This document provides instructions for performing a fecal egg count (FEC) to quantify the number of parasite eggs present in small ruminant feces. It explains that FEC allows farmers to monitor pasture contamination, assess increases in worm numbers, determine when to move animals, and test for drug resistance. The procedure involves weighing feces, mixing it with a flotation solution, straining the mixture, counting eggs observed under a microscope, and calculating eggs per gram. FEC has limitations as eggs cannot be identified to species level and counts may not be accurate, but it provides a quantitative measure of parasite burden to inform management decisions.

1. FECAL EGG COUNTING
PRIMER
Dahlia O’Brien
Small Ruminant
Extension Specialist
Virginia State University
dobrien@vsu.edu
(804) 524-6963

2. What are Fecal Egg Counts
• Fecal egg counts (FEC) are a quantitative measure of specific number of
eggs present per gram of feces (epg; using a known quantity of feces and
flotation solution)
• Qualitative Analysis
• Shows presence or absence of eggs
• Shows general trends

3. What do FEC tell us?
• Monitor the rate of pasture
contamination
• Provide valuable information on whether or
not worm numbers are increasing on a pasture
• Helps determine when to move animals off of
a particular pasture
• How many samples do you need to take?
• Depends on the number of animals you have
in your flock/herd
• 40 animals - reliable estimate of the group
average would be around 12 to 15 random
samples

4. What do FEC tell us?
• Determine drug resistance
• FEC done at treatment and 10 – 14
days later
• Need more animals to test (10-
15/dewormer)
• Minimum fecal egg count of 250 epg
• Individual or pooled samples can be
used
• Get % resistance

5. What do FEC tell us?
• Selecting or culling particular animals
• Parasite resistance and resilience are both
heritable traits
• Parasite resistant animals
• Low FEC, low FAMACHA© scores, and rarely
require deworming
• Parasite resilient animals
• Low FAMACHA© scores, no other signs of
parasitism, but has high FEC
• Both of these animals are productive, but a
resistant animal is most desiredConducting routine FEC allows the identification
of resistance or resilient animals to select for
breeding

6. What do FEC tell us?
• Should fecal egg counts be used to
determine need to treat?
• In most cases, no
• Deworming is advisable if;
• An animal has an extremely high FEC even with no
other indicator of parasitism (limits pasture infestation
and exposure of more susceptible animals to worm
larvae)
• Use in conjunction with FAMACHA© andFive Point
Check©
• Can use along with weight gain or loss to determine
treatment

7. Modified McMaster Technique
• Most common counting technique for
ruminants
• Principle of differential density
• Parasite eggs sink in water and float in more
dense solutions
• Used to count the number of oval shaped
strongyle/trichostrongyle eggs (barber
pole and related worms
• Strongyle eggs look the same and cannot
be differentiated at the egg state
www.vetslides.com; www.eggzamin.com
2-chamber slide - $17.95 - $20
3-chamber slide - $60
FEC kits - $289 - $439

8. Modified McMaster Technique
• Microscope
• Monocular or binocular, 10x eyepiece,
light source(internal best), mechanical
stage
• Floatation solution
• Salt, sugar, sugar and salt, Epsom salts
solution can be used
• Commercial (Fecasol® or Feca Med) Sodium chloride (pickling salt): 180 grams per 500 mls of
water. ¾ of a cup of salt to 1 pint (16 ounces) of water –
this would do about 16 fecal samples

9. Modified McMaster Technique
• What else do you need?
• Gloves for sampling
• Form of lubricant
• Small snack bag for sample
• Sharpie to label
• 2-4 g of feces
• Small cooler with ice
• Scale
• Small cups
• Tongue depressors/craft
sticks/spoons
• Tea strainer/cheesecloth
• Tuberculin syringe/pipette

10. Modified McMaster Technique
• STEP #1 – Collect and store
fecal samples
• Use a rubber glove and lubrication
to extract feces directly from the
rectum
• Collect freshly passed feces that is
uncontaminated by soil or bedding
• Need at least 2g (≈8 pellets)

11. Modified McMaster Technique
• Fecal storage
• Place samples in labeled snack bag or
gloves
• Evacuate all air and seal bag
• Fecal egg counting
• Fresh samples work best
• Keep sample cool/refrigerated until
analysis
• Eggs will hatch within 12 to 24 hrs. if
not placed in cooler/refrigerator
• Analyze within 1 week of collection

12. Modified McMaster Technique
• Step #2 - Weigh 2 – 4g feces
into labeled cup/container
• More increases accuracy
• Check consistency, presence of
blood, mucus, and color
No scale - Add 28 ml of saturated solution to a 50
ml centrifuge tube and add feces until volume of 30
ml is reached

13. Modified McMaster Technique
• Step #3 – Add saturated
solution to fecal matter and
mix
• To the 2-4g fecal sample, add
28-26 ml of sugar and salt
solution
• Use a tongue depressor/craft
stick to mix and thoroughly
break up fecal sample
Principle of differential density
Parasite eggs sink in water
and float in more
dense solutions

14. Modified McMaster Technique
• Step #4 – Strain fecal
slurry into a clean labeled
cup
• Using a tea strainer or
cheesecloth, strain fecal
slurry into a separate
container/cup

15. Modified McMaster Technique
• Step #5 – Transfer slurry to slide
• Immediately after straining, stir and fill
pipette/tuberculin syringes/eye dropper
with a sample of the suspension
• Fill both chambers of McMaster slide
• Mix fecal solution and refill syringe if it
takes long between filling chambers
(more than a few seconds)
• Let slide sit for 2-5 minutes but no
longer than 1 hr.

16. Modified McMaster Technique
• Step #6 – count eggs inside grid area
• Using low power 10X objective, count
the number of eggs (oval shaped
strongyle/trichostrongyle eggs) in the
sample going up and down the 6 lanes
inscribed on each counting chamber
• Do not count strongyloides, tapeworm
eggs or coccidian – make a note of their
presence
• Don’t count eggs outside of chambers

17. Modified McMaster Technique

18. Modified McMaster Technique
• What do I count?
• Barber pole and related parasites
(strongyle or trichostrongyle
eggs)
• Oval, presence of a shell,
contains a number of cells
that form larva

20. Air bubble Tapeworm
Coccidia, strongylid and strogyloides
Adapted from https://web.uri.edu/sheepngoat/files/McMaster-
Test_Final3.pdf
Pollen
Modified McMaster Technique

21. Modified McMaster Technique
• Step #7 – Calculate eggs per
gram (epg)
• Multiply total eggs in chamber
by 50, 33, or 25 if used 2, 3, or
4 g respectively
• Example – using 2g of feces
• (10 + 15) * 50 = 1250 epg

22. Modified McMaster Technique
• Limitations of FEC
• Not very accurate, especially when low
• Worms will vary in egg producing
capacity
• Inhibited larvae do not lay eggs
• Strongyle eggs look the same and
cannot be differentiated at the egg state
• Peanut –agglutination test
• Larval identification to determine
species
• Eggs are not evenly distributed in fecal
matter and there is day-to-day variability
• Loose stools/diarrhea underestimate
FEC
• Procedure varies by lab and technician

23. American Consortium for SMALL
RUMINANT Parasite Control (ACSRPC)
http://www.wormx.info
The American Consortium for Small Ruminant Parasite Control was
formed in response to the critical state of the small ruminant industry
associated with the emergence of anthelmintic resistant worms. The
ACSRPC is a group of scientists, veterinarians, and extension specialists
devoted to (1) developing novel methods for sustainable control of
gastro-intestinal nematodes in small ruminants and (2) educating the
stakeholders in the small ruminant industry on the most up-to-date
methods and recommendations for control of gastrointestinal
nematodes

24. Thanks for you attention