Enterobius vermicularis

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Enterobius vermicularis
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Taxonomical position

• Phylum Nematoda
• Class Secernentea
• Order Oxyurida
• Super family Oxyuroidea
• Family Oxyuridae
• Genus Enterobius
• Species vermicularis

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Common names

• Pin worm
• Thread worm
• Seat worm
• History
• Leukart first described the complete life
  cycle in 1865

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Distribution

• Cosmopolitan
• More common in temperate and cold climate than
  warm climate
• Habitat
• LARGE INTESTINE
• - Caecum
• - Appendix
• - Ascending colon

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Morphology

• ADULT
• Short, white, fusiform
• Pointed ends
• Resemble white threads
• Cervical Alae
• - At the anterior end
• - Three in number
• - Wing like cuticular expansions
• - Transversely striated
• Oesophagus- DOUBLE BULB

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MALE WORM

• Posterior end is curved
• Copulatory spicule
• Length 2-5 mm
• Thickness 0.1- 0.2 mm
• Life span 7 weeks

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FEMALE WORM

• Thin, pointed, pin like tail
• Reproductive organs
• - T shaped
• - paired
• OVIPAROUS
• Length 8 - 13 mm
• Thickness 0.3 - 0.5 mm
• Life span 5 - 13 weeks

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EGG

• Colourless, non-bile stained
• Shape Planoconvex
• Shell Double layered
• Transparent
• Sticky outer albuminous layer
• Contains tadpole shaped,
• coiled larva
• Viable up to 2 weeks

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LIFE CYCLE
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Life cycle

• Simplest of all the intestinal worms
• Host
• MONOXENOUS- single host Human
• Infective form embryonated egg
• Route Faeco-oral transmission
• Eggs transform in to larvae in 5 weeks in small
  intestine
• Larva undergo moulting in ileum and finally
  mature in to adult in caecum with in 15 to 30
  days
• Male dies after fertilization

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Conti

• Egg
  
  
• 5 weeks
  (small intestine)
  
• Larva
  
  
  
• 
  moulting(ileum)
  
• 15-30 days
  maturation(caecum)
  
  
  
• 
  
• 
  Adult
  
  
• male
  female
  
• 
  
• dies after fertilization
  
  
  

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Conti

• 
  
• 
  
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  migrate to rectum
• 
  
• 
  
• 
  
• come out through anus
  during night time
  
  
• 
  
• 
  
• 
  
• 
  
  
• 
  
  
• Eggs laid on
  perineal, peri anal skin
  
  
• 
  
  
• 
  
• 
  

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Conti

• 1 worm 5000 17000 eggs
• Become infective in 6 hrs
• Completes life cycle in 2 weeks 2 months

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Pathogenesis

• Adult worm
• Egg
• - mucoid secretions adherence of egg
• - irritation
• - Characteristic NOCTURNAL PERINEAL /
  PERIANAL
• 
  ITCHING

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Clinical manifestations

• ENTEROBIASIS Pruritis ani
• Scratching, excoriation of skin
• Disturbed sleep, irritability, nocturnal
  enuresis, weight loss, abdominal pain
• Severe infection
• Neurosis
• Nail biting
• Grinding teeth at night

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Complications

• Vulvo- vaginitis
• Chronic salpingitis
• Prostatitis
• Urethritis
• Endometritis
• Granulomata with dead worms, eggs

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Epidemiology

• Group infection School children
• Prevalent in temperate countries
• USA, European countries
• Source Infected humans
• others like bedding, night
  clothing, table tops,
• door knobs,taps etc.,
• Transmission Auto infection
• contaminated articles
  / direct contact
• inhalation of eggs
• Retroinfection

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Diagnosis

• H/O perianal pruritis
• LAB DIAGNOSIS
• Demonstration of Adult worm
• - On the surface of stool sample
• - On the perianal skin
• - In the stool after an enema
• Demonstration of Eggs
• - As they are seldom excreted in faeces,
  stool sample
• is not useful for diagnosis
  

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1. NIH swab

• 2.Scotch tape swab
• Atleast 3 specimen collected
• in 3 consecutive days
• 3.Dirt from finger nails.

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Treatment

• Single dose
• Pyrantel - 11mg/kgwt
• Mebendazole - 100mg/kgwt
• Albendazole - 400mg/kg wt
• Piperazine - 65mg / kg wt 1 week
• Pyrantel causes spastic
• paralysis of the worm

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Prophylaxis

• Health education on personal hygiene
• Group chemotherapy

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