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Egg Counts: Techniques and Timing

Rolling Nematodes
Used to examine the morphology of small nematodes in order to classify to species.

Place a worm on a slide with a few drops of water and a coverslip.
Place the slide on your microscope under low power and roll the worm by moving the coverslip around.
If the worm is a male try to get it in such a position that the bursa is spread out so the dorsal ray is visible. If the specimen is a female, roll it until the vulva is visible.


Egg Count Significance
These are only approximate and should be considered in association with the clinical signs.

condition egg count (EPG, eggs per gram)
Parasitic gastritis in lambs 2000 - 6000
Parasitic gastritis in cattle 300 - 600
Strongylosis in equines 1500 - 2500
Fascioliasis in sheep 300 - 600
Fascioliasis in cattle 100 - 200


Egg laying Capacity of Some Nematodes

species egg-laying capacity
Haemonchus contortus 5000 - 10000 eggs per day
Ostertagia and Trichostrongylus spp. 500 - 2000 eggs per day
Nematodirus filicollis 50 - 250 eggs per day


Severity of Infection
Fatal effects seldom seen with less than:

species body load
Haemonchus contortus 1,000 worms
O. circumcincta 8,000 worms
Trichostrongylus spp. 10,000 worms
Chabertia ovina 100 worms


Fecal Egg Count Reduction Test (FECRT)
time needed before 2nd count is run:

drug days post-treatment
Levamisole, Pyrantel 7
Benzimidoles 10
Avermectins 14



Copyright © 2006 - University of Pennsylvania School of Veterinary Medicine, All rights reserved.
Faculty: Dr. Thomas Nolan
Students: Molly Church V'09, Diana Knight V'08, Douglas Gilson V'05, Chris Dykhouse V'04, Kimberly Mah V'00

Comments or Questions contact Dr. Tom Nolan at: