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Collecting samples and faecal egg counting

Choosing the right sample

Fresh poo: warm, pliable and shiny with flies buzzing around

Avoid old poo: dry, hard with a dull appearance

 

horse sampling

Collecting samples

Roundworm eggs are not evenly dispersed throughout horse faeces.

It is important to collect samples correctly to maximise the accuracy of the test results:

  • Take 5 small pinches from at least 3 dung balls from a fresh dung pile
  • The sample should weigh at least 5g

Storing samples

  • Remove air from bags to avoid worm eggs developing
  • Post/deliver samples ASAP – ideally samples should be taken on the day of testing
  • If you need to store samples, keep them in the fridge and ensure they are tested within 5 days

There are lots of different egg count providers who could test your samples, including vet surgeries and diagnostic labs

microscope

This is how to do a faecal egg count

  1. Mix faecal sample well and weigh out 3g into a plastic bag
  2. Add 42ml of saturated salt solution
  3. Mash up the sample – make sure no lumps of faecal material remain
  4. Pour mixture over a tea strainer into a plastic beaker. Squeeze out the moisture and discard the debris
  5. Mix the liquid well (but don’t stir in circles as this will collect eggs in the center!)
  6. Fill plastic pipette with liquid and load the McMaster chambers
  7. Leave to stand for 2 minutes (this allows eggs time to float to the top of the chambers)
  8. Examine under the microscope and count the number of strongyle eggs under both of the grids…see below for pictures of the eggs

When you are ready to count, focus the microscope on the air bubbles in the sample (see picture below) – these float to the same level as the eggs so you will know where to look!

 

All equipment needs to be rinsed thoroughly with water between egg counts (no detergent needed).

The sensitivity of the test depends on how you count the McMaster slide

McMaster

To calculate the eggs per gram of faeces:

The McMaster slide has 2 chambers, each with a grid.

If you count 1 grid,

If you count the eggs in both grids, the sensitivity of the test is 50 eggs per gram of faeces (EPG). Each egg you count using this method represents 50 eggs in the sample, therefore the multiplication factor (MF) = 50.

EPG = (grid 1 count + grid 2 count) x 50

Example: there were 6 eggs in grid one and 4 eggs in grid two… (6+4) x 50 = 500 eggs per gram

 

Counting the full chamber increases the sensitivity of the test:

Counting 1 chamber, MF=30

Counting 2 chambers, MF=15 

More sensitive tests (e.g. counting both chambers for a sensitivity of 15 epg) are recommended when conducting faecal egg count reduction tests to assess how well a wormer worked.

microscope

Faecal egg count equipment for home testing

  • A compound microscope (40X magnification)
  • McMaster slide
  • Tea strainer
  • Graduated syringe
  • Pasture pipette
  • Plastic beaker
  • Weigh balance
  • Saturated salt solution