SOP 2: Centrifugal Faecal Floatation

The zinc sulfate (SG 1.18) centrifugal floatation procedure is suitable for the isolation and identification of a protozoan cysts and oocysts in canine and feline faeces, in particular cysts of Giardia duodenalis. Centrifugal floatation is also more sensitive for the isolation of heavier nematode eggs such as those of Trichuris vulpis and Spirocerca lupi, in which a heavier floatation solution with a SG of 1.25 is utilised (e.g. sheather’s). These methods are inexpensive however does require use of a centrifuge

Definitions

SG       = Specific Gravity

FF        = Faecal Float

dH20    = Distilled water

Preparation of flotation solutions

Zinc sulfate solution (SG 1.18)

Dissolve 331 g sodium nitrate in 900 ml warmed dH2O. Add more dH2O until the entire solution weighs 1180 grams (this equates to a SG of 1.18). Mix solution and then check SG with hydrometer.

Sheather’s solution     (SG 1.25)

To 355 ml hot water, add (while stirring) 454 g sugar. Add 6 ml formalin per 454 g sugar. Adjust to ensure SG is 1.25 using a hydrometer.

Method                                                                     

  • Place ~2 g faeces into a wide-mouthed plastic disposable cup
  • Add ~10 ml flotation solution to the jar and mix with faeces thoroughly
  • Add a further 40 ml flotation solution to the jar and mix again
  • Pour / Filter this faecal suspension through a tea strainer into a new jar
  • Empty the contents of the jar into a 50 ml test-tube supported in a rack or stand
  • Centrifuge at 2000 rpm for 10 min
  • Carefully add more flotation solution until a positive meniscus forms at the top of the test tube and place a coverslip on top.
  • Stand for a further 5-10 minutes
  • Carefully life the coverslip with the drop of fluid adhered to the bottom of it and place it on a microscope slide
  • Scan for helminth stages under low power (10 ×) and for protozoal stages under high power (40 ×).

Safety Precautions

  • Wear lab coat and disposable gloves
  • Wash hands thoroughly when finished

Clean Up Procedures

  • Pour sodium nitrate into appropriate chemical waste container
  • Dispose of all slides and cover slips in a sharps container
  • Clean all equipment (tea strainer, glass test tubes) thoroughly with a 10% bleach solution
  • Wipe down work area with 70% Ethanol