In this article we will discuss about the Laboratory Examinations of Parasites.
I. Blood Examination for Parasites:
Thick or thin blood smear can be stained by Leishman’s or Giemsa or Field’s or JSB stain to detect blood parasites. Method of Leishman staining: Leishman’s stain should be poured from the dropper bottle and diluted to twice its volume with neutral distilled water.
Drying should be prevented by covering the stained slide with a Petri dish for 10-15 minutes. Then the slide should be washed with tap water, dried and examined under oil immersion lens.
II. Stool Examination for Parasites:
Direct method:
Two cover glass preparations are prepared on one microscopic slide far apart from each other:
(1) Saline Preparation:
1-2 mg of the faecal material should be mixed in a drop or two of physiological salt solution for the left hand preparation; and
(2) Iodine Preparation:
1-2 drops of iodine solution (Lugol’s iodine can be used if it is diluted five times in distilled water). These films should be thin without air bubbles. Cyst can be detected in the saline preparation. While examining the unstained preparation for clearer view, the condenser should be racked down and the iris diaphragm is partially closed to cut down the illumination.
The saline preparation is useful to study living parasites (trophozoites, helminth eggs, chromatoid bar) whereas the iodine preparation to study the characteristic features (nucleus, glycogen mass) of cyst of E. histolytica and flagella of parasites. The direct method is quick, simple and easy; but it cannot detect infections (Fig. B I, II).
Fig. B 1-1, 2, 3 cyst of E. histolytica, 2, cyst of E. coli; 3, cyst of G. intestinalis; 4, (fertilised, 5 un-fertilised egg of A, lumbricoides; 6, A. duodenale or N. americanus; 7, egg of, E. vermicularis; 8. T. trichiura; 9. T. saginata or solium; 10, H. nana; 11. F. buski; 12. G. hominis, 13, P. westermani; 14, C. sinensis; 15. D. latum; 16. S. japonicum; 17, S. haematobium; 18. S. mansoni, Fig. B-II-1-5, Various yeasts, 6, 7, squamous cell from mucosa; 8. microphage without nuclei; 9, 10, polymorphis; 11, 12, pollen grains; 13, 14, starch granules; 15, plant hair; 16, 17, vegetable materials; 18, vegetable spiral, 19, B. hominis.
Aids Associated Parasites (supplement):
Pneumocystis carinii, Toxoplasma gondii, Isospora belli, Leishmania sp. Cryptosporidium and Microsporidia.
