Neglected tropical diseases
Neglected tropical diseases are a diverse group of tropical infections that are common in low-income populations in developing regions of Africa, Asia, and the Americas. They are caused by a variety of pathogens, such as viruses, bacteria, protozoa, and parasitic worms and mites. These diseases are contrasted with the "big three" infectious diseases, which generally receive greater treatment and research funding. In sub-Saharan Africa, the effect of neglected tropical diseases as a group is comparable to that of malaria and tuberculosis. NTD co-infection can also make HIV/AIDS and tuberculosis more deadly.
Some treatments for NTDs are relatively inexpensive. For example, praziquantel for schistosomiasis costs about US $0.20 per child per year. Nevertheless, in 2010 it was estimated that control of neglected diseases would require funding of between US$2 billion and $3 billion over the subsequent five to seven years. Some pharmaceutical companies have committed to donating all the drug therapies required, and mass drug administration efforts have been successful in several countries. While preventive measures are often more accessible in the developed world, they are not universally available in poorer areas.
Within developed countries, neglected tropical diseases affect the very poorest in society. In developed countries, the burdens of neglected tropical diseases are often overshadowed by other public health issues. However, many of the same issues put populations at risk in developed as well as developing nations. For example, other problems stemming from poverty, such as lack of adequate housing, can expose individuals to the vectors of these diseases.
Twenty neglected tropical diseases are prioritized by the World Health Organization, though other organizations define NTDs differently. Chromoblastomycosis and other deep mycoses, scabies and other ectoparasites, and snakebite envenomation were added to the WHO list in 2017. These diseases are common in 149 countries, affecting more than 1.4 billion people and costing developing economies billions of dollars every year. They resulted in 142,000 deaths in 2013, down from 204,000 deaths in 1990.
Reasons for neglect
The importance of neglected tropical diseases has been underestimated since many are asymptomatic and have long incubation periods. The connection between death and a neglected tropical disease that has been latent for a long period is often not realized. Areas of high endemicity are often geographically isolated, making treatment and prevention much more difficult.There are three other major reasons that these diseases have been overlooked: they mainly affect the poorest countries of the developing world; in recent years public health efforts have focused heavily on decreasing the prevalence of HIV/AIDS, tuberculosis, and malaria ; and neglected tropical diseases do not currently have a prominent cultural figure to champion their elimination.
Stigma
Neglected tropical diseases are often associated with social stigma, making their treatment more complex. Public health research has only recently begun to focus on stigma as a component of the issue. From the 1960s onward, approximately one citation a year related to social stigma. In 2006, there were 458.Stigma greatly affects disease control by decreasing help-seeking and treatment adherence. Disease control programs since the 1980s have begun to integrate stigma mitigation into their offerings. In India, a leprosy program prioritized the message that "leprosy is curable, not hereditary" in order to inspire optimism in highly affected communities. The goal was to make leprosy a disease "like any other", so as to reduce stigma. At the same time, medical resources were optimized to fulfill the promise that the disease could be cured.
Economic incentives
Treatment and prevention of neglected tropical diseases are not seen as profitable, so patents and profit play a reduced role in stimulating innovation compared to other diseases. Like all non-commercial areas, communities affected by these diseases are reliant on governments and philanthropy. Currently, the pharmaceutical industry views research and development as highly risky. For this reason, resources are not often put into the field of NTDs, and new chemical products are often expensive. A review of public and private initiatives found that of the 1,393 new chemical products that were marketed between 1975 and 1999, only 16 were related to tropical diseases or tuberculosis. The same review found that there was a 13-fold greater chance of a newly marketed drug being for central nervous system disorders or cancer than for an NTD.Because of a lack of economic incentives for the pharmaceutical industry, successful NTD treatment programs have often relied on donations. For instance, the Mectizan Donation Program has donated over 1.8 billion tablets of ivermectin. While developed countries often rely on government-run and private partnerships to fund such projects, developing nations frequently have significantly lower per-person spending on these diseases.
A 2006 report found that the Gates Foundation funded most extra activities to counter these diseases.
Neglected diseases in developed nations
Since 2008, the concept of "neglected diseases of poverty" has been developed and explored. This group of diseases, which overlaps with neglected tropical diseases, also pose a threat to human health in developed nations. In the United States alone, there are at least 12 million people with neglected parasitic infections. They make up a hidden disease burden among the poorest people in wealthy societies. In developed nations, lack of knowledge in the healthcare industry and lack of conclusive diagnostic tests perpetuate the neglect of this group of diseases.In the United States, rates of parasitic infection can be distributed along geographic, racial, and socio-economic lines. Among African Americans, there may be up to 2.8 million cases of toxocariasis. Toxocariasis, trichomoniasis, and some other neglected infections occur in the United States at the same rate as in Nigeria. Within the Hispanic community, neglected infections are concentrated near the US–Mexico border. Vector-borne illnesses are especially high, with some rates approaching those of Latin America. Chagas disease was found in the US as early as the 1970s. However, in the developed world, diseases that are associated with poverty are often not addressed comprehensively. This may be due to a lack of economic incentives and public policy failings. A lack of awareness prevents effective policy generation and leaves healthcare services unequipped to address the issue. Additionally, little effort is put into creating and maintaining large data sets on neglected diseases in the United States and other developed nations. The first summit on the issue was held by the Adler Institute on Social Exclusion in the United States in 2009.
In Europe, a similar trend is seen. Neglected tropical diseases are concentrated in eastern and southern Europe, where poverty levels are highest. The most prevalent diseases in this region are ascariasis, trichuriasis, zoonotic helminth infections, and visceral leishmaniasis. Migration paths to Europe, most notably to Spain, have brought diseases to Europe as well. As many as 6,000 cases of Chagas disease have been introduced in this way. In response to a growing awareness of the burden on these populations, the European Centre for Disease Prevention and Control has laid out ten public health guidelines. They cover a variety of topics, from health education and promotion to community partnerships and the development of a minority healthcare workforce.
List of diseases
There is some debate among the WHO, CDC, and infectious disease experts over which diseases are classified as neglected tropical diseases. Feasey, a researcher in neglected tropical diseases, notes 13 neglected tropical diseases: ascariasis, Buruli ulcer, Chagas disease, dracunculiasis, hookworm infection, human African trypanosomiasis, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis, trachoma, and trichuriasis. Fenwick recognizes 12 "core" neglected tropical diseases: the same as above, excluding hookworm.These diseases result from four classes of causative pathogens: protozoa ; bacteria, helminths or metazoan worms ; and viruses.
The WHO recognizes the twenty diseases below as neglected tropical diseases.
The World Health Organization's 2010 report on neglected tropical diseases offers an expanded list including dengue, rabies, yaws, cysticercosis, echinococcosis, and foodborne trematode infections.
| Disease | DALYs | Deaths/Yr | Global Prevalence | Population at Risk |
| Schistosomiasis | 4.5 | 280,000 | 207 | 780 |
| Hookworm | 22.1 | 65,000 | 576 | 3200 |
| Ascariasis | 10.5 | 60,000 | 807 | 4200 |
| Leishmaniasis | 2.1 | 51,000 | 12 | 350 |
| Trypanosomiasis | 1.5 | 48,000 | 0.3 | 60 |
| Chagas disease | 0.7 | 14,000 | 8 | 25 |
| Trichuriasis | 6.4 | 10,000 | 604 | 3200 |
| Leprosy | 0.2 | 6,000 | 0.4 | Not Determined |
| Lymphatic filariasis | 5.8 | 0 | 120 | 1300 |
| Trachoma | 2.3 | 0 | 84 | 590 |
| Onchocerciasis | 0.5 | 0 | 37 | 90 |
| Cryptococcosis | 12 | 400,000 | 1 | 8 |