SEATTLE, Washington — The WHO designates 17 diseases that it considers “neglected tropical diseases, “ meaning that these diseases are prevalent in tropical areas but have less coverage and research than more well-known diseases. However, thanks to efforts from the WHO and nonprofit organizations, six of these neglected tropical diseases are now “under control” per WHO guidelines. These diseases used to be scourges of poorer populations — now they are controlled or even eliminated in most areas.
6 Neglected Tropical Diseases the WHO has Under Control
- Schistosomiasis: Schistosomiasis is second only to malaria as the most devastating parasitic disease in the world. The parasites that cause schistosomiasis mature in freshwater snails, then leave the snail and live in freshwater reservoirs for up to 48 hours where they can find human hosts. Complications from the disease can cause liver failure, bladder cancer and an increased risk of HIV/AIDS. More than 200 million people are affected by this neglected tropical disease worldwide and approximately 280,000 people in Africa die from schistosomiasis each year. WHO controls the disease primarily through preventative doses of praziquantel, the leading drug treatment for schistosomiasis. In 2017, the WHO provided preventative treatment to approximately 46 percent of at-risk populations. Additionally, a September 2019 study developed “super shrimp” that could further reduce the population of snails carrying the disease.
- Hookworm: Hookworm is another parasite spread through unsanitary conditions. Residents of warm climates with inadequate access to sanitation have the highest risk of contracting hookworm, as the eggs thrive in moist, warm areas and spread through contact with feces. Serious infections cause abdominal pain, diarrhea, loss of appetite, weight loss, fatigue, anemia and stunted growth in children. Even mild infections can cause severe cognitive impairment. The WHO has been working to eradicate hookworm and similar parasites since 2001, focusing on preventative treatment and improved sanitation. In 2017, WHO programs provided preventative treatment to 69 percent of the approximately 8 million children at risk of contracting the disease.
- Lymphatic filariasis: Lymphatic filariasis is a neglected tropical disease caused by microscopic worms that travel from host to host via mosquito bites. The worms infect the lymph system, which monitors and balances the body’s fluid balance and fights infections. While a number of hosts may never know they have lymphatic filariasis, a percentage of hosts have a catastrophic malfunction of the lymphatic system, leading to fluid collection and swelling of body parts. From 2000 to 2019, 120 million people were infected, with 40 million suffering from disability and disfigurement due to the disease. WHO began a large-scale, global fight against lymphatic filariasis in 2000, and as of April 2019 have delivered over 7.1 billion treatments around the world. WHO started the program by providing preventative chemotherapy. However, due to education and sanitation programs, 554 million people no longer require this preventative medicine.
- Onchocerciasis: The second most common preventable cause of blindness in the world is onchocerciasis, also known as river blindness. This neglected tropical disease is spread through blackfly bites and causes parasitic infections in the skin and eyes
. Ninety percent of onchocerciasis cases come from impoverished communities in Africa, and in some communities over 50 percent of men are blind from the disease. Initial control of this neglected tropical disease was large-scale bug spraying to reduce the number of black flies, but as of 2019 WHO devotes most of its resources to medicine distribution. WHO’s work resulted in 145 million people receiving treatment in 2017, roughly 70 percent of onchocerciasis cases in the world.
- Trachoma: Trachoma is a bacterium that is the leading preventable cause of blindness in the world. It is also highly contagious, spread by personal contact, shared towels and other toiletries, or flies that have landed on the eyes or nose of an infected person. In 2003, WHO launched the SAFE program to help increase surgery for advanced stages of trachoma, improve sanitation and environmental standards, and provide additional antibiotics to treat early cases. WHO predicts that the SAFE program will eliminate trachoma by 2020. As of 2019, the WHO reports that the number of trachoma cases has decreased by 91 percent.
- Guinea Worm: Guinea worm disease (GWD), caused by the parasite Dracunculus medinensis (aka Guinea worms), is one of the most successfully-controlled neglected tropical diseases in the world. The titular worms infect a host through unsanitary water. The worms travel through the body via subcutaneous tissues, usually ending their journey in a host’s foot or ankle. Then, each worm causes an extremely painful blister where it eventually emerges. Though fatality is rare, GWD causes temporary or even permanent disability due to the painful blisters. However, GWD is predicted to soon be eradicated — from 1980 to 2018, the number of confirmed Guinea worm infections dropped from 3.5 million cases to only 28, with the number of human cases reduced to only two, through large-scale education programs and improved access to clean water. The WHO predicts GWD could be eradicated by 2030.
Neglected tropical diseases that do not dominate the news cycle are a major issue in developing areas that do not always get the attention they need. But the above successes with neglected tropical diseases show that disease is not an insurmountable problem. The WHO and other organizations have made amazing strides forward in disease research and control.
– Melanie Rasmussen