The Filarial Genome Network The Filarial Genome Network
Dracunculus medinensis, commonly known as guinea-worm is a parasite of the dog, horse, cow, wolf, leopard, monkey, and baboon that also commonly infects man. The majority of human infections occur in parts of West Africa, East Africa, and India.
The guinea-worm like all filarial nematodes goes through six developmental stages. The however unlike any other filarial parasite that can be transmitted to humans the infective larvae enter the body through the ingestion of various species of freshwater crustacea Cyclops (see picture below taken from Peters and Gilles 1991).
After the ingested Cyclops is destroyed by stomach acids the free larvae penetrate the gut lining and migrate to subcutaneous tissues via the lymphatics. This process takes approximately 43 days and once in subcutaneous tissue the worms mature slowly, reaching full development in one year. They then mate and the small male (1.2-2.9 cm long) dies and is absorbed into the larger female (60cm in length). When the embryos in the female's uterus reach maturity she migrates to areas of the body in contact with water (90% move to the feet and legs). Once in these areas the worm penetrates the skin, extrudes its uterus through its mouth, and discharges larvae into the water and dies(see picture below taken from Peters and Gilles 1991).
The larvae, which measure between 500 and 700 micrometers, can live for 6 days in clean water and 2 to 3 weeks in muddy water(see picture below taken from Peters and Gilles 1991).
The larvae are then ingested by Cyclops which actively chase them. Once ingested, the larvae mature into their infective stage in approximately 14 days and can then reinfect humans.
The female guinea-worm lives in the connective tissues of the limbs and truck where she usually does not cause any noticable pathological conditions (see X-ray below taken from Peters and Gilles 1991).
Although heavy infestations in the joint can cause arthritic conditions and require the removal of the worms (see picture below taken from Peters and Gilles 1991), most pathology is associated with infection occuring when the female dies after discharging her larvae.
The death of the worm causes the formation of a sterile abscess, which when secondarily infected results in cellulitis and local blistering of the skin (see picture below taken from Peters and Gilles 1991).
However, chills fever and local painful swellings commonly precede the emergence of the worm. D. medinensis has also been found coiled in the hernial sac and retroplacentally causing bleeding in pregnancy.