IDCM CME 1-4: The Guinea Worm: Going...Going...

Post Date: 
2018-04-26

Author: Chris Lippincott, MD, MPH

The Guinea Worm: Going...Going…

In 1947, an estimated 48 million people worldwide were affected by Guinea worm disease.1 Today, only a half century later and without any medication or vaccines, this ancient disease is on the brink of global eradication. How did we get from there to here?  

Historical Significance
Dracunculiasis (also called Guinea worm disease, or GWD) was first mentioned in the Egyptian Ebers papyrus in the fifteenth century BC.1,2  Human infection is known to have occurred around this time due to the discovery of a female worm in the leg of a mummy in the tomb of Parennefer, and advisor to an Egyptian pharaoh of the 18th dynasty.3 It is believed that the “fiery serpents” striking down the Israelites in the Old Testament may be a reference to GWD.1

The term “Guinea worm” comes from disease prevalence in the Gulf of Guinea, although GWD has been described throughout history by Greek, Roman, Arab, Persian, and Indian physicians.1,2 Carl Linnaeus, a Swedish physician, zoologist, and botanist (1707-1778), is credited with naming numerous helminth infections including Gordius medinensis, which was later named Dracunculus medinensis — the causative agent of dracunculiasis, or GWD.2

 

Pathogenesis & Transmission

  • Dracunculus medinensis is a helminth, specifically a nematode (round worm).4
  • Life outside of humans:

         o   D. medinensis larvae live in intermediate hosts called copepods, which are small crustaceans that are
              ubiquitous in freshwater habitats.4

  • Human infection:

         o   Upon ingestion of contaminated fresh water, copepods die and release D. medinensis larvae, which
              enter the stomach.4
         o   The larvae later penetrate the abdomen and peritoneum, where they mature into adults and reproduce.4
         o   Adult male worms then die, while adult female worms can grow to 70-120 cm long.4

  • Human transmission:

         o   The adult female worms migrate through subcutaneous tissue towards the skin surface of the infected
              host over a period of 10-14 months.4
         o   The adult female worm ultimately causes a painful blister (typically on the lower extremities in 80-90%
              of cases) which later ruptures with the adult female worm eventually emerging.4
         o   When the adult female worm comes into contact with water, larvae are released and consumed by
              copepods, and the cycle begins anew.4
 

Figure 1. Life Cycle of Dracunculus medinensis4

Life cycle image and information courtesy of DPDx

Disease and Diagnosis

  • After a prolonged period of asymptomatic infection, about one year, the infected human host develops a mild fever, rash, and abdominal symptoms (nausea, vomiting, diarrhea).4
  • As the blister develops, it causes a burning sensation that is alleviated by cool water (hence propagating the transmission).4
  • Significant disease morbidity occurs through bacterial superinfection of the blister including cellulitis, abscess, septic arthritis, and even tetanus.4

Treatment and Prevention

  • Unfortunately, there is no medication or vaccination to treat or prevent GWD. The only available treatment is worm removal.
  • Worm removal is performed by:1,4

         o   Submerging the affected limb in a container of water to encourage worm emergence
         o   Cleaning the wound
         o   Slowly rolling the worm around a stick; however, this process is associated with significant pain and substantial
              risk as worm breakage can precipitate further infection
         o   Dressing the wound

Eradication Efforts and Current Progress
The National Guinea Worm Eradication Program was launched in 1983. In 1986, the World Health Organization (WHO) declared global elimination of GWD as a goal.1,5 At that time, an estimated 3.5 million cases affected 20 Asian and African countries.5 Within 11 years, in 1997, GWD was eradicated within Asia and the Middle East.1 Countries are certified as being Guinea worm free by WHO after demonstrating appropriate surveillance with no reports of indigenous cases during 3 consecutive years.5 Throughout the late 1990s and 2000s, 12 additional African countries were deemed to be free of GWD.1

Active case surveillance and detection have been critical components to GWD prevention.5 Disease transmission prevention efforts utilize the following 4 steps:5

  • Community education within endemic regions regarding the need to avoid submerging affected body parts in drinking water sources
  • Filtering drinking water through cloth or pipe filters when potential contamination is suspected
  • Treating potentially contaminated water sources with organophosphate insecticides
  • Procuring sanitary drinking water sources via bore-holes or wells.

In the early 2000s, GWD was thought to be eradicated in Chad. However in 2010 more than a decade after the last documented case of GWD, an outbreak of 10 indigenous cases was documented.5 Based on atypical transmission patterns, and an uptick in suspected cases of Guinea worm infection in dogs, investigators began to suspect that GWD may be transmitted from dogs to humans.6 While dogs and other mammals have been known to develop similar infections resembling GWD, true D. medinensis infection in dogs had never been proven; humans were the only known hosts for D. medinensis.6 A 2014 study has since confirmed that dogs in Chad have GWD secondary to D. medinensi. It is suspected that dogs are now infecting humans, a likely cause of GWD re-emergence in Chad.6 Case-control studies of GWD in humans and dogs are forthcoming, and many suspect that addressing GWD in dogs will be a critical aspect of GWD eradication in Chad, and thus globally.5-7 

Since 2015, only 4 countries account for all human cases of GWD: Chad, Ethiopia, Mali, and South Sudan.5 Mali and South Sudan have not had a documented case since 2015 and 2016, respectively.5,8 As of December 2017, the only cases documented worldwide have occurred in Chad and Ethiopia.8 If no further cases of GWD are detected in Mali or South Sudan in the next two years, then they may be the next countries to have successfully eradicated GWD. Should the current trends of GWD continue, it will mark an important triumph in global health as the first infection to be eradicated using fundamental public health principles without the aid of medicines or vaccines.4 

Table 1. Worldwide indigenous reported cases of human dracunculiasis from January 2015-December 20175,8

Bottom line: Guinea worm disease is caused by a round worm with a complex life cycle. 
Despite the lack of any medication or vaccine for treatment or prevention of Guinea worm
disease, multifaceted public health campaigns have successfully led to a dramatic reduction
of cases and near eradication of this ancient disease.

 

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References

    1.  Biswas G, Sankara DP, Agua-Agum J, Maiga A. Dracunculiasis (guinea worm disease): eradication without a
         drug or a vaccine. Phil Trans R Soc B Biol Sci. 2013 Jun 24;368(1623):20120146.
    2.  Cox, FE. History of human parasitology. Clin Microbiol Rev. 2002 Oct;15(4):595-612.
    3.  Nunn JF, Tapp E. Tropical Diseases in Ancient Egypt. Trans R Soc Trop Med Hyg. 2000 Mar-Apr;94(2):147-53.
    4.  CDC. Guinea Worm. https://www.cdc.gov/parasites/guineaworm/index.html (accessed April 10, 2018)
    5.  Hopkins DR, Ruiz-Tiben E, Roy SL, Weiss AJ. MMWR Morb Mortal Wkly Rep. 2017 Dec 8;66(48):1327-1331.
    6.  Eberhard ML, Ruiz-Tiben E, Hopkins DR, et al. The Peculiar Epidemiology of Dracunculiasis in Chad. Am J
         Trop Med Hyg. 2014 Jan;90(1):61-70.
    7.  Callaway E. Dogs thwart effort to eradicate Guinea worm. Nature. 2016 Jan 7;529(7584):10-1.
    8.  The Carter Center. https://www.cartercenter.org/news/pr/guinea-worm-worldwide-cases-jan2018.html
         (Accessed April 23, 2018)