Guinea worm, river blindness and elephantiasis are among the world’s neglected tropical diseases. A battle is on to wipe them out

In this 2001 photo, a volunteer pulls a Guinea worm out of the foot of a patient in the Alek region of then southern Sudan.
(Khalil Senosi / Associated Press)

One infection known as dracunculiasis can cause people to suffer a burning blister that bursts as a parasite called the Guinea worm breaks through the skin.

Another one, elephantiasis, causes grotesque swelling in limbs. Yet another, known as river blindness, occurs when the larvae of parasitic worms, transmitted by the bite of blackflies, migrate into the eye and cause blindness.

Although those diseases and others with ties to contaminated water or food or insects, such as mosquitoes, are among the ones eliminated from most parts of the world, there are not gone from everywhere. Such illnesses, known as neglected tropical diseases, have typically afflicted the world’s poorest and most vulnerable, in recent years burdening more than 1.5 billion people in 149 countries.


The diseases have historically received scant attention compared with more commonly known illnesses, such as malaria and polio, but their effect on communities can be devastating. They can reduce life expectancy, keep children out of school and wreck livelihoods when infected people are unable to work.

In response, the combined efforts of governments, nonprofit organizations, academia and the private sector have helped combat neglected tropical diseases, or NTDs, during the last five years, according to a report published Thursday by Uniting to Combat Neglected Tropical Diseases, the collective of partners.

“In 2016, we reached over a billion people with treatments for NTDs, and … today, there are 400 million less people that actually require treatment than previously,” said Katey Owen, director for neglected tropical diseases at the Bill and Melinda Gates Foundation, one of the partners.

Treatment reduces the risk of developing a disease, decreases reinfection and ultimately interrupts transmission of the sickness.

The progress is not quite on the magnitude of the problem, but certainly the progress is also very substantive,” Owen said.

The success has been largely driven by a combination of factors, including donations from the pharmaceutical industry of more than 1.8 billion treatments to impoverished communities. Since 2012, government donors and private philanthropists have invested close to $300 million a year toward control and elimination of the diseases, and in April governments and private donors pledged $812 million over the next five to seven years. Academic research and aggressive intervention programs, such as the mass dispensation of drugs by national governments, have also contributed to the progress in combating the diseases, the report says.


The milestones come five years after the consortium of partners signed the so-called London Declaration on Neglected Tropical Diseases aimed at radically controlling, eliminating or eradicating 10 illnesses by 2020. The plan builds on a road map laid out by the World Health Organization in 2011 to tackle 17 neglected tropical diseases by 2020.

Here is some information from the consortium on diseases on which significant progress has been made.

Guinea worm disease

Cases of this parasitic infection caused by drinking water with fleas contaminated by Guinea worm larvae plummeted from 1,060 in 2011 to 26 reported cases so far this year. Three decades ago, there were more than 3 million cases of the incapacitating disease, mainly across sub-Saharan Africa. Most of this year’s cases were reported in Chad, where eating improperly cooked, cured or fresh aquatic food was noted as a possible reason for transmission of the disease. Suspected cases were also reported in Ethiopia.

A nurse at a village in Chad checks for parasite symptoms of sleeping sickness by examining ganglions on a patient's neck.
(Patrick Robert / Corbis via Getty Images )

Sleeping sickness

Last year, 2,184 cases of sleeping sickness, also known as human African trypanosomiasis, were reported worldwide, down from 6,747 in 2011. Infection occurs when a parasite transmitted through the bite of an infected tsetse fly multiplies in the lymph nodes and the blood of the person who has been bitten, causing symptoms such as headaches, fever, weakness, pain in the joints, disease in the lymph nodes and stiffness, according to the World Health Organization. Over time the parasite travels to the central nervous system, causing various neurological changes, including sleeping disorders — hence the name “sleeping sickness” — and other ailments that can lead to death.

A 2008 photo shows a blind man suffering from onchocerciasis, or river blindness, in the Ivory Coast town of Kouadioa-Allaikro.
(Issouf Sanogo / AFP/Getty Images )

River blindness

River blindness disease, spread by repeated bites from infected black flies, has been eliminated in nearly all of the Americas, and since 2012 Colombia, Ecuador, Guatemala and Mexico have been confirmed as being free of the disease, also know as onchocerciasis. The parasitic disease causes unsightly bumps on the skin that may itch and eye infections that can lead to vision changes and blindness. About one-third of the 198 million people needing treatment have not received medication.

A woman receives an eye examination for trachoma at a medical center in Hiep Hoa, Vietnam, in 2005.
(AFP/Getty Images )


Cambodia, Mexico, Morocco, Oman and Laos have eliminated trachoma as a public health problem. The disease, caused by a contagious bacterial infection of the eye is usually spread when contaminated hands, clothes or flies touch a person’s eyes or nose. About 85 million people were treated with antibiotics for trachoma elimination last year, representing 45% of the population in need. Antibiotics clear the infection, according to the World Health Organization. The blindness caused by the disease is irreversible.

A severely disfigured foot of a woman suffering from elephantiasis in Santo Domingo, Domincan Republic.
(Thomas Van Houtryve / Associated Press )

Lymphatic filariasis

Lymphatic filariasis, commonly known as elephantiasis, is a mosquito-transmitted disease caused by parasitic worms. It damages the lymphatic system, causing pain and disfigurement through the abnormal enlargement of body parts such as the arms, legs, breasts and genitals. As of last year, close to 500 million people worldwide no longer needed treatment for elephantiasis, and this year, the World Health Organization certified the Marshall Islands, Thailand, Togo and Tonga as having eliminated the disease as a public health problem. Many countries continue to struggle with the disease, the report says.

A 2015 photo from Doctors Without Borders shows a man suffering visceral leishmaniasis, also known as kala-azar, black fever and dumdum fever, being helped by his wife, right, and a relative at one of the agency’s hospitals in South Sudan.
(Karel Prinsloo / AFP/Getty Images )

Success was also seen in the battle against soil-transmitted helminths, “a group of intestinal parasites that thrive in places where the soil is warm and humid and sanitation is poor,” the report says, and visceral leishmaniasis, which is caused by parasites when a person is bitten by infected sand flies.

Challenges remain

Despite the significant breakthroughs, challenges persist. For example, “no significant, measurable progress” has been made toward eliminating schistosomiasis, also known as bilharzia and snail fever, according to the report. The illness develops when people come into contact with water contaminated by certain snails carrying parasites that penetrate the skin and infect the body. The disease is found in parts of Africa, Asia and South America.

A slight increase was recorded in the number of new cases of leprosy, known as Hansen’s disease, from 2015 to 2016. “The persistent incidence of new cases, a substantial proportion of whom are children, is concerning and indicates that progress towards interruption of transmission has halted,” the report says

The infectious disease is caused by bacteria mainly spread when untreated leprosy patients cough or sneeze. It causes skin lesions and nerve damage. There were about 230,000 new cases of the disease in 2016.

A patient at the leprosy hospital in Srinagar, the summer capital of Indian-controlled Kashmir, in January. World Leprosy Day is observed annually on Jan. 30 to increase public awareness of the disease.
(EPA/Shutterstock )

Progress has been made in controlling the transmission in Latin America of Chagas disease, a parasitic infection caused by contact with the feces of infected bloodsucking bugs. But difficulties reaching vector control targets remain in the Amazon basin and Gran Chaco regions of South America and in the border area between Guatemala and El Salvador, the report says.

Also called the “kissing bugs,” the insects infest people’s homes. The illness can be spread through contaminated food, blood transfusions and organ transplants, and to children at birth, according to the report.

Although more than a billion people received treatment for at least one neglected tropical disease in 2016, 500 million infected people did not, according to the report. The World Health Organization estimates that an additional $300 million to $400 million would be needed per year through 2020 to reach all those affected by these diseases.

“We need to keep the pedal to the metal,” Owen said. “The gas has got to stay on. If we back off, what will happen is exactly what has happened with some of these diseases. They will start to come back.”

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