Dracunculus medinensis (Guinea worm)

Epidemiology: 1) incidence of human infection has declined because of irradication efforts 2) Sudan & West Africa 3) infection acquired through ingestion of contaminated water containing larvae from Cyclops 4) Cyclops is a crustacean intermediate host Pathology: 1) ingested larvae penetrate the stomach or intestinal wall, mate & mature 2) the male probably dies 3) the female develops over a period of 1 year & migrates to subcutaneous tissues, generally in a lower extremity 4) female measures 30 cm to 1 meter in length, but thin 5) a blister forms in the skin at the site of the female which breaks down & ulcerates 6) through the ulcer, large numbers of rhabditiform larvae can be released into stagnant water 7) 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) 2) fever 3) generalized allergic symptoms a) periorbital edema b) wheezing c) urticaria 4) pain & swelling with emergence of worm 5) rupture of blister (generally as a result of immersion in water) is associated with relief of symptoms (as well as release of larvae) 6) the ulcer surrounding the adult worm heals in weeks to months 7) secondary infection of ulcer may occur Laboratory: 1) diagnosis is made by detection of rhabditiform larvae in blisters or ulcers Management: 1) gradual extraction of the worm by winding a few cm on a stick each day 2) surgical excision of female worms 3) antihelmintic agents may provide relief from symptoms but have no proven activity against the worm a) thiabendazole 25 mg/kg BID for 3 days b) metronidazole 250 mg po TID for 10 days

Properties

KINGDOM: animal PHYLUM: helminth

References

Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 1216