Dracunculiasis

The first signs of dracunculiasis occur around a year after infection, as the full-grown female worm prepares to leave the infected person's body.[12] As the worm migrates to its final site – typically the lower leg – some people have allergic reactions, including hives, fever, dizziness, nausea, vomiting, and diarrhea.[13] Upon reaching its destination, the worm forms a fluid-filled blister under the skin.[14] Over several days, the blister grows larger and begins to cause severe burning pain.[12] When an infected person submerges the blister in water to soothe the pain, the blister ruptures revealing the female worm.[14] The wound remains intensely painful as the worm slowly emerges from the wound over the course of several weeks to months.[15] An infected person can harbor multiple worms – up to 40 at a time – which will emerge from separate blisters at the same time.[13]

As the worm emerges, the open blister often becomes infected with bacteria, resulting in redness and swelling, the formation of abscesses, or in severe cases gangrene, sepsis or lockjaw.[12][2] When the secondary infection is near a joint (typically the ankle), the damage to the joint can result in stiffness, arthritis, or contractures.[2][16]

Life cycle of Dracunculus medinensis

Dracunculiasis is caused by infection with the roundworm Dracunculus medinensis.[17] D. medinensis larvae reside within small aquatic crustaceans called copepods. When humans drink the water, they can unintentionally ingest infected copepods. During digestion the copepods die, releasing the D. medinensis larvae. The larvae exit the digestive tract by penetrating the stomach and intestine, taking refuge in the abdomen or retroperitoneal space.[18] Over the next two to three months the larvae develop into adult male and female worms. The male remains small at 4 cm (1.6 in) long and 0.4 mm (0.016 in) wide; the female is comparatively large, often over 100 cm (39 in) long and 1.5 mm (0.059 in) wide.[14] Once the worms reach their adult size they mate, and the male dies.[13] Over the ensuing months, the female migrates to connective tissue or along bones, and continues to develop.[13]

About a year after initial infection, the female migrates to the skin, forms an ulcer, and emerges. When the wound touches freshwater, the female spews a milky-white substance containing hundreds of thousands of larvae into the water.[15][13] Over the next several days as the female emerges from the wound, she can continue to discharge larvae into surrounding water.[15] The larvae are eaten by copepods, and after two to three weeks of development, they are infectious to humans again.[19]

Dracunculiasis is diagnosed by visual examination – the thin white worm emerging from the blister is unique to guinea worm disease.[20] Dead worms sometimes calcify and can be seen in the subcutaneous tissue by X-ray.[2][20]

There is no vaccine or medicine to treat or prevent Guinea worm disease.[21] Instead, treatment focuses on slowly and carefully removing the worm from the wound over days to weeks.[22] Once the blister bursts and the worm begins to emerge, the wound is soaked in a bucket of water, allowing the worm to empty itself of larvae away from a source of drinking water.[22] As the first part of the worm emerges, it is typically wrapped around a piece of gauze or a stick to maintain steady tension on the worm, encouraging its exit.[22] Each day, several centimeters of the worm emerge from the blister, and the stick is wound to maintain tension.[13] This is repeated daily until the full worm emerges, typically within a month.[13] If too much pressure is applied at any point, the worm can break and die, leading to severe swelling and pain at the site of the ulcer.[13]

Treatment for dracunculiasis also tends to include regular wound care to avoid infection of the open ulcer while the worm is leaving. The U.S. Centers for Disease Control and Prevention (CDC) recommends cleaning the wound before the worm emerges. Once the worm begins to exit the body, the CDC recommends daily wound care: cleaning the wound, applying antibiotic ointment, and replacing the bandage with fresh gauze.[22] Painkillers like aspirin or ibuprofen can help ease the pain of the worm's exit.[13][22]

Dracunculiasis is a debilitating disease, causing substantial disability in around half of those infected.[2] People with worms emerging can be disabled for the three to ten weeks it takes the worms to fully emerge.[2] When worms emerge near joints, the inflammation around a dead worm, or infection of the open wound can result in permanent stiffness, pain, or destruction of the joint.[2] Some people with dracunculiasis have continuing pain for 12 to 18 months after the worm has emerged.[13] Around 1% of dracunculiasis cases result in death from secondary infections of the wound.[2]

When dracunculiasis was widespread, it would often affect entire villages at once.[16] Outbreaks occurring during planting and harvesting seasons severely impair a community's agricultural operations – earning dracunculiasis the moniker "empty granary disease" in some places.[16] Communities affected by dracunculiasis also see reduced school attendance as children of affected parents must take over farm or household duties, and affected children may be physically prevented from walking to school for weeks.[23]

Infection does not create immunity, so people can repeatedly experience dracunculiasis throughout their lives.[24]

There is no vaccine to prevent dracunculiasis, and once infected with D. medinensis there is no way to prevent the disease from running its full course. Consequently, nearly all effort to reduce the burden of dracunculiasis focuses on preventing the transmission of D. medinensis from person to person. This is primarily accomplished by filtering drinking water to physically remove copepods. Nylon filters, finely woven cloth, or specialized filter straws are all effective means of copepod removal.[25][13][26] Additionally, sources of drinking water can be treated with the larvicide temephos, which kills copepods.[27] Where possible, open sources of drinking water are replaced by deep wells that can serve as new sources of clean water.[27] Sources of drinking water can also be protected through public education campaigns, informing people in affected areas how dracunculiasis spreads, and encouraging those with the disease to avoid soaking their wound in bodies of water that are used for drinking.[13]

Logarithmic scale of reported human cases of guinea worm by year, 1989–2017 (2017 data is provisional)[28]

In 2020 there were just 27 cases of dracunculiasis worldwide: 12 in Chad, 11 in Ethiopia, and 1 each in Angola, Cameroon, Mali, and South Sudan.[3] This is down from 54 cases reported in 2019, and dramatically less than the estimated 3.5 million annual cases in 20 countries in 1986 – the year the World Health Assembly called for dracunculiasis' eradication.[29]

Dracunculiasis is a disease of extreme poverty, occurring in places where there is poor access to clean drinking water.[30] Cases tend to be split roughly equally between males and females, and can occur in all age groups.[31] Within a given place, dracunculiasis risk is linked to occupation; people who farm or fetch drinking water are most likely to be infected.[31]

Cases of dracunculiasis have a seasonal cycle, though the timing varies by location. Along the Sahara desert's southern edge, cases peak during the mid-year rainy season (May – October) when stagnant water sources are more abundant.[31] Along the Gulf of Guinea, cases are more common during the dry season (October – March) when flowing water sources dry.[31]

The campaign to eradicate dracunculiasis began at the urging of the U.S. Centers for Disease Control and Prevention in 1980.[32] Following smallpox eradication (last case in 1977; eradication certified in 1981), dracunculiasis was considered an achievable eradication target since it was relatively uncommon and preventable with only behavioral changes.[33] In 1981, the steering committee for the United Nations International Drinking Water Supply and Sanitation Decade (a program to improve global drinking water during the decade from 1981 to 1990) adopted the goal of eradicating dracunculiasis as part of their efforts.[34] The following June, an international meeting termed "Workshop on Opportunities for Control of Dracunculiasis" concluded that dracunculiasis could be eradicated through public education, drinking water improvement, and larvcide treatments.[35] In response, India began its national eradication program in 1983.[35] In 1986, the 39th World Health Assembly issued a statement endorsing dracunculiasis eradication and calling on member states to craft eradication plans.[33] The same year, the Carter Center began collaborating with the government of Pakistan to initiate its national program, which then launched in 1988.[35] By 1996, national eradication programs had launched in every country with endemic dracunculiasis: Ghana and Nigeria in 1989; Cameroon in 1991; Togo, Burkina Faso, Senegal, and Uganda in 1992; Benin, Mauritania, Niger, Mali, and Côte d’Ivoire in 1993; Sudan, Kenya, Chad, and Ethiopia in 1994; Yemen and Central African Republic in 1995.[36][33]

Each national eradication program had three phases. The first phase consisted of a nationwide search to identify the extent of dracunculiasis transmission and develop national and regional plans of action. The second phase involved the training and distribution of staff and volunteers to provide public education village-by-village, surveil for cases, and deliver water filters. This continued and evolved as needed until the national burden of disease was very low. Then in a third phase, programs intensified surveillance efforts with the goal of identifying each case within 24 hours of the worm emerging and preventing the person from contaminating drinking water supplies. Most national programs offered voluntary in-patient centers, where those affected could stay and receive food and care until their worms were removed.[37]

In May 1991, the 44th World Health Assembly called for an international certification system to verify dracunuliasis eradication country-by-country.[35] To this end, in 1995 the WHO established the International Commission for the Certification of Dracunculiasis Eradication (ICCDE).[38] Once a country reports zero cases of dracunculiasis for a calendar year, the ICCDE considers that country to have interrupted guinea worm transmission, and is then in the "precertification phase".[39] If the country repeats this feat with zero cases in each of the next three calendar years, the ICCDE sends a team to the country to assess the country's disease surveillance systems and to verify the country's reports.[39] The ICCDE can then formally recommend the WHO Director-General certify a country as free of dracunculiasis.[38]

Since the initiation of the global eradication program, the ICCDE has certified 15 of the original endemic countries as having eradicated dracunculiasis: Pakistan in 1997; India in 2000; Senegal and Yemen in 2004; Central African Republic and Cameroon in 2007; Benin, Mauritania, and Uganda in 2009; Burkina Faso and Togo in 2011; Côte d’Ivoire, Niger, and Nigeria in 2013; and Ghana in 2015.[40]

Endemic countries

Four countries continue to have endemic dracunculiasis: Chad, Ethiopia, Mali, and South Sudan.[40] For many years the major focus was South Sudan (independent after 2011, formerly the southern region of Sudan), which reported 76% of all cases in 2013.[41] In 2017 only Chad and Ethiopia had cases.[42]

Date	South Sudan	Mali	Ethiopia	Chad	Total
2011	1,028[43]	12[43]	8[43]	10[43]	1058
2012	521[43]	7[43]	4[43]	10[43]	542
2013	113[43]	11[43]	7[43]	14[43]	148 (including 3 exported to Sudan)
2014	70[43]	40[43]	3[43]	13[43]	126
2015	5[43]	5[43]	3[43]	9[43]	22
2016	6[43]	0[43]	3[43]	16[43]	25
2017	0[44]	0[44]	15[44]	15[44]	30
2018	10[45]	0[45]	0[45]	17[45]	28 (including one isolated case in Angola)
2019	4[45]	0[45]	0[45]	47[45]	54[46][47] (including one isolated case each in Angola and Cameroon)[49]
2020	1[50]	1[50]	11[50]	12[50]	27[50] (including one isolated case each in Angola and Cameroon)
2021	4[51]	2[51]	1[51]	8[51]	15[51]

Rod of Asclepius

Dracunculiasis has been with humans for at least 3,000 years, as the remnants of a guinea worm infection have been found in the mummy of a girl entombed in Egypt around 1,000 BCE.[52] Diseases consistent with the effects of dracunculiasis are referenced by writers throughout antiquity. The disease of "fiery serpents" that plagues the Hebrews in the Old Testament (around 1250 BCE) is often attributed to dracunculiasis.[30][52][note 1] Plutarch's Symposiacon refers to a (now lost) description of a similar disease by the 2nd century BCE writer Agatharchides concerning a "hitherto unheard of disease" in which "small worms issue from [people's] arms and legs... insinuating themselves between the muscles [to] give rise to horrible sufferings".[52] Many of antiquity's famous physicians also write of diseases consistent with Dracunculiasis, including Galen, Rhazes, and Avicenna; though there was some disagreement as to the nature of the disease, with some attributing it to a worm, while others considered it to be a corrupted part of the body emerging.[52]

• In the 18th century, Swedish naturalist Carl Linnaeus identified D. medinensis in merchants who traded along the Gulf of Guinea (West African Coast).
• Guinea worms were described by Oliver Wendell Holmes Sr as "[burrowing] into the naked feet of West-Indian slaves..."[53]

This is nearly the same treatment that is noted in the famous ancient Egyptian medical text, the Ebers Papyrus from c. 1550 BC.[7]

It has been suggested that the Rod of Asclepius (a symbol that represents medical practice) represents a Guinea worm wrapped around a stick for extraction.[54] According to this thinking, physicians might have advertised this common service by posting a sign depicting a worm on a rod. However plausible, there is no concrete evidence in support of this notion.

The Russian scientist Alexei Pavlovich Fedchenko (1844–1873) during the 1860s while living in Samarkand was provided with a number of specimens of the worm by a local doctor which he kept in water. While examining the worms Fedchenko noted the presence of water fleas with embryos of the guinea worm within them.[55]

In modern times, the first to describe dracunculiasis and its pathogenesis was the Bulgarian physician Hristo Stambolski, during his exile in Yemen (1877–1878).[56] He correctly inferred that the cause was infected water which people were drinking.

In the 19th and 20th centuries, dracunculiasis was widespread across nearly all of Africa and South Asia.[31]

Until recently humans and water fleas (Cyclops) were regarded as the only animals this parasite infects. It has been shown that baboons, cats, dogs, frogs and catfish (Synodontis) can also be infected naturally. Ferrets have been infected experimentally.[58]

In March 2016, the World Health Organization convened a scientific conference to study the emergence of cases of infections of dogs. The worms are genetically indistinguishable from the Dracunculus medinensis that infects humans. The first case was reported in Chad in 2012; in 2016, there were more than 1,000 cases of dogs with emerging worms in Chad, 14 in Ethiopia, and 11 in Mali.[59] It is unclear if dog and human infections are related. It is possible that dogs may spread the disease to people, that a third organism may be able to spread it to both dogs and people, or that this may be a different type of Dracunculus. The current (as of 2014) epidemiological pattern of human infections in Chad appears different, with no sign of clustering of cases around a particular village or water source, and a lower average number of worms per individual.[60]

• "Guinea Worm Disease Eradication Program". Carter Center.
• Nicholas D. Kristof from the New York Times follows a young Sudanese boy with a Guinea Worm parasite infection who is quarantined for treatment as part of the Carter program
• Tropical Medicine Central Resource: "Guinea Worm Infection (Dracunculiasis)"
• World Health Organization on Dracunculiasis