Neglected tropical diseases: types, targets and prevention strategies

Since 2023, WHO has included the following 21 conditions or groups of conditions in its list of neglected tropical diseases:

1. Buruli ulcer. When the bacterium Mycobacterium ulcerans passes from the environment to humans, by a mechanism that is still not well understood, it secretes a toxin that damages the skin and sometimes the bone, causing permanent disfigurement and long-term disability. It affects 33 countries, although the number of cases reported annually has been falling, down to 1,370 in 2021. Clinical diagnosis requires training and differential diagnosis against other ulcers, while laboratory diagnosis by PCR currently takes too long to guide treatment properly, which requires a combination of antibiotics over several weeks (WHO, 2023a).
2. Chagas disease or American trypanosomiasis. This condition is caused by a protozoan parasite, Trypanosoma cruzi, and is closely linked to the many species of an insect vector that typically live in cracks in the walls and roofs of homes, animal pens or storage buildings, although there are other routes of transmission. After an initial phase that is often asymptomatic, the parasites remain hidden for years in the muscles of the heart and digestive tract, until they produce symptoms there or in the nervous system. It is concentrated in 21 Latin American countries and causes some 10,000 deaths a year. There are medicines that eliminate the parasite and cure the disease if given at the start of the acute phase, but their use in the chronic phase only slows the disease's progression, can require up to two months of treatment and has very frequent adverse reactions (WHO, 2026a).
3. Dengue and chikungunya. These two virus-borne diseases are transmitted to humans through infected Aedes mosquitoes and have similar symptoms, such as fever and severe joint pain, which makes them hard to diagnose and the exact number of cases hard to establish. The incidence of dengue has resurged strongly in recent decades, rising from 500,000 reported cases in 2000 to 14.6 million in 2024 (WHO, 2025b), while the chikungunya virus has been detected in more than 110 countries (WHO, 2025a). Neither disease has a specific treatment, and the medicines used to relieve symptoms can increase the risk of haemorrhage.
4. Dracunculiasis. This disease is caused by a parasite, the Guinea worm, transmitted through tiny crustaceans that people swallow when drinking contaminated stagnant water. About a year after infection, a very painful blister usually forms on the leg. Despite there being no vaccine to prevent the disease and no medicines to treat it, only around 13 or 14 cases are now reported each year (WHO, 2025c).
5. Echinococcosis. This disease, caused by parasitic tapeworms of the genus Echinococcus, is a zoonosis. The host animal becomes infected by eating the meat of animals that had ingested the parasite's eggs. Humans become infected by ingesting the eggs shed in those animals' faeces, through contaminated food, water and soil. It can remain asymptomatic during an incubation period of several years, until the cyst or tumour grows and causes clinical manifestations that may be fatal. The disease occurs worldwide, with its highest prevalence in rural areas, where older animals tend to be slaughtered. Diagnosis requires imaging and in many cases only happens at advanced stages. Treatment is also expensive and complicated, requiring cyst drainage, surgery or prolonged anti-infective therapy, depending on the circumstances (WHO, 2021a).
6. Foodborne trematodiases. This group of zoonotic diseases, whose hosts are freshwater snails, fish and crustaceans, reaches humans through the consumption of these animals and of contaminated aquatic plants. Although the early stages are usually asymptomatic, they cause severe illness where the parasite load is high, as they reach certain organs and in chronic phases. They have been reported in more than 70 countries worldwide, but the true picture of their prevalence and disease burden is unknown (WHO, 2021c).
7. Sleeping sickness or human African trypanosomiasis. This disease, endemic in sub-Saharan Africa, is caused by protozoan parasites transmitted mainly through the bite of certain species of tsetse fly. Depending on the parasite subspecies, it can cause an acute or a chronic illness, and in both cases it can attack the central nervous system. There have been major epidemics of this disease in the past, especially in rural populations that are hard to reach and have limited health services. Diagnosis may require serological and cerebrospinal fluid tests that are not always available in these settings. The longer the disease takes to diagnose, the lower the chances of successful treatment, and without treatment it is usually fatal (WHO, 2023h).
8. Leishmaniasis. This disease, caused by multiple species of the protozoan parasite Leishmania and transmitted through the bite of infected sandflies, takes three forms: visceral, cutaneous and mucocutaneous. The cutaneous form is the most common, producing between 600,000 and 1 million new cases each year, with skin lesions that are generally ulcerative and leave lifelong scars, causing severe disability and considerable stigma. The visceral form is the most serious, being fatal in 95% of cases, with between 50,000 and 90,000 cases occurring each year (WHO, 2023c).
9. Leprosy or Hansen's disease. This is a chronic infectious disease caused mainly by the bacterium Mycobacterium leprae, which affects above all the skin and the peripheral nerves. It therefore produces physical deformity and progressive, permanent disability, giving rise to considerable stigma and discrimination. The disease can be treated with a combination of three antibiotics over several months, which is curative as it kills the pathogen. Some 200,000 new cases of leprosy are still reported each year (WHO, 2026c).
10. Lymphatic filariasis or elephantiasis. This disease is caused by infection with nematodes known as filarial worms, transmitted through the bite of Culex, Anopheles and Aedes mosquitoes. It damages the lymphatic system, which over time produces painful, severely disfiguring and highly disabling manifestations that in turn cause stigma, isolation, discrimination, mental health problems and poverty. An estimated 36 million people are currently living with these chronic manifestations of lymphatic filariasis (WHO, 2024a).
11. Mycetoma, chromoblastomycosis and other deep mycoses. This group of diseases, caused by various fungi and bacteria, destroys the skin, deep tissues and bones. Although their incidence and global disease burden are not well known, they produce deformities and a progressive, painless deterioration in the functional capacity of the affected body parts. Treatment is not straightforward. In the case of mycetoma, it requires multiple expensive medicines that are rarely available and generally of limited efficacy, so amputations are common (WHO, 2022a). For chromomycoses there are several treatment options which, if started early, can give good results after several months or even a year (WHO, 2023b). Sporotrichosis, caused by fungi found in plants, cats and other mammals, has easier and more effective treatments, but in some cases these can also run for several months (WHO, 2023g).
12. Noma. This is a disease that remains insufficiently understood to this day. It is caused by multiple microorganisms and is linked to risk factors such as malnutrition, immunodeficiency, poor oral health and extreme poverty. It mainly affects children aged 2 to 6 and presents in its early stages as an aggressive, necrotising inflammation of the gums. If diagnosed and treated at this stage, the lesions can heal. But if it reaches the gangrenous phase, it can cause visible perforation of the face and disfigurement, which in turn leads to difficulties in breathing, swallowing and speaking, as well as isolation, stigma and discrimination (WHO, 2023d).
13. Onchocerciasis or river blindness. This condition, which today mainly affects rural populations in Africa and Yemen, is transmitted through the bite of blackflies that have previously ingested microfilariae. Once in the human body, these form nodules under the skin and, on dying, trigger an intense inflammatory response with severe itching. They also cause eye damage that can lead to permanent blindness. Treatment can last for years and sometimes causes serious adverse effects (WHO, 2025e).
14. Rabies. This disease is caused by a virus which, in 99% of human cases, is transmitted through dog bites and scratches. It is present worldwide and claims tens of thousands of lives every year. Once the first signs of infection appear, and unless post-exposure prophylaxis is given to prevent it, the virus travels to the central nervous system, where it causes progressive inflammation that gives rise to different clinical forms and ultimately results in death (WHO, 2026d).
15. Scabies and other ectoparasitoses. This condition is a parasitic infestation caused by the mite Sarcoptes scabiei, which lays eggs on entering the skin, causing itching, rashes, ulcers and even serious complications in other organs. Some of its forms are highly contagious. It is one of the most common skin diseases, mainly among people with fewer resources and in densely populated warm regions, where prevalence among children ranges from 5% to 10%. Diagnosis is usually clinical and it can often be treated with topical creams (WHO, 2023e).
16. Schistosomiasis. This is a parasitic disease caused by trematodes, when their larval forms penetrate the skin during contact with contaminated water. Once inside the body, they develop into adult schistosomes that lay eggs, some of which trigger an immune reaction in the body tissues where they lodge. Depending on their location, they produce different clinical manifestations, chronic consequences, disability and even death (WHO, 2026e).
17. Soil-transmitted helminthiases. These diseases are among the most common parasitic infections in the world, with an estimated 24% of the global population infected. The contaminated faeces of infected people contaminate the soil wherever sanitation is poor, and from there infect more people. They are caused by several species of soil-transmitted helminths, such as Ascaris lumbricoides, Trichuris trichiura, Necator americanus, Ancylostoma duodenale and Strongyloides stercoralis. They affect the nutritional status of those infected, by feeding on their blood and tissues, causing chronic intestinal blood loss, leading to malabsorption and reducing appetite. Beyond their acute manifestations, they also cause anaemia and delayed and reduced growth and physical development (WHO, 2023f).
18. Snakebite envenoming. This is the only neglected tropical disease that is not infectious. It is caused instead by multiple toxins present in the venomous saliva of various types of snake, transmitted through their bite. Each year 5.4 million people suffer such bites, between 1.8 and 2.7 million are envenomed, and between 80,000 and 140,000 die. It is a forgotten public health priority on which little data exists, which has reduced demand for antivenoms and with it their supply, leaving them expensive and inaccessible in many countries across Africa and Asia (WHO, 2026f).
19. Taeniasis and cysticercosis. These are infestations by intestinal tapeworms or their larvae, known as cysticerci. They are contracted by eating raw or undercooked beef or pork and drinking contaminated water. Cysticerci can develop in muscles, the skin, the eyes and the central nervous system, where, besides causing symptoms such as blindness, headaches, seizures and epilepsy, they can prove fatal (WHO, 2022b).
20. Trachoma. This disease, caused by the bacterium Chlamydia trachomatis, is the leading infectious cause of blindness in the world, affecting 1.9 million people, above all in Africa. It is transmitted mainly within households through the eye and nose secretions of preschool-age children, among whom prevalence can reach 90% in endemic areas. It therefore affects women in particular, as they usually have closer contact as carers. With repeated infection over several years, the scars that form inside the eyelid cause it to turn inwards, making the eyelashes rub against the eyeball and damage the cornea. If left untreated, scarring on its surface can cause visual impairment, generally between the ages of 30 and 40 (WHO, 2026g).
21. Yaws. This is a group of bacterial infections caused by a subspecies of Treponema, affecting mainly children, principally those aged 6 to 10. Most reported cases occur in Western Pacific countries. It manifests in the skin, bones and cartilage, and is transmitted from person to person through contact with the lesions. It can be cured with well-established antibiotics, but without treatment it causes disfigurement and permanent, debilitating disability (WHO, 2023j).

This list is not fixed and over the years diseases have been removed from it and added to it. The WHO list is not exhaustive either. The diseases it includes are restricted because resources and accountability are committed to each one. Other institutions regard as neglected tropical diseases some that are not on the WHO list (PLOS NTDs, n.d.). These are diseases of poverty that are the subject of research, but are not necessarily tied to public health programmes and global control targets.