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.
5. Wood’s lamp may be used to reveal the scolices if the patient has been given quinacrine dyes; the worms will have absorbed the dye, and they fluoresce at a wavelength of 360 nm. Also, after the use of quinacrine, tapeworm proglottids appear yellow.
Procedure Limitations for the Tapeworm Scolex Search
1. Niclosamide or praziquantel therapy leads to dissolution of the tapeworm. Therefore, the scolex and other proglottids may be difficult to recover unless the patient receives a saline purge soon after taking the medication.
2. It is often difficult to identify proglottids without staining. Identification may be achieved by staining with India ink.
India Ink Injection Procedure for Tapeworm Proglottids
Identification of adult worms usually involves examination of a tapeworm proglottid. A Taenia proglottid must be gravid, containing the fully developed uterine branches. Using a syringe (1 ml or less) and a 25-gauge needle, India ink is injected into the central uterine stem of the proglottid, filling the uterine branches with ink, or into the uterine pore. The proglottid can then be rinsed in water or saline, blotted dry on paper towels, pressed between two slides, and examined. After the identification has been made, the proglottid can be left between the two slides (place a rubber band around the slides), dehydrated through several changes of ethyl alcohol (50, 70, 90, and 100%), cleared in two changes of xylene, and mounted with Permount for a permanent record. After the xylene step, the proglottid will be stuck to one of the two slides; do not try to remove it (it is very brittle and will crack) but merely add the Permount to the proglottid and then add the coverglass (Fig. 4.9).
Figure 4.9 Taenia gravid proglottids after India ink injection of the uterine branches. (Left) Taenia fresh gravid proglottid prior to India ink injection. (Middle) Taenia saginata gravid proglottid. (Right) Taenia solium gravid proglottid. doi:10.1128/9781555819002.ch4.f9
It is important to remember that even when submitted in fixative, the tapeworm eggs within the branched uterine structure may not be killed and may remain infective. Since this procedure is usually limited to tapeworms in the genus Taenia, if eggs of Taenia solium (pork tapeworm) are present, they present a potential danger in terms of possible egg ingestion/inhalation/swallowing leading to cysticercosis. This becomes a possibility when performing the actual ink injection. If the needle accidentally pokes through the tapeworm proglottid, an aerosol can be created that may contain infectious eggs. ONE SHOULD WEAR A MASK, GLOVES, AND LABORATORY COAT AT ALL TIMES WHEN PERFORMING THIS PROCEDURE.
Procedure for the Tapeworm India Ink Injection (MASK, LABORATORY COAT, AND GLOVES MUST BE WORN AT ALL TIMES WHEN PERFORMING THIS PROCEDURE)
1. Using a 1-ml syringe and a 25-gauge needle, fill the syringe with approximately