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Chapter 1.3. Neglected Diseases

Authors: 

Md. Murad Hossain, Maria E. Sarmiento, Armando Acosta, Mohd Nor Norazmi

Art work
Title: 
Malaria-patients
Most patients in poor countries are treated without 
access to laboratory tests
This hungry child, 
hurts me like a great thorn
Miguel Hernández
The child of the ploug

Introduction

Neglected diseases, often termed neglected tropical diseases (NTDs), are endemic in 149 countries, affect over one billion of the world’s poorest people, claim an estimated 534,000 lives annually, and cause a disease burden of 57 million disability-adjusted life years (DALYs) [1-3]. Although billions of people are still affected by NTDs, considerable progress has been made towards controlling and eliminating them. According to the third World Health Organization (WHO) report on NTDs published in 2015, over 74 countries worldwide are ready to implement national NTD master plans, six countries have eliminated lymphatic filariasis, the incidence of human African trypanosomiasis has been reduced by 90% in African countries, and 27 countries have achieved the WHO target of 75% treatment coverage of school-age children to prevent soil-transmitted helminthiases by 2014 [1].

In 2011, the WHO Strategic and Technical Advisory Group (STAG) for NTDs adopted a roadmap named “Accelerating work to overcome the global impact of neglected tropical diseases” for the control, elimination, and eradication of NTDs. In this roadmap, the WHO has recommended five strategies for the prevention and control of NTDs: preventive chemotherapy, intensified case management, control of disease vectors, provision of clean water, and sanitation and veterinary public health measures [4]. Preventive chemotherapy with community-based mass drug administration plays a central role in the prevention and control of NTDs in endemic areas. For many NTDs, low-cost, safe, and effective treatments are available; however, they are often only accessible to people living in endemic areas and face a high risk of infection. Some other NTDs require complex diagnosis and expensive treatment. Therefore, adopting preventive measures such as combined preventive chemotherapy, increased access to clean water, improved sanitation, reduction of disease transmission, and execution of integrated control measures might play a crucial role in the confinement of these diseases.

The WHO roadmap of 2011 has set numerous targets and milestones for the eradication, elimination, and control of NTDs by 2015 and 2020 [4]. In 2013, the 66th World Health Assembly adopted resolution WHA66.12, which calls for intensified, integrated measures and planned investments to improve the health and social wellbeing of people affected by NTDs. The WHO is working with member states to ensure the implementation of the 2011 roadmap and the WHA66.12 resolution. In April 2015, the 8th meeting of the STAG for NTDs took place, and the agenda focused on the progress in achieving the WHO’s 2011 roadmap targets and increased the domestic investment targets for the control, elimination, and eradication of NTDs.  

Neglected diseases

Neglected diseases are a group of infectious, chronic, and debilitating disorders that are endemic to populations in low-income settings in tropical and subtropical countries. They are caused by bacterial, protozoal, helminthic, ectoparasitic, fungal, and viral agents, and are mostly prevalent in the tropics and subtropics. Such diseases remain truly neglected, and are therefore often termed NTDs.

NTDs are closely associated with poverty and exert negative effects on social-ecological systems. They have emerged as a severe health burden on the world’s poorest economic regions in Africa and Asia. NTDs typically affect the poorest people, particularly those living in areas with inadequate sanitation, unsafe drinking water, substandard housing, and little or no access to healthcare. These diseases cause an estimated 0.5–1 million deaths per annum, which ranks them as a higher global disease burden than HIV/AIDS. Moreover, the co-incidence of NTDs with HIV/AIDS and tuberculosis can make these diseases more lethal. At present, effective therapeutic drugs for some NTDs do exist; but, ironically, these drugs are not universally available to the poor people in developing areas who suffer from NTDs the most.

List of neglected diseases and the causative pathogen

There has been some discussion among the WHO, the Centers for Disease Control and Prevention (CDC, USA), and infectious disease experts as to which diseases should be classified as NTDs. Feasey et al. (2010) listed 13 NTDs, namely ascariasis, Buruli ulcer, Chagas disease, dracunculiasis, hookworm infection, human African trypanosomiasis, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, schistosomiasis, trachoma, and trichuriasis [5]. Another NTD expert, Fenwick (2012), included 12 of the diseases mentioned above in his list of NTDs, but excluded hookworm infection [6]. The WHO recognized 17 diseases as NTDs: African trypanosomiasis, Buruli ulcer, Chagas disease, cysticercosis and taeniasis, dengue fever, dracunculiasis, echinococcosis, leishmaniasis, leprosy, lymphatic filariasis, onchocerciasis, rabies, snakebite, schistosomiasis, soil-transmitted helminthiasis, trachoma, and yaws [7].

However, over the course of time, the list of NTDs has been greatly expanded and currently comprises over 40 diseases [8]. These NTDs result mainly from four different causative pathogens: bacteria, protozoa, helminths, and viruses. In addition to these, a few NTDs are also caused by fungal or ectoparasitic infections. Table 1 presents the causative agent(s) and the endemic areas of these potential NTDs [3].

Table 1. List of neglected tropical diseases (NTDs), their causative agents, and the potential endemic areas of these NTDs.

Why neglected diseases are called neglected?

Neglected diseases are said to be neglected because they are often overlooked by the country’s public health programs, drug developers, government officials involved in drug access, and by the media. Why do neglected diseases remain neglected? There are many reasons. One explanation is the lack of visible danger because neglected diseases do not usually cause dramatic outbreaks or kill large numbers of people over a short period. Instead, they usually take their toll over a longer period of time, leading to crippling deformities, severe disabilities, and/or a relatively slow death [9]. Neglected diseases do not receive high priority for treatment or prevention because they typically affect the poorest people in tropical areas and do not affect those who live in developed countries. Private pharmaceutical companies usually focus on profit and are typically not very interested in investing in the development of treatment tools for diseases that persist in developed countries. Such companies cannot recover the cost of developing and producing drugs/treatments for the NTDs as the consumers are mainly the world’s poorest people. The most important reason may be that there is too much emphasis on the “big three” diseases: malaria, tuberculosis, and HIV/AIDS. The “big three” constitute a major global health burden, causing high mortality and morbidity rates and accounting for several million deaths every year.

The “big three” are also responsible for millions of DALYs that cumulatively have a massive negative impact on the social and economic development of the most severely affected countries, which in turn exacerbates poverty [10, 11]. Owing to their devastating effect, the majority of funding is spent on developing new tools for controlling, preventing, and eventually eliminating the “big three.”

Other reasons for the neglect of certain diseases could be the scarcity of data regarding local and global burden estimates, inadequate political will, weak leadership, and a lack of lobbying on behalf of the people who are most severely affected by them. Insufficient financial support for control and prevention could also be responsible [12, 13].

Global burden of neglected tropical diseases

The Global Burden of Disease Study 2010 (GBD 2010) and its related articles attempted to comprehensively quantify the burden of almost 300 diseases, including NTDs [14]. The GBD 2010 introduced the DALY metric to assess and compare the relative impact of a number of diseases both locally and globally [15]. The DALY values are the summation of two components: years of life lost owing to premature mortality (YLLs) and years lived with disability (YLDs) [14]. Therefore, the DALY estimates represent a measure of the burden caused by NTD infections. Table 2 presents estimated DALYs caused by the major NTDs. Recent studies suggest that most NTDs are disablers rather than killers. Therefore, the DALYs for many NTDs (such as hookworm disease and the food-borne trematodiases schistosomiasis, intestinal nematode infections, trachoma, cysticercosis, and onchocerciasis) result from YLDs (i.e., disability, not deaths).

Table 2. Estimated global burden (in DALYs, YLDs and YLLs) of the NTDs from the Global Burden of Disease Study 2010.

Intestinal nematode infections were the most severe NTDs considering the DALY estimates in the GBD 2010. Among intestinal nematode infections, hookworm disease was estimated to have the largest YLDs, which accounted for 62% of the DALYs. The huge contribution made by hookworm disease to the YLDs caused by nematodes is due to moderate and severe anemia across several different populations, including children and pregnant women [16, 17].

Schistosomiasis is another important NTD that results in chronic pain, inflammation, exercise intolerance, and malnutrition, among other morbid sequelae. In certain scenarios, schistosomiasis generates higher number of DALYs than malaria or other better-known conditions [18]. A recent study showed a link between female urogenital schistosomiasis and the risk of acquiring HIV/AIDS [19]. Trachoma and onchocerciasis are the major NTDs linked to blindness. Trachoma affects more than 40 million people in over 50 countries, and over 8 million people are at immediate risk of irreversible blindness [4]. The food-borne trematodiases cysticercosis and echinococcosis might be considered globally important pathogens of disability. Two other key food-borne trematodiases, clonorchiasis and opisthorchiasis, have been shown to be associated with cholangiocarcinoma in Southeast Asia [20, 21]. Cysticercosis is involved in causing epilepsy, severe chronic headaches and hydrocephalus, depressive disorders, stroke, gliomas, and other neurological sequelae [22].

NTDs such as dengue, rabies, and African trypanosomiasis are considered killer NTDs, and practically no disability is associated with the nonlethal effects of these diseases. However, according to the 2011 roadmap, dengue fever affects millions of people worldwide. In 2010, dengue fever was reported in all six WHO regions, and indigenous outbreaks were reported for the first time in Europe. Dog-mediated rabies causes the death of nearly 55,000 people every year in Africa and Asia. More than 14 million people worldwide receive post-exposure prophylaxis following bites from suspected rabid animals [4].

It is argued that the collective global burden of NTDs is higher than that of malaria and tuberculosis, and is close to that of HIV/AIDS. Technical reports from the WHO and the World Health Report 2004 Annex Table 3 show that the collective global burden of the initial set of the 13 most important NTDs (56.6 million DALYs), as recognized by the WHO, is higher than that of tuberculosis (34.7 million DALYs) and malaria (46.5 million DALYs), which is a strong argument for the integrated control of NTDs [23]. According to the GBD 2010, the collective global burden for NTDs is estimated to be almost 48 million DALYs, which is comparable to tuberculosis (49 million), and is almost half those of malaria (83 million DALYs) and HIV/AIDS (82 million DALYs) [24]. However, it is worth mentioning that substantial uncertainties and limitations are associated with the estimation of global burden, which has proved to be particularly challenging with regard to NTDs.

Although the global burden of diseases has been measured in terms of DALYs, they do have some shortcomings. DALYs only take into account the direct effects of NTDs on health, and do not consider their detrimental economic impact on school attendance and child development, agriculture (especially from zoonotic NTDs), and overall economic productivity [12, 25]. They do not take into consideration the direct costs of treatment, surveillance, and prevention measures. Moreover, many NTDs are associated with social stigma and its knock-on effects for family and community members [26, 27], and for loss of tourism [28] and health system overload (e.g., during dengue fever outbreaks) are not reflected in the DALYs. Ultimately, NTD control and elimination efforts can have social and economic benefits not necessarily reflected in DALY metrics, especially among the most affected poor communities.

Interventions to prevent NTDs

In the “Roadmap 2011” to overcome the global impact of NTDs approved by the STAG for NTDs, the WHO adopted five strategies for the prevention, control, elimination, and eradication of NTDs [4].

Preventive chemotherapy

Preventive chemotherapy intends to optimize the large-scale use of safe, single-dose medicines that can effectively reduce the extensive morbidity associated with four helminthiases (lymphatic filariasis, onchocerciasis, schistosomiasis, and soil-transmitted helminthiases). Moreover, the large-scale administration of azithromycin, a key component of the SAFE (Surgery, Antibiotics, Facial cleanliness and Environmental improvement) strategy against trachoma, is amenable to close coordination (and, in future, possibly co-administration) with interventions targeted at helminthiases. Since 2001, the WHO has promoted preventive chemotherapy as a potential intervention to significantly reduce the morbidity caused by five widely distributed NTDs (lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiases, and trachoma). At the end of 2009, 705 million people suffering from these five NTDs were not receiving preventive chemotherapy.

Preventive chemotherapy with high coverage will reduce morbidity and halt the recurrence of the five targeted NTDs mentioned above, which will fulfill the WHO’s goals of eliminating those NTDs by 2020. Some intermediate milestones for their elimination can be achieved by 2015. These objectives depend on two critical assumptions: (1) that solutions be found to make praziquantel widely available along with the other donated medicines in the preventive chemotherapy package, and (2) that funding for implementation accompanies the scaling-up of interventions, through sustained commitment of international donors and enhanced in-country support by the health and education sectors.

Intensified case-detection and case management

Intensified case detection and management intervention targets the prevention and control of NTDs in those who have no available medicines for appropriate preventive chemotherapy. These interventions provide care for infected people and for those who are at risk of infection. The key processes are: (a) making the diagnosis as early as possible, (b) providing treatment to reduce infection and morbidity, and (c) managing complications. Under the intensified case management strategy, the WHO focuses on the prevention and control of Chagas disease, Buruli ulcer, leishmaniasis, human African trypanosomiasis, leprosy, and yaws. The new focus on better access to specialized care through improved case detection and decentralized clinical management aims to prevent mortality, reduce morbidity, and interrupt transmission. It is important to highlight the relevance for this kind of intervention,  of the availability of suitable diagnostic methods adapted to the conditions of the areas where NTDs are endemic.

Vector and intermediate host control

Vectors, and the intermediate control of their hosts, constitute an important cross-cutting intervention that aims to enhance the impact of preventive chemotherapy and intensified disease management. Almost all NTDs involve transmission by vectors (insects) or intermediate hosts (such as aquatic snails). Therefore, the control of vectors and intermediate hosts is crucial for the prevention of the transmission of NTDs. Vector control is particularly important for controlling dengue fever and Chagas disease, and for preventing some forms of leishmaniasis. Vector control intervention can play a major role in the elimination phase of diseases such as lymphatic filariasis and schistosomiasis.

The WHO is implementing vector control through its integrated vector management (IVM) approach, which is a combination of different intersectoral interventions aimed at improving the efficiency, ecological soundness, and sustainability of disease control measures against vector-borne NTDs, including the sound management of public health pesticides.

Veterinary public health at the human–animal interface

Veterinary public health at the human–animal interface implements those actions that are essential to prevent, control, and eliminate suffering and economic loss caused by neglected zoonotic diseases (NZDs) in both humans and animals. Veterinary public health deals with the health of people as well as that of animals. An integrated human and animal health program will be effective in the prevention, control, and elimination of a number of NZDs (such as human-dog-mediated rabies, cystic and alveolar echinococcosis, fascioliasis, and foodborne trematodiases) and NTDs with a zoonotic component (including zoonotic trypanosomiasis, and visceral and cutaneous forms of zoonotic leishmaniasis).

Provision of safe water, sanitation and hygiene

According to a United Nations estimation, 900 million people have no access to safe drinking water and 2,500 million live without appropriate sanitation. The targets of the Millennium Development Goal 7 are safe water and improved sanitation and hygiene, especially in the WHO’s African and Southeast Asian regions.

If the current goals of “access to safe water, improved sanitation, and hygienic life styles” are not achieved, many NTDs and other communicable diseases cannot be eradicated.

Eradication, elimination and control of NTDs: Target 2015 and 2020

In the roadmap approved in 2011 for “Accelerating work to overcome the global impact of neglected tropical diseases,” the WHO set important targets and milestones for the eradication, elimination, and control of NTDs.

Eradication

Of the 17 NTDs, the WHO currently aims to globally eradicate two NTDs: dracunculiasis (guinea-worm disease) by 2015 and endemic treponematoses (yaws) by 2020.

Dracunculiasis (guinea-worm disease)

A dracunculiasis eradication campaign was started in the early 1980s. Since then, there has been a significant decline (more than 99%) in the annual incidence of the disease, from 892,055 cases in 1989 to 1,058 in 2011. Several initiatives, such as active searches for dracunculiasis infection in endemic villages, rapid case-containment, enhanced surveillance, and access to improved drinking water, have helped to drastically reduce the prevalence of dracunculiasis infection. Dracunculiasis is now on the verge of eradication.

The WHO roadmap for overcoming the impact of NTDs announced in 2011 set a target of global eradication of dracunculiasis infection by 2015. To fulfill the WHO’s goal (interruption of transmission by 2015), heightened surveillance should be enforced and the momentum should be maintained, even when a country or a particular area of an endemic region has interrupted transmission completely, until global eradication has been achieved.

Endemic treponematoses (yaws)

Endemic treponematoses (yaws) infection is the only other NTD that is targeted for global eradication by 2020. Yaws mainly affects children. According to the estimation by the WHO, 460,000 infectious cases were reported in 1995, mostly in west and central Africa (400,000 cases), Southeast Asia (50,000), and other tropical regions. In 2007, the WHO launched a global program for the elimination of yaws and other endemic treponematoses. Since then, yaws has been eliminated from many endemic countries. In India, no new cases of infection have been reported since 2004. Two endemic countries in Southeast Asia, Indonesia and Timor-Leste, set a goal of yaws elimination by 2012. Currently, three countries (Papua New Guinea, the Solomon Islands, and Vanuatu) in the Western Pacific Region remain endemic.

The WHO’s goal is to eliminate yaws from the Western Pacific and Southeast Asia regions by 2015, and from Africa by 2020, which will lead to global eradication of the disease.

Elimination

Some of the NTDs are aimed to eliminate their transmission or to reduce their burden regionally or globally by 2015, while some others are targeted for global elimination by 2020.

Dengue

Millions of people are affected by dengue fever. Dengue is mostly prevalent in poor populations of crowded urban and peri-urban areas. However, it also affects affluent neighborhoods in tropical and sub-tropical countries. In 2010, the incidence of dengue fever was recorded in all six WHO regions, and indigenous outbreaks were reported for the first time in Europe. The principal vectors, Aedes aegypti and Aedes albopictus, are gradually spreading in Europe and Africa. Intensive efforts to control the spread of the vectors and to apply sustainable control measures are required to stop the tide by 2015. The current aim is to reduce the rate of morbidity by at least 25% and mortality by 50% by 2020 by implementing an integrated vector management approach.

Human dog-mediated rabies

Domestic dogs are the major source of human rabies. Children are the usual victims, and between 30 and 50% of human cases of dog-mediated rabies (and therefore rabies-related human deaths) occur in children aged below 15 years. About 55,000 people die from dog-mediated rabies every year in Africa and Asia. More than 14 million people worldwide receive post-exposure prophylaxis following bites from suspected rabid animals. Therefore, controlling the disease in dogs is necessary for its elimination. The WHO is coordinating pilot studies in the Philippines, South Africa, and the United Republic of Tanzania for the immunization of dogs to prevent dog-mediated rabies in humans.

A mass dog vaccination program in Latin American countries that was initiated in 1983 has stopped the progress of dog-to-dog transmission in most countries. Elimination of human dog-mediated rabies and dog-to-dog transmission is achievable by 2015 in all endemic areas in Latin America, and in all affected countries in WHO’s Southeast Asia and Western Pacific regions by 2020. Intensified control and enhanced surveillance should lead to a 50% reduction in the number of human rabies deaths in these two regions by 2015.

Buruli ulcer

A combined antibiotic treatment with rifampicin and streptomycin, recommended by the WHO in 2004, has radically changed the prospects for Buruli ulcer treatment. Almost 36,000 people benefited from this combined treatment during 2004–2010, 50% of whom were children aged less than 15 years. Combined antibiotic treatment has reduced the need for surgery by almost 50%. The WHO aims to develop oral antibiotic therapy for full incorporation into control and treatment by 2015. The WHO also aims to cure 70% of all cases with antibiotics in all endemic countries by 2020.

Cysticercosis

Cysticercosis is caused by the development of Taenia solium cysticerci in human tissues. Cysticercosis may also develop in the central nervous system, when it is called neurocysticercosis. The infection is prevalent in all six WHO regions. Currently, China is the only country that is running a national surveillance and control program for cysticercosis. Elimination of cysticercosis requires improved sanitation, chemotherapy for humans, pig husbandry and marketing practices, and pig treatment combined with improved vaccination. The WHO aims to launch a sustainable strategy for the control and elimination of T. solium taeniasis/cysticercosis by 2015, and to scale-up interventions in selected countries in Africa, Asia, and Latin America by 2020.

Chagas Disease

The WHO is leading a global awareness campaign to interrupt global transmission of Chagas disease through blood transfusion and organ transplantation. Over the years, sustained vector control has become successful and has significantly reduced the transmission of Chagas disease in Latin America. The WHO has set a target for the elimination of the disease in Latin America through interruption of vector transmission via intra-domiciliary infestation by 2015, and via peri-domiciliary infestation by 2020. Interruption of transmission via blood transfusion in Latin America, Europe, and the Western Pacific has also been set as a target to be achieved by 2015. As well as a vector control strategy, the WHO also provided first-line treatment with benznidazole and second-line treatment with nifurtimox in endemic areas during 2007–2010 to achieve the goal of global elimination.

Echinococcosis

Echinococcosis is a globally prevalent zoonotic disease that is caused by the larval stages of the dog tapeworm Echinococcus granulosus. Approximately 200,000 new cases of cystic echinococcosis are diagnosed annually. Elimination of echinococcosis transmission has been achieved in developed countries by adopting interventions such as treating dogs regularly, carrying out strict controls during the slaughter of livestock, destroying infected offal, and public education. However, these interventions may not work in low or middle-income countries, and may require an alternative strategy in addition to traditional interventions.

The WHO is now willing to validate the efficacy of echinococcosis/hydatidosis control strategies in selected countries by 2015 to scale-up interventions in selected countries in North Africa, Central Asia, and Latin America for the control and elimination of the disease as a public health problem by 2020.

Foodborne trematode infections

More than 56 million people worldwide suffer from one or more foodborne trematode infection (e.g., clonorchiasis, fascioliasis, opisthorchiasis, and paragonimiasis). The WHO is working to expand preventive chemotherapy to include foodborne trematode infections, which can be treated with praziquantel or triclabendazole.

The WHO aims to control morbidity associated with foodborne trematodiases in selected countries by 2015 and in all endemic countries by 2020.

Human African trypanosomiasis in selected countries

Human African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei gambiense, which is endemic in 24 countries of west and central Africa, and by T. brucei rhodesiense, which is endemic in 13 countries of eastern and southern Africa. Sleeping sickness is highly prevalent in WHO’s African Region (90% of reported cases) and in the Eastern Mediterranean Region (the remaining 10%). The incidence of new cases was reduced by 75% during 1999–2010.

The WHO has implemented a new strategy for sustaining case detection at the peripheral level in countries with low endemicity and foci. The WHO’s current initiatives aim to enhance wider patient accessibility to eliminate the disease in 80% of foci by 2015, and to achieve 100% elimination of the foci globally by 2020.

Soil-transmitted helminthiases (intestinal worms)

More than 1 billion people are infected with nematodes that cause soil-transmitted helminthiases. Significant progress has been made in controlling these infections over the past 10 years. In 2010, 31% of all preschool and school-aged children in the world at risk of soil-transmitted helminthiases were dewormed. However, the target of bringing 75% of school-aged children under coverage by 2010 was not achieved. The WHO now aims to achieve 75% coverage in all endemic countries by 2020.

Onchocerciasis

An onchocerciasis elimination program is actively working to interrupt transmission in the Latin America region. Elimination of transmission by 2015 seems feasible in Latin America (13 foci in 6 endemic countries: Venezuela, Brazil, Colombia, Ecuador, Guatemala, and Mexico) where approximately 0.5 million people are at risk of onchocerciasis infection.

Yemen adopted a national plan to eliminate onchocerciasis transmission by 2015 through mass distribution of ivermectin and vector control. Onchocerciasis control in Africa is being monitored through the African Programme for Onchocerciasis Control (APOC) and the former Onchocerciasis Control Programme in West Africa (OCP). In Africa, 23 countries (12 APOC countries and 11 ex-OCP countries) out of a total of 31 endemic countries are expected to achieve elimination through surveillance activities and mass drug administration with ivermectin by 2020.

Schistosomiasis

Under the current scheme, the elimination of S. haematobium is reasonable in the countries of the Eastern Mediterranean Region such as Egypt, Libya, Saudi Arabia, and the Syrian Arab Republic by 2015. Continuous surveillance is needed to confirm that the transmission of S. haematobium has ceased in Iran, Jordan, and Morocco. By 2015, the WHO also aims to eliminate S. haematobium infections in the Bolivarian Republic of Venezuela, Saint Lucia, and Suriname, S. japonicum infections in Indonesia, S. mansoni infections in the Caribbean, and S. mekongi infections in the Mekong River basin. It is predicted that S. mansoni and S. japonicum infections will be eliminated in Brazil and the Western Pacific Region, respectively, by 2020. S. mekongi infections have been targeted for elimination from parts of the Western Pacific Region, such as two endemic provinces from each of Cambodia and Lao People’s Democratic Republic, by 2020.

However, the elimination of Schistosomiasis, particularly S. mansoni, from sub-Saharan Africa has not yet been scheduled, even by 2020, primarily due to a lack of sufficient quantities of medicine. Necessary steps should be taken immediately for the elimination of the infection in Africa. A large-scale preventive chemotherapy program has endured for at least 5 years in some African countries including Uganda, Burkina Faso, and Niger. If the necessary medicines (especially praziquantel) can be made available, the elimination of schistosomiasis as a public health problem could be achieved in many African countries by 2020, and globally by 2025 with WHO guidance

Blinding trachoma

More than 40 million people in over 50 countries are affected by trachoma, and over 8 million are at immediate risk of irreversible blindness. The prevalence of trachoma has decreased significantly since 1998 as a result of the implementation of the SAFE strategy. There is an intention to eliminate blinding trachoma globally by 2020. Some countries such as Ghana, Gambia, Iran, Morocco, and Oman may achieve that target, whereas others require support from the WHO to achieve the target within the deadline set by resolution WHA51.11. It was expected that the ultimate intervention goal (UIG) would be attained in 10% of endemic countries by 2013. By 2016, 40% of endemic countries are expected to achieve the UIG and to enter the post-endemic surveillance phase. By 2020, the WHO aims to achieve the UIG in all endemic countries and to be free from blinding trachoma as a public health problem.

Leprosy

Leprosy was endemic in 122 countries. Interestingly, the infection has been successfully eliminated as a public health problem from 119 of those countries (elimination is defined as achieving a prevalence of less than 1 case/10,000 population). The incidence of transmission has been reduced by more than 90% since 1985, primarily because of timely case-finding and multidrug therapy. Transmission is prevalent in a few countries or areas where it was previously highly endemic. By 2020, the WHO aims to eliminate transmission globally through the intervention of prompt case-finding and treatment.

Visceral leishmaniasis in the Indian subcontinent

Regional leishmaniasis control programs and the elimination of visceral leishmaniasis in the Indian subcontinent (mainly in Bangladesh, India, and Nepal) over the past 5 years have strengthened capacity, improved access to medicines, and enhanced surveillance. Leishmaniasis affects people in more than 90 countries, and can be eliminated by early case-finding and prompt treatment. The WHO has set a target of detecting at least 70% of all cutaneous leishmaniasis cases and treating a minimum of 90% of all detected cases in the Eastern Mediterranean Region by 2015. With sustained effort in the Indian subcontinent, 100% case-detection and treatment of visceral leishmaniasis is feasible by 2020, i.e., less than 1 case per 10,000 population at district and subdistrict levels can be achieved.

Lymphatic filariasis

The Global Programme to Eliminate Lymphatic Filariasis is the key to controlling lymphatic filariasis and interrupting transmission through integrated interventions of regular treatment with preventive chemotherapy, vector control, and morbidity management. Despite significant success, the goal of elimination as a public health problem by interrupting transmission remains challenging in the many places where clinical cases persist.

If current levels of intervention are maintained, elimination of transmission can be achieved in all Pacific Islands, excluding Papua New Guinea, by 2015. By 2017, 70% of all 81 endemic countries will have met the criteria for stopping intervention and will have entered the post-intervention surveillance phase. By 2020, 100% of all endemic countries will have been verified as free of transmission or will have begun post-intervention surveillance.

Treatment

Among the five strategies recommended by the WHO for the prevention and control of NTDs, preventive chemotherapy (intervention using drugs) is the best affordable measure. Large-scale, community-based drug intervention has become the key strategy for the developing world where poor people are mostly affected. However, because these are neglected diseases and the people affected are mostly the world’s poorest, little money has been spent on researching and developing drugs to treat these diseases due to a lack of market incentives [29]. Recently, public–private partnerships for drug development have been formed, which have increased funding for research and drug development (30). Affordable and effective drugs for many NTD infections have been developed. However, access to these drugs often remains limited for people living in NTD-endemic areas [30].

For some NTDs, treatments are easy to administer; non-medical personnel (e.g., school teachers) can deliver these drugs to large populations (e.g., all the children in a school) as a public health measure [31]. Albendazole, mebendazole, ivermectin, and praziquantel are highly effective against most NTDs including soil-transmitted helminthiases. Albendazole and mebendazole are recommended as preventive chemotherapy against hookworm infection, ascariasis, trichuriasis, strongyloidiasis, toxocariasis, and mansonellosis (M. perstans). Ivermectin is useful against strongyloidiasis, lymphatic filariasis, mansonellosis (M. perstans, M. streptocerca), and onchocerciasis. Praziquantel is effective against schistosomiasis, paragonimiasis, clonorchiasis, opisthorchiasis, and intestinal fluke infections. Pentamidine is commonly used to treat human African trypanosomiasis, whereas nifurtimox or benznidazole are used for Chagas disease [3]. Co-administration of these drugs is often recommended. For example, ivermectin and albendazole are used in Africa, whereas diethylcarbamazine and albendazole are used in areas outside Africa for the treatment and elimination of lymphatic filariasis [3, 32]. However, the recommended dosages for the treatment of NTDs may vary in typical endemic and non-endemic settings.

Recently, a combination of five drugs known as the “rapid impact package” has shown much promise in the treatment and prevention of five NTDs (i.e., soil-transmitted helminthiasis, schistosomiasis, lymphatic filariasis, onchocerciasis, and trachoma) [33]. These rapid impact packages are exceptionally cost-effective and only need to be taken once per year; moreover, treatment throughout a child’s school years can offer life-long protection. The major advantages of these drugs are that they do not require refrigeration and are safe to take even if the recipient is not infected, which provides a means of mass prevention of NTDs. Hence, preventive chemotherapy has been endorsed by the WHO as the key strategy for the control of morbidity and socio-economic damages.

Prevention and control of NTDs

"The global effort to control and eliminate neglected tropical diseases must be led by the countries themselves,” said Kesetebirhan Admasu, Ethiopia’s Minister of Health, in the meeting of “The Addis Ababa NTD Commitment, 2014”. In the Addis Ababa declaration, Ministers of Health from the participating countries pledged to increase local funding into research and control efforts for national NTD programs. Recently, endemic countries have begun taking responsibility for their national NTD programs; they have started providing new funding and are pursuing innovative approaches to combat NTDs, which is an encouraging sign. In doing so, they are making a significant contribution to overall global coverage rates under the national NTDs programs, and are thereby making great strides toward the elimination of these diseases. The WHO Director of the Department of Control of NTDs has stated that, “sustained political commitment, innovative domestic financing, and greater coordination can bring about game-changing treatments and care to millions of people and improve the prospects of achieving the WHO’s goal of universal health coverage against NTDs.”

The development of effective and cheap drugs that are safe and can be administered by non-professional health personnel has paved the way for preventive chemotherapy [31]. Therefore, mass drug administration in endemic settings has become the best strategy for the prevention and control of NTDs. However, this strategy has several limitations. For example, it is necessary to repeat some interventions once or twice per year for an unknown period of time. In such cases, compliance becomes an issue: many people feel better after an initial treatment and do not necessarily appreciate the necessity of continuing treatment. Preventive chemotherapy is not available for some diseases in endemic countries, and enhanced patient management is required. Drug administration must be carefully monitored because excessive use can result in resistance. Moreover, recurrence of the infection may occur because preventive chemotherapy does not address the root behavioral, ecological, and socio-economic causes. Therefore, consideration should be given to the adoption of preventive measures, such as increased access to clean drinking water, and improved sanitation and hygiene [34-36]. It is also important to step-up the implementation of integrated control measures, with the combination of two or more interventions that are suitable for an endemic setting and are adapted over time, in order to prevent and control NTD infection. A profound knowledge of the demographic, health, and socio-ecological status could help in tailoring suitably integrated control measures for a particular area or country [34].

Conclusions

The “UK Coalition against NTDs: Annual Report 2014–2015” was published on 24th February, 2015. A key message of the report was that although substantial progress has been made towards combatting NTDs, more effort is needed to reach the WHO’s 2020 targets. Although the WHO has recognized 17 NTDs, the number of NTDs has now reached over 40 (caused by various bacterial, fungal, helminth, protozoal, viral, and ectoparasitic infections). Many of these infections can be effectively treated with a short oral drug regimen (e.g., soil-transmitted helminthiasis, including strongyloidiasis), whereas others require extensive and more costly diagnosis (e.g., leishmaniasis, leprosy) that should be improved to make it affordable. Preventive chemotherapy plays a vital role in the elimination and control of NTDs. In endemic settings where there is very limited or no access to preventive chemotherapy, preventive measures including access to safe drinking water, improved sanitation and hygiene, and awareness programs should be implemented.

To achieve the WHO’s 2020 goals, individual countries should assume increased responsibility and provide funding for innovative research that will eventually lead to the development of new improved tools and strategies that can be used to prevent and control NTDs. In the meantime, a number of endemic countries including Bangladesh, The Philippines, and Honduras have already taken on primary responsibility for financing their NTD control programs, which will significantly contribute to the elimination of individual diseases. In fact, global coverage rates (at least with one drug) increased to 43% in 2015 compared with around 35% in 2008 [37].

Therefore, increased participation from endemic countries, the WHO, and other global partners in funding biotechnology and pharmaceutical companies to develop innovative diagnostics adapted to low resource areas and treatment strategies for the control of NTDs is essential for the ultimate eradication of these devastating diseases.

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