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Zamia poisoning in two heifers
Livestock disease investigation case report
The owner of two heifers on a Darwin rural block noted progressive hind limb lameness in both animals over a period of two months. There were no other clinical signs and the heifers were in good condition. Cattle had been on the block for the previous 12 months. The heifers were hand fed pellets daily but no mineral supplement was provided. Clinical examination revealed severe hind limb ataxia (in-coordination) in both heifers; they knuckled and fell when forced to move. The paddock was found to contain abundant palm-like cycad shrubs (Zamia sp.).
The heifers were euthanized and there were no significant abnormalities of gross tissues on necropsy. The rumen of one heifer contained a large amount of plastic sheeting. The most significant laboratory finding was degeneration of the white matter of the lumbar spinal cord in both animals, consistent with damage caused by chronic Zamia spp. intoxication. Zamia leaves and seeds contain at least two toxins; a chemical that damages the liver and intestines, and an unidentified neurotoxin that causes irreversible damage to the nerves of the spinal cord. All mammals can be poisoned but cattle are primarily affected by the neurotoxin, observed as characteristic ‘zamia staggers’. There is no treatment for poisoning. Transmissible spongiform encephalopathy (TSE) was excluded in both animals. Cattle affected by zamia showing neurological signs may be eligible for testing under the national Transmissible Spongiform Encephalopathy (TSE) or ‘Mad Cow’ surveillance program, with a producer subsidy of $300 per animal.
In this case, inadequate availability of roughage may have led to consumption of unpalatable material by the heifers, with long-term consumption of Zamia shrub contributing to intoxication.
Last updated: 24 June 2016