Parasite concentration methods

Sedimentation techniques

Methods that concentrate parasites by allowing them to settle at the bottom due to heavier weight

Flotation techniques

Methods that concentrate parasites by floating them using high specific gravity solutions

Formalin Ether Concentration Technique (FECT)

Sedimentation method using formalin and ether to concentrate parasites

Acid Ether Concentration Technique (AECT)

Sedimentation method using acid and ether for parasite recovery

Gravity Sedimentation

Simplest method using natural settling of parasites without centrifugation

Centrifugal Sedimentation

Uses centrifuge to speed up parasite sedimentation

MIF Sedimentation

Uses merthiolate, iodine, and formaldehyde for preservation and concentration

Modified Zinc Sulfate Concentration

Flotation method using zinc sulfate solution

Brine Flotation Technique

Flotation method using saturated salt solution

Sheather's Sugar Flotation Technique

Flotation method using sugar solution for coccidian oocysts

Gravity sedimentation definition

Simple method for recovering eggs, larvae, and cysts

Best use of gravity sedimentation

When parasite numbers are low

Advantage of large fecal sample

Increases detection of parasites

Best detected by gravity sedimentation

Schistosome eggs

Use setting of gravity sedimentation

Remote areas with limited resources

Centrifugal sedimentation efficiency

Recovers most helminth eggs, larvae, and protozoan cysts

Preservative used in centrifugal sedimentation

10 percent formalin

Function of ether in sedimentation

Dissolves neutral fats

Alternative to ether

Ethyl acetate

Morphology preservation in formalin

Better preserved parasite structure

Storage of sediment

Can be stored long-term

Formalin Ether Sedimentation characteristics

Rapid, simple, concentrates all parasite stages

Parasites included in FECT

Protozoan trophozoites included

Status of FECT

Method of choice in most laboratories

Reagent requirement of FECT

Few reagents needed

Diagnostic yield of FECT

High percentage of positive cases

Time limit for FECT processing

Within one week after preservation

MIF meaning

Merthiolate Iodine Formaldehyde

Function of MIF

Preserves and stains parasites

Reagents in Acid Ether Sedimentation

40 percent HCl and ether

Function of HCl

Dissolves albuminous material

Function of ether in AECT

Dissolves fats

Best recovered in AECT

Trichuris, Capillaria, trematode eggs especially Schistosoma

Use of AECT

Stool samples from animals like cats and dogs

Disadvantage of AECT

Loss of parasites in debris plug

Effect of AECT on protozoa

Destroys protozoan cysts

Brine flotation definition

Uses concentrated salt solution for flotation

Best for brine flotation

Helminth eggs except operculated and schistosome eggs

Effect of brine on protozoa

Distorts cysts beyond recognition

Recommended use of brine flotation

Hookworm screening in low-resource areas

Effect on larvae in brine

Hookworm larvae and schistosomes shrink

Not useful for brine flotation

Operculated eggs such as Clonorchis and Opisthorchis

Reagent in zinc sulfate flotation

33 percent zinc sulfate solution

Specific gravity of zinc sulfate

1.18 to 1.20

Effect of high SG zinc sulfate

Distorts protozoan cysts

Use of zinc sulfate flotation

Survey work with many specimens

Best detected by zinc sulfate

Roundworm eggs and protozoan cysts

Does not float in zinc sulfate

Fertile Ascaris

Does not float in zinc sulfate

Infertile Trichuris eggs

Does not float in zinc sulfate

Trematode eggs

Does not float in zinc sulfate

Operculated tapeworm eggs

Reagent in Sheather's sugar flotation

Boiled sugar solution with phenol

Best for Sheather's sugar flotation

Coccidian oocysts

Examples detected by Sheather's

Cryptosporidium, Isospora, Cyclospora

Advantage of Sheather's sugar flotation

Better visualization under phase microscopy