Procedure for Counting Fecal Eggs
Conducting a fecal egg count is an easy method for determining the severity of internal parasite infection in a goat. The procedure is simple but does require some special pieces of equipment. However, once all of the required items have been acquired, very little time is needed to count fecal eggs and the information provided to a producer can be very valuable in making health and management decisions. Further, once the procedure has been mastered, it is possible for a producer to test the effectiveness of the dewormer (anthelmintic), whether conventional or alternative, being used through performing a fecal egg count reduction test.
The fecal egg counting procedure described here is a modified version of the McMaster technique. The principle of the procedure is that fecal eggs excreted in the manure will be separated from the manure so that they can be counted. This is accomplished through the use of a flotation solution, a special microscope slide, and a microscope.
The equipment needed to conduct a fecal egg count includes:
- Microscope having a 10X objective and 10X wide field (WF) eyepiece. A mechanical stage allowing ease of movement of the slide is preferable.
- McMaster slide, the special slide in which the fecal eggs are counted. These are available from Chalex Corporation phone 425-391-1169 or www.vetslides.com.
- Thirty cc syringe
- Three cc syringe with the end cut off or
- Balance or scale that weighs accurately to 0.1 grams
- Teaspoon/tongue depressor/popsicle stick/spatula
- Small dish, such as a salsa dish
- Tea strainer
One of the following flotation solutions having a specific gravity of 1.20 needed to float eggs must be made or purchased.
- Add 1 1/4 cup sugar to 1 cup water and mix (easiest to mix) or
- 34% solution of zinc sulfate (used for footbath) or
- Saturated sodium nitrate solution (28%, fertilizer) or
- Saturated solution of salt, rock salt or uniodized salt (requires heating and a lot of stirring) or
- Fecasol, Feca-Med, or generic fecal float solution available for $5-10./gal from a veterinary supply store
Collecting fecal samples
For most producers, it is unrealistic to expect that every goat will be sampled and tested. The following suggestions may serve as guidelines for the number of goats needed to be sampled and tested.
- If the herd consists of fewer than 8 goats, sample all goats.
- For herds up to 50 in number, sample 8 to 12 goats.
- For herds up to 100, sample 15 to 20 goats.
- If goats are sampled several times during the year to monitor fecal eggs, it is best if the same animals are being sampled.
The fecal samples collected must be fresh. This can be accomplished in two ways. A producer can watch his/her goats and collect fresh pellets after defecation or the producer can put on an examination glove, lubricate with water and tease five to six pellets from the rectum. In either case, the pellets should be stored in a ziplock bag and animal number recorded. Pellets can be stored in the refrigerator or on ice for 3 to 4 days but should not be frozen. However, it is best to conduct the test directly after collecting the fecal samples.
- Fill the 30 cc syringe to exactly 28 cc with the flotation solution.
- Add the 28 cc to the small dish.
- Add the correct amount of feces in one of two ways
- If using a balance, weigh 2 grams of feces and place them into the tea strainer sitting in the small dish with the flotation solution. It may be necessary to break a pellet to get within 0.1 grams of 2.0 grams.
- If a balance is not available, mash feces into the 3 cc syringe that has had the end cut off. Form a solid column of feces in the syringe. Push the plunger to the 2 cc mark and cut off the feces protruding from the syringe. Push the 2 cc of fecal material into the tea strainer sitting in the small dish with the flotation solution.
- Use a spoon or other tool to crush and break up feces forming a slurry. This usually takes roughly 2 minutes.
- Lift the tea strainer out of small dish and discard the fecal residue.
- Stir the solution in the dish 8 times with a spoon using a back and forth motion. Then use an eyedropper to fill one chamber of the McMaster slide.
- Repeat the above step and fill the other chamber of the slide.
- Allow slide to sit 5 minutes.
- Look at the slide under microscope. Focusing on air bubbles trapped in the slide will give proper focus.
- Orient the slide to begin in one corner of the marked lanes. The slide has two squares each of which is marked off into 6 lanes. Begin in the corner of one square and start counting up one lane, ensuring that both marked sides of the lane are visible. Move the slide over to the next lane and count down. Repeat this procedure until all 6 lanes are counted.
- The eggs of interest will appear oval and similar to rounded-end footballs in shape.
- While it is possible to identify tapeworm eggs and coccidia, the eggs of most interest are the oval shaped roundworm eggs. These should be counted.
- Count all eggs in 6 lanes in one chamber or half of the slide then repeat on the other half.
- Total the number of eggs from both squares. (The number of eggs in each square should be similar. If this is not the case, the slides may need to be reloaded and recounted.)
- Multiply that number by 50 to calculate eggs per gram feces.
Some general recommendations for deworming are to deworm dry does and bucks when 2,000 eggs per gram of feces are found. All other animals should be dewormed when having 1,000 eggs per gram of feces. After deworming, do not return animals to contaminated pastures.
To see a visual step-by-step of this process, click here.