Enterobius Vermicularis (Pinworms, Thread worm) Diagnosis and Treatment

Sample

1. A fresh stool is preferred.
2. For children, cellophane tape the anal area and then transfer the material to the slide.
   1. The perianal area is the best place to get a sample.
   2. Get multiple samples to rule out pinworm infection.
   3. The stool sample screened to find ova or adult females.

Epidemiology

1. The member of the Oxyurida is called pinworms.
2. This is a cosmopolitan parasitic infestation and is more prevalent in the temperate climate region.
3. These are common in the orphanage and mental hospitals where the spread is easy.
4. This is the disease of school children.
5. The route of spread is oro-fecal through contaminated foods or fomites.
6. If inhaled then followed by ingestion of airborne ova. Larva hatch and migrate back into the intestine.
7. This is very common in the USA.

Morphology 

1. Enterobius vermicularis also called pinworm, seatworm infection, or oxyuriasis. 
2. Male measures 1 to 4 mm in length and have the posterior end curved ventrally.
3. Egg E. vermicularis measures:
   1. Eggs are oval in shape and flattened on the side.
   2. 40 to 60 µm in length.
   3.  20 to 35 µm in width.
   4. The egg contains the developing larva surrounded by the thick-walled colorless shell. 
   5. It contains various stages of the larva, unembryonated and embryonated eggs.

4. Female E. vermicularis (larva stage):
   1. 8 to 13 mm in length.
   2. Up to 0.5 mm in width.
   3. The posterior end extended into a long slender pointed end and give it the name of pinworm.
   4. The female has a vagina, vulva, ovary, uterus, and oviduct.
   5. There is a digestive and intestinal tract.
   6. There are mouth and anus.

5. Male E. vermicularis (larva stage):
   1. These are smaller in size than the female.
   2. 2 to 4 mm in length.
   3. 0.3 mm or less in width.

The life cycle of the parasite

1. The phylum is Nemathelminthes and the class is Nematoda.
   1. This class has two types of parasites:
      1. Intestinal species:
         1. Enterobius vermicularis.
         2. Trichuris trichiura.
         3. Necator americanus
         4. Ascaris lumbricoid.
         5. Strongyloides stercoralis.
         6. Ancylostoma duodenale.
      2. Intestinal – tissue species:
         1. Dracunculus medinensis.
         2. Trichinella spiralis.
2. Human cycle:
   1. Human is the only host of the Enterobius vermicularis (Pinworms).
   2. Infective ova contains rhabdiform larva (infective eggs)  which is ingested by the human.
   3. The larvae are released into the duodenum, then migrate to the lower intestine.
   4. These worms attached to the mucosa of the intestine, feeding on the epithelial cells and bacteria.
      1. Habitat is the cecum and colon.
   5. The copulation of the mature adults takes place in the cecum.
   6. The gravid female migrates to the perianal area. It sheds ova mostly at night.
      1. The female migrates to the anus and lays the eggs on the perianal area. There may be eggs around 15,000.
      2. Following incubation of 4 to 6 hours, eggs become infective.
      3. There may be:
         1. Autoinfection.
         2. Retroinfection.

2. Non-human cycle: Now these ova are shed into the stool and surrounding area.
   2. These ova leads to infection of other people.
   3. The ova (eggs) are present in:
      1. Dust.
      2. Sandboxes.
      3. Linens.
      4. Clothes.
      5. Airborn.

Clinical Symptoms

1. Children are the most common victim of pinworms.
2. It is a self-limited disease.
3. Asymptomatic group:
   1. Some of the patients may not have any clinical symptoms.
4. Symptomatic group:
   1. The most common symptoms are perianal itching and it is very intense (pruritus ani).
   2. The child may have restless sleep due to perianal itching.
   3. There may be a pain, rashes, or skin irritation around the anal area.
   4. The patient may have intermittent abdominal pain and nausea.
   5. In the female, there may be vaginal itching.

Control of the disease

1. Personal hygiene is very important.
   1. Washing of the hands and applying ointment to the perianal area to stop the spread of the eggs.
   2. Avoid scratching the infected area.
2. All bedding should be washed with hot water and clean the whole house to stop the spread of the disease.
3. Children should wear tight-fitting diapers and pajama pants to prevent their contact with the perianal area. This will prevent reinfection.

Laboratory diagnosis

1. Procedure:
   1. 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.
   2. Or touch the slide with the tape.
   3. 50% of the time tap will show ova and if you repeat this procedure three times then positivity is 90%.
2. Stool examination can show ova.

Treatment

1. The most commonly used drugs are:
   1. Mebendazole.
   2. Albendazole.
   3. Pyrantal pamoate.
   4. Piperazine.

---