyanide clinical signs

bright red blood (“cherry colored”) mucous membranes

excitement, muscle tremors

dyspnea

salivation

urination and defecation

Cyanide tx

Sodium nitrite creates methemoglobin which has greater affinity for cyanide than cytochrome oxidase, stripping cyanide from the enzyme.

Sodium thiosulfate reacts with cyanide to form thiocyanate, which can be excreted by urine.

Pigweed, Nightshades, Sorghum, Oat hay, Rye, Alfalfa

Nitrate accumulating plants

Nitrate accumulating plants clinical signs

Dark brown or “chocolate colored” blood

Nitrate accumulating plants tx

1% methylene blue —> reduces methemoglobin

Oleander, Foxglove, Lily-of-the-valley, Yew, Rhododendron

Cardiotoxic plants 

Cardiotoxic plants clinical signs

Salivation, nausea, vomiting (risk of aspiration), hematochezia

Weakness, bradycardia, hypotension

Atrioventricular (A/V) block

Collapse and acute death are possible

Cardiotoxic plants tx

Induce emesis if recent ingestion and minimal signs of weakness

Activated charcoal administration, supportive care (IV fluids, supplemental oxygen)

Atropine for severe bradycardia

Isoproterenol, procainamide, or quinidine for A/V block

St. John’s wort, Brassica spp., Senecio Spp., Microcystis spp., Crotalaria spp., Amsinckia intermedia (Fiddleneck)

Photosensitization plants

Photosensitization clinical signs

■ White skinned areas of the dorsum and lateral body wall

■ Thin and non-pigmented areas (sclera, udder, muzzle)

■ Most common in regions and seasons of more intense sunlight

Primary photosensitization

When ingested or absorbed agent is or is metabolized to become photodynamic (becomes a high energy molecule when exposed to ultraviolet light, causing membrane and free radical damage); restricted to skin with better prognosis

Secondary photosensitization

When impaired hepatic function reduces excretion of plant pigments (such as phylloerythrin, a chlorophyll breakdown product); damage to liver along with skin lesions

Lupine, poison Hemlock, Larkspur, Nightshade, Bracken fern,

Neurotoxic plantsL

Lupine

Sheep

Teratogen in cattle —> 40-70 gestation —> crooked calf syndrome (torticollis, scoliosis, carpal flexure)

Larkspur

Cattle

Cholinergic/nicotinic antagonist

Tx with physostigmine

Nightshade

GI irritant vs neurotoxin

Bracken fern

Thimainase —> polioencephalomalacia

Black walnut trees

Acute onset of laminitis

Gossypol (cottonseed)

Young animals, cardiotoxic

Red urine, pot-bellied appearance

Sudden death

Dumbcane

Irritation of mm., ptyalism, edematous swelling of tongue and lips

Locoweed

Clicking of dewclaws (cracker heels), emphysema in sheep, teratogenesis (contracted tendon)

Waterhemlock

Most toxic plant!

Violent tetanic seizures

Yellow start thistle

Nigropallidal encephalomalacia (“chewing disease”) —> cPerhewing and dropping food

Perilla mint

Pulmonary edema/pleural effusion

Western false hellebore (veratrum californium) 

Teratogenic effects depend on stage of gestation when eaten:

a. Day 14 – classic cyclopean deformity (“monkey faced lambs”)

b. Day 17-18- hind limb motor nerve paralysis

c. Day 12-30- Craniofacial deformities (cleft palate, harelip, brachygnathia)

d. Day 30-36- Shortened legs from metacarpal and metatarsal bone hypoplasia

White snakeroot (Eupatorim ragosum)

myocardial necrosis and CHF

Red maple

anemia, hemoglobinemia/globinuria, icterus

Ponderosa pine

Abortions