Parasitlogy; McMaster Technique for fecal egg count

12:58 AM | Labels: fecal egg count, McMaster technique, parasitology

Aim: To check the effectiveness of the anthelmintics by counting the estimate number of the worm's eggs.

Fecal egg count using modified McMaster technique is currently the main measurement used for selection for parasite resistance.

Equipments

2 beakers or plastic equipment
Weighing scale
Measuring cylinder
Mortar and pastle
Filter
Spatula
Pipette
Saturated salt solution
McMaster slide
Compound Microscope
Animal feces

Procedure

1. Weigh 3 grams of faeces and place into a container.

scales and container into which faeces are being placed

** Feces must be fresh. Wear gloves.

2. Add 45ml saturated salt solution

flotation fluid being added to container

3. By using mortar and pastle grind off the feces (to remove the fiber) and filter the solution into another beaker.

pouring solution from one beaker to the second beaker

4. Stir the solution by using spatula and leave for 2-3 minute (to allow the fiber to become sedimentary at the bottom of the beaker

5. Pipette the solution and fill the first compartment of the McMaster slide

** the second compartment may be filled by other sample

for example: 1st compartment = sample A

2nd compartment = sample B

6. Observe the McMaster slide under the compound microscope at 10x10 mag

** Do not use 40x and 100x because the objective will break the thick upper part plate of the McMaster slide.

7. Identify and count all eggs within the area of both chambers

8.The number of eggs per gram can be calculated as follows:

Count the number of eggs within the grid of each chamber, ignoring those outside the squares. For example:

Sample A Sample B

*Read from the first left row down to the second row up to the third row and next..

Calculation

Sample A

12 eggs x 100 epg = 1200 epg

*100 epg is the times factor for the McMaster technique

Sample B

15 eggs x 100 epg = 1500 epg

Interpretation of the results

More than 3000 epg, the animals must be given anthelmintics or change the deworming drugs because the higher the epg numbers indicates the worm's resistance against the anthelmintic drugs.

Eggs are produced only by fertile adult female (or hermaphrodite) worms and will, therefore, be absent in immature or single sex infections
The daily output of eggs by fertile females is influenced by host-physiological factors such as stress or lactation ( increased ) or immunity ( decreased )
Chemotherapy can also affect egg-production e.g. corticosteroids ( increased ) or sub-lethal anthelmintic doses (decreased)
Some food-stuffs may have a similar effect e.g. tannin-rich forages (decreased )
The concentration of eggs (per gram of faeces) is influenced by the daily volume of faeces being produced by the host, the rate of passage by the ingesta through the intestine, and the distribution of eggs throughout the faecal mass.
Some types of eggs are heavier than others and may not float well in solutions of lower specific gravity (e.g. Fasciola)
Some eggs from different species are indistinguishable (particularly trichostrongylids and strongylids). This complicates clinical interpretation as some species (e.g. Haemonchus) produce many more eggs per day than others (e.g. Ostertagia).

Ruminant eggs (commonly found)