Time to overcome the neglect of neglected tropical diseases

  • Morris K
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In the past year, neglected tropical diseases (NTDs) have moved higher on national and international agendas. To further harness this momentum, the WHO reportWorking to overcome the global impact of neglected tropical diseases, released on Oct 14, emphasises that tackling NTDs comprehensively also has broader benefits, including the alleviation of poverty. But some experts are concerned that recommended interventions are not sufficient by themselves to ensure sustainability of programmes and to truly alleviate poverty.
NTDs, which are all diseases of poverty that also promote poverty, affect one in six people worldwide. WHO now recommends a package of five public-health strategies for prevention and control: expansion of preventive chemotherapy; intensified case detection and case management; improved vector control; appropriate veterinary public-health measures; and provision of safe water, sanitation, and hygiene. WHO Director General Margaret Chan calls this package a “breakthrough” and “a pro-poor strategy on a grand scale”. If implemented widely, control strategies substantially reduce disease burden, “breaking a cycle of infection, disability, and lost opportunities that keep people in poverty”, she says.
Elimination is increasingly thought to be a feasible target. In the past, NTDs disappeared from some areas as socioeconomic standards improved. But, for the world's poorest billion people today, Chan says, “instead of waiting for these diseases to gradually disappear as countries develop and living conditions improve, a deliberate effort to make them disappear is now viewed as a route to poverty alleviation that can itself spur socioeconomic development”.
A major step heralded by WHO is the increasing scale-up of mass chemotherapy programmes. Peter Hotez, editor-in-chief of PLoS Neglected Tropical Diseases told TLID that “low-cost integrated preventive chemotherapy is a highly effective and cost-effective approach to controlling NTDs”. For control of the seven most common NTDs—the three soil-transmitted helminth infections, schistosomiasis, lymphatic filariasis, onchocerciasis, and trachoma—“once or twice-yearly mass drug administration approaches are essential, in addition to ancillary measures that include sanitation and clean water”, Hotez notes.
Louis-Albert Tchuem Tchuenté, director of the Centre for Schistosomiasis and Parasitology, Yaoundé, Cameroon, asserts that there is “an unprecedented opportunity for control of NTDs”. Over the past year, more than half a billion people have had treatment for the most disfiguring, stigmatising, and debilitating NTDs, he states. Tackling morbidity in this manner has, for example, substantially reduced blindness related to onchocerciasis, leading to improved health, a reduced burden on health services, and increased working capacity in adults and learning capacity in children.
Repeated mass chemotherapy can disrupt transmission of some NTDs and is expected to eliminate these diseases in some areas. Tchuem Tchuenté cites lymphatic filariasis as an example, for which 5—6 years of treatment can stop transmission and which is targeted for elimination by 2020. Hotez also notes the elimination of onchocerciasis, trachoma, and leprosy as public-health concerns in some low-income and middle-income countries. For NTDs with the highest prevalence that cannot be eliminated by chemotherapy (ie, hookworm and schistosomiasis), vaccines are being developed to prevent reinfection, reports Hotez, who is also president of the Sabin Vaccine Institute. “Together with integrated preventive chemotherapy and downstream vaccines there is great reason for optimism.”
But some people are concerned that the importance of chemotherapy and other biomedical interventions could be overestimated and will not be sustainable nor alleviate poverty. In a recent paper, Pascale Allotey (Monash University, Selangor, Malaysia) and coauthors agree that there is cause for optimism. But, they write, research and interventions for NTDs “largely neglect the social and ecological contextual factors that make these diseases persist in the target populations, continuing instead to focus on the simple biomedical interventions”.
Burton Singer of the Emerging Pathogens Institute at the University of Florida, FL, USA, also has “a real sense of scepticism” about the ambitions for mass chemotherapy. Onchocerciasis, for example, affects such a broad geographical area, he is “sceptical even in terms of delivery”. WHO acknowledges that insufficient drugs are available to meet targets for control of lymphatic filariasis, schistosomiasis, soil-transmitted helminth infection, and trachoma.
Most drugs for NTDs are donated by major pharmaceutical companies, some of which increased their pledges at the launch of the report. However, Singer asks, even if drugs are available and delivered, how long will preventive chemotherapy be sustained and who sustains that? “These communities can't pay for it”, he says, and “this installs a chain of dependence of the endemic communities on the unsustainable drug pipelines.”
“Even the poorest people have a fundamental human right to access essential medicines for their NTDs”, without precluding measures to address social and environmental determinants, Hotez counters. “Just as people should have access to medicines, they also have a right to innovation, meaningful research, and development to produce new generation drugs, vaccines, and diagnostics to address their NTDs.”
“People need drugs, treatment is important”, Singer continues, “but once you do something about de-worming, unless you do something to prevent re-worming, in a way that local communities can handle themselves, infection rates go back up again.” He cites a seemingly successful drug-based schistosomiasis control programme in China, in which chemotherapy was discontinued after 10 years, and prevalence subsequently returned to more than 40% in some areas.
With a target of morbidity control alone, “automatically you may end up with endless action”, Tchuem Tchuenté explains. But where control is succeeding, more efforts are needed, he says. “Now we have the tools, the elimination of most of these diseases is feasible in many areas, we need to be more ambitious.” But, he emphasises the need to combine several approaches; and as the WHO report notes, the full package of recommended measures is necessary, which requires strengthening of health systems, plus interventions and development of local expertise in water and sanitation, vector control, and animal health.
Health systems remain the major current weakness, Tchuem Tchuenté continues. Chemotherapy and case management need to be integrated into health systems that are often inadequate. “People believe that investing in a health system is expensive and difficult to achieve, but if nothing is done, you cannot solve the problem.” Long-term investment in health systems is needed for NTD programmes to be sustainable and for resources to have a broader impact on health, he explains.
Clean water and sanitation facilities prevent transmission of several pathogens. Singer notes that, in the southern USA, hookworm was eradicated by provision of chemotherapy, toilets, and education. An important benefit of broader prevention efforts today is a reduction in the demand for pharmacological treatments, says Singer. However, just installing new water and sanitation systems is insufficient: “you need an ethos of maintenance and local people trained to maintain”, he urges.
Dracunculiasis is one example of success, and guinea worm disease is on the verge of eradication (global elimination). Transmission is prevented mainly through provision of safe drinking water, while education and communication have led to behaviour change, so that dracunculiasis is expected to be the first disease eradicated without a vaccine.
However, even comprehensive prevention efforts are “not going to do much to alleviate poverty”, Singer believes. He notes that many US areas where hookworm has been eradicated for a century still remain impoverished. Allotey and coauthors conclude that at “the very least increasing standards of living, provision of the basic human rights of food/water, shelter, and clothing are definitive interventions towards the elimination of NTDs”. Furthermore, Singer proposes measures to address economic determinants of sustainable prevention, such as local business creation to expand water purification and sanitation strategies. NTD prevention measures can also be incorporated into national infrastructure development, by governments writing health and social measures into concession agreements with private companies, he says.
Collaboration between all partners and sectors has expanded, notes the WHO report, but poor communication among the various groups remains a major problem, state Allotey and colleagues. Greater coordination is needed at all levels, says Tchuem Tchuenté, because “each partner has their own vision and own interest, and the ones who bring the money also sometimes decide what to do. Sometimes, many people in a country are working for the same thing, but with different targets because there are different donors. Country leadership in the coordination of activities is essential”, he concludes, and local ownership brings many gains, including development of local capacity and expertise.
The Sabin Vaccine Institute's Global Network for Neglected Tropical Diseases is one initiative aimed at advocacy, US$100 million resource mobilisation, and global coordination. But a major concern to Singer is the large effect of donor countries on research and development, emphasising the need for communities to develop systems according to local priorities.
This report is expected to further boost political commitment to tackle NTDs both in endemic countries and from donors; but urges that “donors and agencies beyond disease-endemic countries—the agents of aid to developing countries—will need to

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  • Kelly Morris

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