Unusual presentation: Loss of hindquarter coordination in young cattle.
Time and location: Five cases were reported by the farm manager between August and December on a property in 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.
Gross post mortem findings: The farm management initially thought they were dealing with Bovine Ephemeral Fever and sought veterinary advice as deaths continued. 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).
- A heifer showing signs of aggression and hindlimb ataxia in September (bloods taken) that was euthanased 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.
When investigating nervous conditions
Lee took us back to basics in the 2019 Masterclass:
- Collect fresh spleen from downer or ataxic animals to rule out BEF
- Map where losses have occurred and get a good history (proportion affected, for how long, other species, stock movements, recent rainfall, access to dump sites, new equipment or feed onto the property…)
- The differential diagnoses for nervous conditions in Northern Australia.