Dracunculus medinensis (Guinea worm)

Epidemiology

• incidence of human infection has declined because of irradication efforts
• Sudan & West Africa
• infection acquired through ingestion of contaminated water containing larvae from Cyclops
• Cyclops is a crustacean intermediate host

Pathology

• ingested larvae penetrate the stomach or intestinal wall, mate & mature
• the male probably dies
• the female develops over a period of 1 year & migrates to subcutaneous tissues, generally in a lower extremity
• female measures 30 cm to 1 meter in length, but thin
• a blister forms in the skin at the site of the female which breaks down & ulcerates
• through the ulcer, large numbers of rhabditiform larvae can be released into stagnant water
• the wound heals (if it does not become infected) & the adult female encapsulates & calcifies

Clinical manifestations

1 few or no clinical manifestations until just prior to formation of the blister (see pathology above)

• fever
• generalized allergic symptoms
  • periorbital edema
  • wheezing
  • urticaria
• pain & swelling with emergence of worm
• rupture of blister (generally as a result of immersion in water) is associated with relief of symptoms (as well as release of larvae)
• the ulcer surrounding the adult worm heals in weeks to months
• secondary infection of ulcer may occur

Laboratory

• diagnosis is made by detection of rhabditiform larvae in blisters or ulcers

Management

• gradual extraction of the worm by winding a few cm on a stick each day
• surgical excision of female worms
• antihelmintic agents may provide relief from symptoms but have no proven activity against the worm
  • thiabendazole 25 mg/kg BID for 3 days
  • metronidazole 250 mg po TID for 10 days

More general terms

• Dracunculus