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This article was published in 1955
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
MERCURIAL POISONING IN PIGS
G. CHARLES, B.V.Sc., Inspector of Stock, Forbes.
Most reference books seen appear to confine their remarks re mercurial poisoning to the effects of perchloride of mercury or calomel, the first giving rise to an acute condition and the second to a more chronic complaint. Few give a detailed description of the post-mortem picture, and so it was considered that the following case was worth recording.
The owner of a small piggery on the outskirts of Forbes reported the death of 3 pigs in 5 days, that a further two were sick, and requested assistance. The herd consisted of 1 boar, 6 sows, 30 weaners 4 to 6 months old, and 7 suckers. The pigs were all in good condition and were being hand-fed on wheat and cereal hay, both of good quality. The subject wheat had been fed for a period of 9 days. At the time of examination 1 weaner and 1 sucker were sick. Hygiene was good and there was no possible contact between the two pens in which the affected pigs were found.
On inspection the sick pigs were seen to be depressed and off their feed. All visible mucous membranes were pale and exhibited some petechiation. There was haematuria and some fresh blood about the anus, also red spots of varying size up to 2 cm, in diameter along the belly, on the inner surface of the thighs and in the axillae. These spots darkened after death.
Post-mortem examination showed that these spots were haemorrhages in the submucosae, dermis and fat deposits. On opening the abdominal cavity strings of bloodstained fibrin were seen on the viscera, and there were numerous ecchymoses beneath the visceral and parietal peritoneum. The liver was slightly petechiated, friable and appeared oedematous as if an advanced cloudy swelling were present. The spleen was heavily petechiated, while the kidneys showed no subcapsular haemorrhages. On section the kidneys showed haemorrhagic glomeruli and free blood in the renal pelvis in one case, obviously an acute nephritis. The bladder was intensely inflamed and haemorrhagic, and in one case showed a partially organised blood clot, about the size of a golf ball, within the lumen. The gastro-intestinal tract was almost empty, exhibited numerous submucosal haemorrhages but little free blood within the bowel. There were no ulcers present. There had been some bleeding from the last inch or two of the rectum. The heart was grossly ecchymotic and the pericardial sac contained about 10 ml. of red fluid. There were numerous ecchymoses beneath the parietal pleura. but the lungs appeared normal. The musculature appeared greyish red, shiny and slightly oedematous and there were ecchymoses throughout. The picture presented was very similar to that seen in an acute septicaemic condition, except that there was no apparent involvement of the lungs, and that an acute cystitis was present.
In view of the lack of involvement of the lungs and the acute cystitis, also the lack of contact between affected pigs, an attempt was made to find a common factor and the only one was the feed. The cereal hay was wholesome, while the wheat, of good quality, appeared dusty. On further questioning, the owner stated that the wheat was surplus seed wheat purchased from a farmer who had graded and "dusted" it with bunticide. Further inquiries revealed that the bunticide was "Ceresan", which contains an organic mercurial salt. Withdrawal of the wheat resulted in no further cases developing.
The Director of Veterinary Research reported that no significant bacteria could be isolated from the specimens submitted for examination; and that the post-mortem appearance was consistent with a heavy metal poisoning.
The boar and sows showed no clinical signs of being affected, but the surviving suckers and weaners showed an obvious setback in condition and were very slow to recover. In all, a total of 6 weaners and 2 suckers died.
ACKNOWLEDGMENT: Permission of Mr. D. G. Christie, D.V.O. (W.), to quote from official correspondence, is gratefully acknowledged.