FAQ on Neglected Tropical Diseases (NTDs)

Neglected Tropical Diseases (NTDs) are among the poverty-associated infectious diseases. The World Health Organisation (WHO) has recognised 20 infectious diseases and snakebite envenoming as NTDs, including diseases caused by worms, protozoa, bacteria or viruses. The WHO list includes:

Buruli ulcer, Chagas, dengue and chikungunya, dracontiasis, echinococcosis, trematodiasis, sleeping sickness, leishmaniasis, leprosy, lymphatic filariasis, mycetoma, chromoblastomycosis, river blindness, rabies, scabies, schistosomiasis, worm diseases, snakebite envenoming, taeniasis/cysticercosis, trachoma, and yaws and other endemic treponematoses.

These diseases occur mainly in poorer countries with poor hygienic conditions and tropical climates. There, pathogens and vectors such as certain mosquito species can proliferate. However, due to global warming, global travel and migration, countries in temperate zones are also increasingly affected. Occasionally, travellers also fall ill.

Distribution of NTDs in the world

In 2020, Neglected Tropical Diseases (NTDs) affected 1.7 billion people in 149 countries worldwide, with another two billion at risk. NTDs affect the poorest parts of the population in already poor countries. They usually do not lead directly to death, but often to severe and long-lasting diseases, some of which are chronic. Many patients suffer disabilities, become blind or disfigured, have chronic or recurring pain, become unable to work, experience discrimination and sometimes also become mentally ill.

In June 2022, BNITM signed the "Kigali Declaration on Neglected Tropical Diseases (NTDs)". The declaration supports the WHO's roadmap to reduce the number of infections by 90%, eliminate at least one NTD in 100 countries by 2030 and completely eradicate two NTDs.

BNITM conducts research on various NTDs, including leishmaniasis, snakebites, schistosomiasis and other worm infections. At the same time, researchers have been able to show that other infections, for example with the eye worm Loa loa, also represent a significant burden of disease for affected individuals, contrary to earlier assumptions.

Among NTDs, schistosomiasis ranks first in terms of years of life lost to premature death or disability. The infection is caused by fork-tailed larvae, so-called cercariae, which penetrate the skin of humans when they come into contact with contaminated water. From there, they migrate via the lymphatic and blood vessels into the vascular plexus of the intestinal tract or the urinary bladder. Here, within a few weeks, adult worms about 2 cm in size develop and regularly release eggs. These eggs can then lead to chronic inflammation in the intestinal and bladder tissue as well as in other organs such as the liver and kidneys, with sometimes serious late consequences such as liver fibrosis or bladder cancer.

The link between poverty and neglected tropical diseases is particularly striking in the case of snakebite envenoming. Unlike many other serious diseases, there are highly effective treatment options: namely, antivenoms. According to the Word Health Organisation WHO, most deaths would be completely preventable if safe and effective snake antivenoms were more available and accessible. With them, most symptoms resulting from snakebites can be prevented or reversed. They are included in the WHO list of essential medicines and should be part of any primary health care for snakebite.

"I had my pivotal moment as a doctor in training in the intensive care unit of a provincial hospital in Laos: a patient had been bitten on the right foot by a Malayan pit viper and had developed life-threatening anaemia. My Lao colleagues and I stood at the patient's bedside, perplexed. No one had experience in treating venomous snakebites. An antivenom was not available in our hospital pharmacy or elsewhere in Laos. Fortunately, the patient survived after receiving more than ten blood transfusions. With antivenin we could have quickly fixed the massive blood clotting disorder and prevented the anaemia with the necessary transfusions."

Dr Jörg Blessmann, Working Group Leader

Leishmaniasis infections occur worldwide, both in humans and in animals, mostly rodents. The Leishmania parasites are transmitted to mammals by bloodsucking sandflies. They can cause self-healing skin lesions, known as Oriental bumps, as well as large dry and non-healing skin ulcers. Visceral (internal) leishmaniasis (kala-azar) is almost always fatal if left untreated.

WHO estimates that more than 12 million people are currently infected and more than 1 million people become newly infected each year. In North Africa and the Middle East, and especially in Syria, cutaneous leishmaniasis is particularly widespread, while European visceral leishmaniasis predominantly affects dogs and usually only causes disease in immunocompromised people. Thus, leishmaniasis is considered an important complication of HIV infections, as both misdirect the human immune system. This favours both HIV infection and leishmaniasis and makes treatment of leishmaniasis much more difficult.

The World Health Organisation (WHO) estimates that one in four people is still infected with parasitic worms, so-called helminths. Again, the link between poverty and disease, poor sanitation and transmission routes is particularly striking: the poorest and most disadvantaged communities with poor access to clean water and sanitation are affected, especially in sub-Saharan Africa, Asia and South America. Helminths are transmitted by eggs in human faeces, which in turn contaminate the soil in areas with poor sanitation.

Helminth infections disrupt child development and growth; infected women and girls of childbearing age suffer from iron deficiency due to blood loss. This increases the risk of maternal and infant mortality and low birth weight. There are safe and effective drugs to treat helminth infections.