The effect of selection with levamisole on benzimidazole resistance in Ostertagia spp. of sheep
Donald, A.D., Waller, P.J., Dobson, R.J. and Axelsen, A. (1980) The effect of selection with levamisole on benzimidazole resistance in Ostertagia spp. of sheep. International Journal for Parasitology, 10 (5-6). pp. 381-389.
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A field population of Ostertagia spp. (predominantly O. circumcincta) in sheep, found to be resistant to oxfendazole, was exposed to selection with1 levamisole in the laboratory and the field. Progeny of the survivors of a single dose of levamisole in penned sheep showed a significantly lower level of resistance to oxfendazole in an anthelmintic assay, and a similarly lower level of resistance to the ovicidal activity of thiabendazole in vitro compared with the progeny of the survivors of a single dose of oxfendazole, although they remained more resistant than a known susceptible strain of 0. circumcincta. The progeny of worms present in grazing sheep after three doses of levamisole at 4-weekly intervals, and subjected to the same tests, behaved in a similar fashion. They also showed a substantial fall in benzimidazole resistance compared with the progeny of worms not exposed to any anthelmintic for 6 months. The results suggested that levamisole selected positively against benzimidazole resistance. In these circumstances some form of alternation in the use of different anthelmintics could delay the development of a high level of resistance and maintain the practical usefulness of existing anthelmintics.
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|Copyright:||© 1980 Published by Elsevier Ltd.|
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