An Overview of Neglected Tropical Diseases

Neglected tropical diseases (NTDs) are a diverse set of infections that primarily impact impoverished communities in tropical regions around the globe. Found in 149 countries and more than a billion individuals, NTDs affect more people than malaria, tuberculosis, and HIV combined worldwide, and result in approximately 57 million years of life lost when you take into consideration the premature death and disability they cause.

Many of these diseases are easily preventable with low-cost medications, but logistical and economic challenges of the areas where these infections are common make it difficult to combat them. Even so, the impact of NTDs has gained more attention in recent years, and significant progress has been made in eliminating some of these infections.

Examples of NTDs

As of June 2018, the WHO has recognized at least 21 infections and conditions as NTDs, many of which have been eliminated from wealthy countries already but remain in the world’s most impoverished areas. These diseases thrive in the absence of medical care, safe drinking water, or adequate sanitation, yet many are treatable for as little as 50 cents per person, per year.

The WHO, along with organizations like the Centers for Disease Control and Prevention (CDC) and UNICEF have made an effort to bring more attention to NTDs, in an effort to garner more political will and resources to address them, but these infections still affect roughly one in six people worldwide.

The first major turning point for combatting NTDs happened in 2007 when a group of roughly 200 people from various public and private organizations from around the globe met at the WHO headquarters in Switzerland to discuss how the world could collaborate to fight these diseases. Since then, the WHO and its partners have established plans to eradicate or reduce NTDs, calling on those in wealthier nations to pitch in.

NTDs can be broken down roughly into four categories: bacteria, helminths (worms or worm-like organisms), protozoa (parasites), and viruses. They are spread through animals (like bugs), from person to person, or by consuming or coming into contact with contaminated food or water sources.

As of June 2018, the list of NTDs identified by the WHO includes:

• Buruli ulcer
• Chagas disease
• Dengue
• Chikungunya
• Dracunculiasis (guinea worm disease)
• Echinococcosis
• Foodborne trematodiases
• Human African trypanosomiasis (African sleeping sickness)
• Leishmaniasis
• Leprosy (Hansen's disease)
• Lymphatic filariasis
• Mycetoma, chromoblastomycosis, and other deep mycoses
• Onchocerciasis (river blindness)
• Rabies
• Scabies and other ectoparasites
• Schistosomiasis (snail fever)
• Soil-transmitted helminthiases
• Snakebite envenoming
• Taeniasis/Cysticercosis
• Trachoma
• Yaws (Endemic treponematoses)

Who Is Impacted

Despite their diversity, all NTDs have one common link: they disproportionately impact people living in poverty. Many areas around the world still lack access to basic sanitation, clean water, and modern medical care. Typically (though not always) these infections are found in tropical regions, especially where communities live around animals, livestock, or insects that carry or transmit the pathogens and parasites.

The enormous impact NTDs have on the planet is jaw-dropping. More than a billion people worldwide are currently infected with at least one NTD (many have more than one), and over half the world's population lives in an area where there is a risk of infection. An estimated 185,000 people are estimated to die every year as a result of having at least one NTD, and millions more live with chronic infections.

When people survive them, NTDs can be debilitating, causing long-term health issues, personal and financial stress, and physical suffering. They keep people from working or learning, perpetuating and worsening a cycle of poverty in populations that are already the poorest of the poor.

On an individual level, this can lead to financial hardship but amplified across communities and countries where these diseases are common, it can be economically devastating. According to one estimate, nations with lymphatic filariasis (elephantiasis) lose $1 billion a year and up to 88% of their economic activity due to that one disease alone.

In addition to the impact NTDs have on the physical health of those infected, research shows that it can affect their mental health and psychological development, too.

• Children with early and frequent parasitic infections are at a greater risk for malnutrition and anemia, which can significantly (and sometimes irreversibly) affect their learning and cognitive abilities.
• Adults permanently disfigured or disabled as a result of NTD infections often face stigma; discrimination; or exclusion from educational institutions, employment opportunities, or society in general—something that can greatly impact their mental health.

While developing nations are hit the hardest by NTDs, poor people in wealthy nations aren't immune—including in the United States. Southern states along the Gulf Coast and Mexico border with high poverty rates are particularly vulnerable, as well as U.S. territories like Puerto Rico. 

Researchers estimate there are nearly 37,000 current cases of Chagas disease in the state of Texas alone, for example, with more than 200,000 believed to be found throughout the rest of the United States.

Outbreaks of mosquito-borne NTDs like dengue virus and chikungunya have happened in the country and its territories, too, with some researchers worried that cases will become more frequent as global temperatures increase and international travel becomes more common.

Challenges

Calling these diseases “neglected” wasn’t an accident. Many NTDs are overlooked by government bodies, public health agencies, or research institutions in wealthier nations because these diseases don’t typically affect them.

Unfortunately, countries that are affected by NTDs are often poor and unable to combat the diseases on their own. International coalitions led by the WHO have made progress in recruiting more wealthy nations and global partners to eliminate NTDs, but it's an uphill due to a lack of information, resources, and coordination.

Lack of Information

The first step to combating diseases is to understand them: where they are, who they’re impacting, what treatment is most effective, etc. But because NTDs occur primarily in low-income and often rural or remote communities, health officials on the ground frequently lack the tools they need to identify or report the diseases effectively. Without that information, however, it can be difficult for international organizations to send the right materials to the right places.

Lack of Resources

Each NTD requires a different strategy to combat or control it. Some need massive medication distribution programs, while others need vector control (like mosquito spraying) or some combination of the two.

For their part, many pharmaceutical companies donate large amounts of medications to treat NTDs, but getting the drugs to affected communities takes significant resources, including fuel to reach remote areas and personnel to administer them.

For those infections without effective treatment or methods of prevention, developing new medications or vaccines is so expensive and difficult that few companies or organizations are attempting to take it on.

Lack of Coordination

Worms, viruses, parasites, and bacteria don’t confine themselves to geopolitical borders, but often disease control efforts are conducted that way. More can be done with fewer resources when organizations and governments pool their knowledge and assets to collaborate on things like controlling insect populations or distributing medications. This coordination requires active involvement by those from both wealthy nations willing to help and those on the ground in areas most impacted by NTDs.

The WHO is working with a wide range of organizations and governments to do this, but juggling and directing all the players—each with their own agendas and needs—can be like herding cats, and acquiring and distributing the right materials to the people who need them can be tough to do in areas where local leaders aren't interested in help from outsiders.

Lack of Political Will

Eliminating NTDs on a global scale requires an enormous amount of energy and resources, which requires a lot of political will. Those in power —governments, international nonprofit organizations, billionaires, and philanthropic corporations—have to get involved, or there won't be enough resources or momentum to make any headway.

There has been increasing interest around the globe from wealthy nations and nonprofits (like the Carter Center) to combat NTDs, but much more is needed. To stimulate more political will, more individual constituents in rich countries will need to reach out to their elected officials to urge them to support funding for and participation in NTD elimination programs.

WHO Recommended Solutions

Given the scale, diversity, and logistical challenges to combatting NTDs, fighting them is a difficult battle but not impossible. The WHO recommends five strategies for addressing NTDs, many of which will take massive coordination and investment from public, private, and academic partners in countries all over the world.

Preventive Treatments and Therapies

In cases where there is already an effective single-dose treatment available, the WHO advocates large-scale programs to give these medications preemptively to populations at risk for infections on a regular basis as a complement to other strategies, such as improved sanitation. Rather than wait for each individual to be diagnosed and then treated in a specialized medical setting, these programs work by preemptively administering the treatment to everyone in a given population already identified to be at risk.

These programs rely on volunteers or other non-specialized personnel, rather than nurses in a clinic, to administer the medication in a non-clinical setting—for example, giving all school children in southern Rwanda a medication to treat soil-based helminths. The benefit of this strategy over traditional one-on-one treatment in a clinic is that public health agencies and governments can reach more people than they otherwise would and in a more cost-effective way.

Innovation in Disease Management

Many NTDs are hard to detect or diagnose, difficult to treat, and lack effective prevention strategies like vaccines. To combat NTDs in a meaningful way, researchers and health officials will need to develop or modify techniques to be better suited to the places where NTDs are found. This includes more cost-effective or easier-to-administer diagnostic tests or medications, and safe and effective vaccines that don’t require refrigeration or highly trained medical professionals to administer them.

Vector Control

Because many NTDs are transmitted through insects or pests, managing those populations is an important part of controlling and preventing the diseases they spread. Wealthy countries have invested in keeping vector populations (like mosquitoes) under control inside their borders, but many impoverished nations don’t have the resources to do the same.

The WHO has called for global partners to assist in reducing or controlling vectors in high-risk areas with safe and well-managed pesticides distributed in a way that works for each individual community on the ground.

Basic Sanitation

Roughly one in three people worldwide don’t have access to a toilet or other forms of improved sanitation, according to the CDC. An estimated 780 million lack safe drinking water. Many NTDs spread through contaminated food and water or contact with feces, including several that overwhelmingly impact children in critical stages of development.

Working with these communities to find locally adapted solutions for human waste and water purification could go a long way to scaling back many of these debilitating infections that perpetuate the cycle of poverty from generation to generation.

Control of Zoonotic Diseases

Humans aren’t the original targets of several NTDs. Many helminths and parasites, in particular, primarily affect animals, and diseases like rabies could be potentially eradicated in humans if it could first be prevented in dogs. So long as NTDs affect certain animal populations—especially livestock or domesticated animals—combatting them in humans will be an uphill battle. Efforts to control or eliminate NTDs in humans have to go hand-in-hand with reducing these infections in animals, too.

Progress Toward Elimination

While there is still a significant burden caused by NTDs worldwide, a substantial amount of progress has been made. Efforts by a coalition of African nations, for example, has resulted in a 90% reduction in African trypanosomiasis (sleeping sickness). Advances in technology and mapping has allowed for more effective treatment programs. Nearly a billion people were treated for at least one NTD in 2015—up some 36% since 2011.

One of the biggest success stories, however, is dracunculiasis, or guinea worm disease. A massive coordination campaign spearheaded by the Carter Center has almost eradicated the disease from the planet, causing the number of cases to plummet from an estimated 3.5 million in 1986 to just 30 cases total in 2017. It wasn't easy.

A massive amount of funding, political will, and mobilization was needed to get there. Villages were mapped, systems for identifying and reporting cases were put in place, and communities were given the tools and education they needed to filter their water and control the small crustacean population that serves as a vector for the parasite.

If these programs are successful, guinea worm could be the second human disease (after smallpox) to be completely eradicated, giving a much-needed win to those working to combat some of the world's most neglected diseases.