Nicotiana glauca
An evergreen, bluish green shrub or small tree, up to 6 metres tall, which reproduces only by seeds. The stems are slender and loosely branching. The evergreen leaves are alternate, up to 15 cm broad and up to 7 cm long. They are bluish green, egg shaped, and hairless, but covered with a whitish powder which rubs off easily. The margins are smooth or slightly wavy. The long tubular flowers are yellow, about 30-40 mm long, and are borne on large leafless branches at the ends of the stems. The flower tube is densely short hairy on the outside, and opens during the day. However, the 5 lobes are very short, so there is little spread. The calyx is unequally 5 toothed, and about 100 mm long. The seedpods are brown, many seeded, approximately 100mm long, somewhat egg shaped or oblong, on curving stalks so they hang downward. The kidney shaped seeds are dark brown, about 16mm long, with a honeycombed and roughened surface.
A variety of related plants are grown in gardens. Most are poisonous.
Tree tobacco is a shrubby weed of waste places, naturalized from South America. It grows in sandy or gravelly soils along roadsides, near cultivated areas, around old dwellings and ditch banks. Although it is rarely seen in NZ, tree tobacco is occasionally sold in garden centres, and thus may be found in garden escapes around the country.
The alkaloid anabasine. Nicotine is absent or in only a very low concentration. Anabasine is more toxic than nicotine. The pharmacological action of the two alkaloids is similar, but anabasine has a greater depressant effect than nicotine. Like nicotine, anabasine exerts its effects through G.I. irritation and on the nervous system by nicotinic stimulation. The leaves and young stems of tree tobacco are the most toxic parts of the plant. The plants are poisonous to all kinds of livestock and to humans. Although tobacco plants are distasteful, and where ranges provide ample forage, livestock usually do not eat them, therefore, poisonings from these plants are rarely reported.
Usually grazing or browsing animals on wasteland areas are affected by tree tobacco poisoning, especially if grass levels are low and animals are forced to browse on shrubs.
Animals pass into a state of deep depression with diminished pain sensitivity and an inhibited response to conditioned reflexes. Toxic signs included excess salivation, irregular gait, wobbling while walking or standing, recumbancy and death. Death appears to be caused by depression of the central nervous system followed by respiratory then heart failure. However, in animals which have profuse diarrhoea most of the toxic plant material is excreted within 24 hours and spontaneous recovery will frequently occur. In pregnant animals that survive, teratogenic effects can occurred in offspring especially when fed the anabasine toxin between the 30th 60th day of gestation. Teratogenic expression includes limb defects such as arthrogryposis, with or without lateral or medial rotation of fore or rear limbs, lordosis, irregular shaped head or cleft palate.
Hyperaemia of the alimentary tract, often with severe haemorrhage, together with a generalized congestion of the visceral organs.
History, clinical signs and stomach contents.
Gastro intestinal signs could indicate a large number of poisonous plants or toxins, whilst neurological signs could point towards Organophosphate poisoning (nicotine acts as a cholinesterase inhibitor), carbamate poisoning and blue green algae poisoning. and hemlock poisoning.
Removal of the source of poisoning, placing the animal in a quiet area with minimum stress and symptomatic treatment (fluids and activated charcoal if a large quantity has been ingested).
Prognosis is good, provided the animal is decontaminated by activated charcoal. Due to the gastro intestinal irritation, diarrhoea may result in most of the toxic material being excreted within 24 hour, thus spontaneous recovery is likely to occur. If ingested by pregnant animals, teratogenic birth defects are likely to occur. The degree to which these limit survival of the newborn animal depends largely on the toxic dose, and the time of gestation the plant was ingested.
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