MICROBIOLOGY

• Pinworms are intestinal nematodes (aka roundworms).
• Disease is also known as Enterobiasis or threadworm disease, caused by Enterobius vermicularis.
• Epidemiology: worldwide. Most common nematode infection in U.S., with 40 million cases per year.
  
  • Infection is mostly seen in children.
  • Increased prevalence with congestion, institutionalization and infestation within family members.
    • Larger family size is associated with increased risk.
• Lifespan of worm is 11-35 days, so chronic disease is due to reinfection rather than persistent infection.
  
  • Eggs are deposited nocturnally in perianal/perineal regions.
  • Self-infection can occur by transferring eggs to the mouth after scratching the perianal area.
  • Eggs are transferred under contaminated fingernails, in dust and through contaminated clothes or linens.
• Life cycle: (Figure 1)
  • Eggs are deposited on perianal folds by gravid females and transferred to the mouth by contamination of hands, clothes or bed linens.
  • Ingested eggs hatch into larvae in the small intestine.
  • Larvae mature into adults in the colon and gravid females migrate nocturnally outside the anus to lay eggs.
  • Each female worm can produce more than 10,000 eggs. Eggs remain viable for an average of 1-2 weeks. Infectivity decreases within 1 to 2 days in dry, warm environments.