Special Techniques

• Stool culture method - uses a Harada-Mori culture for the recovery and identification of nematode larvae
• Hookworm filariform larvae - move downwards against the capillary movement of the water
• Perianal swab - use of scotch tape to recover Enterobius vermicularis and Taenia spp. eggs
• Staining of stool specimen - allows for the examination of nuclear characteristics of amoebae; also useful for the identification of intestinal protozoans like Balantidium and Giardia
• The developmental stages of Wuchereria bancrofti and protozoan parasites (Plasmodia, trypanosomes, Babesia) can be examined in the blood.
• Wet or fresh preparation is used for microfilariae and trypomastigotes that are large and motile in fresh blood preparations. Species identification is not possible in this method.
• Stained smears - thick films are prepared from 2–3 drops of blood which is then mixed and spread over an area with continuous movement; films are thoroughly dried and dehemoglobinized before staining
• A finger-prick blood sample is used in the capillary tube method of blood collection. Three layers are observed after centrifugation:

  • Top layer: Plasma
  • Middle layer: White cell layer (buffy coat)
  • Bottom layer: Red cell layer (RBCs)
• Trypanosomes and Leishmania are concentrated at the buffy coat portion.
• Sputum - the first morning specimen is considered the best specimen to examine
• Microscopic examination of sputum - requires a wet mount with saline or iodine; useful when searching for protozoan parasites
• Urine examination - best used for diagnosis of Trichomonas vaginalis and Schistosoma haematobium
• Cutaneous or tissue aspirates - used in cases of cutaneous leishmaniasis
• Stools for culture should not be refrigerated as some species fail to develop at lower temperatures.
• Strongyloides larvae - move upwards and accumulate at the upper end of the filter paper strip
• Acid-fast staining is used for Cryptosporidium. Oocysts in clinical specimens may be difficult to detect without special methods.
• Giemsa stain - recommended stain for the detection and identification of blood parasites
• Delafield hematoxylin - stain that is useful in demonstrating detailed structures of microfilariae
• Canada balsam - used to permanently mount stained smears
• Sputum - can be used to recover migrating larvae of Ascaris lumbricoides, Strongyloides stercoralis, and hookworms
• Pulmonary amoebic abscesses - sample from which Entamoeba histolytica trophozoites can be collected
• 10% sodium chloride or hydrogen peroxide - used to increase the amount of sputum collected
• 3% NaOH is added to the sputum before centrifugation.
• Supernate - liquid that is discarded after centrifugation
• Sediment - sample that is examined after centrifugation
• Muscle biopsy - useful for the diagnosis of Trichinella spiralis infection where encysted larvae are located in muscle fibers