Hello everyone, welcome to the fifth episode of ‘What We Don’t Know’, a podcast that explores the boundaries of human knowledge, investigating the unanswered questions and theories that unravel them at the frontiers of science. During this podcast I hope to get you interested in new areas of science, maths and technology, teaching you about existing concepts and igniting a curiosity for the things we have yet to know.
This episode is a bit different to the previous ones because neglected tropical diseases (NTDs) have treatments, so their biology is not beyond the horizon of science. However, in sharp contrast to how curable they are, 1.7 billion people still suffer their effects, and few of the general public elsewhere are aware of the terrible socioeconomic problem they present.
At the end of 2020, the first vaccines for COVID-19 had passed Phase 3 clinical trials. Vaccines were ready for delivery. People felt hopeful that the end of this pandemic was finally in sight, but, as with most global problems, it would not be that simple. Barriers to manufacturing, varying financial abilities, vaccine hoarding and political blockades have produced a global vaccine inequity whose effects will be devastating, economically and socially, for millions around the world. Some sources show a vaccination timeline stretching into 2023. The World Health Organisation warns that poorer countries – in some of which health workers are still not vaccinated – may not reach pre-COVID-19 growth levels until 2024.
The scientific achievement of vaccine creation did not ensure global immunisation, did not set the whole world on the path to recovery. A scientific solution does not always equal a social one.
The disconnect between potential medical treatments and patients who are treated in reality is not a new phenomenon. After a drug is created, it still has to reach those in need. For example, in 2019 there were an estimated 229 million cases of malaria worldwide, a life-threatening disease both preventable and curable, usually with a artemisinin-based combination therapy. Access to healthcare largely determines the treatments available to you; a miracle cure is useless if you cannot afford it, or are too far from the hospital where it is administered.
There is one class of diseases where this fact crystallises most clearly: neglected tropical diseases, or NTDs.
When was the last time you had a mosquito bite? Last week? Last month? Over the summer I was bitten tens of times, and each one had the most irritating itch. Of course, scratching the itch spreads the poison, making it worse. What if you felt itchy everywhere, all over your legs and arms and torso and face, a constant, inescapable buzzing under your skin. Even conjuring such an image makes my skin crawl, but that is what people with river blindness experience after being bitten by an infected black fly. Early stages (called microfilariae) of the parasitic worm invade the body, mature and live inside for up to 15 years, every day releasing around 1000 new microfilariae. These microscopic monsters cause itchy skin, rashes, skin nodules, eventually lesions and bacterial infections. If they spread to the eyes, vision impairment follows, and after years of severe infection, blindness.
River blindness is one of twenty neglected tropical diseases recognised by the World Health Organisation. Others include bilharzia, also known as schistosomiasis, second only to malaria as the most devastating parasitic disease, and the leading cause of mortality among NTDs. 229 million currently require treatment. Trachoma is where the eyelid turns inward, eyelashes scratching at the cornea of your eye until you turn blind. 177 million require treatment. For lymphatic filariasis, a parasite enters your lymphatic system which grows. Severe stages become elephantiasis, characterised by baggy, thickened skin in your body’s lower half, where swelling can make walking difficult. 893 million require treatment.
Currently, 1.7 billion people suffer from NTDs. This means that 1 in 7 people suffer from at least one neglected tropical disease; often, people are afflicted with multiple. They are infections associated with low-income populations in developing regions of Africa, Asia and the Americas. NTDs are global supervillains, producing immense pain and suffering for millions upon millions of individuals, culminating in death – around 170,000 per year – long-term disability, social isolation and stigma from blindness and deformity.
Clearly, the social effects of NTDs are devastating. But it is clearer now more than ever the economic problems disease can cause. Children, around one billion, have stunted growth, cognitive impairment, and sometimes cannot go to school. Adults may find work difficult, so are left unable to provide for their families. The health infrastructure - hospitals, hygiene standards, antibiotic availability - lacks money to improve, so people continue to be infected. This sends affected communities into a downwards spiral of poverty and illness.
Knowing the suffering and perpetuation of poverty that NTDs cause, perhaps you think that lots of money is invested into finding cures. You’d be wrong. Every neglected tropical disease is preventable or treatable. Ivermectin antibiotic programs treat river blindness, bilharzia requires a single annual dose of praziquantel. Trachoma, when the eyelid turns inwards so eyelashes scratch at the eye, is solvable with a 10-minute surgery. The solutions are there for the taking.
Why, then, do 1.7 billion still experience these diseases? Once again, a scientific solution does not equal a social one.
Like the cruelest supervillains, neglected tropical diseases attack those least able to defend themselves: remote, rural communities where the nearest hospitals may be many miles away, urban slums or conflict zones. The parasites thrive in conditions of poverty.
Hospital inaccessibility is one of many barriers to drug distribution. Weak health infrastructure struggles to facilitate the long-term medical programs needed for sustainable change. For NTDs to be controlled, every person in a high risk area must receive the drugs, often for multiple diseases at once, over the course of several years. Surveillance systems face problems tracking the diseases and collecting data on where each one is endemic; without data it is hard to formulate a plan for elimination. Political instability may result in external funding getting cut off. Finally, the low profile of NTDs compounded with the quiet political voice of sufferers results in NTDs largely being overlooked in favour of malaria, HIV/AIDS and tuberculosis, especially since NTDs are not always fatal.
Neglected tropical diseases have plagued humanity for millennia. Evidence in Assyrian medical texts and Ancient Egyptian papyri reported symptoms resembling schistosomiasis. As we built our civilisations, NTDs disappeared for many of us. For many others in the tropics, they clung on, parasites in every way.
But recently, humanity decided that nobody should suffer from NTDs any longer. Big pharmaceutical companies banded together to manufacture the necessary drugs for free. And the industrialised production of medicine speeds up this process. As a result, the cost of treatment is astoundingly low: on average, 90 cents per treatment, though average praziquantel treatment for bilharzia costs 20 cents.
Great progress can be achieved. A good example is the near eradication of guinea worm, which went from 3.5 million human cases in 1986 to 28 in 2018. International, national and local organisations all worked together for the shared common good of saving millions of people. NTD treatment programs were integrated and succeeded in training local health workers, coordinating national ministries, normalising treatment, mapping the disease, and greatly improving water supplies.
The Mectizan Donation Program (MDP) was established by Merck, who partnered with the World Health Organisation and the World Bank to eliminate river blindness, using Mass Drug Administrations of ivermectin. They later expanded to include albendazole for lymphatic filariasis, the NTD co-existing with river blindness that causes the lower half of the body to swell massively. The MDP reaches 300 million people annually.
Great change can be achieved. It is no longer a matter of program or drug innovation, since cures exist, and governments know how to supplement health infrastructure.
It is a matter of global collaboration. The world came together to defeat the COVID virus with a vaccine, and it should stay together to defeat neglected tropical diseases. It has done so before. Such collaboration should be a cause for hope. Funding and work on combating NTDs must continue. If it does, then successes will multiply, neglected tropical diseases will finally be eradicated, and humanity will be one step closer to a world without suffering.
Thank you for listening.