A producer from the Louth area rang with regards to a 3 month old male Santa Gertrudis calf presented with pronounced ventral oedema extending from under the jaw along the entire ventral midline and prepuce. This calf was the second affected calf in one week in a herd of 47 cows and calves. The cows and calves were on agistment and had been grazing in the paddock for 12 months. Both calves that were affected were standing but in respiratory distress.
The calf presented with very pronounced ventral oedema under the jaw, down the neck and brisket and extending under the belly to the prepuce, and was in respiratory distress. The calf had rapidly lost a lot of condition and had foul smelling diarrhoea. The calf was depressed, was reluctant to move and had pale mucus membranes. The remainder of the mob were in good condition, condition score 3-4. A post mortem was performed on one of the sick calves.
Post mortem revealed extensive subcutaneous oedema and generalised pale tissues. The Thoracic cavity was filled with large volumes of fluid that was brown/ red in colour. The lungs appeared pale pink with a 10cm section at the bottom of the left caudal lung lobe that appeared depressed and a darker pink, and the pleural surface of the lung had a diffuse roughened dark red to yellow areas with strands of friable yellow material. The liver was enlarged, paler red in colour and irregular in shape with rounder margins of the liver lobes.
Severe Chronic Diffuse Hepatic Phlebectatic Peliosis (Blood filled spaces in the liver, sinusoidal dilation; which occurs in pimelea poisoning in cattle).
With a Chronic-active severe Haemorrhagic Hydropleuritis.
Pimelea Toxicity occurs in the drier regions of NSW, QLD and Northern South Australia.
The four most toxic plants include;
Simplexin toxin is the principal toxin found in the above Pimelea species. Simplexin toxin activates the enzyme protein kinase C. This enzyme acts on cell proteins particularly myosin, resulting in the contraction of thick muscled vessel walls. The constriction of these vessels takes blood away from the heart and lungs. Constriction causes a build up of pressure, which leads to fluid leakage into the chest, right sided heart dilation and subcutaneous oedema.