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This article was published in 1948
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Trombidiosis in Sheep in New South Wales
L. A. W. McTIER. B.V.Sc., Inspector of Stock, Moree.
In Service Publication No. 2 (1947) issued by the Division of Veterinary Hygiene, Canberra, reference is made to the recording by Gill, Moule and Riek (1945) of the presence of Trombicula sarcina in Queensland; but apparently this mite has not been recorded hitherto in N.S.W.
In May, 1946, the attention of the writer was directed to a peculiar scabby condition on the lower portion of the legs of some sheep on a property some six miles east of Warialda. These sheep were being shorn, and the shearers were objecting to handling any animals so affected.
The report submitted at the time read, inter alia, as follows:— "Inspected about 50 aged merino ewes which had been yarded for examination. About 75 per cent. of these sheep had scabs varying in size from about half an inch by half an inch to two inches by one inch, on various parts of the lower portion of the legs; but only in odd cases did they extend above half way from the coronet to the knee or hock. The scabs were quite thick and resembled those seen in Contagious Pustular Dermatitis. Many sheep were affected on all four legs; some in two, and others on three. One of the commonest parts involved was behind the fetlock joint."
The owner stated that a few days prior to my visit he had examined a few cases and found pus under the scabs; but in all cases seen personally pus was detected in not more than three or four, and then only in sufficient quantity to make a smear.
Smears and portion of scabs were submitted to Glenfield, following which the D.V.R. advised to the effect that although the site of the lesions suggested that Trombidiosis might be the cause of the condition, examination failed to reveal any acarine parasites.
The lesions on these sheep resolved without any treatment, and the condition has not re-appeared on that particular property.
In May, 1947, a scabby condition affecting the legs of a mob of four-year-old wethers was investigated on a property about 11 miles west of Warialda. The affected sheep in this instance showed crumbly scabs from the coronet to the knee or hock joints; these lesions being very similar to those illustrated by Gill and his fellow workers in the reference already quoted. Some sheep had only one or two scabs near the heels, while others showed all degrees of variation between the two conditions described. It was not possible to find in this mob any sheep which did not show a lesion. Severely affected animals were very much poorer than those only slightly affected; these latter being in very good to fat condition. The wool of the severe cases lacked condition.
A close examination was made for mites on these sheep, both under the scabs and by making scrapings, but it was not possible to detect any by either method. Scabs and scrapings were forwarded to the D.V.R., who reported as follows: "Examination of scrapings revealed one larval mite indistinguishable from Trombicula sarcina. Apparently the mites are not easily demonstrated in material from old chronic lesons, so that we were somewhat fortunate in finding the single mite."
About two weeks later this owner advised that all the affected sheep had recovered, while the severely affected ones had picked up in condition and their wool had improved so that it was almost indistinguishable from that on sheep which had been affected only slightly. The owner attributed the recovery of the sheep to his treatment of them with sump oil and kerosene (4 to1), but the opinion is expressed that the lesions seen at the initial investigation would have resolved completely in 7-10 days, without any treatment. Enquiries have been made concerning the possible incidence of Trombidiosis in the Warilda P.P. District, and it is believed that this disease occurred on a number of properties there some years ago. The writer is quite satisfied that the condition seen on the first property referred to in this note actually was Trombidiosis.
Reference:
Gill, D. A., Moule, G. R. and Riek, R. F. (1945): Aust. vet. J., 21 : 22.