Various plants contain pyrrolizidine alkaloids, which damage the veins in the liver. It is possible that the pyrrolizidine alkaloids themselves are not responsible for the damage, but their metabolites. These poisonous substances are present in various Crotalaria, Senecio and Heliotropium species, among others. Occlusive lesions are produced in the centrolobular hepatic veins (obliterating endophlebitis). Subendothelial oedema, narrowing and occlusion of the lumina, atrophy and necrosis of liver cells with portal hypertension are the results. Isolated cases occur if for example tea from these herbs is drunk over long periods. In Jamaica such a drink is known as "bush tea". If these herbs are used in small amounts from time to time, there are no immediate clinical consequences. Veno-occlusive disease with ascites and liver failure may occur as an epidemic if for example the grain harvest contains these plants. This was the case in Tadjikistan in 1992. Due to a military blockade there was a late wheat harvest. Because of this, weeds were able to thrive in the fields. The harvest contained large amounts of the seed of Heliotropium lasocarpium. The first cases occurred 6 weeks after contaminated bread was consumed. By the spring of 1993 there had already been more than 3900 cases. Patients at stage I had abdominal pain, nausea, vomiting and asthenia. In stage II hepatomegaly followed. Stage III was characterised by ascites. In the final stage there is hepatic encephalopathy. Treatment is symptomatic. There is no antidote. Further exposure should of course be prevented. Occasional use should be discouraged. If the grain harvest becomes contaminated, it is best that the government intervenes, forbids further trade on flour, purchases the contaminated flour urgently and exchanges it quickly for normal flour. Advice against use of the contaminated flour should be made widely available via an information campaign.

*

Crotalaria species (in particular Crotalaria retusa) also contain monocrotaline, which in animals is toxic for the lungs. It probably produces the same lesions in humans, if tea from this plant is drunk.