Enterobius vermicularis

1. Enterobiusvermicularis Dustin and Mohamud

2. What Is it? • Kingdom: Animalia • Phylum: Nematoda • Class: Secernentea • Order: Rhabditida • Family: Oxyuridae • Genus: Enterobius • Species: vermicularis Enterobius vermicularis is known as the human pin worm of temperate climate zones. Most common anywhere poor hygiene is practiced.

3. General Info • Geographic Distribution- cosmopolitan, but more in temperate areas. • Host: humans are the only normal host of vermicularis other species infect goats, sheep, horses, rabbits and others. • No intermediate host (direct life cycle)

4. Morphology • Has three lips surrounding the mouth and a bulb on the posterior end of the esophagus. • Males are 1 to 4 mm long and have the posterior ends strongly curved (button hook) and have a single spicule which is 100 to 141 um long. • Females measure 8 to 13 mm long and have the posterior end extended into a long, slender point. • Each has two uteri that can contain thousands of eggs that are elongate-oval and flattened on one side, measuring 50 to 60 um by 20 to 30 um

5. Visual Aids

6. Life Cycle (in words) • Eggs are deposited at night by the gravid females. • Eggs are ingested via person-to-person transmission through the handling of contaminated surfaces (such as clothing, linen, curtains, and carpeting), or airbourne eggs may be inhaled and swallowed. Self-infection may also occur if eggs are transferred from to the mouth by fingers that have scratched the perianal area. • After ingestion, larvae hatch from the eggs in the small intestine. The adults then migrate to the colon. The life span of the adults is about two months. Adults mate in the colon, and the males die after mating. • Gravid females migrate nocturnally to the anus and ovideposit eggs in the perianal area. The females die after laying their eggs. The time period from ingestion of infective eggs to the ovideposition of eggs by females is approximately one month. • The larvae develop and the eggs become infection within 4-6 hours. Newly hatched larvae may also migrate back into the anus, and this is known as retroinfection.

7. Life Cycle (in picture)

8. Pathogenesis • Enterobiasis is the medical condition of being infected with pinworms • Asymptomatic other than itching of the anus, due to excretions of the female worm. • Children may experience loss of appetite, abdominal pain, insomnia and restlessness are the usual symptoms associated with pin worm infections • Vaginitis may occur in young girls with pin worm infections. http://content.nejm.org/cgi/content/full/354/13/e12/DC1

9. Epidemiology • Clothing and beading become infested quickly, also found in dust in school rooms and cafeterias. • Most commonly infection occurs form soiled fingers or objects • Airborne eggs can also be inhaled and swallowed. 20-30% of elementary school children in the United States. • Worldwide it is estimated that 500 million people are infected

10. Diagnosis, Treatment, and Control • Diagnosis: often made clinically by observing the female worm (or many worms) in the peri-anal region, but can also be made using the "scotch-tape" test, or anile swab. • Treatment: Albendazol, and mebendazol are 95% effective but do not kill eggs so two or more treatments may be needed. • Control: good hygiene, sanitation of clothing beading and environment

11. Sources • http://ucdnema.ucdavis.edu/imagemap/nemmap/ent156html/nemas/enterobiusvermicularis • http://www.path.cam.ac.uk/~schisto/Nematodes/Enterobius.html • Gerald D. Schmidt and Larry S. Robert’s Foundations of Parasitology by Larry S. Roberts and John Janovy, Jr., 7th edition