Zamia staggers in heifers and weaners

Time and location: Aug-Dec 2018, Katherine NT.

Case definition: Sporadic cases of hindleg ataxia in Brahman heifers and weaners. Affected animals are found dead or have difficulty standing and become recumbent, none recover.

Disease mapping: Five cases were reported by the farm manager in the latter half of 2018. The farm management initially thought they were dealing with Bovine Ephemeral Fever and sought veterinary advice as deaths continued. 

Gross findings: Two cases were seen by the vet: a weaner with ascending paralysis that died mid-October, an abundance of cycad seeds were found in the rumen (no samples taken, no other post mortem changes noted); and a heifer showing signs of aggression and hindlimb ataxia in September (bloods taken) that was euthanised mid-December after calving.

Laboratory findings: Bloods taken from a two year old heifer in September were negative for BEF virus (PCR test) and positive for BEF antibody (VNT). No parasites were seen on the blood smear. The creatine phosphokinase level was high, probably a result of muscle damage. The spinal cord of a heifer necropsied in December had histopathology consistent with Zamia toxicity: regional bilateral demyelination and axonal degeneration. No other abnormalities were seen in the brain, intestinal tract, skeletal muscle or peripheral nerves. There were foci of lymphocytes in the liver (but not the damage characteristic of the hepatic-intestinal form of cycad toxicoses).

Animal / management / environment risk factors: Livestock eating cycads, eg for two weeks or more based on experiments in the 1960s (see info from Queensland DAF).

Recommendations to the producer: Prevent access to Zamia plants, especially at times when they are producing seeds or young fronds.