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This article was published in 1951
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
CHOREA IN YOUNG PIGS
W.B. HARDING. B.V.Sc., Inspector of Stock, Tamworth.
During February, 1949, a farmer at Dungowan in the Tamworth district, reported an unusual condition in a litter of pigs. Investigation disclosed that the litter consisted of nine pure-bred Tamworth suckers, nearly three weeks old. All were affected with a peculiar muscular twitching or trembling. The sow had farrowed eleven pigs and two were found dead shortly after birth. At that time all the young pigs showed violent trembling and this led to the owner calling the condition "Shakes" or "Trembles".
When seen by the writer the suckers were reported to be slightly improved; but all were showing symptoms consisting of a marked trembling of the head, body and limbs. In some the condition was more pronounced than in others. Trembling was accentuated when the pigs were forced to move, and they usually stumbled and fell over. Apart from the muscular spasms the suckers appeared to be normal, reasonably well grown and displayed a keen appetite.
Trembling of new-born pigs, believed to be a similar condition to the Dungowan case, has been reported from various overseas countries. Also, Hindmarsh (1937) encountered the condition at Glenfleld Research Station in pigs received there for examination. In 1935 a Stock Inspector forwarded to the Station a sucking pig from a farm at Narromine. He described a condition of "chronic shivers" affecting the litter of a Tamworth sow. There were six pigs in the litter, one of which died soon after birth. The remaining five only trembled when disturbed and were apparently normal when lying down and sleeping. On the same farm two other sows had litters similarly affected. One sow was a daughter of the previously mentioned Tamworth sow and the other was a Berkshire. ll three litters were by the same boar, indicating the possibility of a hereditary factor. However, two of these sows were mated again with the same boar and the litters were normal.
Hindmarsh also encountered trembling in two week-old Berkshire suckers. These were from separate litters, all the pigs in which had been affected. The owner of these pigs had also had other litters affected. Apparently there was no close blood relationship between the sows; and the litters had been sired by different boars.
Hindmarsh, in reviewing the literature, mentions that Nissley (1932) described a condition which he called "Shivers in Pigs", but was unable to determine the cause. Payen and Fournier (1934) described a trembling in suckers which they called "Porcelets Trembleurs". Those workers came to the conclusion that the condition was not due to rachitis, thyroid or parathyroid deficiency, nor bacterial cause; and that it was hereditary.
Hughes and Hinman (1936) reported a "marked trembling" in two litters of pigs, but advanced no theory as to the possible cause.
Knilans (1936) reported several litters of "shaky" pigs. The dams were related.
The litter at Dungowan was seen again by the writer when the pigs were about five weeks old, when only a slight trembling was noticeable. Their condition was good and they had grown well. From then on their progress was uneventful and they were later marketed as bacon pigs.
Examination of the breeding history of this sow disclosed that her first litter was unaffected. Her second litter was the one discussed here and the sire of this litter came from a neighbouring farm. As far as could be ascertained there was no relationship between the boar and the sow. Further, on enquiring about the boar's previous breeding history there was no evidence that he had sired litters of pigs affected with "trembles". The sow subsequently had a third litter to a different boar and these pigs were unaffected. The writer is unable to offer any suggestion as to the cause of this condition.
Reference
Hindmarsh, WL (1937)—Aust. vet. J., 13 249