Routine Techniques

• Stool samples - best collected in clean, wide-mouthed containers made of waxed cardboard or plastic with a tight-fitting lid to ensure retention of moisture and to prevent accidental spillage
• Direct fecal smear (DFS) - primarily useful in the detection of motile protozoan trophozoites and helminth eggs and larvae
• Kato thick smear - is useful in mass stool examination for detecting STH eggs
• Kato-Katz method - AKA cellophane covered thick smear; useful for assessing the intensity of infection in schistosomiasis and common soil-transmitted helminthiasis
• Concentration techniques are applicable in cases of light infections and if there is a need to recover more parasites.
• Acid ether concentration technique (AECT) - recommended for the recovery of Trichuris, Capillaria, Schistosoma, and other trematode eggs
• 40% HCl - used in AECT dissolve albuminous material
• Zinc sulfate flotation requires an ideal specific gravity of 1.18 to 1.20. If parasites are exposed to high specific gravity, distortion and shrinkage of protozoan cysts and thin-walled nematode eggs may occur.
• Brine flotation - uses a saturated table salt solution in which stools are directly mixed with; no need for centrifugation since helminth eggs rise to the surface of the solution
• Sheather's sugar flotation - uses boiled sugar solution that is preserved with phenol; used for the recovery of coccidian cysts such as Cryptosporidium, Cyclospora, and Isospora
• Sedimentation techniques are used if the parasite has a higher specific gravity than the reagent.
• Flotation techniques are used if the parasite has a lower specific gravity and will float to the surface of the preparation.
• Formalin ether concentration technique (FECT) - useful in the recovery of both helminth eggs and protozoan cysts
• Brine flotation is not useful for operculated eggs like Clonorchis, Opisthorchis, and heterophyids because these do not float in brine solution.
• Ether - used to dissolve neural fats in stool
• Ethyl acetate - may be used as an alternative to ether, but it is not as efficient in the extraction of fat or mucoidal material from the stool
• 10% formalin - used in FECT as an all purpose fixative