Manual of basic techniques for a health laboratory - libdoc.who.int

4. Parasitology 143Fig. 4.79 Filling the template with the sieved faecal sample10. Do not lift the slide straight up or it may separate fromthe cellophane. Gently slide the microscope slidesideways while holding the cellophane.Preparation of the slide is now complete. Wipe off any excessglycerol with a piece of absorbent tissue to ensure that thecellophane stays fixed. With practice you can obtain perfectpreparations.Strongyloides stercoralis (Fig. 4.81)S. stercoralis eggs are rarely seen in formed stools becausethey hatch before evacuation to produce larvae. They may,however, be found in liquid stools (and occasionally in theformed stools of carriers of certain strains).S. stercoralis eggs are very similar to those of Ancylostomaduodenale (see Fig. 4.42).Size: 50–80mm (slightly smaller than A. duodenale).Shape: oval with slightly flattened poles.Shell: very thin; appears as a black line.Content: a thick larva curved around itself one or more times and sometimes motile.Colour: pale grey; dark brown after staining with iodine solution.Taenia saginata and T. solium (Fig. 4.82(a))The “eggs” 1 of these two tapeworms are practically identical. They may be found instools and eggs of T. saginata can also be collected from the skin around the anus(see page 136).Size: 30–80mm.Shape: round.Shell: very thick, smooth, with transverse lines (reduce the illumination).Content: a round granular mass enclosed by a fine membrane, with three pairs ofshiny lancet-shaped hooklets (adjust the focus).Fig. 4.80 Covering the faecal sample with a glycerolsoakedcellophane stripFig. 4.81 Strongyloidesstercoralis eggs1The correct name for these “eggs” is “embryophores”, embryonated eggs that have lost theirouter sac.