What is Dracunculiasis?

Dracunculiasis, or Guinea worm disease, is caused by infection with a parasitic roundworm known as a Guinea worm. The disease manifests as painful and disfiguring sores. Guinea worm disease is considered to be in the late stages of global eradication.

Global Burden

Dracunculiasis

As of 2010, there were fewer than 2000 reported cases of dracunculiasis, all in isolated areas of Sub-Saharan Africa. 94% of the cases occurred in Sudan, while Mali, Ethiopia, and Ghana each reported fewer than 100 cases.1

Since 1989, there has been a 99% reduction in dracunculiasis incidence worldwide; 187 countries are certified free of transmission. Efforts to eradicate the disease worldwide have focused on surveillance and interrupting transmission.2

Causative Agent

life cycleDracunculiasis is caused by drinking water containing water fleas of the genus Cyclops that have been contaminated with guinea worm (or Dracunculus medenensis) larvae. Once ingested by a human, these larvae emerge from the digested water flea and migrate through the lining of the stomach, and into the tissues of the extremities, where they grow and can reach up to one meter in length. After approximately one year, a blister forms on the skin of the lower leg or foot. The extremely painful burning sensation of the blister causes the infected individual to immerse their leg in water—at which point the worm releases thousands of larvae into the water supply. These larvae are ingested by water fleas, thereby completing the life cycle.3

Pathogenesis

example

The emergence of the worm from the lower extremity causes a painful blister that becomes abscessed due to the host’s immune reaction. As the worm is removed from the wound, its track through the tissues can become infected and debilitating to the host. Disability resulting from infection is permanent in less than 1% of cases.3

The pain caused by the blister during the emergence of the worm can be extremely incapacitating. It is estimated that the disease caused an economic loss of $20 million in rice-growing areas of Nigeria before its eradication in that country, primarily due to decreased productivity among the infected.3

Current Control Strategy

The near-eradication of dracunculiasis can be seen as a triumph of advocacy and partnership on the part of private foundations, especially the Carter Center, and the World Health Organization, the World Bank, and UNICEF.3

Because there are so few remaining cases, isolated in one geographic area, the current control strategy for dracunculiasis focuses on education and surveillance in order to interrupt transmission. Humans are the only host of the Guinea worm, so halting transmission would effectively eliminate the disease.2

The eradication campaign has been helped by the limited spectrum of water sources that can support transmission. Fast-moving water sources and deep wells rarely carry the requisite water fleas, whereas shallow pools, ponds and cisterns are usually implicated in transmission. Building and maintaining a safe water supply has thus been of paramount importance in the eradication campaign. This is accomplished both through filtration, but also by preventing patients with an abscessed wound coming into contact with the water supply.3

Existing Products

Drugs

The standard of care for treatment of the Guinea worm infection is to slowly extract the worm from the wound by winding it around a stick a few centimeters a day until it is fully removed. There are no drugs available to treat dracunculiasis and attempts to repurpose other antiparasitic compounds to treat dracunculiasis have been largely unsuccessful. The benzimidazole class of antiparasitic drugs was shown to reduce inflammation secondary to infection, but have no direct effect against the parasite. Ivermectin was found to have no effect against the worms. In clinical trials mebendazole often caused the worms to migrate to other places in the body, causing even more complications.3

Vaccines

There is no vaccine to prevent dracunculiasis, and infection does not result in natural immunity.

Diagnostics

A visual diagnosis based on the presence of a dracunculiasis blister is most common. ELISA tests can be used to confirm a visual diagnosis. However, no circulating antigens have been identified that can be used to diagnosis infection before blister formation.3

References

  1. WHO. “Dracunculiasis Epidemiology”.
  2. WHO. “Dracunculiasis".
  3. Cairncross et al. (2002). “Dracunculiasis (Guinea Worm Disease) and the Eradication Initiative"Clinical Microbiology Reviews15(2).
  4. Iriemenam et al (2008). “Dracunculiasis—the saddle is virtually ended”. Parasitology Research 102(3)

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Drugs

There are currently no drugs in development for dracunculiasis. However, the success of eradication campaigns thus far suggests eradication may be possible without the use of drugs.1

Vaccines

There are no vaccines in development for dracunculiasis.

Diagnostics

Although there is some evidence that host immunoglobulin G4 antibodies may be sufficient biomarkers for early Guinea worm infection, the development of new diagnostics is not a priority at this time.2

References

  1. Iriemenam et al. (2008). “Dracunculiasis—the saddle is virtually ended.” Parasitology Research 102(3)
  2. Cairncross et al. (2002). “Dracunculiasis (Guinea Worm Disease) and the Eradication Initiative"Clinical Microbiology Reviews15(2).

Get Involved

To learn how you can get involved in neglected disease drug, vaccine or diagnostic research and development, or to provide updates, changes, or corrections to the Global Health Primer website, please view our FAQs.

The tools available for the development of drugs, vaccines, and diagnostics for dracunculiasis are extremely limited. However, as this disease is near eradication at this time and new product development is not considered a priority, tools for this disease are not provided here.

References

Get Involved

To learn how you can get involved in neglected disease drug, vaccine or diagnostic research and development, or to provide updates, changes, or corrections to the Global Health Primer website, please view our FAQs.