Techniques

Abstract

Symbiotic protozoa which inhabit the alimentary canal of their hosts may be obtained for study either post-mortem or by the collection of fecal specimens. Usually the latter contain only encysted forms, unless the stool is diarrheic, when trophozoites of amebae, flagellates and ciliates may be found. Many free-living protozoa (coprozoic forms) multiply rapidly in old, moist feces, and care has to be taken not to confuse them with symbiotic forms in samples which are not fresh. Specimens which cannot be examined immediately should be refrigerated at 4 °C if possible, and kept in closed vessels. Specimens may also be preserved by emulsification in 10% formol in 0.9% saline solution (formol-saline). “Formol” or “formalin” is a 40% aqueous solution of the gas formaldehyde (HCHO), thus a 10% formol solution contains 4% formaldehyde. Fecal samples may be examined either directly or after concentration.