McMaster Faecal Egg Counting Procedure

Materials:

  • Scale
  • Two yellow-top urine containers
  • Faecal flotation solution (a saturated solution of Epsom salts (MgSO4)
  • Magnesium sulfate (Epsom salts):  Approximately 125 grams per 500 mls of water.
  • 30 cc syringe
  • Mixing instrument (wooden handle of swabs)
  • unfolded gauze squares
  • 1 ml plastic bulb syringe
  • McMaster slide (2 or 4 chamber)
  • Microscope
  • Timer

Technique:

  1. Lay out 2 urine containers (if doing more than one sample at a time-use the numbered lids to keep the samples straight).
  2. Tare one cup on scale.
  3. Measure two grams of faeces into cup on scale
  4. Dispense 28 ml flotation solution into the cup, mix and let soak for approximately 5 minutes.
  5. Return to the first sample and mix again. Place gauze on top of the second cup (don’t stretch fabric tight across the cup). Pour the mixture of faeces and flotation solution through, pressing fluid through with the wooden stirrer.
  6. Immediately, fill both chambers of the McMaster slide using the plastic bulb syringe. If large bubbles are present, empty the slide and refill. Fill the entire chamber, not just the area under the grid.
  7. Set slide aside for at least 5 minutes to allow parasite eggs to float to the surface.
  8. Place McMaster slide onto the microscope stage.
  9. Bring the grid lines on the McMaster slide into focus using the low power (4X) objective and the coarse adjust knob. Turn to the 10X objective and refocus grid lines using the fine adjust knob. You can also focus on the air bubbles.
  10. Count all eggs inside of the grid areas using the 10X objective (include eggs on the grid line if greater than ½ of egg inside grid) in both chambers.
  11. Count both chambers. Total egg count:  (chamber 1 + chamber 2) * 50 = eggs per gram (EPG).

 

This multiplication factor of 50 is specific to the ratio of faeces (2 grams) to flotation solution (28 ml) described in this procedure. Each egg observed represents 50 eggs/gram therefore, this procedure will not detect fewer than 50 eggs/gram, which is equivalent to seeing one strongyle egg on the McMaster slide.