Clinically Important Parasites: Introduction,Common and Scientific Names, Keynotes, and Related Pictures

Introduction of Clinically Important Parasites

Some common clinically important parasites are Giardia lamblia, Entamoeba histolytica, hookworms, roundworms, Strongyloides stercoralis, Plasmodium species and Leishmania donovani.

Clinically Important Parasites Common and Scientific Names

Common and Scientific Names of Some Clinically Important Parasites are as follows-

S.No.	Common Name	Scientific Name
1	Roundworm	Ascaris lumbricoides
2	Pig roundworm	Ascaris scum
3	Pork tapeworm	Taenia solium
4	Beef tapeworm	Taenia saginata
5	Dog tapeworm	Echinococcus granulosus
6	Dwarf tapeworm	Hymenolepsis nana
7	Rat tapeworm	Hymenolepsis dimunata
8	Fish tapeworm	Diphylobothrium latum
9	Hookworm	Ancyclostoma duodenale
10	American Hookworm	Nectar americanus
11	Human whipworm	Trichuris trichiura
12	Pinworm/threadworm/ sheat worm	Enterobius vermicularis
13	Filarialworm	Wuchererchia bancrofti
14	Eyeworm	Loa loa
15	Blood fluke	Schistosoma
16	Cat liver fluke	Opisthorchis felineus
17	Chinese live fluke	Clonorchis sinensis
18	Liver fluke	Fasciola hepatica
19	Oriental lung fluke	Paragonimus westermani
20	Guinea worm	Dracunculus medilensis
21	Largest human intestinal fluke	Fasciolopsis buski
22	Malarial parasite	Plasmodium species

Keynotes on Common and Scientific Names

• Protozoa, helminths, and ectoparasites are three main classes of parasites which is responsible for causing diasease in human.
• Enterobius vermicularis, Giardia lamblia, A. duodenale, N. americanus, and E. histolytica are the common intestinal parasites of United States of America.

Related Pictures

Giardia cysts in stool

Giardia is a protozoan parasite that can infect humans and cause an illness called giardiasis. The parasite can be found in the intestines of infected individuals and is shed in their feces in the form of cysts. These cysts can contaminate water and food, leading to further transmission of the infection.

To diagnose giardiasis, a stool sample is collected and examined for the presence of Giardia cysts. This can be done through several methods, including:

1. Microscopic examination: The stool sample is examined under a microscope to identify the presence of Giardia cysts. This is a simple and inexpensive method but may have lower sensitivity compared to other methods.
2. Enzyme immunoassays (EIAs): These are rapid tests that detect Giardia antigens in stool samples. They are easy to perform and have higher sensitivity compared to microscopy, but may have a higher rate of false positives.
3. Nucleic acid amplification tests (NAATs): These tests detect the DNA of Giardia in stool samples using PCR (polymerase chain reaction) or other amplification techniques. They have high sensitivity and specificity but may be more expensive and require specialized equipment.
4. Stool culture: In this method, the stool sample is cultured in a laboratory to grow the Giardia parasite. This method may take longer and is less commonly used compared to the other methods.

Once Giardia cysts are detected in the stool, appropriate treatment can be initiated to help resolve the infection.

Cyst of Giardia in Methyle blue staining

Methylene blue staining is a common staining method used to visualize Giardia cysts in stool samples. Here are the steps for staining and visualizing Giardia cysts using methylene blue:

1. Collect a stool sample and prepare a wet mount slide by placing a small amount of the sample on a microscope slide and adding a drop of saline solution.
2. Mix the stool and saline solution together and place a coverslip over the mixture.
3. Examine the slide under low magnification to locate Giardia cysts. They are oval-shaped and can be identified by their characteristic shape and size (10-14 microns).
4. Once Giardia cysts are located, remove the coverslip and allow the slide to air dry.
5. Flood the slide with methylene blue stain for 1-2 minutes.
6. Rinse the slide with tap water to remove excess stain.
7. Air dry the slide and examine under high magnification.

Giardia cysts will appear blue-purple in color. It can be easily identified under high magnification. This staining method allows for easy visualization of Giardia cysts and helps with the diagnosis of giardiasis.

Entamoeba cyst in Iodine wet mount

Iodine wet mount is a common staining method used to visualize Entamoeba cysts in stool samples. Here are the steps for staining and visualizing Entamoeba cysts using iodine wet mount:

1. Collect a stool sample and prepare a wet mount slide by placing a small amount of the sample on a microscope slide and adding a drop of saline solution.
2. Mix the stool and saline solution together and place a coverslip over the mixture.
3. Examine the slide under low magnification to locate Entamoeba cysts. They are round to oval-shaped. It can be identified by their characteristic shape and size (10-20 microns).
4. Once Entamoeba cysts are located, remove the coverslip and add a drop of iodine solution.
5. Allow the iodine solution to sit for 2-5 minutes.
6. Rinse the slide with tap water to remove excess iodine solution.
7. Examine the slide under high magnification.

Entamoeba cysts will appear dark brown in color and can be easily identified under high magnification. This staining method allows for easy visualization of Entamoeba cysts and helps with the diagnosis of amoebiasis.

Hookworm egg in feces saline wet mount microscopy

A saline wet mount is a common microscopy technique used to visualize hookworm eggs in feces. Here are the steps for preparing and visualizing hookworm eggs using a saline wet mount:

1. Collect a small amount of feces and place it onto a microscope slide.
2. Add a drop of saline solution onto the feces.
3. Mix the feces and saline solution together using a wooden applicator stick.
4. Place a coverslip over the mixture.
5. Examine the slide under low magnification to locate hookworm eggs. Hookworm eggs are oval-shaped and have a smooth, thin shell. They are typically 60-80 microns in length and can be identified by their characteristic shape and size.
6. Once hookworm eggs are located, examine them under high magnification to confirm their identification.

Hookworm eggs will appear brown and have a characteristic thin, smooth shell when visualized under high magnification. This staining method is useful for identifying hookworm infections in fecal samples.

Hymenolypsis nana egg in feces microscopy

To visualize Hymenolepis nana eggs in feces, a direct fecal smear and a fecal concentration technique like the formalin-ether sedimentation technique can be used. Here are the steps to observe H. nana eggs in feces under microscopy:

1. Take a small amount of feces and place it onto a microscope slide.
2. Add a drop of normal saline solution onto the feces and mix it well.
3. Place a coverslip over the mixture.
4. Observe the slide under low power magnification (10X objective lens) to locate the Hymenolepis nana eggs.
5. Once you have located the eggs, examine them under high power magnification (40X objective lens) to confirm their identification. Hymenolepis nana eggs are oval-shaped, have a thick, clear shell, and measure around 30-40 microns in length.

It is important to note that microscopy is not always reliable for the diagnosis of Hymenolepis nana infections. Molecular techniques like PCR and ELISA may also be required for accurate identification of the parasite.

Taenia egg in stool

To visualize Taenia eggs in stool, a direct fecal smear and a fecal concentration technique like the formalin-ether sedimentation technique can be used. Here are the steps to observe Taenia eggs in stool under microscopy:

1. Take a small amount of feces and place it onto a microscope slide.
2. Add a drop of normal saline solution onto the feces and mix it well.
3. Place a coverslip over the mixture.
4. Observe the slide under low power magnification (10X objective lens) to locate the Taenia eggs.
5. Once you have located the eggs, examine them under high power magnification (40X objective lens) to confirm their identification. Taenia eggs are oval-shaped and measure around 30-40 microns in length.

It is important to note that microscopy may not always be reliable for the diagnosis of Taenia infections. Molecular techniques like PCR and ELISA may also be required for accurate identification of the parasite.

Strongyloides in culture microscopy

To visualize Strongyloides larvae in culture, the Harada-Mori filter paper culture method can be used. Here are the steps to observe Strongyloides larvae in culture under microscopy:

1. Take a small amount of fresh feces and mix it with a small amount of charcoal in a container.
2. Add enough water to the container to make a suspension and mix it well.
3. Soak a filter paper in the suspension and place it onto a culture plate.
4. Incubate the culture plate at 28-30°C for 48-72 hours.
5. After incubation, remove the filter paper from the culture plate and place it onto a microscope slide.
6. Add a drop of lactophenol cotton blue solution onto the filter paper and place a coverslip over it.
7. Observe the slide under low power magnification (10X objective lens) to locate the Strongyloides larvae.
8. Once you have located the larvae, examine them under high power magnification (40X objective lens) to confirm their identification. Strongyloides larvae are small, thin, and elongated, measuring around 200-300 microns in length.

Note

It is important to note that microscopy may not always be reliable for the diagnosis of Strongyloides infections. Serological tests like ELISA may also be required for accurate identification of the parasite.

Enterobius vermicularis, also known as pinworm, is an intestinal parasite that typically infects the gastrointestinal tract. It is not usually found in urine, but rather in stool or perianal area. Therefore, it is unlikely to find its egg in urine microscopy. The diagnosis of enterobiasis is usually made through the use of the “Scotch tape test,” where a piece of tape is pressed against the perianal area and examined under a microscope for the presence of pinworm eggs.

The adult pinworm (Enterobius vermicularis) is a small, white, thread-like nematode that measures about 2-5 mm in length and 0.5 mm in width. Under the microscope, it appears as a slender, cylindrical worm with a pointed head and a blunt tail.

The head contains a mouth and three lips. The tail is curved and tapered. The body covers with a smooth, cuticle-like surface, and there are no obvious external features such as bristles or spines. The digestive tract can be seen as a dark line running the length of the body. Overall, the adult pinworm is quite simple in appearance, but its distinctive shape and size can be useful in identifying it under the microscope.

Further Reading

• https://www.cdc.gov/parasites/about.html
• https://www.aafp.org/pubs/afp/issues/2004/0301/p1161.html
• Merkell and Voge’s medical parasitology-9th edition.
• Parasitology: 12th edition- K. D. Chatterjee
• District laboratory practice in Tropical countries –Part-I.
  By Monica Chesbrough.
• Atlas of Medical Helminthology and protozoology -4th edn  -P.L.  Chiodini, A.H. Moody, D.W. Manser
• Medical Parasitology by Abhay R. Satoskar, Gary L. Simon, Peter J. Hotez and Moriya Tsuji
• Atlas of Human Parasitology, Lawrence R Ash, Thomas C. Orihel, 3 rd ed, Publisher ASCP Press, Chicago.
• https://www.cdc.gov/dpdx/strongyloidiasis/index.html