Francesca Tomasi received her B.A. from the University of Chicago and currently does microbiology research.
A Historical Plague
On Infective Perspective, you have read about several “ancient” diseases – infections that date back at least to the beginning of human history. Some that immediately come to mind for many are leprosy, tuberculosis, cholera, and
Like malaria, Guinea worm disease is caused by a parasite. Instead of the mosquito-borne Plasmodium that causes malaria, however, Guinea worm disease is caused by an aquatic flea-borne roundworm called Dracunculus medinensis, which means “Little dragon from Medina.” Historically, D. medinensis was present in virtually any untreated, stagnant body of water in Africa, Asia, and the Middle East. Archaeologists have detected it in calcified Egyptian mummies. Ancient texts by the Greek writer Agatharchides depict an affliction of little serpents in individuals living along the Red Sea, in present-day Sudan. Nonetheless, D. medinensis’s namesake is the city of Medina, in present-day Saudi Arabia, where cases of the infection were higher than average. The more colloquial name Guinea worm disease comes from a similar, unusually high incidence of illness noted along the Guinea cost in West Africa.
It Takes the World…
Guinea worm disease causes frightening symptoms. Individuals become infected when they drink contaminated water, which is home to tiny fleas that carry D. medinensis larvae. Once someone has ingested infected water, the worm larvae are released in the stomach and cross through the digestive tract into the body cavity. Female larvae grow for the next 10-14 months into full-size adults, which can be up to 3 feet long (and, as the CDC page on Guinea worm points out, the width of a cooked spaghetti noodle). Patients have no symptoms until this point.
Once the female is ready to emerge for procreation, it generates a small blister on its unsuspecting human host’s body, usually on the legs or feet. This blister causes a painful burning sensation and ultimately bursts 1-3 days after appearing. When infected individuals develop blistering pain, they tend to immerse themselves in water to relieve the pain. However, this allows the worm to emerge and release millions of little larvae into the water, starting the infection cycle all over again for anyone who consumes that water.
You may be familiar with the Rod of Asclepius (or Staff of Asclepius). It dates back to the Ancient Greek god Aesculapius, deity of healing. In mythology, he always wielded a large stick entwined by a snake. Today, this same sign is the symbol of all medicine. One historical interpretation of this specific symbol for ancient medicine looks to the traditional treatment regimen for Guinea worm disease: instead of letting the worm release its larvae into cool water, healers would slowly pull the worm out of a person’s blister. This process was very slow and took days to weeks, as only a few centimeters could be pulled out every day without breaking the worm. As the worm was removed, it was wound around a stick to keep it whole and isolated. Modern treatment of Guinea worm disease is essentially the same, except the stick has been replaced with sterile gauze.
No other treatment for Guinea worm disease exists; today, prevention is key. Preventive efforts against the disease revolve around constantly decontaminating water. Water can be filtered with cloths or pipe filters, and commercial larvicides are often used to kill the water fleas that ingest Guinea worm larvae. Individuals infected with the parasite are prevented from entering bodies of water used for drinking or bathing in order to avoid releasing millions of larvae.
In 1980, the UN declared a global campaign to be headed by the CDC to eradicate Guinea worm disease. A sad truth to certain infectious diseases, however, is neglect – hence the title Neglected Tropical Disease to describe microbial diseases causing substantial illness in the poorest areas of the world. A lack of international social and economic incentive to address these infections has allowed them to flourish on the backburner of public health campaigns. Political and societal barriers in Guinea worm-endemic nations were another hurdle to eradication, as nations plagued with the parasite lacked the political and health infrastructure required for such an immersive program. Nonetheless, finally, by 1986 the World Health Assembly resolved to eradicate Guinea worm disease. By that year, an estimated 3.5 million people in 20 different countries were infected with D. medinensis every year. The World Health Assembly’s definition of eradication would be the absence of Guinea worm disease – and thus, the disruption of transmission – for three or more years.
…And an Eradicable Disease
Not every disease can be successfully (permanently) eradicated. For instance we have recently seen flare-ups of polio, once thought to be eliminated from the human race. Other infections, such as the flu, will likely never be eradicated due to the existence of animal reservoirs that harbor these viruses. Guinea worm disease, however, like smallpox, fits the bill for an eradicable disease. The parasite’s life cycle relies exclusively on human infection: as a result, once the last human case occurs, there is no chance for the disease to re-emerge. The infection itself, like smallpox, has very specific symptoms, making it easy to recognize and address immediately to prevent additional cases from water contamination. Fortunately, unlike with smallpox, Guinea worm disease does not spread like wildfire from human to human. As a result, vaccination campaigns and strict quarantines are not part of the Guinea worm eradication program, which eliminates a large source of interference (during smallpox eradication, it was extremely difficult to get full compliance in every affected country for both vaccination and quarantine).
The World Health Assembly passed the resolution to eradicate Guinea worm disease in 1986. In 2015, only 22 cases in 2 countries were reported of the infection. As you can see, enormous progress has been made in the last thirty years. As of January 2015, 198 countries, territories, and areas have been certified Guinea worm transmission-free. The remaining 8 countries in the world yet to be certified are Angola, Democratic Republic of the Congo, Kenya, Sudan, Chad, Ethiopia, Mali, and South Sudan. In 2015, 9 of the 22 total cases were reported in Chad. The rest were clustered between Ethiopia, Mali, and South Sudan.
The fundamental pillars of public health practice are responsible for the gloriously imminent eradication of Guinea worm. Surveillance, case containment, and the basic preventive interventions described above have been incredibly powerful against this neglected disease. Guinea worm, a main character in human history, is about to remain forever in the books. The Rod of Asclepius will not only be a symbol of medicine and healing; soon, it will represent the power of public health and the successful eradication of an ancient plague.