Evaluation of a larval development assay for the detection of anthelmintic resistance in Ostertagia circumcincta

dc.contributorUniversidade Estadual Paulista (UNESP)
dc.creatorAmarante, AFT
dc.creatorPomroy, W. E.
dc.creatorCharleston, WAG
dc.creatorLeathwick, D. M.
dc.creatorTornero, MTT
dc.date2014-05-20T15:26:37Z
dc.date2016-10-25T18:01:16Z
dc.date2014-05-20T15:26:37Z
dc.date2016-10-25T18:01:16Z
dc.date1997-03-01
dc.date.accessioned2017-04-05T23:57:58Z
dc.date.available2017-04-05T23:57:58Z
dc.identifierInternational Journal For Parasitology. Oxford: Pergamon-Elsevier B.V., v. 27, n. 3, p. 305-311, 1997.
dc.identifier0020-7519
dc.identifierhttp://hdl.handle.net/11449/36759
dc.identifierhttp://acervodigital.unesp.br/handle/11449/36759
dc.identifier10.1016/S0020-7519(96)00183-X
dc.identifierWOS:A1997WU57500009
dc.identifierhttp://dx.doi.org/10.1016/S0020-7519(96)00183-X
dc.identifier.urihttp://repositorioslatinoamericanos.uchile.cl/handle/2250/880213
dc.descriptionTwo experiments were carried out to evaluate a larval development assay for the detection of anthelmintic resistance in O. circumcincta. In Experiment I, the dose responses to levamisole (LEV), thiabendazole (TBZ) and ivermectin (IVM) of 8 isolates of O. circumcincta were measured 34 days after infection (DAI). Four of these isolates were shown to be resistant to 1 or more anthelmintics. With 2 exceptions, all isolates considered to be resistant had higher LD50 values than the susceptible isolates for that anthelmintic. One exception was isolate RM8, which was considered to be resistant to all 3 anthelmintics based on faecal egg count reduction tests in goats, but the LD50 value for LEV did not differ from that for the susceptible isolates. The other exception was an isolate considered to be susceptible to TBZ which had a relatively high LD50 value. In an unrelated trial that was prompted by this finding, this isolate was confirmed to be benzimidazole-resistant. Isolate RM8 and an isolate susceptible to all 3 anthelmintics (SK2) were used in the second experiment, which was conducted to monitor changes in the LD50 values of LEV, TBZ and IVM over time following a single infection of 35 000 infective larvae in young sheep. Faecal samples were collected weekly from 24 to 115 DAI. With all 3 anthelmintics, the LD50 values increased with time to a peak around 50-60 DAI, and then declined to levels similar to those observed soon after patency. This trend was consistent for both isolates. The highest mean LD50 values for isolates SK2 for IVM and TBZ and RM8 for IVM and RM8, respectively, were 1.7 and 1.8 times, and 2.2 and 2.9 times higher than the initial mean LD50 values. There was a clear distinction in LD50 values between isolates at each sampling day for both IVM and TBZ. However, as a consequence of the changes in LD50 values with time, the peak LD50 values of IVM for isolate SK2 were higher than the minimum LD50 values of isolate RM8. As there was no apparent difference in LEV efficacy between these 2 isolates, the data were pooled. The highest mean LD50 value was 2.3 times higher than the initial LD50 value. (C) 1997 Australian Society for Parasitology.
dc.languageeng
dc.publisherElsevier B.V.
dc.relationInternational Journal for Parasitology
dc.rightsinfo:eu-repo/semantics/closedAccess
dc.subjectnematode
dc.subjectanthelmintic resistance
dc.subjectin vitro assay
dc.subjectsheep
dc.subjectivermectin
dc.subjectthiabendazole
dc.subjectlevamisole
dc.titleEvaluation of a larval development assay for the detection of anthelmintic resistance in Ostertagia circumcincta
dc.typeOtro


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