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Parasite concentration methods

Fri Mar 12 14:44:29 EST 1999

    I am a MT (ASCP) (I also have a Masters Degree in Microbiology). When I 
    graduated from the Univ. of Illinois School of Medical Technology in 
    1967, I was taught to perform a direct saline and iodine prep, a 
    formalin-ether concentration and a stained smear(hematoxylin) on fecal 
    specimens received for parasitology work-up. I worked in hospital 
    microbiology labs for twenty years at four different hospitals in 
    different cities in Illinois. A few minor changes took place. We 
    switched from ether to ethyl acetate. We switched to a Trichrome stain 
    from HE. We added a direct acid-fast stain in the 1980's when we 
    learned about Cryptosporidia. When I left human medicine in 1990 and 
    started working in Veterinary microbiology,  I learned flotation 
    concentration techniques for the first time. My laboratory (the 
    Wisconsin Animal Health Laboratory) switched from sucrose flotations to 
    ZNSO4 floatations about five years ago. (Our observation was that ZNSO4 
    was superior to sucrose for Giardia and we occasionally found bovine or 
    feline lungworm on our ZNSO4 flotations. Yes, I know the Baermann 
    technique is best for lungworm but it is not part of our routine set-up 
    unless the submitting veterinarian suspects lungworm and specifically 
    requests a Baermann).
    When I left human medicine in 1990, the most common parasites we found 
    in the northern Illinois hospital I was working in were Giardia and 
    Cryptosporidia (about 50-50). I find it surprising that many human 
    clinical microbiology laboratories do not include a test for 
    Cryptosporidia as part of the "routine" parasitology workup.
    Finally, I think that many inexperienced Medical Technologists who are 
    asked to perform parasitology exams have trouble recognizing the small 
    parasites such as Giardia and Cryptosporidia. I found this to be the 
    case time and time again in hospital laboratories where I worked. Also, 
    I don't expect expertise to improve as Medical Technologists are being 
    required to perform as generalists instead of specializing in a 
    specific area of the laboratory.
    Kathleen Strelow, MS,MT(ASCP),SM(AAM)
    Wisconsin Animal Health Laboratory
    Madison, WI

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