9/9 - Plant Toxicology Liver

Cycas

What genus of plant is also known as the Sago palm? The seeds, leaves, and pulp are hepatotoxic to dogs and small ruminants, containing methylazoxymethanol glycosides. Signs include periodic episodes of persistent vomiting, excess salivation, increased water consumption, anorexia, diarrhea, constipation, icterus, decreased platelets, elevated serum bilirubin, hepatic enzyme elevations, and elevations of BUN and creatinine. There will be an enlarged nutmeg liver and microscopic centrilobular hepatic necrosis. Treatment is supportive.

Lantana

What genus of flowers are most toxic in the leaves, containing lantadenes which are biotransformed in the liver and excreted in bile, damaging the bile duct membranes and microvili, leading to obstructive cholangitis? Signs include initial GIT signs, depression, loss of appetite, decreased rumen motility, constipation, diarrhea, liver-related effects after 2-3 days, icterus, photosensitization, elevated serum bilirubin/AST/ALT, and death. The liver will be swollen and orange due to bile staining, the gallbladder will be enlarged with edematous walls, and the gut mucosa will be red and edematous. Microscopically there will be mild-moderate centrilobular necrosis. Treatment is with activated charcoal or bentonite in acute cases, plus fluids, glucose, electrolytes, and sodium thiosulfate IV.

Horsebrush

What plant is in the genus Tetradymis and mainly affects sheep on open range? Bighead is the condition associated with it, in which sheep eating it are exposed to bright sunlight and have swelling of the head. Hepatic biotransformation turns tetradymis to tetradymol, which affects the ability of the liver to clear phylloerythrin. Signs include abrupt onset, loss of appetite, lethargy, depression, photosensitiziation, and increases in serum AST and ALT. Pathology is with an enlarged and tan liver, distended gallbladder, and centrilobular hepatic necrosis on microscope.

Cocklebur

What plant is in the genus Xanthium? The seeds, new cotyledons, and new sprouts are most toxic, containing Carboxyatractyloside (CAT), inhibiting oxidative phosphorylation in mitochondria. Signs in pigs include abrupt onset, depression, weakness, loss of appetite, vomiting, hypothermia, ataxia, spasmodic muscular activity, recumbency, and death. Signs in calves are similar. Pathology is with protein-rich abdominal and thoracic fluid, edematous gallbladder, swollen and accentuated liver on the cut surface, and severe-diffuse centrilobular necrosis. Treatment is with parenteral glucose and milk/lard for protection in pigs.

Rattlebox

What plant in the genus Crotolaria contains pyrrolizidine alkaloids including monocrotaline, which are metabolized in the liver to reactive pyrroles, which alkylate DNA? It also alters RNA and protein synthesis, impairing cell division, leading to hepatocytomegaly and karyomegaly. Signs include anorexia, weight loss, ataxia, icterus, stupor, severe weakness, and horses can get sleepy, dragging rear legs, circling, leaning against objects, restlessness, and self-mutilation. Cattle can have similar signs, plus excess salivation, bloat, tenesmus, rectal eversion, and tar-like diarrhea. Pathology includes firm shrunken blue-tan mottled nutmeg liver, edematous omentum, distended gallbladder, hepatic necrosis, bile duct proliferation, hepatocellular megalocytosis, karyomegaly, and central vein fibrosis. Treatment is with nursing care, parenteral fluids, and high quality feeds with good protein.

Pyrrolizidine

What type of alkaloids are found in Senecio, Crotalaria, and Cynoglossum plants, and become cumulative hepatotoxins after bioactivation in the liver, becoming pyrroles? These are protein electrophiles which bind to and cross-link DNA, proteins, AAs, and glutathione. The effects are cytotoxic and antimitotic, and adducts may persist for months or years. There will be dose-dependent hepatocyte swelling and necrosis and biliary duct proliferation. No treatment is truly effective and prognosis is poor-grave. Hepatic cripples can occur, with clinical liver failure and photosensitivity when put to stress.

Senecio

What genus of plants is also called ragwort or groundsel and contains pyrrolozidine alkaloids with varying potency, specifically senecionine? Peak liver concentrations occur after 2 hours and readily cross the placenta. Pigs are most susceptible. Signs and pathology are similar to Crotalaria.

Cynoglossum

What genus is also called Hound’s tongue? Signs include poor BCS, weight loss, icterus, head pressing, aimless pacing, ataxia, chewing, yawning, intermittent drowsiness, tenesmus, constipation, and diarrhea. It contains pyrrolizidine alkaloids, specifically heliosupine. Pathology and treatment is the same as Crotolaria.