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Comparison of calculation methods used for the determination of anthelmintic resistance in sheep in a temperate continental climate

Falzon, L. ; van Leeuwen, J. ; Menzies, P. ; Jones-Bitton, A. ; Sears, W. ; Jansen, J. ; Peregrine, A.

In: Parasitology Research, 2014, vol. 113, no. 6, p. 2311-2322

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    Titel
    • Comparison of calculation methods used for the determination of anthelmintic resistance in sheep in a temperate continental climate
    Autor
    • Falzon, L.. Department of Population Medicine, Ontario Veterinary College, University of Guelph, N1G 2 W1, Guelph, ON, Canada
    • van Leeuwen, J.. Centre for Veterinary Epidemiological Research, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, C1A 4P3, Charlottetown, PE, Canada
    • Menzies, P.. Department of Population Medicine, Ontario Veterinary College, University of Guelph, N1G 2 W1, Guelph, ON, Canada
    • Jones-Bitton, A.. Department of Population Medicine, Ontario Veterinary College, University of Guelph, N1G 2 W1, Guelph, ON, Canada
    • Sears, W.. Department of Population Medicine, Ontario Veterinary College, University of Guelph, N1G 2 W1, Guelph, ON, Canada
    • Jansen, J.. Veterinary Science and Policy, Ontario Ministry of Agriculture and Food, N0B 1S0, Elora, ON, Canada
    • Peregrine, A.. Department of Pathobiology, Ontario Veterinary College, University of Guelph, N1G 2 W1, Guelph, Ontario, Canada
    Dokumententyp
    • Postprint
    Sprache
    • Englisch
    Veröffentlicht in
    • Parasitology Research, 2014, vol. 113, no. 6, p. 2311-2322. Springer Berlin Heidelberg
    Andere elektronische Ausgabe
    OAI-PMH-ID
    • oai:doc.rero.ch:326041
    Summary
    This study compared results obtained with five different fecal egg count reduction (FECR) calculation methods for defining resistance to ivermectin, fenbendazole, and levamisole in gastrointestinal nematodes of sheep in a temperate continental climate: FECR1 and FECR2 used pre- and posttreatment fecal egg count (FEC) means from both treated and control animals, but FECR1 used arithmetic means, whereas FECR2 used geometric means; FECR3 used arithmetic means for pre- and posttreatment FECs from treated animals only; FECR4 was calculated using only arithmetic means for posttreatment FECs from treated and control animals; and FECR5 was calculated using mean FEC estimates from a general linear mixed model. The classification of farm anthelmintic resistance (AR) status varied, depending on which FECR calculation method was used and whether a bias correction term (BCT, i.e., half the minimum detection limit) was added to the zeroes or not. Overall, agreement between all methods was higher when a BCT was used, particularly when levels of resistance were low. FECR4 showed the highest agreement with all the other FECR methods. We therefore recommend that small ruminant clinicians use the FECR4 formula with a BCT for AR determination, as this would reduce the cost of the FECRT, while still minimizing bias and allowing for comparisons between different farms. For researchers, we recommend the use of FECR1 or FECR2, as the inclusion of both pre- and posttreatment FECs and use of randomly allocated animals in treatment and control groups makes these methods mathematically more likely to estimate the true anthelmintic efficacy.