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

4. Parasitology 141Shell: smooth, very thin.Content: a well-formed broad ciliated embryo surrounded by a membrane (internalshell).Colour: grey or pale yellow.Schistosoma intercalatum (Fig. 4.75)Similar in appearance to S. haematobium (see Fig. 4.74), but found in stools.Size: 140–180mm (slightly larger than S. haematobium).Shape: spindle-shaped; less broad than S. haematobium (sides particularly flattenedtowards the rounded pole).Spine: terminal spine; longer and more tapered than S. haematobium.Content: a ciliated embryo surrounded by a membrane with two depressions orindentations, one on each side near the middle.Fig. 4.74 Schistosomahaematobium eggS: spine.Schistosoma japonicum (Fig. 4.76)Size: 70–100mm.Shape: oval, almost round.Spine: difficult to see, lateral and very small; may be hidden by small granules oftenfound on the surface of the egg.Content: a broad ciliated embryo.Colour: transparent or pale yellow.Schistosoma mansoni (Fig. 4.77)Size: 110–180mm.Shape: oval, with one well-rounded pole and one conical pole.Spine: lateral, near the rounded pole; large and triangular (if hidden underneath,adjust the focus of the microscope).Shell: smooth, very thin.Content: a broad ciliated embryo, surrounded by a membrane (internal shell) as inall Schistosoma spp.Colour: pale yellow.Fig. 4.75 Schistosomaintercalatum eggD: depression;S: spine.Cellophane faecal thick-smear technique for diagnosis of Schistosomamansoni infection (Kato–Katz technique)The Kato–Katz technique has proved to be an efficient means of diagnosingS. mansoni and certain other intestinal helminth infections. The slides can be preparedin the field, stored in microscope-slide boxes, and shipped great distances,for examination at a central laboratory if required. The technique is not suitable fordiagnosing strongyloidiasis or infections with Enterobius vermicularis or protozoa.Fig. 4.76 Schistosomajaponicum eggG: granules;S: spine.Materials and reagents● Flat-sided applicator stick, wooden●●●●●Screen, stainless steel, nylon or plastic, 60–105 meshTemplate, stainless steel, plastic or cardboardMicroscopeMicroscope slidesCellophane, 40–50mm thick, in strips 25mm ¥ 30mm or 25mm ¥ 35mmFig. 4.77 Schistosomamansoni eggS: spine.