The guinea worm disease, also known by its scientific name of dracunculiasis, is caused by the nematode Dracunculus medinensis. This parasite is usually transmitted by the ingestion of water contaminated with water fleas containing parasite’s larvae (link to causes of parasitic diseases). It is important to note that there is actually no vaccine or effective treatment against this parasite.
The parasite responsible for the guinea worm disease is an excellent candidate for an eradication program. Actually, human is an obligate host for this parasite and was the only known reservoir until recently, meaning that infection of human is necessary for the reproduction and the dissemination of this parasite. The absence of a non-human reservoir is usually a required condition for the success of any eradication program. In fact, it means that if the infection in human is eradicated, the parasite will become extinct from the surface of the Earth, as infections of human is necessary for its effective reproduction and survival. This is what happened in 1979 when the virus responsible for the smallpox was declared successfully eradicated from the surface of the Earth. It was the first infectious disease to be eradicated, proving that the theoretical concept of the eradication of infectious disease was possible. However, only a small proportion of the existing infectious agents respond to the conditions required for a successful eradication.
The life cycle of the parasite responsible for the guinea worm disease is though quite particular. People infected with this worm will eventually, about one year after the primary infection, suffer from agonisingly painful blisters mainly on the leg, as the adult worm(s) leave the body. To relieve the burning pain, infected people usually immerse their leg in water. During this process, thousands of larvae are release from the emerging adult worm within the water. These larvae become infectious when water fleas ingest them. Consequently, if this disease were eliminated in human, no more larvae would be released in the water from infected people, preventing the reoccurrence of the infection.
At the beginning of the 1980s, about 20 countries, mainly in Africa, reported having guinea worm infections. At this time, there were approximately 3.5 million cases worldwide per year. In 1981, the World Health Organization and the Centers for Disease Control and Prevention elaborated a strategy with the help of other collaborators in order to eradicate the guinea worm disease. This strategy includes mainly drinking water treatment, control of the water fleas population, monitoring of the infected people, prevention of the transmission of the disease by the infected people and education.
However, throughout the years, many difficulties challenged this eradication program. For instance, insecurity and lack of political will in the affected countries, as well as lack of funds were the main challenges faced by the eradication program. Furthermore, the civil war in southern Sudan, a conflict that lasts from 1983 to 2005, slowed down the efforts of the eradication program, as this country was one of the most affected. Recently, the World Health Organization faced another challenge as the type of guinea worm present in human was detected in several dogs in Chad. This fact might be linked to the reoccurrence of guinea worm disease cases in Chad in 2010 after 10 years without any reported cases. As such, the World Health Organization follows the evolution of this situation with great care, as it could undermine the eradication efforts. Infected dogs are then now monitored and treated in Chad in order to prevent further infections in human.
Nevertheless, the eradication program is now doing very great. In fact, the number of reported cases decreased dramatically within the years. For instance, according to the World Health Organization, 1797 cases were reported in 2010, 1058 in 2011, 542 in 2012, 148 in 2013 and only 126 in 2014. New cases are now reported in only 4 countries, namely Chad, Ethiopia, Mali and South Sudan. However, the majority of the reported cases are now located in South Sudan. From the beginning of January to the end of July 2015, only 11 cases were reported so far. However, this number is unofficial and the official number of cases might be a little bit greater than that. These low numbers of new cases are very encouraging and it is very likely that the guinea worm disease will be the first human parasite to be eradicated from the Earth within the next few years. In fact, it will be effectively the case when there will be no new reported infection for a least three consecutive years.
Sources: Centers for Disease Control and Prevention; World Health Organization