Lynne Shore Garcia

Diagnostic Medical Parasitology


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for the in vitro cultivation and cryopreservation of Dientamoeba fragilis: new techniques set to fast track molecular studies on this organism. Parasitology 137:1867–1878. PMID 20609278

9 Fixation and Special Preparation of Fecal Parasite Specimens and Arthropods
Fixation of parasite specimens and arthropods Protozoa Solutions to induce relaxation in adult helminths Nematodes Trematodes Cestodes Helminth eggs and larvae Arthropods Mounting and staining of parasite specimens for examination Nematodes Trematodes Cestodes Mounting of arthropods for examination Mites Fleas and lice Ticks Miscellaneous arthropods

      Adequate fixation of parasites is important not only for diagnostic procedures but also as a means of preserving positive material for personnel and student training. There are many fixatives and preservatives available; however, only the more common ones are presented here.

      Although this chapter does not include commentary related to the histopathology laboratory, some information about formalin fixatives may be helpful. Concerns about the toxicity of formalin, particularly in the quantities used in a routine histology laboratory, have led to trials of alternative methods of tissue fixation that do not require formalin. Alcohol-based fixatives have been proposed as optimal for immunohistochemical and nucleic acid methods and may be useful for diagnostic light microscopy. Some laboratories have converted to use of an alcoholic fixative (containing 56% ethanol and 20% polyethylene glycol). Although comparative scores between the two were slightly in favor of the formalin, there were no significant differences in terms of tissue architecture, cell borders, cytoplasm, nuclear contours, chromatin texture, red blood cell membranes, and uniformity of staining. Alcohol-polyethylene glycol appears to be a satisfactory alternative to formalin in routine diagnostic surgical pathology (1). In another study, Histochoice produced a staining intensity that was comparable, and in many cases superior, to that