Control of the Neglected Tropical Diseases in sub-Saharan Africa: the unmet needs

Article Outline

• Summary
• 1. The Neglected Tropical Diseases in sub-Saharan Africa
• 2. Current status of integrated NTD control programmes by preventive chemotherapy in sub-Saharan Africa
• 3. Estimation of the target population and the needs for intervention
• 4. Mozambique as an example
• 5. Additional support for implementing countries
• 6. Starting a national integrated NTD control programme
• 7. Ownership of the programme and concerted action in implementation
• 8. Prospect for a full-scale implementation against NTDs in sub-Saharan Africa
• Funding
• Conflicts of interest
• Ethical approval
• Author's Contributions
• Acknowledgements
• References
• Copyright

Summary 

The neglected tropical diseases (NTDs) are widespread in sub-Saharan Africa with several infecting many millions of individuals. Various integrated control programmes against up to seven NTDs are now being implemented in a few countries in sub-Saharan Africa, but the total coverage is estimated to be only a quarter of the population in need of treatment. We estimate that approximately $200+ million per year is needed to fully implement the proposed integrated NTD control programmes in the rural populations in all the countries in sub-Saharan Africa, and an annual sum for 5-7 years would be needed to reduce morbidity to below public health importance. To date, the Bill & Melinda Gates Foundation, the United States Agency for International Development, the British Government, Geneva Global (an international philanthropic organisation) and other donors have committed some funds for NTD control; however, more effort is needed from a broader spectrum of donors to reach our targets. Unless more funds are committed and concerted actions are taken across all the sub-Saharan African countries, NTDs will be controlled in some but still be a major public health problem for the foreseeable future in the majority of countries.

Keywords: Neglected Tropical Diseases, NTDs, sub-Saharan Africa, Control, Integrated programme

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1. The Neglected Tropical Diseases in sub-Saharan Africa 

The neglected tropical diseases (NTDs) are a group of chronic and debilitating conditions, caused by parasitic, bacterial, and other infections.¹ These diseases are poverty-driven and are most prevalent in the poorest populations in the world.² The sub-Saharan African countries in which most people live in poverty according to the United Nations Human Development Report 2007/2008,³ have a striking number of infections with several of these NTDs,⁴, ⁵ and often individuals are infected with multiple NTDs (Figure 1). World attention has focussed on the ‘big three diseases’ (malaria, HIV/AIDS and TB),⁶ and the Global Fund provides resources for their control. Conversely, there is no similar ‘NTD fund’, and due to the lack of recognition of the importance of these diseases to sustainable economic development, there has been negligible expenditure on research and control against NTDs.⁷ While the ‘big three diseases’ are immediately life threatening and are found in both urban and rural communities, NTDs are chronic, less overtly life-threatening, and in many cases (e.g. intestinal helminthiasis and schistosomiasis), not overtly symptomatic especially in the early stages of infection. They are therefore often neglected not only by the policy makers, but also by the very rural people who are most affected.

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• Figure 1. 

  Distribution of NTDs in Africa (modified according to Figure 1 in Ref 4) and countries with integrated NTD control programmes in sub-Saharan Africa. Those currently covered by the integrated NTD control programmes assisted by the Schistosomiasis Control Initiative and other organizations are indicated. Zambia was included in SCI schistosomiasis and STH control programme but due to funding the programme is currently interrupted. The NTD control programme in southern Sudan is not indicated in the map.

Contrary to this perception of NTDs as being mostly asymptomatic except for some unfortunate individuals, these diseases are in fact the cause of important chronic health problems in sub-Saharan Africa. They cause blindness (trachoma and onchocerciasis) and disfigurement (lymphatic filariasis), and are often life-threatening at a later stage of the disease (schistosomiasis).⁸, ⁹, ¹⁰, ¹¹ They are also related to various clinical complications such as anaemia, and malnutrition due to hookworm infections, ascariasis, trichuriasis and schistosomiasis,¹², ¹³, ¹⁴ and are among the top 10 causes of life-years (DALYs) lost due to long term disability and premature death worldwide.²

Among the NTDs, seven (ascariasis, hookworm infections, lymphatic filariasis, onchocerciasis, schistosomiasis, trichuriasis, and trachoma) are preventable by simple annual oral drug treatment with albendazole, ivermectin, mebendazole, praziquantel, or azithromycin.¹⁵ In the case of lymphatic filariasis, elimination is possible after seven years of annual treatment.¹⁶, ¹⁷ Of these drugs, all except for praziquantel are currently donated in whole or in part by pharmaceutical companies, while praziquantel and albendazole (which is only partially donated) can be bought at a relatively low cost.¹⁸

Prior to the millennium, sub-Saharan Africa could boast only a few control programmes or small-scale projects on individual NTDs usually supported by international organisations or partnerships. The most successful has been the Onchocerciasis Control Programme which virtually eliminated river blindness from 15 countries by insecticide use initially and subsequently through ivermectin (Mectizan, Merck) delivery. It was followed by the African Programme for Onchocerciasis Control (APOC) which has been responsible for delivering over 90 million treatments annually for onchocerciasis in 19 participating countries.¹⁹ As part of the Global Alliance to Eliminate Lymphatic Filariasis (GAELF) programme, mass drug administration has been conducted since 2000 in 11 countries in sub-Saharan Africa.²⁰ Similarly, the Schistosomiasis Control Initiative (SCI) has delivered over 40 million treatments against schistosomiasis and many more against intestinal helminths in six countries.²¹ SCI thus implemented integrated national control programmes against schistosomiasis and soil-transmitted helminthiasis (STH), including hookworm infections, ascariasis and trichuriasis. The International Trachoma Initiative (ITI) has delivered over 100 million doses of azithromycin (Zithromax, Pfizer) since 2000 in 11 countries to push towards elimination of trachoma as a leading cause of preventable blindness.²² Since 2006 there has been a growing movement towards greater integration of NTD control from WHO, the Gates Foundation and the United States Agency for International Development (USAID). SCI, ITI, APOC and GAELF have embraced this concept as have several country's Ministries of Health.²³, ²⁴

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2. Current status of integrated NTD control programmes by preventive chemotherapy in sub-Saharan Africa 

Each individual programme or project has proven success in its own limited areas or territories. To ‘scale-up’ and expand each success to achieve greater coverage and to reduce the overall operational costs, an integrated ‘rapid impact’ package has now been proposed at an average cost of $0.50 per person per year. This is possible because some drugs are donated, leaving the cost of delivery, training and monitoring plus the purchase of praziquantel where required all that is needed for the treatment of schistosomiasis, STH, lymphatic filariasis, trachoma and onchocerciasis. WHO has recently published a guideline for the use of anthelminthic drugs in preventative control interventions.²⁵ The growing successes in each control programme on individual NTDs has increased awareness of these diseases significantly within the international community and demonstrated the feasibility of an integrated control strategy for NTDs. However more funds need to be committed to integrated control of NTDs from international governments and organisations, with the total requirement for sub-Saharan Africa estimated at between $1 billion to $2 billion over a seven year period. This is but a fraction (<5%) of the sum already earmarked for the ‘big three diseases’.⁷

To date some funds have been committed by the Bill & Melinda Gates Foundation (for advocacy), the USAID (up to $100 million, with the likelihood of more in years to come), the Geneva Global ($8.9 million), the British Government (up to £50 million pledged for several NTDs) and other donors. The aforementioned partners are currently assisting 10 countries (Burkina Faso, Burundi, Ghana, Mali, Niger, Rwanda, Sierra Leone, Southern Sudan, Tanzania, and Uganda) in sub-Saharan Africa to implement their national programmes using integrated NTD control (Figure 1). Emphasis is on using the ‘rapid impact’ package of integrated drug delivery according to WHO guidelines. The funds available are not yet sufficient for these countries to scale up completely, but compared to just six years ago (2003) progress has been phenomenal. Approximately 40 million people in these countries have so far received integrated treatment. However, the purpose of this paper is to highlight just how many people do not have access to the drugs which could eliminate their current chronic suffering and save them from terrible disability and death in later life.

As shown in Figure 1, most of the countries in sub-Saharan Africa are still in need of support, and hundreds of millions of people, in particular children, are suffering from at least one NTD which remains untreated. National control programmes are not yet underway for Nigeria (except for two states where the Carter Center are assisting implementation) and the Democratic Republic of Congo, the two African countries with the highest NTD prevalence and disease burden.⁵ NTD endemic distribution does not recognise national borders, and thus because cross-border movement of populations, often on a large scale, is very common, the effect of a successful NTD control programme in one country may be offset by incoming populations from neighbouring countries in which there are no NTD control programmes. Concerted action across the whole of the sub-Saharan region is vitally important in order to gain the full benefit of the integrated NTD control programmes and prevent erosion of the gains already made. There is a need for expansion of integrated NTD control programmes to those countries currently not yet covered.

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3. Estimation of the target population and the needs for intervention 

In 44 countries in sub-Saharan Africa, there is an estimated total population of approximately 785 million according to WHO 2006 data (Table 1).²⁶ Data presented in Figure 1, suggests that all these countries harbour at least two NTDs, and most of these countries have four or more of the seven most common NTDs. Therefore, after excluding the urban populations of the various national capital cities, we suggest that to effectively cover all these countries with an integrated NTD control programme, 590 million rural people in total will need to be targeted, including just over 300 million children (<15 years old). Because some countries are currently implementing an integrated national NTD control programme as indicated in Table 1, we estimate that there are over 400 million people including over 200 million children in sub-Saharan Africa still in need of treatment. Using the estimated average cost of $0.50 per person per year, therefore, an extra $200+ million per year will be needed to implement the proposed integrated NTD control programmes in the rural populations in the remaining countries in sub-Saharan Africa, a total of just over $1 billion for a 5–7 year programme.², ¹⁵, ²⁷

Table 1. Estimated target population and cost for one year control package by country in sub-Saharan Africa.

Note: Total population for each country was the predicted population for 2006 according to the World Health Organization data (Ref 26). A proportion of 40% of total population was used to calculate the under 15 population. Target population was calculated using a proportion of 75% of total population excluding those too young, too old or too sick to be treated and those in the capital cities.

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4. Mozambique as an example 

Mozambique is one of the countries ready for an immediate fast start if funding could be identified for an integrated NTD control programme. With assistance from WHO, SCI and GAELF, the Ministry of Health has conducted epidemiological mapping of six out of seven NTDs included in the ‘rapid impact’ package (Figure 2).²⁸ The national surveys revealed the extensive distribution of these NTDs in the country, and the Ministry of Health with support from SCI have prepared a national NTD control plan, for which there is a need for immediate support to start progressive expansion of the national integrated NTD control programme.

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• Figure 2. 

  Geographical distribution of Schistosoma haematobium (A), S. mansoni (B), STH (C) and lymphatic filariasis (D) in Mozambique.

Urinary schistosomiasis (caused by Schistosoma haematobium) is widely distributed across the country, with prevalence of over 50% in more than half of the districts, particularly in the northern half of the country (Figure 2a). There are some foci of intestinal schistosomiasis (caused by Schistosoma mansoni) in the country, but with relatively low prevalence (Figure 2b). STH are also widely distributed across the country (Figure 2c). Lymphatic filariasis is prevalent mainly in the north (Figure 2d) (data from the Ministry of Health of Mozambique). A recent WHO survey concluded that onchocerciasis is hypo-endemic in Mozambique (Dr Olga Amiel, Ministry of Health of Mozambique, personal communication). A mass treatment for onchocerciasis is not warranted, but case treatment is still necessary. Little information is available on trachoma distribution in Mozambique, however, a survey in 2002 in three districts in Manica province (central Mozambique) showed that there was a 39% infection with follicular trachomatous inflammation (TF) and intense trachomatous inflammation (TI) in children, and a 4% infection of trichiasis in older age groups (>40 years old), particularly in women.²⁹

Based on the epidemiological data for each NTD and the size of population in each district, the treatment target for each NTD is estimated according to the treatment strategy for each NTD in WHO guidelines (Table 2). For implementation of an integrated NTD national control programme, an estimated $5 million per year is needed.

Table 2. Estimated treatment target for each NTD in Mozambique.

Population			Estimated Treatment Targets
Total	0-14 years	5-14 years	Schistosomiasis		STH		Lymphatic Filariasis	Trachoma		Onchocerciasis
			5-14 yrs	15 yrs & above (if p≥50%)	0-14 yrs (p<50%)	0-14 yrs (p≥50%)	Total pop (p≥1%)	0-4 yrs	≥5 yrs	No CDTI
21m	9m	5.46m	5.46m	5.6m	5m	4m	11.7m	3.5m	16.8m	?

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5. Additional support for implementing countries 

In countries that are currently implementing integrated NTD control programmes as mentioned above, there is also a need for additional support for continued expansion of the programme coverage within the country, e.g. Burkina Faso, Ghana, Mali, Niger, Sierra Leone, Tanzania and Uganda. Except for Tanzania, each of those currently receives some support from the USAID NTD programme, but need more funding to complete the coverage. In addition, each country has different needs. Ghana is implementing an NTD control programme supported by the USAID funds; however, the funds only allow the programme to cover five out of a total of 10 regions in the country. Using schistosomiasis as an example, epidemiological mapping, with SCI assistance, showed that schistosomiasis is distributed throughout the country, particularly along the north border and in the southern half of the country (Figure 3a) (Biritwum NK et al. unpublished data). As indicated in Figure 3b, the densely populated regions in the middle-south and the east, particularly around Lake Volta, are not covered by the programme. An estimated 3.2 million school age children in these regions (from a total of 4.9 million in the country) are therefore not yet treated. In order to expand the programme into these regions, about $1.5 million is needed each year. Similar needs can be demonstrated for each of the current countries with integrated NTD control. The partners within the Global Network for NTD Control are assisting with fund raising for countries already implementing their integrated NTD control programmes, but also countries still in need of support in developing their national NTD control plan.⁷

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• Figure 3. 

  Distribution of schistosomiasis (A) and coverage of the NTD control programme (B) in Ghana.

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6. Starting a national integrated NTD control programme 

The cost effectiveness of an NTD control programme in sub-Saharan African countries has now been proven. The demand for such control programmes in other countries is growing, with more and more countries joining the queue for support, although some are more ready than others for an immediate start. In order to start a national integrated NTD control programme, the following important steps need to be taken. Firstly, the national programme needs the support of the central government because political will from the national leaders is vital for a successful implementation of such a programme. Secondly, a national team dedicated for NTD control should be assembled, including a full time National Coordinator and experts in each of the endemic diseases. The preliminary preparatory work for mapping could be supported by WHO and other international groups. In most of sub-Saharan Africa, the distribution data of the NTDs is based on scattered epidemiological data. As soon as a decision is made to prepare a national plan, a more evidence-based knowledge of the distribution of NTDs in the country needs to be collected so that a detailed map and treatment strategy can be developed. The resulting map of NTD burden in the country should encourage political action by the national leaders and preparation of a national NTD control plan. Finally with a prepared national plan, the funding requirements can be calculated more accurately.

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7. Ownership of the programme and concerted action in implementation 

For a successful control programme, it is also vitally important to ensure that the ownership of the programme lies with the country and its people. Implementation of the programme should be led and coordinated by the Ministry of Health. Community involvement in the programme is as important as the political support to ensure the coverage of treatment in targeted population.³⁰ The communities involved in the programme are not only the recipients, but also the donors in their time and support. With the NTDs becoming ‘less neglected’, more international organisations are entering the NTD control field. All the international organisations working on NTDs within the country must collaborate under the umbrella of integrated action led by the Ministry of Health, so that the available resources can be utilised in an effective and integrated manner to avoid repetition and waste.

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8. Prospect for a full-scale implementation against NTDs in sub-Saharan Africa 

Since 2002, there has been growing recognition of the importance of NTDs, and more funds have been committed to control of these diseases. However, it is not enough, and existing programmes which have funding for only a few years do need to have their funding guaranteed so that the control programmes can be more sustainable. The Bill & Melinda Gates Foundation has so far committed approximately $100 million for NTD advocacy and control. The US Government in 2006 committed $100 million to an NTD control project based on Mass Drug Administration, and a further $250 million may be committed in the future. The British Government also earmarked £50 million for NTDs including guinea worm control over the next five years. Another international philanthropic organisation to have provided funds is Geneva Global which has donated funds for a three year control programme in both Rwanda and Burundi. These funds in total however are less than a quarter of the continent's needs.

There is therefore a requirement for more donor countries and foundations to support the NTD cause, and a need to expand the current mandate of the Global Funds for AIDS, TB and Malaria to provide coverage for NTD control or elimination. What a difference to 500 million lives just over $1 billion over five to seven years would make.

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Funding 

Schistosomiasis Control Initiative receives support from the Bill & Melinda Gates Foundation, the United States Agency for International Development, the Geneva Global and other donors.

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Conflicts of interest 

None declared.

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Ethical approval 

Not required.

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Author's Contributions 

All authors have undertaken all the duties of authorship. Alan Fenwick is guarantor of the paper.

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Acknowledgements 

The authors acknowledge the great help received from our colleagues Dr. O. Amiel, Dr G. Augusto and Dr. N. Biritwum in Mozambique and Ghana respectively, and we thank Peter Hotez for his comments on the paper. This work was partly funded by the USAID funded NTD control program.

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