Presentation on theme: "Enterobius vermicularis"— Presentation transcript:
1 Enterobius vermicularis Presented by Sandra Thorbus & Samantha Todd
2 HostsDefinitive Host: HumansNot associated with socioeconomic status
3 Geographical Distribution WorldwideMost common worm infection in the United States & Western Europe.In the United States, a study by the CDC reported incidence rate of 11.4% among all ages, 33% among children.Prevalence in children as high as 61% in India, 50% in England, 39% in Thailand, 37% in Sweden, and 29% in Denmark.
4 Morphology Egg has five membranes Eggs are translucent and are covered in a material that allows them to stick to environmental objectsMembrane makes the eggs “itchy”Eggs have a thick shell that is flattened on one sideThe eggs small size (50-60 micrometers)May contain an embryo or fully-developed larvaLarvae molt twice before hatching
6 Larvae Morphology Larvae grow to 140-150 micrometers in length Larvae are smaller and more coiled than the adultsMolt twice before becoming adults
7 Adult MorphologyWhite, small roundworm with cylindrical body surrounded by 3 layered cuticleThe female has a sharply pointed posterior end(8-13 mm long x 0.5 mm thick)Have alae on anterior part of body wallCan lay up to eggs/dayMale has a curled posterior end measuring 2 to 5 mm long x 0.2 mm thickBoth sexes have three lips
9 Transmission Human-to-human contact by ingesting infectious eggs Eggs remain viable in moist environment for up to three weeksOnce eggs are deposited near anus they can contaminate other surfaces such as:FingernailsHandsClothing and bed linensThen onto food, water, furniture, toys, bathroom fixtures and pets.
10 PreventionWash hands after using the bathroom and before preparing food.Wash bedding and underclothing frequently, especially those of any affected family members.
11 Life Cycle Eggs are ingested Hatch in S.I. Larvae emerge and migrate through small intestine to colonMolt twice to become adultsGravid female attaches to intestinal mucosa in ileum, cecum, appendix or ascending colonIngest colon contents until entire body is filled with eggs
12 Life CycleGravid females migrate through the colon towards the rectum at a rate of cm/hourFemale emerges from anus and deposits eggs bycontracting and expelling,dying and degrading,or bodily rupture due to the host scratching.The female comes out of the anus so the eggs can be exposed to oxygen to matureAfter laying eggs, the female becomes opaque and dies.Under optimal conditions larvae within the eggs will develop within 4-6 hrs. after being laid making them extremely infective
13 Pathogenesis Causes Enterobiasis Retroinfection-larvae migrate back up the bowel to the G.I. tractPinworms as seen in colonoscopy
14 Symptoms Intense itching in the anal region, especially at night Restless sleepInfection can migrate to the vagina and cause vaginal dischargeItching leads to secondary bacterial skin infectionAbdominal pain and nausea are associated with high populationSome are asymptomatic
15 Diagnosis Itching around perianal region is indicative of infection Worms are visible in the anal region, especially 2 to 3 hours after sleep,Look like tiny pieces of white threadEggs are rarely seen in stool samples
16 Most reliable method to detect eggs “Scotch Tape Test”Most reliable method to detect eggsPiece of cellophane tape is placed sticky side down to the skin around the anusPinworm eggs will stick to the tape and then the tape can be viewed under a microscopeTest should be done immediately after the person wakes up in the morning before washing, going to the bathroom, or getting dressed since eggs may be removed during these processes.
17 TreatmentMebendazole or Albendazole commonly prescribed for entire family OTC Pyrantel Pamoate 1 dose is given immediately, then wait two weeks for another dose. The second dose is to kill any adult worms that may have hatched in the meantime
18 Review How many times do pinworms molt? What is the tell tale sign of a pinworm infection?What is one method of diagnosis?Where do females lay their eggs?How can you prevent pinworm infection?
19 Works Cited http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002137/