Enterobius vermicularis Thread worm Seat worm Pin worm

Enterobius vermicularis Thread worm Seat worm Pin worm Oxyuris Linnaeus, 1758

• Females have slender, sharp-pointed tails • Only endoparasite with haplodiploidy – Females are diploid • Develop from fertilized egg – Males are haploid • Develop from unfertilized egg

• Short life span – Females die after oviposition – Males die after copulation • Infections become large, however, due to autoinfection and reinfection • More common industrialized countries due to increase in bedding, drapery, etc. in the home • Because of low pathology, very little effort to eradicate this species • Caucasians are much more susceptible than non. Caucasians

• Definitive Host: Humans • Distribution: Cosmopolitan but more common in cool or temperate zones in industrialized countries. – Infects approximately 400, 000 (10%) worldwide • Second only to Ascaris lumbricoides (1, 000, 000 or 25%) – Most common endoparasite in Europe and U. S. • Incidence between 30 -80% in Caucasian children

• Transmission: Eggs are infective stage. They are light and can float. 3 modes: – Hand to mouth (fecal/oral contamination) • Eggs are picked up on the fingers and transferred to mouth – Inhalation • Eggs float and are inhaled, trapped by mucus membrane, then swallowed – Reinfection • Eggs hatch and larvae crawl back through anus • Location in definitive host: Large intestines from cecum to anus, appendix

Morphology Pin worm

Eggs of Enterobius vermicularis Larva Unembryonated Embryonated 60µm

LIFE CYCLE

Adults in the Large Intestines Copulate and Males die Female goes to anus Lays eggs outside anus Mature J 2 larvae craw back into anus Molt twice as move to Large Intestine Eggs hatch near anus J 2 larvae hatch in small intestine Eggs become airborne Eggs swallowed Eggs coughed up

Enterobiasis

Pathology and Symptoms • 1/3 of cases are completely asymptomatic • Most cases, the worst symptom is intense itching – Female migrates out of anus at night to lay eggs – Causes small breaks in skin which are invaded by bacteria – Host scratches area, results in more breaks in skin and more bacterial infections and more itching

Pathology and Symptoms • Can rarely cause fatal infections – Worms do attach to the mucosa, resulting in ulcerations • Lead to secondary bacterial infections which can be fatal – Worms occasionally penetrate submucosa leading to death – Worms may also wander up through the vagina, to uterus, up oviducts and lodge in peritoneum • Causes peritonitis and granulomas around the worm

Pathology and Symptoms • Pinworm Neurosis – Female lays 15, 000 eggs – The eggs get into everything • • Bedding Clothing Curtains Stuffed animals

Heavy Infection of Enterobius vermicularis

Diagnosis: • Two preferred techniques: – Scotch tape technique • Early morning, pat the area around the anus with a piece of Scotch tape (or any other transparent tape) • Place tape on microscope slide with a drop of acetone. • Examine slide for eggs – Flashlight technique • Shine a flashlight on the anus during the middle of the night • You can see the adult females crawling out to lay eggs.

Teste “Anal swab”

Treatment • Mebendazole (Vermox). Must treat entire family and repeat after 10 days Bedding, towels, and clothing should be washed in hot water

Prevention and Control • Prevention is difficult among children, especially those attending day care facilities and lower grades in school.

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