universe84a

  Enterobius Eggs

Enterobius vermicularis eggs in a saline wet mount of the stool as seen with 40X objective under a microscope.

Identification features of Enterobius eggs

Following are the features to identify the organism as Enterobius vermicularis:

1. Asymmetric in shape: Ventral side flattened and dorsal side convex giving planoconvex appearance.
2. Size of length 50-60µm X breadth about 30µm
3. Colorless
4. It floats in a saturated common salt solution.
5.  Presence of coiled larva inside the eggshell.
6. Eggshell is transparent and double-layered.

Keynotes

1. Instead of a stool specimen, the Enterobius egg is better to see in the morning National Institute of Health (NIH) swab.
2. There is little difference between normal and physiological saline. Physiological saline is  0.85% NaCl whereas normal saline is 0.9% NaCl.
3. Gram’s iodine is not applicable for staining parasitic organisms and for this D’Antoni’s iodine uses.
4. Oil immersion examination is also preferred in parasitology for the permanent stained smear of parasites.
5. Intestinal protozoa can not conform on the basis of a wet mount alone and thus permanent stained smears require to confirm the specific identification of suspected organisms.

Principle of the Saline Wet Mount of Stool

Saline wet mount preparation for stool is the simplest and basic method of analyzing a stool specimen in coprology (study of feces). It utilizes a physiological saline solution (0.85% NaCl ) as an isotonic media to maintain the cellular structure of the various organisms that are found in stool and that we like to examine.

Requirements for saline wet mount

• Physiological saline (  0.85% NaC)
• Specimen: stool
• Sterile bamboo sticks or low cone on the end of a wooden applicator stick
• Clean and grease-free slides and
• Cove slips(22 by 22 mm)
• Microscope
• Gloves

Saline wet mount of stool Preparation

1. Take a clean and grease-free slide.
2. Add one drop of physiological saline and then add a stool equivalent to a match stick head (2 mg)  with the help of a stick.
3. Mix it properly and apply a coverslip over a uniform suspension without creating bubbles.
4. Note: If a fresh stool specimen is received and if blood and mucus are present, the specimen should be examined as a direct mount making sure to sample the bloody areas.
5. Examine the entire 22by 22-mm coverslip systematically with the low power objective (10X ) and low light intensity.
6.  If any suspicious objects encounter, examine with the high dry objective (40X).

//Eggs of Enterobius vermicularis in a saline wet mount of stool under the microscope as shown in video-

Result Interpretation

Presence of active trophozoite/s: Motile retractile bodies

Cyst, oocyst, egg, inactive trophozite/s, larvae: Retractile bodies and finally focus at high dry power field as shown above video

Limitations of saline wet mount for stool examination

1. Due to the lack of stain, it is difficult to get morphological details.
2. Inappropriate preparation of the smear may hide parasites
3. Improper adjustment of the microscope in relation to the objective may create problems.

Bibliography

1. Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji
2. Atlas of Medical Helminthology and protozoology -4th edn  -P.L.  Chiodini, A.H. Moody, D.W. Manser
3. Merkell and Voge’s medical parasitology
   9th edition.
4. Parasitology: 12th edition
   By K. D. Chatterjee
5. District laboratory practice in Tropical countries –Part-I.
   By Monica Chesbrough.
6. Isenberg clinical microbiology procedures Handbook
   2nd edition. Vol. 2
7. http://www.med-chem.com/para-site.php
8. https://www.cdc.gov/parasites/pinworm/biology.html