Native to Australia, Pimelea plants are found throughout inland NSW and several other states. The plants can have significant impact on the cattle industry as a result of production losses (including stock deaths), and costs associated with feed supplementation. Although these plants are usually winter and spring annuals, they have been known to germinate at other times proceeding adequate rainfall, especially drought-breaking rains.
A farmer reported three dead mixed breed juvenile cattle in mob of 90 (between 6-18 months of age). The cattle were recently purchased from Alice Springs and placed on short-term agistment at an organic property in Murray Bridge, South Australia, before ending up at final destination in the Far West of NSW. The animals were losing condition significantly and scouring in the past 5 days and some had swelling evident under the jaw. All animals appeared to still be eating. They had been out on fresh pasture, with Pimelea present but producer did not observe them eating the suspected plant and positive identification of the plant was not made. The owner was advised to remove the animals from the pasture and provide hay.
The property was visited in April 2020. Numerous animals were noted to be in poor condition, depressed, with rough coats and significant submandibular oedema. Malodourous scours were collected from three animals. The holding paddock contained marshmallow (Marva parviflora) and sheep bones. The pasture paddock where the suspected Pimelea plant was had evidence of paddy melon (Cucumic myriocarpus) and sheep bones. Plant differentiation and identification was difficult due to immature stage of growth. The farmer mentioned the plant suspected was growing on the sandy flat patches.
No recently deceased animals were available for necropsy.
Live animal samples included a fine needle aspirate of submandibular oedema fluid revealing a clear watery substance. Bloods collected ruled out pestivirus by PACE ELISA. Faecal testing ruled out Yersinia and internal parasites, with a FEC of 0 and low Coccidia (+). Haematology revealed a mild hypofibrinogenemia, mild microcytosis, and mildly decreased MCH. Biochemistry demonstrated a mild to moderate hypoproteinaemia, a mild to moderate hypoglobulinaemia, a mild to moderate hypocalcaemia, mildly increased GLDH and a mild azotaemia. Haematology and biochemistry results supported the diagnosis of Pimelea poisoning, particularly in regards to loss of protein. However, there was no anaemia which is often attributed to Pimelea poisoning.
In the same week following Easter, photographs of two plants were sent through to Senior Land Services Officer in Wilcannia from another property in the region which the producer believed to be responsible for the death of 10 cattle on his property. One of the plants was identified as as Pimelea simplex (desert riceflower, the same plant suspected in the above disease investigation). The second property reported having lost 10 cattle. Owner of the first property subsequently mentioned the loss of 10 more animals and he predicted that he would lose many more, as even healthier appearing animals lose condition rapidly over two days before dying.
A media release was organised and interviews with local radio stations were undertaken to alert local landholders of the unseasonal presence of the Pimelea plants.