This article is being cross-listed with the Harvard graduate student publication Signal to Noise, Special Edition on Infectious Disease.
Health equity is based on the idea that all lives, anywhere in the world, have equal value.
Neglected Tropical Diseases (NTDs) are a group of 18 infectious diseases – caused by parasites, viruses, or bacteria – that disproportionately affect the poor and cause significant health and financial burdens. NTDs are endemic – meaning that they regularly infect humans – in 149 countries, with over 1 billion people infected and 2 billion people at risk. These diseases are largely treatable and preventable through control of the insects that carry these diseases, improved water quality and sanitation, and the efficient delivery of drug treatments already donated by major pharmaceutical companies. The control and elimination of NTDs cuts across the United Nations’ eight Millennium Development Goals for 2015. Controlling NTDs would not only reduce disease burden but would also improve maternal health, reduce childhood mortality, reduce malnutrition, improve school attendance, and help to empower women. With just a year left on the Millennium Development Goals clock and these diseases still constituting a major burden, we are at a pivotal time for infectious diseases and global health. By defining a clear way forward in the post-2015 development era, we stand to make major progress toward the control, elimination, and eradication of NTDs and other diseases.
What are Neglected Tropical Diseases?
The World Health Organization (WHO) prioritizes 17 neglected tropical diseases (NTDs) (Figure 1) that affect over a billion of the world’s poorest people and pose a significant economic burden to developing economies (scabies was just added to the list in June of 2014, bringing the count to 18). NTDs are a heterogeneous group of infections caused by parasites, viruses, and bacteria. What makes NTDs different from non-neglected diseases is that these diseases are disablers rather than killers. Indeed, these infections are co-endemic: an individual may be infected with more than one NTD in addition to other well-known diseases such as HIV, tuberculosis, and malaria. For example, the parasite infection schistosomiasis can make women and girls more susceptible to HIV infection, saps micronutrients and iron from developing children to stunt their growth, and renders children less likely to attend school. A chronic helminth parasite infection known as lymphatic filariasis (LF) may reduce vaccine efficacy by broadly modulating the immune system. LF causes severe swelling (lymphedema) in 40 million people rendering them socially stigmatized and largely unable to work. In addition to schistosomiasis and LF, many more NTDs are characterized by chronic disabilities, increased susceptibility to infectious and non-infectious diseases, social stigma, and an economic burden on the individual, the family, and the country.
NTDs don’t just affect low- and middle-income countries, although their victims are often socioeconomically disadvantaged. Cysticercosis, echinococcus, toxocariasis, Dengue virus, West Nile virus, and Chagas disease all have appeared in the United States, disproportionately afflicting the poor. Peter Hotez of the Sabin Vaccine Institute and Baylor College of Medicine has estimated that half of the 20 million people living in poverty in the US are infected with at least one NTD.
How NTDs cut across the Millennium Development Goals
The Millennium Development Goals (MDGs), established following the Millennium Summit of the United Nations in 2000, are a list of 8 objectives aimed at lifting the world’s poorest countries out of poverty by 2015. MDG 6: Combat HIV/AIDS, malaria, and other diseases, most directly applies to NTDs, which fall into the “other diseases” category. The idea that NTDs fall under the “other diseases” umbrella is also now an old one, as NTDs have rightly gained much more attention over the past 10 years as a significant development burden.
The Global Network for Neglected Tropical Diseases issued a report outlining the contribution of NTDs to hindering progress on several other MDGs. With respect to MDG 4: Reduce Childhood Mortality, for example, a child infected with any of the helminth parasites will be anemic and malnourished with a compromised immune system, making it much more likely that that child will succumb to another infection. Children harboring one or more NTDs are also less likely to have regular attendance in school, contributing to MDG 2: Achieve Universal Primary Education. In fact, a study of schools in Western Kenya demonstrated that treating intestinal parasite infections by mass drug administration programs can improve school attendance by up to 25%.
One metric that captures the impact of diseases that disable rather than kill, like many of the NTDs, is the Disability Adjusted Life Years (DALYs) calculation. One DALY can be thought of as one lost year of healthy life to an individual, either by mortality or by disability. Estimates place the burden of Disability Adjusted Life Years (DALYs) lost to NTDs at 26.6 million in 2010, but this is likely a gross underestimate if we consider the secondary effects of NTDs. For example, NTDs contribute to an estimated 15-30% of lost productivity in endemic countries. The coordinated effort to control, eliminate, and eradicate NTDs is not only an issue of human health, but one of economic development.
Recent Progress: NTDs are a Big Bang for the Development Buck
In addition to improving human health and health equity, combating NTDs is a strong and cost-effective method of increasing economic growth. For example, the early results of the Global Programme to Eliminate Lymphatic Filariasis has generated a return on investment of $20-$60 for every US$1. Recognizing this opportunity, the US Congress committed funding support through USAID for the integrated control of NTDs in 2006, and in 2008 the UK Department for International Development also committed funding for NTD eradication. The Bill and Melinda Gates Foundation and the World Bank have also committed significant aid to fighting NTDs over the past decade, followed more recently by other international aid funds.
The First WHO Report on Neglected Tropical Diseases published in 2010 brought NTDs to the forefront. The WHO released a follow-up report in 2012, closely followed by the 2012 London Declaration to control, eradicate, or eliminate by 2020 ten NTDs (lymphatic filariasis, trachoma, soil-transmitted helminths, onchocerciasis, schistosomiasis, leprosy, guinea worm, visceral leishmaniasis, Chagas disease, and human African trypanosomiasis). The London Declaration has been notably effective in kick-starting a strategic and directed effort in the battle against NTDs. It brought together global health leaders including the Gates Foundation and the CEOs of ten pharmaceutical companies to guarantee the donation of an unlimited amount of medicines for these 10 NTDs for the foreseeable future. The NTDs agenda has been characterized by these strong public-private partnerships, which will be key for continuing progress.
Uniting to Combat NTDs, the coalition of partners and individuals formed during the London Declaration, issued their second progress report in 2014. The report highlights a large upwelling in political will in countries where one or more NTDs are endemic. For instance, demand for drugs for NTDs has increased by 35% and has been matched by industry donations, and there has been an increase in mass drug administration programs. Funding for NTDs has also increased, led by USAID, the UK Department for International Development (DFID), the World Bank, and the Bill and Melinda Gates Foundation. New rapid diagnostic tests for Human African Trypanosomiasis will streamline diagnosis and treatment, and there is now a new pediatric formulation of praziquantel to treat childhood schistosomiasis.
We have effective drugs for most NTDs. The major challenge, and the cost, is effectively and efficiently delivering those drugs to endemic regions. We are now in the position to ask, “What kind of mass drug administration (MDA) regime might lead to local eradication? And can we coordinate the delivery of multiple drugs for multiple diseases at the same time? With the end of 2015 only a year away, we must also ask, “What’s next?”
Looking Ahead: Innovation for NTD Elimination and Control
Since the London Declaration, some successes indicate that control and eradication are possible. Colombia recently became the first country in the world to eradicate onchocerciasis. Niger, Nigeria, and the Ivory Coast have also recently eradicated Guinea worm. Twenty-three countries treated at least 75% of children at risk for soil-transmitted helminth infections, and a massive disease mapping program of blinding trachoma using mobile technology has cut the unmapped regions of the world for this disease in half.
However, we still have a long way to go. It has been estimated that of all the drugs approved for distribution, only 65-75% are reaching the people who need them. Implementation and operational research on how to carry out mass drug administrations effectively must be a priority. Even when control programs go well, they can be quickly derailed by political unrest, natural disasters like Superstorm Haiyan, or even epidemics like the ongoing Ebola outbreak that have overwhelmed the existing health systems in Liberia and Sierra Leone. Furthermore, disease boundaries for mosquito-transmitted diseases are especially sensitive to changing temperature and precipitation patterns due to climate change.
Last November in his keynote address to the American Society of Tropical Medicine and Hygiene, Bill Gates highlighted a need for global health innovations, citing the example of the new diagnostic test for human African trypanosomiasis. Gates urged the community to take the digital revolution and apply it to disease surveillance to determine where to concentrate disease-fighting efforts The Bill and Melinda Gates Foundation is a strong proponent that “big data” health care informatics solutions must be apart of efficient disease control programs, and this will represent a burgeoning area of global health research in the near future.
As the clock on the 2015 Millennium Development Goals runs out, planning for the post-2015 Sustainable Development Goals. is well underway. What do you think are the biggest issues facing human development today and in the near future? You can take a look for yourself to see if NTDs will make the cut by reviewing the proposals for the Sustainable Development Goals using the Overseas Development Institute’s http://tracker.post2015.org.
Rachel Cotton is a PhD student in the Harvard Immunology Program, with an interest in infectious disease, global health, and science policy. Her past research has included the immunobiology of parasitic diseases. Follow her on Twitter @RachCotton.