Fecal Examination Using the Stoll Egg Counting
The Stoll Egg Counting Technique is a method for determining
the number of nematode eggs per gram of feces in order to estimate the
worm burden in an animal. The advantage of this technique is that it requires
no specialized equipment. The disadvantage is that the counting takes a
long time because of the amount of extra (non-egg) material on the slides.
- Weigh out 3 grams of feces
- Measure out 42 ml of water and place it into a dish.
Using a tongue depressor, push the 3 grams of feces through a sieve into
the water. Lift the sieve and hold over the dish. Push out any remaining
water from the feces.
- While stirring the water-feces mixture, take 0.15 of
the suspension and spread over 2 slides. Cover each slide with a long coverslip
(or 2 regular coverslips).
- Examine both slides for worm eggs. The total amount of
eggs counted X 100 represents the number of eggs per gram of feces.
The mathematics: 0.15 ml is 1/300 of 45 ml (42
ml water and 3 grams of feces) so the number of eggs in 0.15 ml X 100 is
equal to 1/3 of the total number of eggs in the original 3 grams (and thus
equal to eggs per gram = EPG).