Pimelea poisoning is potentially fatal for cattle but also affects sheep and horses. It is most common in south-west Queensland, north-west New South Wales and northern South Australia. It is also known as St. George disease, Marree disease, big-head and flaxweed poisoning.
Pimelea poisoning is caused by the ingestion of toxic varieties of the plant Pimelea such as native rice-flower, flaxweed and poverty weed varieties. In some cases, inhalation of plant dust can also cause poisoning.
Conditions when pimelea poisoning in cattle is likely to occur
- light red, sandy and less fertile soils, particularly in overgrazed pastures and old cultivation paddocks
- pastures with obvious bare areas without vigorous perennial grass
- between August and January
- in years when a relatively dry summer is followed by early light winter rain and a dry spring
- bulls and breeding cows are more susceptible.
Identifying and diagnosing pimelea poisoning
Pimelea poisoning can be either acute or chronic.
Acute poisoning is caused by the consumption of green plants and results in severe, life-threatening diarrhoea. Cattle, sheep and horses can be affected.
Chronic poisoning occurs in cattle and is caused by on-going consumption or inhalation of dry plant material.
Clinical signs include:
- chronic diarrhoea
- loss of condition, poor appetite
- rough coat
- prominent jugular veins in the neck, oedema (soft swelling) of the head, brisket and abdomen
- increased respiration rate
- heart rate can be heard from a distance
- reluctance to move
- sudden death, commonly during exertion.
Prevention strategies for pimelea poisoning
Prevention and control of pimelea poisoning requires careful monitoring of cattle during high-risk seasons and grazing management strategies to minimise contact between susceptible stock and Pimelea plants.
Despite extensive research, there is no effective vaccine or antidote for pimelea poisoning.