Taxonomy: Helminths
Animal: Leeuwenhoek 9 04.jpg
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Comment:
Antonie Philips van Leeuwenhoek called the Father of Microbiology. In 1673, he observed protozoa in pond water. Microscopy is still the gold standard for parasitology. Clinical notes and travel history are essential in determining tests required. If faeces is not examined within 1/2 hour of passing to see motile trophozoites OR fixed immediately with PVA fixative, protozoan parasites deteriorate and may be missed; this is particularly relevant for liquid or soft stools specimens from people who have travelled to areas of poor hygiene and children less than 10 years. It is essential for identification to examine stained (FeHX or Trichrome) smear as well as saline and iodine preparations. Formed faeces may be kept for several days at 4C or fixed with 10 percent formalin. A modified acid fast test is essential to diagnose Cryptosporidium and Cyclospora sp. In addition, if indicated by clinical notes, a modified Trichrome-blue stain for microsporidia should be done on faeces, sputum or urine etc. A modified formalin-ether concentration technique should be performed on faeces to detect protozoan cysts as well as helminth ova. Preferably 3 specimens collected on alternate days over 10 days should be examined; if amoebiasis is suspected, 6 specimens over 14 days should be examined. To ensure cure, specimens should be examined 3-4 weeks after treatment. To detect light infections of hookworm, Strongyloides or Trichostrongylus sp. faeces should not be refrigerated and should be cultured; modified agar plate method (Koga KS et al 1991) is recommended; warranted in those travelling from endemic areas or ex-prisoners of war. Similarly, urine concentration techniques may be needed for light infections of schistosomiasis or to detect microfilariae. If schistosomiasis is suspected (Those travelling from areas endemic to these diseases), incubate faeces or urine for egg hatching. Serological tests are useful for some diseases such as amoebiasis, schistosomiasis, strongyloidosis. EM, biopsies, duodenal aspirates and various molecular tests may also be useful. Whole or segments of worms may need to be identified after fixing with formalin. Sticky tape method is used to detect pinworm eggs and indian ink to observe uterine branches in Taenia. Whole flukes should be fixed in hot 5 percent formalin, cestodes relaxed in tap water and fixed with boiling 10 percent formalin, nematodes in 10 percent formalin. To examine: small nematodes can be mounted in glycerine or glycerine jelly ringed with nail polish or chlorlactophenol or dehydrated, cleared and mounted as permanent preparations. Flatworms need to be stained with Mayers haemalum, dehydrated, cleared and mounted. Measurements are vital for id of parasites.
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