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

4. Parasitology 125Shape: round or oval, sometimes with angular irregular edges.Colour: very shiny when unstained; the vacuole is not stainedby iodine solution, but the periphery is pale yellow.Content: one large vacuole taking up almost the whole cell;the compressed cytoplasm forms a granular ring round it.Some physicians request that the presence of B. hominis bereported, particularly in children’s stools.Leukocytes (white blood cells) (Fig. 4.37)Size: 10–20mm.Shape: round or slightly elongated, with an irregular outline.Nucleus: indistinct, sometimes with a star-shaped “falsekaryosome”.Content: shiny cytoplasm, clear and granular with tiny vacuoles.Fig. 4.35 FungiPus (Fig. 4.38)Pus appears to the naked eye as opaque, greyish streaks (nottransparent like mucus). Under the microscope it appears asa mass of degenerated leukocytes.The presence of pus should be reported as it is a sign ofinfection.Fig. 4.36 Blastocystis hominisFig. 4.37 LeukocytesFig. 4.38 Pus4.4 Intestinal helminthsHelminth infections cause a variety of clinical symptoms including abdominalcramps, fever, weight loss, vomiting, appendicitis, blood loss, anaemia and eosinophilia.There are three groups of medically important helminths:— nematodes (roundworms)— cestodes (tapeworms)— trematodes (flukes).Helminth infections are usually diagnosed by detecting eggs and larvae. Less frequently,infections are diagnosed by detecting adult worms (e.g. Ascaris lumbricoidesand Enterobius vermicularis) or proglottids (segments) of adult worms (e.g. Taeniasaginata and T. solium). However, for most helminth infections, eggs are used foridentification.