Fleece derangement of merino sheep infested by the itch mite Psorergates ovis |
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| Authors: | AN Sinclair MVSc FRCVS MACVSc |
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| Institution: | School of Wool and Pastoral Sciences , University of New South Wales , Kensington, N.S.W. |
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| Abstract: | Abstract Extract Fleece derangement, characterized by matted chewed wool in a region accessible to the sheep's mouth — i.e., behind a line approximately from elbow to hip, — indicates a typical behavioural response by sensitive sheep infested with Psorergates ovis. The condition was recorded by Bekker (1928) Baker, J. A. F. 1968. Some clinical aspects of itch mite (Psorergates ovis) infestation of Merino sheep in South Africa. Jl S. Afr. vet. med Ass., 39: 53–68. Google Scholar] long before the mite was found (Carter, 1941 Bekker, J. G. 1928. Undescribed skin diseases of sheep in South Africa. Jl S. Afr. vet. med Ass., 1: 51–57. Google Scholar]; Womersley 1941 Carter, H. B. 1941. A skin disease of sheep due to an ectoparasitic mite, Psorergates ovis Womersley 1941. Aust. vet. J., 17: 193–201. Google Scholar]). Fleece derangement is seen easily at flock inspection and so is used as anindication of P. ovis infestation in a flock, though Baker (1968) Graham, N. P. H. 1943. Some observations on the bionomics of the itch mite (Psorergates ovis) of sheep and its control with lime sulphur dips. J. Coun. scient. ind. Res. Aust., 16: 206–214. Google Scholar] showed that a greater proportion of sheep in which heavy skin scurf was present, with or without fleece derangement, may be infested. Inspecting individual sheep closely for scurf is slow, while examining skin scrapings limits the number of sheep that can be inspected to less than about twenty per day, so the ready convenience of observing fleece derangement favours its use. |
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