Enterobius: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, and Prevention

Enterobius: Introduction, Morphology, Pathogenicity, Lab Diagnosis, Treatment, and Prevention

Introduction

Enterobius vermicularis, also known as pinworm, is a small, white, thread-like nematode (roundworm) that infects the human gastrointestinal tract. It is the most common parasitic worm infection in the United States and Europe, especially among children.

The adult female pinworm migrates to the anus and lays her eggs on the perianal skin, which causes intense itching and scratching. This can lead to further transmission of the eggs to other people, objects, or surfaces.

The infection is usually diagnosed by identifying the characteristic eggs in stool samples or by using the “scotch tape test,” in which a piece of transparent adhesive tape is pressed against the perianal skin and then examined under a microscope for the presence of eggs.

Morphology of Enterobius

E. vermicularis, commonly known as the pinworm, is a small, white, thread-like nematode (roundworm) that measures about 8-13 mm in length and 0.5 mm in width. The male and female worms have a similar appearance, except for the presence of a pointed tail in the male worm.

The body of the pinworm is cylindrical and unsegmented, with a long, slender, and pointed anterior end and a more blunt posterior end. The mouth is located at the anterior end and is surrounded by three lips. The esophagus is long and slender and leads to the intestine, which runs the length of the worm.

The reproductive system of E. vermicularis is dimorphic, meaning that the male and female reproductive organs are different. The male has a single spicule, a copulatory bursa, and two equal-sized testes. The female has a long, coiled uterus and an ovary that is located near the anterior end of the worm.

The eggs of E. vermicularis are oval-shaped, measuring about 50-60 μm in length and 20-30 μm in width. They have a thick, smooth shell and are usually deposited on the perianal skin of the infected individual. The eggs are infectious and can survive on surfaces for up to two weeks, which can lead to transmission to other individuals.

Pathogenicity of Enterobius

It  is a pathogenic parasite that can cause a condition called enterobiasis or pinworm infection. The pathogenicity of Enterobius vermicularis is mainly attributed to its ability to colonize the human gastrointestinal tract and cause inflammation and irritation of the mucosal lining, as well as the intense itching and scratching of the perianal area, which can lead to secondary bacterial infections.

Enterobiasis is usually a self-limiting infection and is rarely associated with severe complications. However, in severe cases, the pinworm infection can cause a range of symptoms, including abdominal pain, nausea, vomiting, and diarrhea. In rare cases, the worms can migrate to other organs, such as the appendix, fallopian tubes, and urinary tract, and cause complications such as appendicitis, salpingitis, and cystitis.

Furthermore, the intense itching and scratching of the perianal area can lead to skin irritation, redness, and inflammation, as well as the formation of secondary bacterial infections. In addition, the eggs of E. vermicularis can survive on surfaces for up to two weeks, which can lead to the transmission of the infection to other individuals and cause outbreaks in institutions such as schools and daycare centers.

Overall, while Enterobius vermicularis is not typically associated with severe morbidity or mortality, it can cause significant discomfort and inconvenience, as well as the potential for complications and transmission to others. Therefore, prompt diagnosis and treatment of pinworm infection are essential for controlling the spread of the infection and reducing its impact on affected individuals.

Lab Diagnosis

The diagnosis this parasite  can be made through a combination of clinical and laboratory methods. Some of the commonly used laboratory methods for diagnosing Enterobius vermicularis infection include:

  1. Scotch tape test: This is a simple and non-invasive method for collecting pinworm eggs from the perianal area. A piece of transparent adhesive tape is pressed against the perianal skin and then attached to a glass slide. The slide is then examined under a microscope for the presence of eggs.
  2. Stool examination: Examination of stool samples for pinworm eggs can also be performed using the direct smear technique or the concentration technique. The eggs are oval-shaped, measuring about 50-60 μm in length and 20-30 μm in width, and have a thick, smooth shell.
  3. Enterotest: This is a specialized test in which a gelatin capsule containing a string is swallowed, and then the string is retrieved after a few hours. The string is examined under a microscope for the presence of pinworm eggs.
  4. Colonoscopy: In rare cases, colonoscopy may be used to visualize the pinworms in the colon or cecum.

It is important to note that the scotch tape test is the most commonly used method for diagnosing E. vermicularis infection due to its simplicity, non-invasiveness, and high sensitivity. The test can be performed at home or in a clinical setting, and it is suitable for all ages.

Treatment

Enterobius vermicularis infection, also known as pinworm infection, can be treated with medication and good personal hygiene practices to prevent reinfection. Some of the commonly used medications for treating Enterobius vermicularis infection include:

  1. Mebendazole: Mebendazole is an anthelmintic drug that works by preventing the worms from absorbing glucose, which leads to their death. It is usually given as a single dose, followed by a second dose after two weeks to ensure complete eradication of the worms.
  2. Albendazole: Albendazole is another anthelmintic drug that works in a similar way to mebendazole. It is also given as a single dose, followed by a second dose after two weeks.
  3. Pyrantel pamoate: Pyrantel pamoate is an antiparasitic drug that works by paralyzing the worms, making them easier to be expelled from the body. It is usually given as a single dose, followed by a second dose after two weeks.

 

Prevention

Enterobius vermicularis infection, also known as pinworm infection, can be prevented by following some simple measures, including:

  1. Practice good personal hygiene: Frequent hand washing with soap and water, especially after using the toilet, before eating, and after touching potentially contaminated surfaces, can help to prevent the spread of pinworm eggs.
  2. Keep your living spaces clean: Regular cleaning of floors, furniture, and bedding can help to remove any pinworm eggs that may be present in the environment.
  3. Avoid sharing personal items: Personal items such as towels, bedding, and clothing should not be shared with others to prevent the spread of pinworm eggs.
  4. Avoid nail biting: Nail biting can increase the risk of ingesting pinworm eggs that may be present under the fingernails.
  5. Cook food thoroughly: Proper cooking of food, especially meat, can help to kill any potential pinworm eggs that may be present.
  6. Treat infected individuals: Prompt diagnosis and treatment of infected individuals can help to prevent the spread of pinworms to others.

By following these preventive measures, the risk of Enterobius vermicularis infection can be significantly reduced. Good personal hygiene practices and cleanliness can help to prevent the spread of pinworm eggs, which is the main mode of transmission of this infection.

Further Reading

  1. “Enterobiasis (Pinworm Infection)” by Centers for Disease Control and Prevention (CDC). Retrieved from https://www.cdc.gov/parasites/pinworm/index.html
  2. “Enterobius Vermicularis” by StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK459214/
  3. “Enterobiasis” by World Health Organization (WHO). Retrieved from https://www.who.int/news-room/fact-sheets/detail/enterobiasis
  4. “Enterobius vermicularis infection” by UpToDate. Retrieved from https://www.uptodate.com/contents/enterobius-vermicularis-infection
  5. “Enterobiasis: diagnosis and treatment” by British Medical Journal (BMJ). Retrieved from https://www.bmj.com/content/365/bmj.l1858
  6. “Enterobius Vermicularis” by Merck Manual. Retrieved from https://www.merckmanuals.com/professional/infectious-diseases/nematodes-enterobius,-trichuris,-and-hookworms/enterobius-vermicularis
  7. “Enterobiasis (Pinworm Infection)” by Medscape. Retrieved from https://emedicine.medscape.com/article/212601-overview
  8. “Enterobius vermicularis (pinworm)” by Healthline. Retrieved from https://www.healthline.com/health/pinworms
  9. “Enterobiasis” by DermNet NZ. Retrieved from https://dermnetnz.org/topics/enterobiasis/
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