An investigation into the pathology and immunology of a dermatitis of sheep common in the south-east of Scotland, and its comparison with similar conditions elsewhere

1. A comparative study of three dermatoses of sheep, namely Border Uri', L,ontagious Pustular Dermatitis and Strawberry Foot Rot, has been carried out.

2. In all three diseases the natural lesions are clinic indistinguishable from each other, although affecting different sites - Border Orf and STAR the legs, and CPI) the lips and nostrils.

3. Under experimental conditions the development and appearance of the lesions of Border Orf and GP]) are identical, as is their histological structure, both exhibiting the stages of papule, vesicle, pustule and scab. SFR can readily be distinguished by its rapidly-forming pustular eruption in which no vesicle stage is observed. Histoloically this latter disease is characterised by marked proliferation of the epidermal cells and by hyperkeratesis.

4. Border Off and CPI) were alike in failing to infect either rabbits or guinea pigs. Lesions were readily produced in both these species by SFR.

5. Border orf has been sl]own to be caused by a filtrable virus, which has been isolated in the form of a purified elementary body suspension, and which is morphologically and serologically identical with the virus of CPD. No evidence of virus etiology could be found n SFR.

6. Immunologically Border orf and CPD have been shown to identical. In the experimental sheep infection with either of these viruses produces a solid immunity lasting for three months only. Thereafter in certain animals the level of immunity rapidly diminishes. SFR is immunologically unrelated to Border orf or CPD, and fails to produce any demonstrable immunity in the experimental animal

7. A micro-organism of the genus Actinomyces, not previously reported in association with sheep dermatitis in this country, has been isolated from SFR. Pure cultures of this organism reproduce exactly the experimental lesion of SFR. When inoculated into experimental sheep, no demonstrable immunity is produced, and the organism itself is inhibited or destroyed by treatment with ether. It is therefore suggested that it plays an important part in the etiology of SFR. The haemolytic staphylococci invariably found in association with this organism have been shown to exert en inhibitory effect on its growth in vitro. In morphology and cultural characteristics this organism closely resembles Actinomyces dermatonomus, which has previously been isolated from outbreaks of Lumpy Wool diee in Merino sheep in Australia.

8. A micro-organism identical to that described above ha been isolated from a field outbreak of dermatitis in a flock of Blackface sheep in Argyllshire.

9. It has been possible to examine only one natural case of SFR during this investigation. The lesions in this ease were proved to contain orf virus. It is therefore suggested that in this instance a case of Border orf was mistakenly called SFR on the clinical appearance of the lesions.