Stool testing (Equipment)

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You don't need much equipment to be able to observe helminth eggs.

  • Microscope - Binocular + 100x magnification + Mechanical stage. Around $100-$400.
  • Microscope slides and cover slips (22mm x 22mm) - A few $ from ebay.
  • Fecalyzers - Buy on ebay or vet supplies for about $50 a box of 50.
  • Float solution - Make your own from salt or sugar, or buy commercial float solution from a vet supplies.
  • Digital Scales - Measurement range at least 0.1 - 100.0 gm. A few $ off ebay.
  • Eye Dropper and Measuring Container - We need to move about 14 ml of float solution to the fecalyzer.
  • USB digital camera (Optional). Around $30-$50

Microscopes

You can pay a lot of money for a microscope. However Microscopes such as the Indian or Amscope $180+ student microscopes we find work fine for our needs.

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Microscope Discussion

  • Binocular - Stereo (binocular) eyepiece is recommended. You will be counting for about 10-15 mins per slide and binocular is very comfortable on the eyes. You can save $50 by going monocular but it won't be as comfortable.
  • Trinocular - If you have a spare $100, go for the 3rd viewing port (see pic above). You can attach a USB camera ($50) to this permanently. Usually a lever flips you between binocular and 3rd port view.
  • Eye Piece & Objective Lenses - Most microscopes come with 10x eye piece, and 4x/10x/40x/100x objective lenses (on a rotating turret above sample). This gives a total magnification of 40x/100x/400x/1000x. We use the 100x to count eggs and the 400x to optionally zoom in for a detailed look at an egg. The 40x & 1000x magnification are not used (1000x needs an oil film).
  • Mechanical Stage - You really need this feature. The X & Y panning knobs make it a snap to move around the slide in a systematic way and count the eggs.
  • Focus Knobs - Use the course focus to find the slide. At 100x magnification use the fine focus knob to focus on the underside of the cover slip where the eggs are. As you scan for eggs (using the mechanical stage), tweak the fine focus back and forth to make sure you find any eggs hidden outside the current focal plane.
  • Slides and Cover Slips - Often you will get a box of microscope slides & cover slips with your new microscope. Otherwise they are cheap to buy off ebay. For our counting technique we use cover slips = 22 x 22 mm. Some people prefer slides or slips with grids to help make counting easier.
  • USB Camera - A $50 camera is sufficient. There's no need to pay any more. eg. USB Microscope Camera. This option allows you to share observations with others. Note that you will always get better quality views optically, so a digital-only microscopes is not recommended. Normally you remove an existing microscope eye piece and replace it with the camera. No need to install the camera software as Microsoft Movie Maker will view and capture your video. USB Cameras often have a higher magnification than your eyepiece of around 15x.

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Fecalyzers

A fecalyzer (fecalizer, fecalyser) is a cheap device that takes much of the mess out of observing helminth eggs. [3] [4]

Fecalyzers can be bought on eBay and possibly also Amazon. A box of 50x fecalyzers costs about $50 including postage. They are also available in bulk from veterinary supply companies, e.g., here and here, and you should be able to obtain a few fecalyzers from any local veterinary practice. Vets hand these out to pet owners so they can take a stool sample from their cat or dog for analysis by the vet.

If a fecalyzer is not available, you can start looking for eggs using a test tube and something to hold this, plus a metal tea strainer and flotation solution.

To use a fecalyzer, you add a gram of poo, half fill with float solution, rotate the green cage to break up the poo and release the eggs, then overfill with float solution and place a 22x22 mm cover slip on top for 20 mins. The eggs will float up to the underside of the cover slip. Pop the cover slip onto a microscope slide and observe any eggs under the cover slip.

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Fecal Float Solution

Whether using a McMasters Slide or Fecalyzer we use a saturated salts solution that causes the eggs to float to the top and the faecal debris to sink to the bottom.

Specific gravity refers to weight of object compared to equal volume of water. Specific gravity of water is 1.000. ParasiteAn organism that lives in or on another organism (its host) and benefits at the host’s expense. (The organisms used in helminthic therapy are, strictly speaking, not parasites, but mutualists, because they have a mutually beneficial symbiotic relationship with their hosts.) eggs have a specific gravity of around 1.1 (hookwormA helminth that lives in the small intestine. Necator americanus (NA) is the only hookworm species used in helminthic therapy. Its microscopic larvae are applied periodically to the skin. eggs = 1.055). Fecal debris is >= 1.3. So a solution with a specific gravity of around 1.2 will allow the fecal debris to sink, while the free eggs float to the surface.

Most labs use Sodium Nitrate (NaNO3) or Zinc Sulfate (ZnSO4). These pre-made solutions can be purchased from any good vet supplier. See Lamberts. You can also buy pharma-grade Magnesium Sulfate (MgSO4) (Epson Salts) cheap off ebay. Simple saturated salt or sugar solution also works ok.

When you look through the microscope at 100x magnification, focus on the plane just below the cover slip. This is where the eggs are.

Mix your own Float Solution

Normally we want to make up a saturated salts solution (where no more salt will dissolve in solution). [5]

Quantities to produce around 1.2 sp. gr.

  • Sugar: 454g / 355ml water ≈1.27 sp. gr. (easy & cheap to make but can be sticky)
  • Sodium Chloride: 400g / 1000ml water ≈ 1.2 sp. gr. (easy & cheap to make but can be corrosive)
  • Magnesium Sulfate (Epson Salts): 400g / 1000ml water ≈ 1.2 sp. gr. (buy pharma grade MgSO4 off ebay).
  • Zinc Sulfate: 371g / 1000ml water ≈ 1.18 – 1.2 sp. gr. (source ZnSO4 through vet supplies)
  • Sodium Nitrate: 400g / 1000ml water ≈ 1.18 – 1.2 sp. gr. (source NaNO3 through vet supplies)

Note figures may differ slightly between various web sites. For example vetlab.com gives the following figures.
I suspect this is not too critical and you may want to experiment.

  • Sodium Chloride: Saturated Salt (NaCl; SG 1.18–1.20) 350 g NaCl 1,000 ml tap water
  • Magnesium Sulfate (MgSO4; SG 1.20) 450g MgSO4 in 1000 ml tap water
  • Zinc Sulfate (ZnSO4; SG 1.18–1.20) 331g ZnSO4 1,000 ml warm tap water
  • Sodium Nitrate Solution (NaNO3; SG 1.18–1.20) 338g NaNO3 1,000 ml tap water

For a discussion about the preparation of a float solution, see the comments from 13 Jan 2016 onwards in this discussion group thread.

Digital Scales

In our technique we use 1 gram of faeces in the ~ 10 gram fecalyzer. So scales of about 0.01 - 100.00 gram range will do the job. About $10 from eBay or Amazon.

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Other Supplies

These other suggestions may help

  • Eye Dropper and Measuring Container - We need to move about 14 ml of float solution to the fecalyzer. A chemist/drug store is a good place to buy these.
  • Paper plates - Put down newspaper and work on a couple of paper plates to catch any spills. Also makes clean up easy as you can just fold and staple the paper plates together later.
  • Icy-pole (Popsicle) sticks - From the $2 shop. May be useful for handling poo. However the Fecalyzer built-in scoop is usually good enough.
  • Latex Groves - Most people like to have a latex glove on at least one hand. Once you get use to it you may not need gloves, but you will want to wash your hands a lot.
  • Lab Coat - Some people like extra splash protection. Although fecalyzers are mostly trouble free.
  • Hand Tally Counter - Don't lose count. A small $5 tally device in the hand can help accuracy. [1]

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See also

Source: The first iteration of this page was imported from Counting Club on 19 June 2017, with permission.

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