McMaster Testing Methods

FEC Source Recommends The Following Modified McMaster Testing Method

  • Fast, easy Fecal Egg Count.

Flotation solution uses plain table salt.
Incremental introduction of fecal material to flotation solution eliminates the need for a scale.

Use of a Mechanical Stage Microscope recommended.

  1. Flotation solution: Combine 16 oz warm water and 3/4 cup table salt.
  2. Add bits of feces to 26ml of flotation solution until it reaches 30ml.
  3. Crush and mix the sample.
  4. While stirring with a pipette, suction liquid.
  5. Fill the McMaster chambers and place within the microscope stage.
  6. Count the parasite eggs for each species in both chambers and record separately.
  7. Multiply the total number per species by 25. This is your Eggs Per Gram.

Record result for each species separately. This method will provide a quantitative estimate of eggs per gram (EPG) for relevant species of parasites. It can be used to identify animals most in need of anthelmintics treatment. The information below is accepted as “best practice” by the scientific community.

Fecal Egg Count Reduction Test (FECRT)

Administration of an anthelmintic does not guarantee the animal has been dewormed. A Fecal Egg Count Reduction Test (FECRT) can be used to assess the anthelmintic efficacy by calculating the percentage of parasites that survived treatment of the drug administered. To perform the test:

Conduct a FEC before deworming followed by a second FEC 7, 10 or 14 days post treatment (varies with drug). A reduction of less than 90-95% indicates resistance.

Drug Days Post-Treatment

Pyrantel 7
Benzimidazoles (Fenbendazole) 10
Avermectins (Ivermectin, Moxidectin) 14

FECRT Calculation

EPG (pre-treatment) – EPG (14 day post-treatment) X 100 = FECRT

EPG (pre-treatment)

Pre FEC (500) – Post FEC (25) = 475
475/500 (pre) = 0.95 x 100 = 95%