What are neglected diseases and why are they called that?

NCDs (neglected tropical diseases) affect nearly 2 billion humans worldwide, with serious economic and social consequences, and are spreading to new regions.

“These diseases are ‘neglected’ because they are almost completely absent from global health plans”, recalled the Director General of the WHO, Tedros Adhanom Ghebreyesus, on this January 30, World NTD Day.

1. What are neglected tropical diseases?

WHO currently counts 20 diseases as neglected tropical diseases. Transmission is very simple, whether it is an insect bite or small parasites that penetrate the skin while swimming in a lake.

Without treatment, its consequences can permanently limit life and lead to physical disability and even death.

In case of trachoma infection, which occurs in many regions of the world, there is a risk of blindness; lymphatic filariasis (elephantiasis) causes permanent swelling of the limbs.

Other pathogens attack internal organs such as the kidneys or liver, or destroy nerve cells and cause extensive damage to the heart, as is the case with Chagas disease, which is very common in South America. Millions of humans, especially in tropical countries, are infected with NTDs every year.

Five pathogens (called “the big five”) trigger about 90% of all NTDs: lymphatic filariasis (elephantiasis), river blindness (onchocerciasis), trachoma, bilharzia (schistosomiasis), and geohelminth infestation.

The poorest sections of the population in Africa, Asia and Latin America are particularly affected. Although it is widespread, medical care for NTDs is still often overlooked. This entails not only a serious reduction in the patient’s quality of life, but also economic consequences.

2. Who is affected by NTD in the world?

NTDs affect 1.7 billion people in 149 countries; another 2 billion are threatened, according to the German Network against Neglected Tropical Diseases. It is estimated that direct or indirect victims of NTD reach 500,000 each year.

NTDs are found in all tropical regions of the planet, from Southeast Asia to the Middle East, Africa and South America. “African countries are the hardest hit,” Jürgen May explained to DW. He heads the Bernhard Nocht Institute for Tropical Medicine in Hamburg, where global infections are studied.

Low-income people are particularly at risk, particularly in rural areas or areas with difficult access to health care, where it is often difficult to obtain clean water and food.

“In many countries, there is a vicious cycle of disease and poverty. Disease itself leads to more poverty. And also sanitation problems that go hand in hand with poverty,” says May.

Those who are permanently ill are often no longer able to work and care for their families. And the impairments caused by NTDs can lead to even more stigma and exclusion.

Illnesses are often worse for women and children. Many children are unable to attend school or have developmental disabilities, and there are currently no adequate medications for children for many NTDs.

3. Why are they “overlooked”?

Although billions of people around the world are threatened by NTDs, the fight against them is still underfunded and not the focus of health systems, warn humanitarian organizations such as the NGO CBM, which works worldwide to people with disabilities.

The term “neglected diseases” also shows “how difficult it is to draw attention to NTDs, as well as the neglected population groups that suffer most from them,” explains infectious disease specialist May.

Residents of both rural areas and urban slums are often not prioritized by policy makers and “many are unaware that these diseases are serious and chronic”.

The covid-19 pandemic has caused major setbacks in the fight against neglected tropical diseases in several African countries, as millions of doses of medicines could no longer be distributed to patients.

“In the last two or three years, we’ve fallen 15 years behind,” May calculates. In many tropical countries, the consequences of Covid-19 infections have not been as severe as those of NTDs.

4. What is the role of climate change in the spread of tropical diseases?

NTDs are more common in tropical regions, but due to climate change and global travel, cases are also on the rise in Europe and North America.

Dengue fever, which is transmitted by mosquitoes, not only occurs in Africa, Southeast Asia and South America, but has also reached the Mediterranean region and southern Europe, May said.

Even in African countries, where previously the disease mainly affected the rural population, other areas are now at risk. Rising temperatures also affect insects that transmit pathogens.

“Mosquitoes are now found in ever higher regions, up to 1,500 or 1,800 metres, and also in large African cities where they did not previously live, such as Nairobi, Addis Ababa or Antananarivo in Madagascar.”

Cases of tropical diseases are also on the rise in North America and Central Europe. West Nile virus — which, strictly speaking, is not an NTD, but transmitted similarly to chikungunya or dengue — has also been found regularly in Germany since 2018, May explains. And from “a single mosquito brought to New York in 1999, West Nile virus has now spread throughout the United States.”

The sand fly, which transmits leishmaniasis, has long lived in tourist regions and tourist islands in the Mediterranean. What initially looks like a rash but can be fatal is difficult for European general practitioners to identify.

According to May, NTDs receive no attention in medical education. But more and more institutes for tropical medicine, such as the Bernhard Nocht in Hamburg, are offering further training courses for doctors.

5. What’s the next step in the fight against NTDs?

By 2030, the World Health Organization aims to contain neglected tropical diseases on a large scale worldwide through international cooperation between humanitarian organisations, doctors, governments and the pharmaceutical industry.

May considers the goal “ambitious,” certainly possible for some diseases, but extremely difficult for others. In light of the current many simultaneous crises, specialists fear that the fight against NTDs may lose its importance.

But the results so far also offer hope, says May. Decades of efforts have led to the defeat of at least one NTD in 43 countries and more than 600 million people are no longer in need of medication. Diseases such as onchocerciasis and blindness due to trachoma infections have become much rarer, thanks to better health education and targeted drug delivery.

And the deadly sleeping sickness, once widespread, has been almost completely defeated. “For many years we could only treat sleeping sickness intravenously, with many serious side effects. An oral drug has been available for a few years and it was a game changer. In 2020, we only had 650 patients.”

However, to develop good diagnostics, medicines and, in some cases, vaccines, more resources and even more commitment from governments around the world are needed. Aid organizations and health experts are now calling for financial consequences and more money for NTD programs.

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