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Composite faecal egg count reduction test to detect resistance to triclabendazole in Fasciola hepatica
  1. R. Daniel, BVSc, BSc, MRCVS1,
  2. J. van Dijk, DVM, PhD, MRCVS1,
  3. T. Jenkins, BSc1,
  4. A. Akca, DVM, PhD1,
  5. R. Mearns, MA, VetMB, CertSHP, MRCVS1 and
  6. D. J. L. Williams, BSc, PhD1
  1. 1Animal Health and Veterinary Laboratories Agency (AHVLA) Carmarthen, Job's Well Road, Johnstown, Carmarthen SA31 3EZ, UK
  2. 2Department of Epidemiology and Population Health, Institute of Infection and Global Health, Leahurst, Chester High Road, Neston, Cheshire CH64 7TE, UK
  3. 3Department of Parasitology, Faculty of Veterinary Medicine, University of Kafkas, Kars 36040, Turkey
  4. 4Animal Health and Veterinary Laboratories Agency (AHVLA), Penrith Investigation Centre and Laboratory, Calthwaite, Penrith, Cumbria CA11 9RR, UK
  5. 5Veterinary Parasitology, Institute of Infection and Global Health, University
    of Liverpool, Pembroke Place,
    Liverpool L69 7ZJ, UK
  1. E-mail for correspondence: williadj{at}

A faecal egg count reduction test, using composite samples, was developed in order to assess the efficacy of the flukicide, triclabendazole (TCBZ) on commercial sheep farms in England and Wales. First, a comparison between individual counts and composite counts was conducted using sheep on two farms with different levels of infection. Faecal samples were collected from 50 sheep on each farm at the time of TCBZ treatment and 21 days later. The results showed that a composite fluke egg count (CFEC) was as sensitive as using individual samples, and the test was subsequently validated on an additional 18 sheep farms. The pre- and post-treatment CFECs using five composite samples were subjected to bootstrap analysis. The variance in fluke egg counts of composite samples was high, but analyses indicated that 20 individual samples analysed as two composites was as sensitive as using five composites. The two-composite assay was evaluated on another five farms. On seven out of 25 farms sampled, egg counts either did not decrease significantly or increased following treatment, suggesting TCBZ resistance on these farms. This assay represents a practical field test that can be used in the first instance to evaluate the efficacy of TCBZ on sheep farms where resistance is suspected.

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