WHITLOCK worm egg counting - Calculations

The WHITLOCK worm egg counting slides are particularly designed for the quantative estimation of the number of parasite eggs per gram of faeces in animals.

The overall methods which utilise this information can estimate the degree of infestation in livestock and the efficacy of treatments.


download a compressed (24K ZIP) FREE Excel (4 or later) spreadsheet
calculation program to get you started
A bit of practice looking down the microscope
FREE flash egg counting demonstration
and as a ZIP compressed file
(Note that a lot of antivirus software may try to block this).
The mean of two counts is recommended in calculating egg counts.

To determine the number of eggs per gram (epg) of faeces-

multiply the number of eggs of each type counted in the scanned area of the slide by
Volume of (water + faeces sample)   +   Flotation solution
Volume of faeces sample   *    Measurement volume used
(Volume of faeces sample= weight of faeces sample)
(Measurement volume used may be only a part of the slide)
(This fraction is the FACTOR referred to in the table.)

eg:  For 2g faeces in 58ml of flotation solution (2g:60ml)
place 2g faeces in 2.5ml water (or 0.1% aqueous methylene blue) and 55.5ml flotation solution and measure or count in one chamber (0.3ml for the Whitlock McMaster)
- (for calculations for other Whitlock slides and different dilutions  see Universal , McMaster or Paracytometer):
-  (or click here to download a FREE Excel spreadsheet calculation program to get you started)
epg = #eggs  *  (2.5+2+55.5) / (2 * 1*0.3) = # * 100      where " * "   means  "multiply"
         (in other words, in this instance, multiply the number of eggs counted by 100 to give the epg.)


Details about the techniques which use these slides may be found in the Section on Anthelmintic Resistance in Sheep (para 9.1 in particular) in Australian Standard Diagnostic Techniques for Animal Diseases. - ISBN 0 643 05243 7 636.0896075 developed through the Standing Committee on Agriculture and Resource Management, Animal Health Committee, [SCARM] Sub-committee on Animal Health Laboratory Standards [SCAHLS] and published on their behalf by CSIRO Information Services, Australia.

(Note that the recommended dilution is intended for the Whitlock Universal slide to give a simple Factor as above. Alternatives are permitted)

Available as 1.6Mb pdf on our website at  www.whitlock.com.au/slides/pdf/ASDT-AnthrlmResist-signed.pdf
and on the SCAHLS website at http://www.scahls.org.au/asdts/05-AnthelminiticResistanceinSheep.pdf

JA Whitlock & Co       ABN 70 033 804 404       GST registered  
        phone  (02) 9638 1142
international 61 2 9638 1142  
    slides@whitlock.com.au                 website    www.whitlock.com.au

 Slides main  Page last updated 23 December 2010 by John Whitlock
If you would like to comment on the site please contact webmaster@whitlock.com.au