Details

Common Name
Senecio, groundsel, tansy ragwort
Botanic Name
Senecio species
Plant Family
Asteraceae
Habitat
There are about 70 species of Senecio growing in North America. They are found in a wide variety of habitats and growing conditions ranging from mountain meadows, to disturbed soils, pastures etc.
Animals Affected
Horses, cattle
Senecio spartioides
Toxic Principle
Pyrrolizidine alkaloids. All Senecio species should be considered toxic, some more than others. All parts of the plant are toxic, even when dried. A toxic dose of 15mg of dried plant per kg. bodyweight over 2 weeks induces severe, irreversible liver disease. Pyrrolizidine alkaloids inhibit cell division, affecting primarily the liver. The PA's are cummulative in effect and over a period of months cause severe liver fibrosis and eventual irreversible liver failure. At high doses, PA cause hepatocellular necrosis, while at lower doses necrosis is less severe allowing time for the characteristic pathological changes of megalocytosis, bile duct hyperplasia and fibrosis to occur.
Description
Senecio species are quite varied, but have alternate leaves, and yellow flowers produced in composit heads with disc and ray flowers. Senecio species have a characteristic single layer of touching, but not overlapping greenish bracts surrounding the flower head like a picket fence.
Gastrointestinal
Diarrhea and rectal prolapse
Musculoskeletal
Marked weight loss
Treatment
There is no effective treatment for animals with terminal liver disease due to pyrrolizidine alkaloids as the liver changes are irreversible. Keeping the animal out the sun will relieve the photosensitization but not affect the underlying liver disease.
Cardiovascular system
Hemolysis and anemia
Nervous System
Severe depression, circling, aimless wandering, head pressing, incoordination and other abnormal behavior consistant with hepatic encephalopathy.
Integumentary System
Photosensitization develops as a result of severe liver disease. White skinned (non pigmented) areas become red, swollen, and painful before the skin dies and sloughs-off as if severely burned.
Ocular System
Photophobia, excessive tearing, swelling, redness and increased sensitivity of nonpigmented skin around the eyes.
Hepatic System
Yellow coloration to the mucous membranes (jaundice), weight loss, diarrhea, rectal prolapse, edema of the legs, red urine (hemoglobinurea) are signs of severe liver disease.
Diagnosis
Elevated serum liver enzymes, decreased albumen, liver biopsy-megalocytosis, fibrosis and biliary hyperplasia. Animals exhibiting typical photosensitization without underlying liver disease are most likely to have primary photosensitization due to plants containing photoreactive pigments. Primary photsensitizing plants include St John's wort (Hypericum perforatum), buckwheat (Fagopyrum esculentum), and spring parsely (Cymopterus watsonii). The prognosis for animals with primary photosensitization is much better than with PA induced photosensitization, as they will recover once removed from the plants.
Special Notes
Sheep and goats are quite tolerant of PA poisoning requiring 200-300% of their body weight in green tansy ragwort to develop fatal poisoning. References: 1. Molyneux RJ, Johnson AE, Olsen JD, Baker DC. Toxicity of pyrrolizidine alaaloids from Riddell groundsel (Senecio riddellii) to cattle. Am J Vet Res 1991; 52:146-151. 2.Goeger DE, Cheeke PR, Schmitz JA, Buhler DR. Toxicty of tansy ragwort (Senecio jacobaea) to goats. AmJ Vet Res 1982; 43:252-254. 3. Smith BP. Pyrrolizidine alkaloid-induced hepatic disease in a group of calves. Compendium Cont Ed 1982; 4: 531-533.
Senecio flower showing single layer of bracts
Senecio spartioides
Senecio jacobea (Tansy ragwort)
Senecio vulgaris (common groundsel)
photosensitization