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Global Eradication of Guinea Worm Disease – A new factor to be considered

Global Eradication of Guinea Worm Disease – A new factor to be considered

Guinea worm disease (dracunculiasis) is one of the so-called Neglected Tropical Diseases which have been identified as a candidate for global eradication even though there is no curative treatment for the disease. It is caused by a nematode worm, Dracunculus medinensis, following ingestion of water containing water fleas (Cyclops species) that have ingested the larvae of the worm.

In humans the larvae move from the intestine into body tissues, where they develop into adult worms. Infected individuals may remain asymptomatic for up to a year when the mature female worm (which can be 70-100cm long) migrates through the subcutaneous tissues, to the surface of the skin (normally on the foot), where it classically emerges through a blister which ulcerates. The emergence of the adult worm is accompanied by severe local inflammation, pain, oedema, and generalized symptoms such as fever, nausea, and vomiting over a period of several days. In order to reduce the severity of the pain, the patient often immerses the affected limb in water. Unfortunately, as the female worm emerges it discharges its larvae, thus initiating a new life cycle – if water fleas are present.

Fortunately, the disease can be prevented by provision of safe sources of drinking water, by application of larvicide and by filtering potentially contaminated water. Since it was accepted that the disease could only be acquired as a result of drinking contaminated water, a Global Dracunculiasis Eradication Programme was initiated in 1981. Since that time, national control programmes, the World Health Organization, the U.S. Centers for Disease Control and Prevention, The Carter Center and other partners have coordinated eradication efforts. While it was estimated that that there were approximately 3.5million cases of the disease in sub-Saharan Africa in 1986, only 126 human cases were reported to WHO in 2014 and an even smaller number (22) during 2015 with no cases being imported into endemic countries from outside in the past four years. Currently, indigenous cases are occurring only in Chad, Mali, Ethiopia, and South Sudan.

This remarkable decrease prompted the WHO and others to believe that global interruption of human transmission of Dracunculus medinensis and therefore eradication was within reach.

However, it appears that strains of Dracunculus medinensis identical to those seen in humans have been found in dogs associated with human cases, in Chad and Ethiopia. Clearly if a non- human host proves to be a significant factor in the epidemiology of the disease, control measures will have to be further adapted to ensure true eradication.

The International Commission for the Certification of Dracunculiasis Eradication (ICCDE) has issued the following recommendations:

  • Plan the development and launch of a Global Reward one year after the last human case has been detected to encourage local case finding.
  • Continue with aggressive use of the larvicide, abate (temephos) to kill the intermediate host and minimize any risk of transmission.
  • Ensure early containment of all cases, preferably within 24 hours.
  • Thoroughly investigate all new cases through an intensive case control approach to obtain as much information as possible to define conditions through which the case was acquired;
  • Enhance measures to achieve maximum awareness among all populations in endemic and pre-certified countries on the availability of a cash reward.
  • Continue to scale-up active surveillance in at-risk villages and pursue the integration of guinea-worm disease surveillance into other programmes such as polio, mass drug distribution for neglected tropical diseases, national immunization days.
  • Further increase surveillance in at-risk border areas, notably the Chad–Central African Republic border (if security permits).
  • Initiate focused research to define the role of dogs (particularly in Chad) and understand the unique epidemiology through new technologies such as GPS tracking of dogs and stable isotope analysis of food sources to verify whether aquatic animals are a source of infection in Chad.
  • Maintain and enhance measures to identify infected dogs, institute rewards for reporting dog infections and promote the tethering of dogs to prevent contamination of water sources.