Counting‎ > ‎

Equipment

You don't need much to count 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.

Discussion

Binocular - Stereo (binocular) eye piece is recommended. You will be counting for 10-15 mins per slide and binocular is very comfortable on the eyes. You can save $50 by going monocular but it is not as good.

Trinocular - If you have a spare $100 go for the 3rd viewing port (see pic right). 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 all you need. Don't pay more. eg. USB Microscope Camera 
This option allows you to share observations with others. Note that you will always get better quality views optically (don't buy one of those digital only microscopes). 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.


Fecalyzers

A cheap device that takes much of the mess out of observing eggs. [1] [2]

A box of 50x Fecalyzers is about $50 once you include postage (see amazon, ebay and vet supplies).

Basically 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 over fill with float and drop a 22x22 mm cover slip on top for 20 mins. The eggs will float up to the under surface of the cover slip. Drop the cover slip onto a microscope slide and start counting all eggs observed under the cover slip.

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. Parasite eggs have a specific gravity of around 1.1 (hookworm 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 up solutions can be purchased from any good vet supplies. See Lamberts. You can also buy phama 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).
From http://www.drmichaeldryden.com/file_download/9/Fecal-Flotation-procedures-2010.pdf (thanks Kansas State University)

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 

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.


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 news paper 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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