dracunculiasis dracunculiasis dracunculiasis, also called guinea-worm disease, is a parasitic infection by the guinea worm, dracunculus medinensis. a person typically becomes infected by drinking water containing water fleas infected with guinea worm larvae. the larvae penetrate the digestive tract and escape into the body where the females and males mate. around a year later, the adult female migrates to an exit site – usually a lower limb – and induces an intensely painful blister on the skin. the blister eventually bursts to form an intensely painful wound, out of which the worm slowly crawls over several weeks. the wound remains painful throughout the worm's emergence, disabling the infected person for the three to ten weeks it takes the worm to emerge. during this time, the open wound can become infected with bacteria, leading to death in around 1% of cases. dracunculiasisother namesguinea-worm diseasefiery serpent diseasedracontiasismedina worm diseaseusing a matchstick to wind up and remove a guinea worm from the leg of a humanspecialtyinfectious diseasesymptomspainful blister that a long white string-like worm slowly crawls out ofusual onsetone year after exposurecausesguinea worm-infected water fleaspreventionpreventing those infected from putting the wound in drinking water, treating contaminated watertreatmentslowly extracting worm, supportive care, oral metronidazole to relieve symptoms and to prevent inflammation and abscess formation if the worm breaksfrequency13 cases worldwide (2022)deaths~1% of cases there is no known antihelminthic agent to expel the guinea worm. instead, the mainstay of treatment is the careful wrapping of the emerging worm around a small stick or gauze to encourage its exit. each day, a few more centimeters of the worm emerge, and the stick is turned to maintain gentle tension. too much tension can break and kill the worm in the wound, causing severe pain and swelling at the ulcer site. dracunculiasis is a disease of extreme poverty, occurring in places with poor access to clean drinking water. prevention efforts center on filtering drinking water to remove water fleas, as well as public education campaigns to discourage people from soaking their emerging worms in sources of drinking water. humans have had dracunculiasis since at least 1,000 bce, and accounts consistent with dracunculiasis appear in surviving documents from physicians of antiquity. in the 19th and early 20th centuries, dracunculiasis was widespread across much of africa and south asia, affecting as many as 48 million people per year. the effort to eradicate dracunculiasis began in the 1980s following the successful eradication of smallpox. by 1995, every country with endemic dracunculiasis had established a national eradication program. in the ensuing years, dracunculiasis cases have dropped precipitously, and 15 previously endemic countries have been certified to have eradicated dracunculiasis, leaving the disease endemic in just four countries: chad, ethiopia, mali, and south sudan. a record low 13 cases of dracunculiasis were reported worldwide in 2022. if the eradication program succeeds, dracunculiasis will become the second human disease known to have been eradicated, after smallpox. signs and symptoms blister on the foot of a person with 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. as the worm migrates to its exit site – typically the lower leg, though they can emerge anywhere on the body – some people have allergic reactions, including hives, fever, dizziness, nausea, vomiting, and diarrhea. upon reaching its destination, the worm forms a fluid-filled blister under the skin. over 1–3 days, the blister grows larger, begins to cause severe burning pain, and eventually bursts leaving a small open wound. the wound remains intensely painful as the worm slowly emerges over several weeks to months. in an attempt to alleviate the excruciating burning pain, the host will nearly always attempt to submerge the affected body part in water. when the worm is exposed to water, it spews a white substance containing thousands of larvae. 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. when the secondary infection is near a joint (typically the ankle), the damage to the joint can result in stiffness, arthritis, or contractures. infected people commonly harbor multiple worms – with an average 1.8 worms per person; up to 40 at a time – which will emerge from separate blisters at the same time. 90% of worms emerge from the legs or feet. however, worms can emerge from anywhere on the body. cause life cycle of dracunculus medinensis dracunculiasis is caused by infection with the roundworm dracunculus medinensis. d. medinensis larvae reside within small aquatic crustaceans called copepods or water fleas. 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. 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. once the worms reach their adult size they mate, and the male dies. over the ensuing months, the female migrates to connective tissue or along bones, and continues to develop. about a year after the 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. over the next several days as the female emerges from the wound, she can continue to discharge larvae into surrounding water. the larvae are eaten by copepods, and after two to three weeks of development, they are infectious to humans again. diagnosis dracunculiasis is diagnosed by visual examination – the thin white worm emerging from the blister is unique to this disease. dead worms sometimes calcify and can be seen in the subcutaneous tissue by x-ray. treatment there is no medicine to kill d. medinensis or prevent it from causing disease once within the body. instead, treatment focuses on slowly and carefully removing the worm from the wound over days to weeks. 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. 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. each day, several centimeters of the worm emerge from the blister, and the stick is wound to maintain tension. this is repeated daily until the full worm emerges, typically within a month. 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. 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. painkillers like aspirin or ibuprofen can help ease the pain of the worm's exit. outcomes dracunculiasis is a debilitating disease, causing substantial disability in around half of those infected. people with worms emerging can be disabled for the three to ten weeks it takes the worms to fully emerge. 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. some people with dracunculiasis have continuing pain for 12 to 18 months after the worm has emerged. around 1% of dracunculiasis cases result in death from secondary infections of the wound. when dracunculiasis was widespread, it would often affect entire villages at once. outbreaks occurring during planting and harvesting seasons severely impair a community's agricultural operations – earning dracunculiasis the moniker "empty granary disease" in some places. 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. infection does not create immunity, so people can repeatedly experience dracunculiasis throughout their lives. prevention children in chad holding filter straws used to prevent d. medinensis infection there is no vaccine for 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. sources of drinking water can be treated with the larvicide temephos, which kills copepods. where possible, open sources of drinking water are replaced by deep wells that can serve as new sources of clean water. public education campaigns inform people in affected areas how dracunculiasis spreads and encourage those with the disease to avoid soaking their wounds in bodies of water that are used for drinking. epidemiology dracunculiasis is nearly eradicated, with just 15 cases reported worldwide in 2021 and 13 in 2022. this is down from 27 cases in 2020, 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. dracunculiasis remains endemic in just four countries: chad, ethiopia, mali, and south sudan. dracunculiasis is a disease of extreme poverty, occurring in places where there is poor access to clean drinking water. cases tend to be split roughly equally between males and females, and can occur in all age groups. within a given place, dracunculiasis risk is linked to occupation; people who farm or fetch drinking water are most likely to be infected. 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. along the gulf of guinea, cases are more common during the dry season (october–march) when flowing water sources dry up. history 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. 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. 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 arms and legs ... insinuating themselves between the muscles give rise to horrible sufferings". 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. in his 1674 treatise on dracunculiasis, georg hieronymous velschius first proposed that the rod of asclepius, a common symbol of the medical profession, depicts a recently extracted guinea worm. carl linnaeus included the guinea worm in his 1758 edition of systema naturae, naming it gordius medinensis. the name medinensis refers to the worm's longstanding association with the city of medina, with avicenna writing as early as his the canon of medicine (published in 1025) "the disease is commonest at medina, whence it takes its name". in johann friedrich gmelin's 13th edition of systema naturae (1788), he renamed the worm filaria medinensis, leaving gordius for free-living worms. henry bastian authored the first detailed description of the worm itself, published in 1863. the following year, in his book entozoa, thomas spencer