Neglected Tropical Diseases
Can We Take the ‘Neglected’ Out of the Name?
The Neglected Tropical Diseases (NTDs) are a number of usually chronic but sometimes-acute diseases, which were first grouped together back in 2003 by the World Health Organisation. They have earned the name ‘neglected’ almost by default due to the fact that very little of the funding for health which goes to the poorest countries is directed at them.
Most African countries depend on external funding for support to their Ministries of Health, and while some money goes for salaries, hospitals and infrastructure, and some is directed at individual high priority diseases, very little goes to the treatment of NTDs. The acute killers, including the big three of malaria, TB, malaria and HIV/Aids, can infect tourists, affect people living in major cities and even infect government officials, and as such attract money from major donors. Government funds are also primarily directed at them. NTDs on the other hand attract little money or attention because (1) they affect the poorest of the poor yet rarely affect the well off, (2) the people infected rarely complain of early infections because they are chronic and (3) people visiting remote health facilities will not receive an accurate diagnosis or suitable drugs, and so do not make an effort to go.
In addition to being neglected in terms of patient treatment, NTDs also suffer from a lack of allocated research and control funding both by donors and the pharmaceutical industry. Indeed, with less than 10% of research funds received for NTDs compared with malaria, HIV and TB.
Burden of Disease
In terms of the burden of disease, NTDs cause as much suffering as TB and malaria due to the numbers infected and the period of time over which people suffer from disabilities and a poor quality of life. For example, intestinal worms and schistosomiasis together infect over 1 billion people but, as they are chronic infections, very few deaths are attributable to them. Lymphatic filariasis causes horrible disfigurement, while river blindness and trachoma cause people to go blind - neither kill. On the other hand, some NTDs such as sleeping sickness and visceral leishmaniasis infect relatively few people but are quickly fatal.
The United Nations Millennium Development Goals (MDGs), adopted in 2001, consist of eight international development goals that all 192 United Nations Member States and at least 23 international organizations have agreed to achieve by the year 2015. The MDGs aim to stimulate development by improving social and economic conditions in the world’s poorest countries. There is a case to be made that 5 out of the first 6 MDGs can never be achieved unless we can treat the millions infected by NTDs.
1. Eradicate extreme poverty and hunger – to eradicate poverty we must first treat the worms that cause the poverty.
2. Achieve universal primary education – de-wormed children will go to school feeling fitter and healthier, and with a better nutritional status.
4. Reduce child mortality – if we treat these diseases infants will be less likely to die.
5. Improve maternal health – we can lower anaemia by de-worming and hence improve birth outcomes.
6. Combat HIV/AIDS, malaria and other diseases – again treatment of the ‘other’ diseases will help reach this goal.
The Bottom Billion
The NTDs are usually highly prevalent in rural areas where piped water does not exist and hygiene
and sanitary conditions are poor. This promotes hand to mouth and water borne infections with insect breeding leading to vector borne diseases.
Three species of intestinal worms infect the ‘bottom billion – those people who live in poverty in the poorest areas of the poorest countries of the world. They are hookworm (Necator and Ancylostoma spp) whipworm (Trichuris) and the round worm (Ascaris lumbricoides). These worms inhabit the human gut and live off our ingested food while their eggs are passed out in our faeces. They have no intermediate hosts; in poor hygienic conditions the last two are ingested, while hookworm undergoes a free-living stage before reinvading a human host through the skin.
The misery, malnutrition and anaemia that these worms cause is enormous, yet they can be expelled from the human body with a single 500mg tablet of a drug called Albendazole, which costs as little as one penny per tablet from a generic manufacturer. It has been shown that annual doses of de-worming tablets may have a remarkable effect on a child’s growth, nutritional status and school attendance.
Other NTDs that can and should be easily treated are the schistosomes that cause schistosomiasis or bilharzia. These worms cause a variety of symptoms including blood in the urine and stools in the early stages and then more severe symptoms such as fibrosis of the bladder or liver, and death from bleeding or cancer. An estimated 200 million people are infected globally with schistosomiasis, almost 90% of those infected are found in Africa. Yet these worms can be killed by a single dose of the drug Praziquantel at a cost of less than 50 pence.
Two other worms, which can be easily cured, are onchocerca that causes blindness and lymphatic filariasis that causes horrific swelling of the limbs and scrotum. These worms again can be treated with pills taken once a year – the drugs used, Mectizan and Albendazole, are donated by manufacturers Merck and GSK respectively.
While we can eliminate some of these diseases, there are other NTDs that are not so easy to eradicate and some that are more deadly. These include sleeping sickness, rabies and visceral leishmaniasis – vaccines exist for rabies yet we do not have a safe drug for the others. Other diseases for which money is needed for research include Dengue fever, Japanese encephalitis, and buruli ulcer – all horrible diseases for those infected.
So, in summary, NTDs are a diverse group of infections that tend to affect the poorest of the poor such that, without combating them, the MDGs will never be attainable. For one subset of NTDs an inexpensive rapid impact package of drugs can be delivered annually at minimal cost and could easily control or eliminate the suffering of up to a billion individuals.
Many pharmaceutical companies have been generous in donating products that command high prices in the West, but are unaffordable to those who need them in the poorer countries. However, more drugs and much research funding are needed to fully address the needs of those struggling with NTDS.
We have calculated that if we could raise £200 million every year for 5 years these infections would be virtually gone from Africa, and so we are conducting a campaign to raise funds to eliminate these diseases.
Please find out more and donate online at www.imperial.ac.uk/schisto
Prof. Alan Fenwick OBE is Chair of Tropical Parasitology at Imperial College London and Director of the Schistosomiasis Control Initiative for Neglected Tropical Diseases.