Three decades into the global initiative combatting Guinea worm disease, the incidence has fallen from 3.5 million cases in 1986 to just 22 cases in 2015. The eradication of Guinea worm disease, an infection prevented by education and water filtration, is tantalizingly close.


1973 Dr. Mae Melvin Magnified 125X, this photomicrograph revealed the presence of three Guinea worms, Dracunculiasis medinensis. See PHIL 8209 through 8235 for images captured in Ghana documenting the ravages of this nematode, and the link below diagramming this parasite’s lifecycle.Clinical Features: The clinical manifestations are localized but incapacitating. The worm emerges as a whitish filament (duration of emergence: 1 to 3 weeks) in the center of a painful ulcer, accompanied by inflammation and frequently by secondary bacterial infection. Laboratory Diagnosis:The clinical presentation of dracunculiasis is so typical, and well known to the local population, that it does not need laboratory confirmation. In addition, the disease occurs in areas where such confirmation is unlikely to be available. Examination of the fluid discharged by the worm can show rhabditiform larvae. No serologic test is available.
Guinea worm, Dracunculiasis medinensis.

Guinea worm can only survive in communities that don’t have access to clean drinking water. As water sanitation improved across the Americas, guinea worm disappeared. Now, only a few bastions in Africa remain for these nematodes, but they can’t survive alone. Water fleas eat the first larval stage of the Guinea worm, acting as an incubator. Inside the flea, the larvae mature into an infective form and await ingestion when an unsuspecting person drinks water contaminated by the Trojan water flea.

The worms are released from the water fleas and develop, mate, and grow inside the human host, eventually reaching 80 to 100cm in length. The worms migrate to the lower extremities, where they begin emerging through a painful, burning sore that begs the host to seek relief in soothing water. Upon contact with water, the worm contracts, spewing hundreds of thousands of larvae into the water to continue the cycle.

The worm can be removed from the body by slowly wrapping the exposed portion around a stick as it emerges, a few centimetres at a time. This is a painful process and takes a few weeks to complete, but this is not the end of the infection’s impact. While Guinea worm infection itself is not fatal, secondary bacterial infections are very common and can be incapacitating or dangerous. Researchers have estimated that infected individuals in Nigeria may be unable to work 100 days of the year due to Guinea worm infection and the subsequent complications. A high rate of infection can side-line the majority of a village’s workforce, disrupt planting and harvesting, and result in high revenue losses for communities.

Aside from a healthier global community, rich countries have few self-interested incentives to invest in Guinea worm disease eradication. Unlike with Ebola, outbreaks cannot occur in countries with adequate water treatment, even if the worm travels across our borders. Here, former president Jimmy Carter’s constant dedication to controlling Guinea worm infection, in conjunction with the UN and CDC, proved invaluable. In 1986, the Carter Center, started by Jimmy Carter to “alleviate human suffering,” joined the CDC’s global initiative to eradicate Guinea worm disease.

The path to eradication has been paved with education, not medication. Communities with disease transmission were identified and village-based health care workers were trained to track disease incidence and educate communities.

Interrupting transmission is simple: cloth filtration is sufficient to remove the water fleas harboring the infective worm larvae. This knowledge put the community’s health into the hands of its members, and they were able to see the benefits of their efforts. However, the dissemination of this knowledge required access to affected communities, and political instability threw up many obstacles. Progress in Ghana was halted when a president who was whole-heartedly on board with the project was replaced by a disinterested successor. Stalled for 10 years, Carter finally elicited some interest by suggesting that if Ghana continued the way they were going, Guinea worm may need to undergo a name change – perhaps Ghana worm would be more appropriate? Renewed political interest restarted efforts.

 

The path to eradication has been paved with education, not medication.”

Sudan provided the biggest challenge to Guinea worm eradication. Swampy terrain hindered supply delivery, and a pastoralist lifestyle where members moved with their cattle in the dry season complicated accurate tracking of disease incidence. But undoubtedly, the most difficult obstacle to aid access was the Second Sudanese Civil War, a conflict beginning in 1983 that would continue for the next 22 years. In 1995, Carter negotiated a “Guinea worm ceasefire” to allow health workers access for the distribution of cloth filters. Bolstered by that success, intrepid aid workers continued to distribute supplies in subsequent years, despite dangerous conditions.

By 2005, a 99.5% reduction in Guinea worm disease had been achieved. Ghana, Sudan, and Nigeria were the disease’s strongholds, accounting for over 90% of the remaining cases. Today, with only 11 cases reported so far for 2016, the possibility of Guinea worm eradication looks promising. However, recent reports of dogs contracting Guinea worm complicates the situation. Chad had been on the verge of being classified ‘Guinea worm-free’ in the late 2000’s, but in 2010 a handful of cases reappeared. Concomitantly, a spate of infections in dogs were identified, spurring concerns of a new host reservoir. Guinea worm seems to be on its way to extinction, but it hasn’t sung its swan song yet.

guinea-worm-graphic
BOX 1. Guinea worm disease is caused by a parasitic worm, Dracunculus medinensis, spread through contamination of drinking water sources. The infective larval stage of the worm’s life cycle lives inside water fleas, where the copepods are destroyed by the acid in the stomach, releasing the Dracunculus larvae that then burrow through the intestinal wall. The worms mature over the next 100 days and mate. The fertilized female worms, bearing 3 million fertilized embryos, grow up to 1 metre in length and migrate painfully through the subcutaneous tissue to the extremities. About a year after initial infection, the worm emerges, causing painful burning blisters and edema accompanied by nausea. The burning blisters drive afflicted patients to seek relief by submerging blistered limbs in cool water, which is the worm’s devious and manipulative way of perpetuating their access to hosts. Upon contact with water, the female worm contracts, spewing hundreds of thousands of first stage larvae into the water source where they can survive for a few days. The released larvae are ingested by water fleas where they develop into the infective larval stage and await ingestion by the next unwitting thirsty person to begin a new infection cycle. Image credit: Angela Zhou.

 


References:

  1. Greenaway, C. (2004). “Dracunculiasis (guinea worm disease).” CMAJ. 170(4) :495-500.
  2. Jones, AH et al. (2014). “Logistics of Guinea worm disease eradication in South Sudan.” Am J Trop Med Hyg. 90(3): 393-401.
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