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This article was published in 1950
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Unusual Outbreak of Mycotic Dermatitis in Lambs
A.N.A. HARRIS, B.V.Sc., District Veterinary Officer, Armidale and W.B. HARDING, B.V.Sc., Inspector of Stock. Tamworth.
Mycotic Dermatitis, a skin disease, infectious in nature, is caused by a mould or fungus (Nocardia dermatonomus). This condition has been recognised as occurring in Australian sheep for over the past 20 years. Dr. R.H. Seddon first drew attention to the disease in 1928 and commented on its comparative rarity. Since then it has been encountered by many Field Officers in various parts of New South Wales. Its incidence varies with seasonal conditions and is usually more commonly found during periods of high rainfall. Over the past three years, due to the exceptionally wet season, it has been widespread. The fungus invades wool and hair follicles, forming thick scabby masses which bind the wool together. Usually the back and sides are the sites most favoured. Recently, however, outbreaks have occurred in the Tamworth District in which the head and legs have been involved. One outbreak, having presented some unusual features, is considered worthy of recording.
HISTORY
In July, 1949, a landowner reported a condition in his Merino lambs similar to Contagious Pustular Dermatitis and causing conjunctivitis. Investigation disclosed that a small mob of selected ewes had been purchased during April, 1949, from a nearby property on the Tablelands. The ewes commenced lambing in May, following arrival on the new owner's property. For the first few weeks of lambing the lambs were in good health, and it was not until the middle of June that the condition was noticed.
Examination of the lambs revealed lesions about the mouth and nose, somewhat resembling those seen in Contagious Pustular Dermatitis. Similar scabby lesions were present on the ears and on the legs and about the coronet. There were also scabs around the eyes and evidence of conjunctivitis. In many cases the exudation from the lesions on the eyelids had caused them to close together. Of the 30 lambs in the flock, 24 were affected and gradually losing condition. At the time of inspection many were poor and 8 had died.
The report of the Director of Veterinary Research, Glenfleld, upon the specimens submitted was as follows:—
"The specimens consisted of scabs and skin scrapings from facial lesions. Examination of scrapings failed to reveal the presence of acarine parasites. Transmission experiments likewise have failed to reveal the presence of the virus of Contagious Pustular Dermatitis in the material submitted. Smears of the ground scabs revealed numbers of mycelial strands and conidia: casual organism of mycotic dermatitis. This is the second occasion within the last month in which Actinomyces dermatonomus infection of the face of sheep has been encountered."
TREATMENT
When the outbreak was investigated the owner was advised to swab the affected areas with 5 per cent. Bluestone. The condition did clear up, no further losses occurred, and subsequently the lambs improved in condition. The cure, however, cannot be attributed definitely to the treatment as the condition may have cleared up of its own accord; but the bluestone did appear to have a beneficial effect.
DISCUSSION
The condition was confined to the lambs only; no other sheep on the property were affected. Examination of both the lambs and the ewes failed to reveal any evidence of "Lumpy Wool." Subsequent enquiry was directed to the original owner of the ewes and he was emphatic that before the ewes left his property there was no evidence of Mycotic Dermatitis in the wool. Furthermore. it apparently did not develop amongst any of his sheep: not even in the group from which the ewes had been selected.
Damp conditions prevailed before and after the outbreak was first noticed. The rainfall registered at Tamworth for June was 314 points, and this is higher than normal. Moreover, it was registered over 14 days. During this period the ewes and lambs were grazing on oats and it would suggest that the continual moistening of the skin about the face, ears and legs predisposed to the activation of this fungus.
The points we wish to make in connection with this outbreak are as follows:—
(1) The lesions about the eyes and the concurrent conjunctivitis were unusual.
(2) The disease caused a marked loss of condition and resulted in a 20 per cent, mortality.
(3) To the uninitiated, due to the absence of lesions in the fleece, outbreaks of this type might be confused with Contagious Pustular Dermatitis.
[A second case was reported from the vicinity of Tullamore in the Dubbo P.P. District. This outbreak involved about 300 Merinos with approximately 250 lambs at foot. These were aged from one to five weeks and losses amounted to approximately 100 over a short period. Unlike the Tamworth case, however, lesions extended throughout the fleece.
One affected lamb was forwarded alive to Glenfield, approximately 3 weeks old and showing severe and extensive lesions of dermatitis involving the greater part of the body, the ears, lips and parts of the face and tail. Numerous subcutaneous abscesses were also present.
Smears revealed numerous mycelia and conidia morphologically indistinguishable from Actinomyces dermatonomus.
It was considered remarkable that such severe lesions could be present in lambs only a few weeks old.—EDITOR.]