Abstract
This study was designed to confirm the toxicity of a plant implicated in an outbreak of poisoning of stock in Frankfort, Free State Province, South Africa. Cows died acutely after being introduced into a camp, where an abundant, green shrublet was noted to be heavily grazed. This plant was subsequently identified as Senecio inaequidens DC. (Asteraceae) by the South African National Biodiversity Institute (SANBI). Extraction and chemical analyses for pyrrolizidine alkaloids (PAs) in Senecio inaequidens revealed the presence of 4 different compounds, namely retrorsine and senecionine (known to be hepatotoxic) and 2 unidentified compounds. The average total PA (free base plus N-oxide) concentration in plant parts of S. inaequidens collected at Frankfort during the outbreak was 0.81%, compared with the total alkaloid content in the dried, milled S. inaequidens plant material, collected 7 weeks after the outbreak, of only 0.18%. Male Sprague-Dawley rats (n = 4), aged 8-9 weeks, were dosed per os. Each rat received a different dose of the crude Senecio inaequidens extract, ranging from 0.049 mg/g body weight (b.w.) to 0.25 mg/g b.w. No clinical signs were observed in the rat receiving the lowest dose. Rats receiving higher doses showed depression, an unsteady gait, pilo-erection and jaundice, which was particularly noticeable in the ears. Clinical chemistry evaluation revealed an increase in the activities of ALP (except Rat 4), AST and GGT in all animals. Total serum bilirubin, creatinine and urea concentrations were also elevated. All rats had low serum globulin concentrations with an A/G ratio above 1.2. Post mortem examination of the rats revealed marked hepatic lesions. Histopathologically, these changes were characterised by necrosis (variable in extent) of the centrilobular and midzonal hepatocytes (but sparing the portal hepatocytes), with extensive haemorrhage and congestion. Proliferation of the bile ducts, fibrosis and oedema were also present. Ultrastructural changes in affected rats were characterised by margination of chromatin, the presence of numerous autolysosomes in necrotic hepatocytes, intramitochondrial woolly inclusions and changes in the endoplasmic reticulum. A sheep, also dosed with the crude extract, failed to exhibit clinical signs, clinical chemistry aberrations or macroscopic lesions; however, examination of the liver of this sheep revealed histopathological and ultrastructural changes similar, though milder, to those displayed by the rats. Pyrrolizidine alkaloids were extracted from the liver and kidneys of the rats and the sheep. In the case of the sheep, retrorsine was also detected in the lungs, urine and bile.
Highlights
Tuberculosis (TB) is an infectious and contagious disease common to human and many animal species (Ayele et al 2004; Palmer, Waters & Whipple 2004) and remains a major health threat to both humans and animals throughout the world (Cosivi et al 1995, 1998; Michel 2002)
Bovine TB is a chronic disease of animals caused by the bacterium M. bovis, which is closely related to the bacterium M. tuberculosis, the causative agent of human tuberculosis
The study findings indicate that routine meat inspection protocols utilised in Rwandan abattoirs are able to detect 0.9% of bovine tuberculosis (bTB) lesions at the gross level
Summary
Tuberculosis (TB) is an infectious and contagious disease common to human and many animal species (Ayele et al 2004; Palmer, Waters & Whipple 2004) and remains a major health threat to both humans and animals throughout the world (Cosivi et al 1995, 1998; Michel 2002). For this reason, TB is both an economic and public health threat (Biet et al 2004; Haddad & Durand 2001; Michel et al 2007). Cattle remain the most important source of M. bovis infections to humans and other animals but are at risk as cattle can be reinfected with M. bovis by contact with humans (Aranaz et al 2004; Krauss et al 2003)
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