Enterobius Vermicularis (Pinworms, Thread worm), Diagnosis, Treatment
Enterobius Vermicularis (Pinworms)
Sample of Enterobius Vermicularis
- A fresh stool is preferred.
- Cellophane tape the anal area for children and then transfer the material to the slide.
- The perianal area is the best place to get a sample.
- Get multiple samples to rule out pinworm infection.
- The stool sample was screened to find ova or adult females.
Epidemiology Enterobius Vermicularis
- The member of the Oxyurida is called pinworms.
- This cosmopolitan parasitic infestation is more prevalent in the temperate climate region.
- These are common in orphanages and mental hospitals where the spread is easy.
- This is the disease of school children.
- The route of spread is oro-fecal through contaminated foods or fomites.
- Suppose inhaled then, followed by ingestion of airborne ova. Larva hatch and migrate back into the intestine.
- This is very common in the USA.
Morphology of Enterobius Vermicularis (Pinworms)
- Enterobius vermicularis, also called pinworm, seatworm infection, or oxyuriasis.
- The male measures 1 to 4 mm and has the posterior end curved ventrally.
Egg of Enterobius vermicularis measures:
- Eggs are oval and flattened on the side.
- Length = 48 to 60 µm.
- Width = 20 to 35 µm
- The egg contains the developing larva surrounded by a thick-walled colorless shell.
- It contains various stages of the larva, unembryonated, and embryonated eggs.
Female E. vermicularis (larva stage):
- Length = 8 to 13 mm.
- Width = Up to 0.5 mm.
- The posterior end is extended into a long slender pointed end which gives it the name pinworm.
- The female has a vagina, vulva, ovary, uterus, and oviduct.
- There is a digestive and intestinal tract.
- There are mouth and anus.
Male E. vermicularis (larva stage):
- These are smaller in size than the female.
- Length = 2 to 4 mm.
- Width = 0.3 mm or less.
The life cycle of the parasite
- The phylum is Nemathelminthes, and the class is Nematoda.
- This class has two types of parasites:
- Intestinal species:
- Enterobius vermicularis.
- Trichuris trichiura.
- Necator americanus
- Ascaris lumbricoid.
- Strongyloides stercoralis.
- Ancylostoma duodenale.
- Intestinal-tissue species:
- Dracunculus medinensis.
- Trichinella spiralis.
Human cycle of Enterobius vermicularis (Pinworm):
- Human is the only host of Enterobius vermicularis (Pinworms).
- Infective ova contains rhabdiform larva (infective eggs) ingested by humans.
- The larvae are released into the duodenum, then migrate to the lower intestine.
- These worms are attached to the intestine’s mucosa, feeding on the epithelial cells and bacteria.
- Habitat is the cecum and colon.
- The copulation of mature adults takes place in the cecum.
- The gravid female migrates to the perianal area. It sheds ova mostly at night.
- The female migrates to the anus and lays the eggs on the perianal area. There may be eggs around 15,000.
- Following incubation of 4 to 6 hours, eggs become infective.
- There may be:
Enterobius vermicularis (Pinworm) life cycle
The non-human cycle of Enterobius Vermicularis (Pinworm):
- These ova are shed into the stool and surrounding area.
- These ova lead to infection of other people.
- The ova (eggs) are present in:
Clinical Symptoms of Enterobius vermicularis (Pinworm):
- Children are the most common victim of pinworms.
- It is a self-limited disease.
- Asymptomatic group:
- Some of the patients may not have any clinical symptoms.
- Symptomatic group:
- The most common symptoms are perianal itching, which is very intense (pruritus ani).
- The child may have a restless sleep due to perianal itching.
- There may be a pain, rashes, or skin irritation around the anal area.
- The patient may have intermittent abdominal pain and nausea.
- In the female, there may be vaginal itching.
Control of the Enterobius vermiculars:
- Personal hygiene is very important.
- Washing the hands and applying ointment to the perianal area to stop the spread of the eggs.
- Avoid scratching the infected area.
- All bedding should be washed with hot water, and cleaned the whole house to stop the spread of the disease.
- Children should wear tight-fitting diapers and pajama pants to prevent their contact with the perianal area. This will prevent reinfection.
- Advise washing of the anal skin area every morning soon after getting out of bed and frequently washing the clothes worn at night.
- All family members should be treated at the same time.
Laboratory diagnosis of Enterobius vermicularis:
- Procedure for adhesive tape:
- Put the cellophane tape around the anal area in cases of children. The eggs attach to the tape. Then this tape can be seen under the microscope. Perform this test for three days.
- Or touch the slide with the tape.
- 50% of the time, the tap will show ova; if you repeat this procedure three times, then positivity is 90%.
- Close the condenser iris for contrast. Otherwise, colorless eggs will not be seen.
- You can add a drop of xylene to clear the debris.
- Take a cotton swab, moisten it and rub it to the perianal area.
- Wash the swab in 4 to 5 mL of saline.
- Discard the swab.
- Centrifuge the saline solution and discard the supernatant.
- Put the sediment on the slide and cover it with cover-glass
- Examine under the microscope
- A stool examination:
- It can show ova. May find E. vermicularis worm in the stool or while collecting the sample from the perianal area.
- These are small, measuring 8 to 13 mm in length and resembling small pieces of thread, so-called threadworms.
- These can be seen by magnifying glass, which shows the characteristic shape, long pointed tail, and sharp anterior end.
Treatment of Enterobium Vermicularis (Pinworm):
- The most commonly used drugs are:
- Pyrantal pamoate.
Questions and answers:
Question 1: What is the most common presentation of pinworms in children?
This is perianal itching at night.
Question 2: What is the outcome of the pinworm infestation?
It is a self-limited disease.