Tad Henry

Dracunculiasis: “The Fiery Serpentʼs” Final Stand

Intro

Dracunculiasis, derived from the Latin for “affliction with little dragons” is a parasiticinfection caused be a nematode worm, Dracunculus medinensis [1]. The disease is also known as Medina worm or Guinea worm, named after two places where thedisease was endemic and first recognized [2].

Taxonomy

Dracunculus medinensis belongs to the nematode superfamily Dracunculoidea of theorder Spirurida. Also included in the Spirurida order are the filariae, like Wuchereria bancrofti, Brugia malayi, Onchocerca volvulus, and Loa loa [3].

Morphology

A mature female D. medinensis is one of the longest nematodes, measuring up to 100cm; however, it is only 1 to 2 mm in width. The vulva is halfway down the body, but is plugged up such that the whole body cavity is filled with the uterus, which extendsanteriorly and posteriorly and contains 1 to 3 million first-stage larvae. The gut is completely flattened and nonfunctional. Males have only been recovered doubtfullyfrom humans (usually the male dies after copulation), but those from experimentalanimals measure 15 to 40 by 0.4 mm [4].

History

“The fiery serpent” that afflicted the Israelites during their exodus is said to be the sameas dracunculiasis that endures to this day. The disease is more than 3,000 years old,having been discovered in calcified mummies [5]. Guinea worm was a big enoughscourge that it was recognized by Greek, Roman and Arab-Persian philosophers and physicians [6]. Dracunculiasis is indisputably a disease of antiquity. However, it may not be a human disease of the future. Global eradication efforts spearheaded by the Carter Center in 1986--in partnership with WHO, CDC and UNICEF--have slashed theincidence of the disease considerably: in 1986, there were an estimated 3.5 millioncases of Guinea worm in 20 countries in Africa and Asia [7]; by 2008, there were just 4,587 documented cases in 5 countries all within sub-Saharan Africa [8]. With continued surveillance, monitoring, political will and funding, Dracunculiasis could soonbecome the first parasitic disease to be eradicated--and second human disease to beeradicated, after smallpox. Furthermore, eradication would be achieved solely bybehavioral measures, not by a vaccine or cure--as was done with smallpox.

Life Cycle

A human becomes infected after drinking water with copepods, of the Cyclops genus,that have ingested Dracunculus medinensis larvae. In the stomach, the acidicconditions dissolve the copepod but leave the parasite larvae intact--at which point the

D. medinensis larvae is activated and penetrates the gut wall to mature in the looseconnective tissue. After maturation and copulation, the male worm dies and the female worm (70-120 cm) proceeds to move through a patientʼs subcutaneous tissue. A year after infection (the incubation period), the female worm prepares to exit from the host-so as to distribute its progeny--from one of the lower extremities: usually leg or foot. A blister forms and ruptures, at which point the patient usually seeks out water toameliorate the burning pain. The female worm emerges--taking up to a month to exit-upon contact with water so it can release hundreds of thousands of larvae. The larvae are soon ingested by a copepod and after two weeks--and two molts--the larvaebecome infective. A human may then drink the infected water, thus closing the cycle [9].

[10]

Clinical Presentation

Dracunculiasis is notorious for producing a blister--usually on the leg or foot--that is sopainful one could describe it as being stabbed repeatedly or having the afflicted area on fire. The blister bursts after a few days, giving rise to a shallow ulcer, and then there is an inflammatory response against the cuticle of the entire worm, preventing its removal.After the worm is fully extracted, the lesion resolves quickly. Secondary infections canhappen in up to half of all patients: physical impairments (“locked” knees or other joints),tetanus, septicemia. Female worms sometimes burst in the tissues, resulting in a largepus-filled abscess and severe cellulitis [11].

Diagnosis

Patients in areas of endemicity have no doubt about the diagnosis when the blisterforms. Once the blister has burst, cold water will trigger the release of larvae, which canbe seen microscopically under low power. Immunodiagnostic methods have not yetbeen proven to detect prepatent infections. However, antibodies can be detected in patent infections by enzyme-linked immunosorbent assay or dot-enzyme-linkedimmunosorbent assay, using whole-worm antigens. The most specific reaction seemsto be the detection of immunoglobulin G4. This test may be capable of detectingprepatent infections up to 6 months before emergence, in which case the test would bea practical one, enabling containment to be done in a timely fashion [12].

Treatment, Intervention and Prevention

There are no drugs for the treatment of dracunculiasis. But a couple drugs can help tofacilitate worm removal: Metronidazole and Thiabendazole [13]. Upon release of thelarvae, the female worm dies and must be extracted manually, usually by rolling a few cm of the worm each day on a stick or piece of gauze [14]. A clean dressing and antibiotic ointment to prevent secondary bacterial infection should both be applied [15].The painful worm extraction process can take up to a month.

However, prevention is perhaps even more important than treatment, as cases can be staved off all together. Dracunculiasis can be prevented by protecting water sourcesand filtering potentially contaminated water [16]. New sources of safe drinking watershould also be created--like boreholes or hand-dug wells which people do not wadeinto. Patients with an emerging Guinea worm should never enter a source of drinkingwater--and a piece of fine-mesh cloth should be used to filter out copepods frompotentially contaminated drinking water. Abate (temephos), a larvicide, can also beintroduced to unsafe sources of water to exterminate the infected copepods [17].

The Carter Center, a leader in the Global Dracunculiasis Eradication Campaign, provides families with fine-mesh filter cloths that fit over clay pots used to hold water. Nomadic groups often receive pipe filters, which are small straw-like personal filters thatcan be worn around the neck. Both filter out copepods [18]. These simple butincredibly effective devices enable people to drink water safely.

A Guinea worm is extracted by a health worker from a childʼs foot in Savelugu, Ghana

[19]

Two Sudanese boys make use of pipe filters to filter out potentially infected copepods

[20]

Epidemiology and Socio-Economic Impacts

Ponds and step wells are the main sources of disease. Dracunculiasis is not normallycontracted in rivers or streams which have faster flowing water and do not allow theCyclops copepods the requisite 12 to 14 days to become infective. Deep wells arelikewise rarely implicated in transmission because the lack of light limits the populationof zooplankton, the Cyclops main diet. A preponderance of the infective water sources are man-made: “boullies” or large dew ponds excavated for community water storage incentral Burkina Faso; small dams in northern Ghana; “ataparas” (or valley tanks) innorthern Uganda; hundreds of drinking-water ponds built in Anambra State, Nigeria; and “hafirs” to store water from ephemeral streams in Sudan. Rectangular masonry-linedstep wells, shallow wells and scoop wells have also been implicated in contributing totransmission [21].

Dracunculiasis causes dreadful suffering and disability among the worldʼs most deprivedpeople--people already struggling to maintain health and earn a living. The disease reappears each agricultural season--as the incubation period is about 1 year beforeemergence of the female worm--handicapping workers, mothers, and schoolchildrenalready struggling to make ends meet. The extraction of the worm is slow and painful,incapacitating individuals for weeks, sometimes longer. A review of twelve published studies yielded an average duration of disability caused by Guinea worm disease to beabout 8 weeks (with estimates ranging from 2 to 16 weeks) [22]. Secondary bacterialinfections often accompany the blisters, leading to sepsis, abscesses, arthritis,contracture of joints, and tetanus [23]. In agricultural communities the economic impactscan be severe, as food stocks and savings dwindle and childrenʼs schooling suffers (resulting in further economic losses in the future) [24]. It has been claimed that theeffect of the disease on agricultural productivity can be detected in satellite photographs. The Dogon people of Mali refer to the infection as “the disease of theempty granary.” [25]

Eradication

Several characteristics of Dracunculiasis make it especially amenable to eradication:there is no human carrier state beyond the one-year incubation period; there is noknown animal reservoir; transmission is seasonal and disease is of limited geographicdistribution; diagnosis is easy and unambiguous; the transmission agent, a copepod, isnot a very mobile vector--in comparison to mosquitoes, for instance; and the methodsfor controlling transmission are simple, low-cost, and effective [26]. Furthermore, thereare certain villages of endemicity that can be carefully monitored--for example, villageswith ponds are twice as likely to be endemic [27].

The Global Dracunculiasis Eradication Campaign (GDEC) began at the Centers forDisease Control and Prevention in 1980 and has since been spearheaded by the CarterCenter, at the head of a coalition that includes the ministries of health of endemic countries, CDC, the World Health Organization (WHO), and the United Nations Childrenʼs Fund (UNICEF). Thousands of village volunteers and supervisory healthstaff, as well as donor agencies, governments, foundations and institutions have all been contributing to the eradication effort [28].

In 1986, 20 countries throughout sub-Saharan Africa and Asia were endemic for GuineaWorm disease and there were an estimated 3.5 million cases. The number of endemic countries in 2004 fell to 11 thanks to the GDEC [29]. By 2008, there were just 4,587 documented cases in 6 countries within sub-Saharan Africa [30].

Map of endemic countries in 1986 and 2008 [31]:

Where Guinea Worm Is Found

When The Carter Center began to provide technical and financial assistance to national eradication programs in 1986, Guinea worm disease was found in 20 countries in Africa and Asia. Today the disease remains in six countries, all in Africa: Sudan, Ghana, Mali, Ethiopia, Nigeria, Niger.

* Provisional as of 2/08

Sudan, Nigeria, Niger, Mali and Ghana are to date still affected by dracunculiasis. However, Niger and Nigeria are soon to rid the scourge from their turf, leaving the battlegrounds in just southern Sudan, Mali and Ghana. Niger reported just 11 indigenous cases in 2007, while Nigeria had 73 cases. Nigeria reported 37 cases from January toMarch 2008 from five villages; however, all 37 cases were detected before or within 24 hours of the emergence of the worms and were contained successfully. From Januaryto April, Niger reported just one case of dracunculiasis imported from Mali, which was contained. Thus, three major foci remain: southern Sudan, northern Ghana and easternMali, which respectively reported 61%, 35% and 3% of all cases in 2007 [33].

1000 900

Number of Reported Cases (In Thousands)

(Distribution of 9,570 indigenous cases of Guinea worm disease during 2007 and yearof last indigenous case in other countries) [34]

Sudan has greatly ratcheted up its eradication effort since 2005 when the Comprehensive Peace Agreement was signed, ending a more than two-decade long civil war. 2006 saw an increase to 15,539 cases of Guinea Worm disease, from 5,569 cases in 2005, as a result of reporting from endemic areas that were no longer war-torn.The Southern Sudan Guinea Worm Eradication Program (SSGWEP) has deployed over28,000 village volunteers, supervisors and other health staff to work on the program full time. The SSGWEP was able to slash the number of cases reported in 2006 by 63% to 5,815 cases in 2007. Northern Sudan has reported no endemic cases of dracunculiasissince 2001 [35].

After a decade of frustration and stagnation in Ghana, in 2006 a decisive turnaroundwas achieved. Multiple changes can be attributed to the improved containment andlower incidence of dracunculiasis: better supervision and accountability, active oversightof patients daily by paid staff, and an intensified public awareness campaign. After Jimmy Carterʼs visit to Ghana in August 2006, the government of Ghana declared Guinea worm disease to be a public health emergency. The overall rate of contained cases has increased in Ghana from 60% in 2005 to 75% in 2006 to 84% in 2007 [36].Should the 89% average month-to-month incidence reductions since October 2007 inGhana be sustained during 2008, there is likely to only be 400 cases of Dracunculiasisreported in 2008 [37].

Four of Maliʼs regions (Kayes, Koulikoro, Segou, and Sikasso) have eliminateddracunculiasis, while the disease is still endemic in the countryʼs other four regions(Gao, Kidal, Monti, and Timbuktu). Late detection of two outbreaks, due to inadequate surveillance, in 2007 resulted in a meager 36% containment rate in Mali in 2007 [38].

[39]

Perhaps the greatest challenge in eradicating dracunculiasis will be confronted inSudan: there is much uncertainty with future political benchmarks in Sudan (nationalelections in 2009 and the referendum on the status of southern Sudan in 2011). Sporadic insecurity or widespread civil conflict could at any time ignite and thwarteradication efforts [40]. Mali likewise presents some future challenges. Like Sudan, theremaining endemic communities in Mali are remote, poor and devoid of infrastructure,presenting significant hurdles for effective delivery of interventions against disease. Moreover, residents in these communities are nomadic, moving seasonally with cattle inpursuit of water and pasture, making it very difficult to know where and whentransmission occurred. The peak transmission season coincides with the rainy season,hampering travel by public health workers [41].

Strategically located case containment centers that provide treatment and support topatients with emerging Guinea worms will be an essential aspect to the eradicationeffort. In areas served by these containment centers, incidence dropped by 71% inTogo and 42% in Ghana from 2003 to 2004 [42]. With continued political and social will, monetary aid, and intensified surveillance efforts in regions of high endemicity, dracunculiasis will soon become a disease of the past.

Cost-benefit Analysis of Eradication

Some attempts at estimating the economic losses of dracunculiasis have simplymultiplied the number of days of labor lost by the mean value of production per day orby the wage rate. By multiplying the loss per household, an estimated cost for thewhole region can be achieved. One such study estimated that the rice growing areas in three states of southern Nigeria sustained an annual loss of $20 million due todracunculiasis [43].

But there may be further price tags attached to dracunculiasis than just agricultural loss.A survey in South Kordofan, Sudan found that households where more than half the adults had suffered from dracunculiasis the previous year, children under six years old were nearly three times as likely to be malnourished. And, as mentioned earlier, children miss school when they have Guinea worm disease--in rural Africa, school is generally a long walk away--and when they need to take the place of their parents in thefield because their parents are afflicted by the disease. School attendance suffers during the peak season, and certain schools in areas of endemicity close for up to amonth each year. Thus, the investment of education is hampered--and economiclosses are incurred in the future [44].

Boreholes--for new safe water sources--can cost up to $10,000 to install, and are notalways cost-effective. Typical rural water supplies in sub-Saharan Africa have a mediancapital cost of over $40 per person served, with additional maintenance costs [45].However, the benefits of decreased morbidity and increased agricultural and educational productivity outstrips these costs. Though now a bit dated, a studyconducted by Kim et al. (1997) found, using a project horizon of 1987-1998, aneconomic rate of return of 29%--when comparing expenditure on the GlobalDracunculiasis Eradication Campaign with estimates of increased agriculturalproductivity when infection-related morbidity is reduced [46]. Yet the marginal cost of eradicating each additional case will begin to rise as the few remaining cases becomeharder to monitor--the final few cases will indubitably be the most remote, in areaswhere infrastructure is poor. Vigilance, however, must remain steady, and if the job can be seen out -- that is, total eradication of dracunculiasis -- the benefits will be paid outinterminably because no one will be incapacitated from work or school again by Guineaworm disease.

Useful Web Links

Learn more about the Carter Centerʼs Guinea worm eradication program:< http://thecartercenter.com />

Informative video from the Carter Center showing Guinea worm interventions in S.Sudan and the extraction of Guinea worm from a childʼs foot: < http://www.cartercenter.org/news/multimedia/HealthPrograms/ guinea_worms_last_stand_2008.html >

The World Health Organizationʼs summary of dracunculiasis:< http://www.who.int/topics/dracunculiasis/en/ >

An article from the Journal of American Medical Association on how persistence in the campaign to eradicate dracunculiasis is paying off:< http://jama.ama-assn.org/cgi/content/full/298/16/1856 >

References

[1] WHO. What is guinea worm? Is it a real worm? < http://www.who.int/features/qa/14/ en/ >

[2] Gideon Online Encyclopedia. Dracunculiasis. <http://web.gideononline.com/web/ epidemiology/index.php?disease=10680&country=&view=General >

[3] Cairncross, S., R. Muller, N. Zagaria. Dracunculiasis (Guinea worm isease) and the eradication initiative . Clinical Microbiology Review. 2002 April; 15(2): 223-46. <http:// www.pubmedcentral.nih.gov/articlerender.fcgi?artid=118073 >

[4] Cairncross 2002.

[5] The Carter Center. Guinea Worm Eradication Program. < http://www.cartercenter.org/ health/guinea_worm/index.html >

[6] WHO. Dracunculiasis eradication. <http://www.who.int/dracunculiasis/en/>

[7] MMWR. Progress toward global eradication of dracunculiasis, January 2005 - May 2007 . 2007 August; 56(32): 813-17. <http://www.cdc.gov/mmwr/preview/mmwrhtml/ mm5632a1.htm >

[8] Chart of distribution by country of 4,647 cases of indigenous cases of dracunculiasis reported during 2008. <http://www.cartercenter.org/resources/pdfs/health/guinea_worm/ guinea_worm_cases_country_2008.pdf>

[9] CDC lifecycle diagram. <http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/ Dracunculiasis/body_Dracunculiasis_il2.htm > [10]CDC lifecycle diagram. < http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/A-F/ Dracunculiasis/body_Dracunculiasis_il2.htm >

[11] Cairncross 2002.

[12] Cairncross 2002.

[13] Gideon Online Encyclopedia. Dracunculiasis. <http://web.gideononline.com/web/ epidemiology/index.php?disease=10680&country=&view=General >

[14] Kim, A., A. Tandon. Cost-benefit analysis of the global dracunculiasis eradication campaign (GDEC). 1997. < http://www.cartercenter.org/documents/2101.pdf >

[15] Cairncross 2002.

[16] WHO. Dracunculiasis. <http://www.who.int/topics/dracunculiasis/en/>

[17] Kim 1997.

[18] The Carter Center. Guinea Worm Eradication Program. < http:// www.cartercenter.org/health/guinea_worm/index.html >

[19] Fox News photograph of extraction process. < 0,2933,462433,00.html >

[20] Photograph of pipe filters. < http://www.usaid.gov/press/frontlines/fl_feb05/images/ Millions-Saved-Guinea-worm-.jpg >

[21] Cairncross 2002.

[22] Kim 1997.

[23] Kim 1997.

[24] WHO. Dracunculiasis Eradication. < http://www.who.int/dracunculiasis/en/ >

[25] Cairncross 2002.

[26] Kim 1997.

[27] Cairncross 2002.

[28] Hopkins, D., E. Ruiz-Tiben, P. Downs, P. Withers, and S. Roy. Dracunuliasis eradication: neglected no longer. Am. J. Trop. Med. Hyg., 79(4), 2008, pp. 474-9. < http:// www.ajtmh.org/cgi/content/full/79/4/474 >

[29] Hopkins 2008.

[30] Chart of distribution by country of 4,647 cases of indigenous cases ofdracunculiasis reported during 2008. < http://www.cartercenter.org/resources/pdfs/ health/guinea_worm/guinea_worm_cases_country_2008.pdf >

[31] The Carter Center. Map of endemic countries in 1986 and 2008. < http:// www.cartercenter.org/resources/pdfs/health/guinea_worm/gw_map_jan09.pdf >

[32] The Carter Center. Chart showing the number of reported cases of Guinea worm disease by year, 1989-2007. < http://www.cartercenter.org/resources/pdfs/health/ guinea_worm/gw_cases_07.pdf >

[33] Hopkins 2008.

[34] American Journal of Tropical Medicine and Hygiene. Chart showing the distribution of cases by country in 2007. < http://www.ajtmh.org/content/vol79/issue4/images/large/ 474fig1.jpeg >

[35] Hopkins 2008.

[36] Hopkins 2008.

[37] Hopkins 2008.

[38] Hopkins 2008.

[39] CDC. A chart showing the number of reported dracunculiasis cases by country, as well as local intervention. < http://www.cdc.gov/mmwr/preview/mmwrhtml/figures/ m743a3t1.gif >

[40] Hopkins 2008.

[41] WHO. Weekly Epidemiological Record. No. 18, 2008, 83, 157-68. < http:// www.who.int/wer/2008/wer8318.pdf >

[42] Hochberg N., E. Ruiz-Tiben, P. Downs, J. Fagan, J. Maguire. The role of case containment centers in the eradication of dracunculiasis in Togo and Ghana. Am J Trop Med Hyg. 2008 Nov; 79 (5): 722-8. < http://www.ncbi.nlm.nih.gov/pubmed/18981512? ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_ DefaultReportPanel.Pubmed_RVDocSum >

[43] Cairncross 2002.

[44] Cairncross 2002.

[45] Cairncross 2002.

[46] Kim 1997.