New Dracunculiasis Cases in Chad: A Setback in Global Eradication
Abstract and Commentary
By Mary-Louise Scully, MD
Dr. Scully is Director, Travel and Tropical Medicine Center, Sansum Clinic, Santa Barbara, California, CA
Dr. Scully reports no financial relationships to this field of study
Synopsis: Immense efforts are ongoing toward the goal of worldwide elimination of dracunculiasis (Guinea worm disease). Ten new cases were reported in 2010 in Chad, a country where disease transmission had been interrupted since 2000.
Source: Centers for Disease Control and Prevention. Renewed transmission of dracunculiasis — Chad, 2010. MMWR Morb Mortal Wkly Rep 2011;60:744-748.
During april-june of 2010, 2 new cases of dracunculiasis were confirmed by extracted worm identification of Dracunculus medinensis and polymerase chain reaction (PCR) in Chad, Africa. Chad's National Guinea Worm Eradication Program (NGWEP) initiated an outbreak investigation and with the help of the World Health Organization (WHO) uncovered 8 additional cases, all confirmed by worm collection. The 10 confirmed cases were located in eight different villages within four regions of Chad (see Figure). Six of the eight villages were on the borders of the Chari River, which runs across southern Chad. This large river is a main transportation route in southern Chad, supports local fishing industry, and is crossed frequently by nomadic herdsman, who often travel through Chad to neighboring countries.
In December of 2010, the Centers for Disease Control and Prevention (CDC) joined with the Chad Ministry of Public Health and the WHO to conduct a dracunculiasis outbreak investigation and during January-February of 2011 a survey took place in 210 villages and 15 nomad camps. The results demonstrated that both villagers (55%) and nomads (87%) reported consuming water from unsafe sources, but the percentage of this risk activity among nomads was clearly much higher. Also, only 33% of the surveyed nomads knew about dracunculiasis (recognized a photo) vs. 75% of surveyed villagers. Nomadic populations regularly interact with the sedentary groups by sharing water sources or attending weekly markets. The lack of knowledge and the frequent ingestion of unsafe water make this nomadic population an important target group for prevention efforts. These efforts include filter distribution, education, and case containment, which includes efforts to prevent an infected patient from contaminating water sources.
With the late detection of cases in Chad, none of the 10 patients were prevented from potentially contaminating drinking water sources; therefore, 31 villages were classified as at-risk for further cases of dracunculiasis. Since this CDC investigation, 2 additional cases emerged in Chad in 2011, raising the number of at-risk villages to 36.
The presence of dracunculiasis, or Guinea worm, likely dates back in history to antiquity. It is believed that the "fiery serpent" mentioned in the Old Testament may be referring to Guinea worm. The existence of Guinea worm in Egyptian times was confirmed when the calcified remains of a male Guinea worm was found by radiography in the abdominal wall of a mummy as part of Britain's Manchester Mummy Research Project.1 Carl Linnaeus often is credited with the first suggestion that the disease was indeed caused by a worm and the name "Guinea worm" was likely coined when 17th century Europeans saw the disease during travel to the Gulf of Guinea area of West Africa.
Humans are the only mammalian reservoir for this nematode and are therefore solely responsible for the persistence of the disease. When drinking water from sources contaminated with larvae-infected copepods (tiny "water fleas") is ingested by humans, the Guinea worm larvae are released, penetrate the gut wall, and mate in the retroperitoneal space. The male worm dies shortly after mating, but 10-14 months later the female migrates through subcutaneous tissues, often to the lower extremities, and creates a blister, which eventually ruptures forming a painful ulcer. If the lesion is immersed in water, which relieves the excruciating pain, the worm ejects its larvae into the water, which in turn are ingested by new copepods, perpetuating the life cycle.
There is no effective drug treatment or vaccine for this debilitating illness. The management involves removal of the 3-foot long worm slowly, by rolling it around a gauze or stick a few centimeters per day. This extraction is long and painful for the patient and secondary bacterial infections can complicate the process. In addition, an infected person does not develop any immunity to the disease.
In 1986 it was estimated that dracunculiasis affected 3.5 million people in 20 countries in Africa and Asia. Through the efforts of former President Jimmy Carter and his wife Rosalynn, the Carter Center has spearheaded the international Guinea worm eradication campaign, working with many other global partners. As a result of these efforts, Guinea worm cases have fallen to fewer than 1,800 cases worldwide, a reduction of more than 99% and another likely 79 million cases have been averted.2 Perhaps even more impressive is that this was all accomplished without a drug or a vaccine, but rather with the old fashioned public health tactic of educating people about changing their behavior.3
There are three remaining countries with pockets of dracunculiasis — South Sudan, eastern Mali, and western Ethiopia. Between January and June of 2011, there have been 806 confirmed cases of dracunculiasis from 366 villages. The majority of cases are from South Sudan (793), with very low numbers from Mali (3), Ethiopia (8), and Chad (2).4 Ghana has been declared free of disease with no cases reported in 14 months. This outbreak in Chad, the first cases since 2000, is felt to represent a public health emergency and a setback for the Global Guinea Worm Eradication Program. Unfortunately, the resources needed for active surveillance in Chad are lacking, but any available resources will first be directed toward the 36 at-risk villages identified by this investigation. This outbreak also highlights the need for ongoing disease surveillance in formerly endemic areas after eradication programs end. In Chad, we recently have witnessed this type of setback in global disease eradication efforts with recrudescence of cases of onchocerciasis, polio, and now Guinea worm.
- Archaeology. Under Wraps: Rosalie David in Conversation. Available at www.archaeology.org/online/features/mummies/. Accessed Sept. 4, 2011.
- Guinea Worm Eradication Program. The Carter Center. Guinea worm Fact Sheet. Available at www.cartercenter.org/health/guinea_worm/mini_site/facts.html.
- Barry M. The tail end of Guinea worm — global eradication without a drug or vaccine. N Engl J Med 2007;356:2561-2564.
- World Health Organization Collaborating Center for Research, Training and Eradication of Dracunculiasis. Guinea worm wrap-up No. 206. Atlanta, GA: U.S. Department of Health and Human Services, CDC; 2011. Available at http://cartercenter.org/news/publications. Accessed Sept. 2, 2011.