CASE NOTES

Pimelea simplex (desert riceflower) Poisoning in the Far West of NSW

Jessica van de Weyer, District Veterinarian, Western Local Land Services, Broken Hill

Posted Flock & Herd August 2020

Introduction

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.

History

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.

Clinical Signs

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.

Differential Diagnoses

Plant toxicity e.g. Pimelea
Pestivirus
Internal parasites (recently treated with Dectomax)
Botulism (bones in paddock)
Johne's disease (incorrect age bracket and history i.e. from area of low prevalence)
Exotic diseases:

Haemorrhagic septicaemia
Surra

Diagnostics

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.

Figure 1. Affected animal (right) showing submandibular oedema

Figure 2. Affected animal showing submandibular oedema

Figure 3. Affected cow showing marked submandibular oedema

Discussion

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.

References

Greentree K (2010) A case of Pimelea poisoning. www.flockandherd.net.au
Morrice G (2014) Curved rice flower (Pimelea curviflora) associated with deaths of cattle in the Riverina. www.flockandherd.net.au
Fletcher MT, Chow S & Ossedryver SM (2014) Effect of Increasing Low-Dose Simplexin Exposure in Cattle Consuming Pimelea trichostachya Journal of Agricultural and Food Chemistry 62 pp 7402-7406
Freeman PW, Ritchie E & Taylor, WC (1979) The Constituents of Australian Pimelea spp. I: The Isolation and Structure of the Toxin of Pimelea simplex and P. tvichostachya Form B Responsible for St. George Disease of Cattle. Aust. J. Chem. 32 pp 2495-506
McClure TJ & Farrow BRH (1971) Chronic Poisoning of Cattle by Desert Rice Flower (Pimelea simplex) and its resemblance to St George Disease as seen in North-Western New South Wales Australian Veterinary Journal 47 pp 100-102
Silcock RG, Chow S, Fletcher MT & Wingett M (2008) Pimelea Poisoning - Still a Confusing Story Proceedings of the Australian Society of Animal Production. 27
Silcock RG, Fletcher M, Chow S & McNeale C (2015) Pimelea Poisoning - The Plant Enigmas
Wilson SJ, Taylor JD, Gibson JA & McKenzie RA (2007) Pimelea trichostachya poisoning (St George disease) in horses Australian Veterinary Journal 85: 5 pp 201-205