Parasite

• Stool should be 2 to 5 grams
• The stool is the most common specimen used for parasitic examination.
• Stool should not be retrieved from toilet bowl water because free-living protozoa and nematodes may be con- fused with human parasites.
• water may destroy select parasites, such as schistosome eggs and amebic trophozoites.
• stools are collected into clean containers that have been sterilized by autoclaving or boiling.
• mask possible parasites during examination. Collection of specimens from patients who have taken antibiotics or antimalarial medications should be delayed for 2 weeks following therapy
• The specimen container should be labeled with the patient’s name and identification number, the physician’s name, and the date and time of sample collection.
• The specimen should be placed into a zip lock plastic bag for transport to the laboratory.
• it is recom- mended that liquid specimens be examined within 30 minutes of passage.
• Fixatives are substances that preserve the morphology of protozoa and prevent further development of certain helminth eggs and larvae
• Formalin may be routinely used for direct examinations and concentration procedures, but not for permanent smears.
• Polyvinyl alcohol (PVA) is an adhesive for the stool specimen when preparing slides for staining. This is most often combined with Schaudinn solution, which usually contains zinc sulfate, copper sulfate, or mercuric chloride
• The biggest disadvantage of the use of PVA is that Schaudinn solution contains mercuric chloride. Because of the potential health problems

  caused by mercury
• Sodium Acetate Formalin is a viable alternative to the use of PVA. This preservative can be used for performing concentration techniques and permanent stained smears.

  SAF is easy to prepare, has a long shelf life, and can be used for preparing smears for staining with the modified acid-fast stain to detect coccidian oocysts.

  SAF adhesive properties of SAF are not good, protozoa morphology from SAF-preserved specimens is not as clear.
• Modified Polyvinyl Alcohol - other alternatives to mercury-based PVA use of substitute compounds containing copper sulfate or zinc sulfate. However, these substitute products do not provide the same quality of preservation for adequate protozoan morphology on a permanent stained slide as the mercury-based fixative
• direct wet preparation or direct wet mount is defined as a slide made by mixing a small portion of unfixed stool with saline solution. it is then placed under the microscope to detect motile protozoan trophozites
• Direct saline wet preparation - pace 0.85% saline on a glass slide andmix with unfixed stool. mix for the sample to be thin enough for a text on a paper to be seen.
• direct iodine wet preparaation- used to enhance details of protozoan cysts using Lugol's or D' Antoni's formula.. Also there is a tendency for iodine to kill the protozoan
• 2 types of concentration methods (both use specific gravity):

  1. Sedimentation - parasites are concentrated in the sediment of the tube following centrifugation then examined microscopally
  2. Floatation - parasites are less dense than the solutions used then they float to the surface
• Zinc Sulfate flotation method - this technique separates the parasitic eggs from feces based on their buoyancy. The principle behind this method is that the specific gravity of the parasitic eggs is less than water so they float more slowly than the rest of the material in the suspension. After adding ZnSO4, the supernatant is decanted and the remaining sediment is washed several times with tap water until the washings become clear. Then the sediment is suspended in distilled water and examined under the microscope.
• Formalin Ethyl Acetate Sedimentation Procedure - this technique uses centrifuge to separate parasitic eggs from feces.the parasites are heavier than water so they will sink faster than the rest of the material in the suspension. After centrifuging, the supernatant is discarded and the pellet is resuspended in distilled water and examined under the microscope.
• Permanent stained smear - remains the sample to be intact in the long term. Dientamoeba fragilis is a sample that requires permanent stained smear
• Wheatley Trichrome stain has a long shelf life and is easy to perform
• The iron hematoxylin stain reveals excellent morphology of the intestinal protozoa.
• The cellophane tape prep is the specimen of choice for the detection of Enterobius vermicularis (pinworm) eggs.
• The Enterotest is a simpler method for collecting duodenal material without requiring intubation. The patient swallows a gelatin capsule that contains a coiled length of yarn. The capsule dissolves in the stomach and the weighted string is carried to the duodenum. The free end of the string is attached to the patient’s neck or cheek with tape. After a 4-hour incubation period, the yarn is pulled back out of the patient.
• Examination of sigmoidoscopy (colon) material is often helpful for detecting E. histolytica.
• Blood specimens for parasite study must be collected by aseptic tech- nique. Blood from the fingertip or earlobe is obtained by making a puncture at the site.
• Thick smears are frequently satisfactory for screening purposes, particularly when malaria is suspected. this also provide the best view of the malarial parasites in red blood cells and are recommended

  for species identification.
• Knott technique is designed to concentrate blood specimens suspected of containing low numbers of microfilariae. A simple modified version of this technique consists of combining 1 mL of venipuncture collected blood with 10 mL of 2% formalin in a centrifuge tube.
• Urine is the specimen of choice for the detection of Schistosoma haematobium eggs and may also yield Trichomonas vaginalis trophozoites
• Sputum is typically collected and tested from patients suspected of being infected by the lung fluke Paragonimus westermani.
• Protozoan cysts are more likely to be found in fully formed stools. Helminth eggs and larvae may be found in liquid or formed stools.
• Dientamoeba fragilis is one example and, if a permanent stained smear is not performed, this parasite will likely be missed.
• iron hematoxylin stain reveals excellent morphology of the intestinal protozoa
• Duodenal fluid must be examined because if there are trophozoites present, they will deteriorate rapidly. The material can be examined

  microscopically as a wet preparation. If the

  volume of fluid is sufficient (>2 mL), it should

  be centrifuged and the sediment examined.
• Examination of sigmoidoscopy (colon) material is often helpful for detecting E. histolytica. Mate- rial from ulcers obtained by aspiration or scrap- ing should be examined by direct wet preparations and permanent stains.
• The cellophane tape prep is the specimen of choice for the detection of Enterobius vermicularis (pinworm) eggs
• Parasites that may be recovered in blood include Leishmania donovani and Trypanosoma spp, Plasmodium and Babesia spp and microfilariae
• Gram stain is used to differentiate between gram positive cocci and gram negative bacilli based on their ability to retain crystal violet dye during decolorization with alcohol.