|This is the third in a series of four articles concerning parasite control. These articles are excerpted from Texas A&M University Agricultural Extension Service pamphlets. They have been converted to HTML files from .pdf format for the convenience and education of our readers.
Monitoring Internal Parasite Infection in Small Ruminants
[pamphlet L-5094 6/94]
Frank Craddock, Rick Machen, and Tom Craig
EPG = Number eggs counted X 100 number of grids
Frequently during the spring, summer, and early fall, based on subjective observation, internal parasites are cited as the cause for poor livestock performance. While parasites are frequently the culprit, other performance inhibitors do exist. Fecal egg counts are a practical, cost-effective diagnostic tool for determining parasite burden.
Materials and Equipment
- Microscope -- must have 100X magnification capability. Binocular preferred, monocular acceptable. Mechanical stage preferred but not required.
- McMaster’s slide -- two or three chambered counting slide with grid. (Ed. Note: These slides are available from http://www.advancedequine.com/veterinary/)
- Fecal sample -- 2 grams minimum. Samples should be warm, moist and soft at collection. Eight to 10 pellets per sample is generally a sufficient quantity.
- Vial -- straight sides, glass or plastic, with cap. Fill with 28 ml (cc) of water and mark meniscus. Add 2 ml (30 ml total) and mark meniscus again.
- Tongue depressor
- Medicine dropper
- Saturated salt solution -- prepared by adding salt to boiling water until salt will no longer go into solution. Iodized salt often leaves a white precipitate and is therefore the least preferred. (Ed. note: A commercially prepared solution such as Fecasol® is preferred for consistency.)
Procedure (see diagram)
- Fill vial to 28 ml mark with saturated salt solution.
- Add fecal material until solution reaches the 30 ml mark. Theoretically, 2 grams of material will displace 2 ml of solution. Mashing pellets between thumb and forefinger before adding to solution will facilitate mixing.
- Use tongue depressor (larger depressors can be split longitudinally) to break up and mix pellets in solution.
- Cap vial and mix thoroughly by gently inverting several times (do not shake).
- With eggs evenly dispersed in the solution, remove cap and immediately remove a dropperful of material.
- Holding the slide almost flat with ends of slide between thumb and forefinger, completely fill one chamber. Slightly tilting slide will facilitate filling. Immediately fill dropper again and fill remaining chamber.
- Allow 1 to 2 minutes for eggs to float to upper surface of the counting chamber.
- Examine at 100X magnification (10X ocular, 10X objective). Two focal planes exist. Eggs and air bubbles will be in the upper plane. Focus on air bubbles, then locate (by moving the slide left-right, forward and back) grid.
- Count eggs in each grid. Do not count eggs outside the grid.
- Calculate number of eggs per gram of feces as below:
Dunn, A. 1978. Veterinary
Helminthology (2nd Ed.).
Medical Books Ltd.,
Educational programs of the Texas Agricultural Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin.
Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Edward A. Hiler, Interim Director, Texas Agricultural Extension Service, The Texas A&M University System.
The information given herein is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement by the Cooperative Extension Service is implied.
Frank Craddock, Professor and Extension Sheep and Goat Specialist, San Angelo;
Rick Machen, Assistant Professor and Extension Livestock Specialist, Uvalde;
Tom Craig, Professor, Department of Veterinary Pathobiology, College Station;
The Texas A&M University System.
Original .pdf version produced by Agricultural Communications, The Texas A&M University System