Artikel The toxicity of Senecio inaequidens DC .

INTRODUCTION Seneciosis is one of the most important plant poisonings in South Africa. Certain Senecio species contain toxic pyrrolizidine alkaloids (PAs) which, besides other toxicological effects, induce acute or chronic hepatotoxicity in livestock and man. In the genus Senecio the occurrence of the PAs senecionine, retrorsine and integerrimine is well known. Senecio latifolius, the most important Senecio species responsible for poisoning of livestock in South Africa, contains the alkaloids retrorsine, seneciphylline and platyphylline and both, S. retrorsus and S. isatideus contain retrorsine. According to Röder and co-workers, S. inaequidens contains senecionine and retrorsine; later senecivernine, integerrimine and a retrorsine analogue was added by Bicchi et al. to the list of toxic principles in this species. Senecio species are usually unpalatable and not readily eaten by livestock. Animals may ingest Senecio plant material when other forage is scarce or when the stand of the plant is so dense that it cannot be avoided or differentiated from edible forage. Young plants may also be cropped with grass and poisoning has been described as a result of contamination of hay and silage. Large quantities of Senecio species ingested over a short period induce acute poisoning with death ensuing within a few days of exposure; while a large single non-lethal dose, or multiple lower doses ingested over a longer period, may cause chronic disease . Acutely affected cattle are anorexic, may display abdominal pain and sometimes diarrhoea. Nervous signs characterised by incoordination of the hind limbs, circling and apparent blindness may be present and in these cases death is usually preceded by tremors. The carcass of acutely affected cattle may exhibit icterus, effusion into the body cavities and visceral oedema, pronounced in the abomasal folds, omentum and large intestinal walls. Haemorrhages occur in serosal, visceral and subcutaneous tissue. The liver is typically swollen, with rounded edges and a mottled surface. The gall bladder wall is usually oedematous and the gall bladder is enlarged with excess bile, which may be blood-tinged. Characteristic histopathological features in the liver of acutely affected animals are centrilobular necrosis, which may extend to the midzonal area, with haemorrhaging into the affected areas. Bile duct proliferation and focal accumulation of inflammatory cells are common. During September 2004 a private practitioner from Frankfort (Free State Province, South Africa) reported mortalities in cattle. Cows died acutely after being moved to a camp with a marshy area where a small green shrublet grew abundantly. It was noted that this shrublet was heavily grazed. The plant was collected and submitted for botanical identification. The plant was later identified as Senecio inaequidens DC. by the South African National Biodiversity Institute (SANBI). Necropsy examinations indicated severe hepatic necrosis, multiple haemorrhages and icterus in the longer surviving cases. Histologically, diffuse centrilobular to submassive necrosis and haemorrhage of the liver was reported. Although all Senecio species must be