ENTEROBIUS VERMICULARIS – Histopathology.guru

ENTEROBIUS VERMICULARIS (PIN WORM)

Pin worm or Enterobius vermicularis affects mostly young children but can also infect the individuals in overcrowded conditions and in homosexuals
Modes of transmission –
- Direct infection from the anal and perianal regions by finger nail contamination (Autoinfection)
- Exposure to viable eggs on soiled bed lines and other contaminated environmental objects
- Contamination by dust containing embryonated eggs (from bed clothes, pajamas, toys, furniture and animal fur)
- Retroinfection – After ova hatches on anal mucosa, larvae migrate into sigmoid colon and cecum
Etiology
- Adult pin worm are small yellow white and lancet shaped
- They inhabit typically in the cecum, appendix, and adjacent areas of the ileum and the ascending colon
- Females measure 8mm to 13mm in length and males measure 2mm to 5mm in length
- Gravid females migrate through the anal canal at night and deposits approximately 10,000 egges on the perianal skin and then dies
- Eggs measure 55X25μm in size and have characteristic convexity on one side and flattening on the other side
- These eggs get matured within several hours after being laid and survive for atleast 15 days outside the body
- After ingestion of egg, the larva emerges in the small intestine and migrate distally to the cecum
- In less than a month, newly developed gravid females again discharge ova in the perianal region
Clinical features
- Predominant symptom is anal pruritus
- In children – pruritus leads to irritability, restlessness and insomnia
- Severe scratching may lead to local bleeding and secondary infection
- In female children – worm may lay egg on the vulva producing vulvovaginitis. In rare case adult worms may migrate cervix, uterus, fallopian tubes, ovaries and peritoneum
Gross – Enterobius infection produces ulceration of colonic mucosa
Microscopic features
- Identification of adult worm in section depends upon demonstrating a pair of cuticular crests, typical eggs in the uterus of parasite and the characteristic narrow meromyarian ( a type of musculature that consists of 2 to 3 muscle layers per quarter section divided by four cords)
- Worms are usually found in lumen of appendix
- Some times may manifest as superficial mucosal ulceration, or mucosal and submucosal abscessess
- If the worm invades mucosa, granulomas are formed. Eosinophils, lymphocytes, giant cells and charcot leyden crystal infiltrate the granulomas
- Later granulomas eventually fibrose and hyalinizes
Investigation – stool examination for oval
Treatment – Mebendazole – single dose 100mg orally
Prevention – Maintaining personal hygiene is measure of prevention

Enterobius vermicularis (pin worm): Cut section of three pin worms with two cuticular crests on surface, in the lumen of appendix. Appendix shows mucosa lined by columnar epithelium. Lamina propria shows benign mucosal glands. Mucosa and submucosa shows lymphoid follicles (H&E,X50)

Enterobius vermicularis (pin worm): Ulcerated mucosa of appendix with few benign glands and chronic inflammatory cells. Cut section of pin worm with two cuticular crests are seen (H&E,X100)

Enterobius vermicularis (pin worm): Ulcerated mucosa of appendix with few benign glands and chronic inflammatory cells. Cut section of pin worm with two cuticular crests (Lateral alae) are seen (H&E,X100)

Enterobius vermicularis (Pinworm):Cut section multiple pin worms in the lumen of appendix. Enterobius shows two cuticular crests on surface. One of the worm shows ova in lumen (H&E,X50)

Enterobius vermicularis (Pinworm): Cut section of enterobius showing two cuticular crests on surface, ova in the uterus and adjacent gut (H&E,X400)

Enterobius vermicularis (pin worm): Cut section of three pin worms with two cuticular crests on surface, in the lumen of appendix. Appendix shows mucosa lined by columnar epithelium. Lamina propria shows benign mucosal glands. Mucosa and submucosa shows lymphoid follicles (H&E,X50)

Enterobius vermicularis (Pinworm): Cut section of enterobius showing two cuticular crests on surface and gut in the lumen (H&E,X400)

ENTEROBIUS VERMICULARIS (PIN WORM)

Pin worm or Enterobius vermicularis affects mostly young children but can also infect the individuals in overcrowded conditions and in homosexuals

Modes of transmission –

Direct infection from the anal and perianal regions by finger nail contamination (Autoinfection)

Exposure to viable eggs on soiled bed lines and other contaminated environmental objects

Contamination by dust containing embryonated eggs (from bed clothes, pajamas, toys, furniture and animal fur)

Retroinfection – After ova hatches on anal mucosa, larvae migrate into sigmoid colon and cecum

Etiology

Adult pin worm are small yellow white and lancet shaped

They inhabit typically in the cecum, appendix, and adjacent areas of the ileum and the ascending colon

Females measure 8mm to 13mm in length and males measure 2mm to 5mm in length

Gravid females migrate through the anal canal at night and deposits approximately 10,000 egges on the perianal skin and then dies

Eggs measure 55X25μm in size and have characteristic convexity on one side and flattening on the other side

These eggs get matured within several hours after being laid and survive for atleast 15 days outside the body

After ingestion of egg, the larva emerges in the small intestine and migrate distally to the cecum

In less than a month, newly developed gravid females again discharge ova in the perianal region

Clinical features

Predominant symptom is anal pruritus

In children – pruritus leads to irritability, restlessness and insomnia

Severe scratching may lead to local bleeding and secondary infection

In female children – worm may lay egg on the vulva producing vulvovaginitis. In rare case adult worms may migrate cervix, uterus, fallopian tubes, ovaries and peritoneum

Gross – Enterobius infection produces ulceration of colonic mucosa

Microscopic features

Identification of adult worm in section depends upon demonstrating a pair of cuticular crests, typical eggs in the uterus of parasite and the characteristic narrow meromyarian ( a type of musculature that consists of 2 to 3 muscle layers per quarter section divided by four cords)

Worms are usually found in lumen of appendix

Some times may manifest as superficial mucosal ulceration, or mucosal and submucosal abscessess

If the worm invades mucosa, granulomas are formed. Eosinophils, lymphocytes, giant cells and charcot leyden crystal infiltrate the granulomas

Later granulomas eventually fibrose and hyalinizes

Investigation – stool examination for oval

Treatment – Mebendazole – single dose 100mg orally

Prevention – Maintaining personal hygiene is measure of prevention