Mercurialis annua
Erect, annual herb up to 1m tall, stems sparingly oppositely branched. Leaves are ovate oblong, about 5cm long, bright green, coarsely toothed, stipules small. Male flowers are clustered in small groups on peduncles up to 8 cm long, female flowers are clustered 2-3 together, in leaf axils; the sexes usually on different plants. The fruit are capsules with 2-3 cells.
Common in waste places in Auckland; localised on South Taranaki coast.
Mecurialine, a volatile basic oil, is in part responsible for the toxicity of the plant, together with methylamine and trimethylamine (degradation products of choline). The plant is most toxic in the flowering and seed-bearing stage. Regarded as unpalatable. The ingestion of the plant can have an accumulative effect.
Sheep, cattle, humans, but stock are generally not attracted to this plant due to its unpleasant odour.
Inflammation of the stomach and intestines, red water, urination often painful, foetid diarrhoea following constipation, and in cows cessation of the secretion of milk. Weak, lethargic (often recumbent), jaundice in oral and genital mucous membranes and eyes. Haematuria with profound anemia developing. Rise in temperature, and coma leading to death. Also tachycardia. Lag behind when driven, may die suddenly (sheep and calves).
Acute gastroenteritis, sometimes with sloughing of the mucous membranes, and fatty degeneration of the liver and kidneys. Subcutaneous oedema, haemorrhages of liver, kidney, heart and an enlarged, congested, "nutmeg" liver. Pleural and peritoneal effusions, myocardium mottled with pale areas. Lungs reddish-brown. Spleen friable and brown. Kidneys large and petechiated. Mucosal haemorrhages in small intestine, ileal contents blood stained and large intestinal contents are fluid. Anaemia, raised serum urea.
Clinical signs and history. Blood smear: anisocytosis, polychromasia, normoblasts and Heinz bodies. Neutrophilia and monocytosis. Increased Aspartate aminotransferase and Glutamate dehydrogenase levels indicating liver damage.
Chronic copper poisoning. Nitrate/nitrite poisoning, Ragwort poisoning, bacillary or post parturient haemoglobinurea. Leptospirosis. Brassica, chlorates, Red Maple toxicity.
Remove from source, symptomatic care (fluids, electrolytes, gastric protectants).
Depends on severity of clinical signs. Spontaneous recovery or high mortalities.
Conner H.E. The Poisonous Plants In New Zealand. 1992. GP Publications Ltd, Wellington
Parton K, Bruere A.N. and Chambers J.P. Veterinary Clinical Toxicology, 2nd ed. 2001. Veterinary Continuing Education Publication No. 208
Watson PJ. Suspected Mercurialis Poisoning in cattle. Vet Record (1998) 147, 116-117.
Welchman DdeB et al, Suspected annual mercury poisoning of lambs grazing arable land. Vet Record (1995) 137, 592-593.
4 October, 2007