warm.
8. Examine the illuminated area with a magnifying lens (hand lens) to look for minute white organisms swimming rapidly in a straight line (placing dark cardboard or black paper behind the flask will facilitate observation of the white miracidia against a black background).
Results and Patient Reports from Hatching Schistosome Eggs
Living miracidia may be seen; however, failure to see these larvae does not rule out schistosomiasis.
1. Report as “Miracidia of schistosomes detected, indicating the presence of viable eggs.”
2. Report as “No miracidia of schistosomes detected; presence of eggs is not ruled out by this procedure.”
Procedure Notes for Hatching Schistosome Eggs
1. Both urine and stool specimens must be collected without preservatives and should not be refrigerated before being processed. Regardless of the species suspected, BOTH URINE AND STOOL SHOULD BE EXAMINED FOR EVERY PATIENT WITH POTENTIAL SCHISTOSOMIASIS.
2. Hatching does not occur until the saline is removed and nonchlorinated water is added. If a stool concentration is performed, use saline throughout the procedure to prevent premature hatching.
3. Make sure that the light is not too close to the side arm or top layer of water in the Erlenmeyer flask. Excess heat kills the miracidia.
Procedure Limitations for Hatching Schistosome Eggs
1. The absence of live miracidia does not rule out the presence of schistosome eggs. Nonviable eggs or eggs that failed to hatch are not detected by this method. Microscopic examination of direct or concentrated specimens should be used to demonstrate the presence or absence of eggs.
2. Egg viability can be determined by placing some stool or urine sediment (same material as used for the hatching flask) on a microscope slide. Low-power magnification (×100) can be used to locate the eggs. Individual eggs can be examined under high dry magnification (×400); the detection of moving cilia on the flame cells (primitive excretory system) confirms egg viability.
3. Free-living ciliates may be present in soil-contaminated water. Therefore, it may be necessary to perform the following steps to differentiate those forms from the parasitic miracidia (26).
A. Transfer a few drops of the suspension containing the organisms to a 3 x 2-in. slide, and examine under the microscope.
B. Add a drop of weak iodine solution (weak-tea color) or dilute methylene blue (pale blue).
C. Parasitic miracidia will stop moving, while free-living forms continue to move.
Since the medication used for treatment of tapeworms is usually very effective, a search for tapeworm scolices is rarely requested and no longer clinically relevant. However, stool specimens may have to be examined for the presence of scolices and gravid proglottids of cestodes for proper species identification. This procedure requires mixing a small amount of feces with water and straining the mixture through a series of wire screens (graduated from coarse to fine mesh) to look for scolices and proglottids. Remember to use standard precautions and wear gloves when performing this procedure. The appearance of scolices after therapy is an indication of successful treatment. If the scolex has not been passed, it may still be attached to the mucosa; the parasite is capable of producing more segments from the neck region of the scolex, and the infection continues. If this occurs, the patient can be retreated when proglottids begin to reappear in the stool.
After treatment for tapeworm removal, the patient should be instructed to take a saline cathartic and to collect all stool material passed for the next 24 h. The stool material should be immediately placed in 10% formalin, thoroughly broken up, and mixed with the preservative (1-gal [3.8-liter] plastic jars, half full of 10% formalin, are recommended).
For additional information, see chapter 8 (Fixation and Special Preparation of Fecal Parasite Specimens and Arthropods).
Quality Control for the Tapeworm Scolex Search
1. Follow routine procedures for optimal collection and handling of fresh fecal specimens for parasitologic examination.
2. Review diagrams and sizes of proglottids and scolices of tapeworms.
Procedure for the Tapeworm Scolex Search
1. Mix a 24-h stool specimen (fresh or preserved in 10% formalin) with water, and thoroughly break up the specimen to make a watery suspension.
2. Strain the suspension (or the purged stool) through a double layer of screen wire or a sieve (a coarse-mesh screen placed over a fine-mesh screen).
3. Wash off the sediment remaining from each portion by running a slow flow of tap water over it.
4. Examine the cleansed debris with a hand lens to look for scolices and proglottids (the Taenia scolex is 0.5 to 1 cm long and 1 to 2 mm wide).
5. Repeat steps 3 and 4 for each portion of the suspension strained.
6. Collect the strained sediment in a glass petri dish, and place the dish over a black surface to increase the contrast of organisms against the background.
7. Observe with a magnifying hand lens, and pick pieces of worms with an applicator stick.
8. Rinse gravid proglottids and/or scolices with tap water, blot them dry on paper towels, and place them between two microscope slides separated at the edges by thin pieces of cardboard.
9. Fasten the preparation by placing rubber bands at each end of the slides so that the segments become somewhat flattened. One can also perform the India ink injection of the proglottid (see next protocol below).
10. Observe under the low power of a dissecting microscope for the number of uterine branches and genital pores in the segments and the presence or absence of a rostellum of hooks on the scolex. Quite often, the scolex is broken off from the rest of the strobila (chain of proglottids) and is ∼1 cm long.
Results and Patient Report from the Tapeworm Scolex Search
Tapeworm proglottids may be recovered (either singly or several attached together), and a scolex may or may not be seen.
1. Report as “A search for adult worms reveals the presence/absence of . . . (finding).”
Example: Taenia saginata scolex present
Procedure Notes for the Tapeworm Scolex Search
1. Remember that Taenia solium eggs are infective (cysticercosis), as are the eggs of Hymenolepis nana.
2. Wear gloves when performing this procedure.
3. Specimens preserved in 10% formalin are recommended.
4. If the patient has received niclosamide or praziquantel, a purged specimen is required, which should be immediately preserved in 10% formalin.
