Enterobius Vermicularis

Enterobius vermicularis Classification Kingdom: Animalia  Phylum: Nematoda  Class: Secernentea  Order: Rhabditida  Family: Oxyuridae  Genus: Enterobius  Species: vermicularis    Enterobius vermicularis is known as the human pin worm or thread worm, cause enterobiasis, axuriasis or seat worm infection. Discovered by Leuchart in 1865.  There is common say about this disease= you had this infection as a child, you have it now or you well get it again when you have a children.  Most common any where poor hygiene is practiced.  Almost anybody can become infected with this parasite. No social class is exempt. These parasites soon become "family affairs".  Once one person, usually a child becomes infected, other family members will undoubtedly also become infected. General Information  Geographic Distribution- cosmopolitan, but more in children in temperate areas, 200 million.  Host: humans are the only normal host of E. vermicularis other species infect goats, sheep, horses, rabbits and others.  No intermediate host (direct life cycle)  Transmission  E. vermicularis is transmitted by ingestion of infective eggs  Autoinfection (common in children)  Airborne transmission.  Retro infection. Morphology  Has three lips surrounding the mouth(winglike expansion or cervical alae) 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 .  Females measure 8 to 13 mm long and have the posterior end extended into a long, slender point. Female showing esophageal bulb & cephalic alae posterior end Male with curved Enterobius vermicularis adult female 0.8-1.3cm.in length , spindle-shaped with a long thin sharply tail. The greater part of the body is occupied by the uterus filled with eggs.  Egg  Eggs are elongate-oval and flattened on one side, measuring 50 to 60 um by 20 to 30 um  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) or airborne eggs may be inhaled and swallowed. Self-infection may also occur if eggs are transferred 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 (caecum and appendix). 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 retro infection.  Life Cycle (in picture)  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. Appendicitis.      Diagnosis  Diagnosis: often made clinically by observing the female worm (or many worms) in the perianal region, but can also be made using the “Graham’s scotch-tape" test, (NIH swab).  Use of double-stick tape on a tongue depresser.  This is pressed against the perianal folds where eggs will stick to the tape.  Tape is then stuck onto a microscope slide and examined for eggs.  The eggs can also be discovered from nail washing, urine deposit, duodenal aspirate and Papanicoles smear taken from vagina.  Treatment, and Control  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