This relates to two separate cases, one seen in Barellan in June/ July 2005 (Property 1) and the other (Property 2) under current investigation (Jan/ Feb 2010).
Both properties reported sheep with weight loss and lethargy/ listlessness which appeared unusual for their nutritional status. Deaths are/ were occurring at a rate of nearly one per day when I was called out. The sheep on Property 1 were late pregnant ewes being fully fed on a grain ration with lime and salt provided ad lib. Ewes were in condition score 1 on a diet of 1kg oats/head per day plus oaten hay.
The sheep on Property 2 are on dry improved and native pasture with some barley available. Both mobs have access to piped water, on Property 1 this is in troughs and on Property 2 the water is in dams. On Property 2 there is a recent history of a failed rice crop in which plants tested were shown to have highly elevated iron levels. The sheep were allowed access to this paddock for approximately ten days to graze down the banks during the rice growing period.
The main post-mortem findings on Property 1 were that livers were shrunken (1/2 - 2/3 times normal) and firm; kidneys were observed to have diffuse ochre brown discolouration of the cortex and the spleens were slightly swollen with dark red pulp. There was an increase (approximately 500ml) in straw gold fluid in the abdominal, thoracic and pericardial cavities. Histopathology revealed a severe hepatopathy in all sheep autopsied. This was characterised by abundant cytoplasmic brown granular pigment, consistent with haemosiderin (also seen in the spleen).
Special stains with Perle's stain revealed abundant iron in liver and spleen, with smaller amounts in the kidneys. Several kidneys evidenced haemoglobinuric episodes. Haematology in 2/3 sheep revealed a moderate anaemic haemogram and biochemistry revealed increased total iron in 4 ex 5 sheep sampled (range 47.1 to 184.7Umol/L in those 4) (ref values ovine: 10.0-29.0) along with elevated liver enzymes. These also had low serum calcium levels and low serum vitamin E levels.
On property 2 the only autopsy conducted to date has been on a ewe lamb with evidence of grain toxicity. The main findings relate to biochemistry which has shown mildly elevated total iron levels in 3 ex 6 sheep sampled along with mildly elevated liver enzymes. The sheep also had high faecal egg counts which have been addressed with a drench. Small numbers of cells in the liver and spleen had intracytoplasmic pigment (presumed to be haemosiderin). At the time of writing this, we are waiting on special stains for this case.
On property 1, the cause of elevated iron could not be explained. Other sheep on the property were on the same grain with similar soil type and the water source was the same for many sheep in the district. The case spontaneously resolved after the season broke.
On property 2, the cause of elevated iron levels is also currently unexplained with investigations ongoing.
Haemochromatosis is known to occur as a sporadic event in genetically predisposed individuals, however in these cases this is unlikely to be the cause. Cases of contaminated feed supplements have been recorded as causing haemochromatosis in fruit bats.
Other exogenous causes could not be ruled out on Property 1.
Haemosiderosis (the detection of iron pigments in organs without pathologic effect) has been recorded in liver, spleen and lymph nodes of apparently normal sheep at slaughter.