Sensitivity of two-stage sampling to detect sheep biting lice (Bovicola ovis) in infested flocks

P. J. James, J. A. Garrett, R. D. Moon

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The sampling distribution of Bovicola ovis (Schrank) on sheep was examined in two flocks, one with a light and one with a heavy infestation of lice. The derived distributions were used to calculate the sensitivity of detecting lice on individual sheep and in flocks by fleece parting regimes that varied in number of parts per animal and number of sheep per flock, different scenarios of flock sizes, proportion infested and louse density were examined. Lice were aggregated among fleece partings in the heavily infested flock and described by a negative binomial distribution with k values between 0.3 and 1.92. The distribution was indistinguishable from Poisson in the lightly infested flock. The assumed distribution had little effect on sensitivity, except when only one fleece part per animal was examined. On individual sheep where louse density was 0.5 per 10cm part or greater, there were only marginal gains from inspecting more than 10 parts per animal. Increasing the number of sheep inspected always increased sensitivity more than increasing number of parts per sheep by an equivalent amount. This advantage was greatest in situations where a low proportion of sheep in the flock were infested with a high density of lice, and less where a low proportion of sheep were infested with a low density of lice, or a high proportion of sheep were infested with a high density of lice.

Original languageEnglish (US)
Pages (from-to)157-166
Number of pages10
JournalVeterinary Parasitology
Volume103
Issue number1-2
DOIs
StatePublished - Jan 3 2002

Bibliographical note

Funding Information:
We thank Dan Brown at the North Central Agricultural Experiment Station, Grand Rapids, MN and the staff of Minnipa Research Centre in South Australia for managing sheep and helping record louse counts. The assistance of Janet Moe with graphics and internet file transfer is also gratefully acknowledged. Financial support was provided by an International Wool Secretariat Postgraduate Scholarship (PJJ) and the Minnesota Agricultural Experiment Station (RDM).

Keywords

  • Bovicola ovis
  • Detection
  • Sheep-arthropoda

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