Diagnostic testing holds the key to NTD elimination.

"Fit-for-purpose" diagnostic tests have emerged as a prerequisite to achieving global targets for the prevention, control, elimination, and eradication of neglected tropical diseases (NTDs), as highlighted by the World Health Organization's (WHO) new roadmap. There is an urgent need for the development of new tools for those diseases for which no diagnostics currently exist and for improvement of existing diagnostics for the remaining diseases. Yet, efforts to achieve this, and other crosscutting ambitions, are fragmented, and the burden of these 20 debilitating diseases immense. Compounded by the Coronavirus Disease 2019 (COVID-19) pandemic, programmatic interruptions, systemic weaknesses, limited investment, and poor commercial viability undermine global efforts-with a lack of coordination between partners, leading to the duplication and potential waste of scant resources. Recognizing the pivotal role of diagnostic testing and the ambition of WHO, to move forward, we must create an ecosystem that prioritizes country-level action, collaboration, creativity, and commitment to new levels of visibility. Only then can we start to accelerate progress and make new gains that move the world closer to the end of NTDs.

Towards a comprehensive research and development plan to support the control, elimination and eradication of neglected tropical diseases.

To maximise the likelihood of success, global health programmes need repeated, honest appraisal of their own weaknesses, with research undertaken to address any identified gaps. There is still much to be learned to optimise work against neglected tropical diseases. To facilitate that learning, a comprehensive research and development plan is required. Here, we discuss how such a plan might be developed.

The Importance of Failure: How Doing Impact Surveys That Fail Saves Trachoma Programs Money.

Trachoma programs use annual antibiotic mass drug administration (MDA) in evaluation units (EUs) that generally encompass 100,000-250,000 people. After one, three, or five MDA rounds, programs undertake impact surveys. Where impact survey prevalence of trachomatous inflammation-follicular (TF) in 1- to 9-year-olds is ≥ 5%, ≥ 1 additional MDA rounds are recommended before resurvey. Impact survey costs, and the proportion of impact surveys returning TF prevalence ≥ 5% (the failure rate or, less pejoratively, the MDA continuation rate), therefore influence the cost of eliminating trachoma. We modeled, for illustrative EU sizes, the financial cost of undertaking MDA with and without conducting impact surveys. As an example, we retrospectively assessed how conducting impact surveys affected costs in the United Republic of Tanzania for 2017-2018. For EUs containing 100,000 people, the median (interquartile range) cost of continuing MDA without doing impact surveys is USD 28,957 (17,581-36,197) per EU per year, whereas continuing MDA solely where indicated by impact survey results costs USD 17,564 (12,158-21,694). If the mean EU population is 100,000, then continuing MDA without impact surveys becomes advantageous in financial cost terms only when the continuation rate exceeds 71%. For the United Republic of Tanzania in 2017-2018, doing impact surveys saved enough money to provide MDA for > 1,000,000 people. Although trachoma impact surveys have a nontrivial cost, they generally save money, providing EUs have > 50,000 inhabitants, the continuation rate is not excessive, and they generate reliable data. If all EUs pass their impact surveys, then we have waited too long to do them.

Integration of prevention and control measures for female genital schistosomiasis, HIV and cervical cancer.

Female genital schistosomiasis as a result of chronic infection with Schistosoma haematobium (commonly known as bilharzia) continues to be largely ignored by national and global health policy-makers. International attention for large-scale action against the disease focuses on whether it is a risk factor for the transmission of human immunodeficiency virus (HIV). Yet female genital schistosomiasis itself is linked to pain, bleeding and sub- or infertility, leading to social stigma, and is a common issue for women in schistosomiasis-endemic areas in sub-Saharan Africa. The disease should therefore be recognized as another component of a comprehensive health and human rights agenda for women and girls in Africa, alongside HIV and cervical cancer. Each of these three diseases has a targeted and proven preventive intervention: antiretroviral therapy and pre-exposure prophylaxis for HIV; human papilloma virus vaccine for cervical cancer; and praziquantel treatment for female genital schistosomiasis. We discuss how female genital schistosomiasis control can be integrated with HIV and cervical cancer care. Such a programme will be part of a broader framework of sexual and reproductive health and rights, women's empowerment and social justice in Africa. Integrated approaches that join up multiple public health programmes have the potential to expand or create opportunities to reach more girls and women throughout their life course. We outline a pragmatic operational research agenda that has the potential to optimize joint implementation of a package of measures responding to the specific needs of girls and women.

La schistosomiase génitale féminine, résultant d'une infection chronique à Schistosoma haematobium (également connue sous le nom de bilharziose), continue d'être largement ignorée par les responsables des politiques de santé nationales et internationales. Si le monde lui accorde son attention en vue de mener une action à grande échelle contre la maladie, c'est surtout pour déterminer s'il s'agit d'un facteur de risque pour la transmission du virus de l'immunodéficience humaine (VIH). Pourtant, la schistosomiase génitale féminine est associée à des douleurs, des saignements et peut engendrer l'hypofertilité, voire la stérilité. Par conséquent, celles qui en souffrent sont souvent stigmatisées, et le problème est courant dans les régions endémiques d'Afrique subsaharienne. Cette maladie doit donc être considérée comme composante à part entière d'une approche globale de la santé et des droits humains pour les femmes et filles africaines, à l'instar du VIH et du cancer du col de l'utérus. Chacune de ces trois maladies fait l'objet d'une intervention préventive ciblée qui a déjà fait ses preuves: le traitement antirétroviral et la prophylaxie pré-exposition pour le VIH; le vaccin contre le papillomavirus humain pour le cancer du col de l'utérus; et l'administration de praziquantel pour la schistosomiase génitale féminine. Le présent document se penche sur la manière d'intégrer la schistosomiase génitale féminine dans la prise en charge du VIH et du cancer du col de l'utérus. Un tel programme fera partie d'un cadre plus vaste consacré aux droits et à la santé sexuelle et reproductive, à l'émancipation des femmes et à la justice sociale en Afrique. Les approches intégrées qui regroupent plusieurs programmes de santé publique permettent d'élargir des perspectives ou de créer des opportunités visant à atteindre un plus grand nombre de filles et de femmes tout au long de leur vie. Nous exposons les grandes lignes d'un programme de recherches pragmatiques et opérationnelles capable d'optimiser la mise en œuvre conjointe d'une série de mesures qui répondent aux besoins spécifiques des filles et des femmes.

Los responsables de formular las políticas sanitarias nacionales y globales siguen ignorando en gran medida la esquistosomiasis genital femenina como consecuencia de la infección crónica por Schistosoma haematobium (conocida comúnmente como bilharziasis). La atención internacional para adoptar medidas de gran alcance contra la enfermedad se centra en determinar si es un factor de riesgo para la transmisión del virus de la inmunodeficiencia humana (VIH). Sin embargo, la propia esquistosomiasis genital femenina está vinculada al dolor, las hemorragias y la infertilidad o subfertilidad, lo que conduce al estigma social, además de ser un problema común para las mujeres de las áreas en donde la esquistosomiasis es endémica en el África subsahariana. Por consiguiente, la enfermedad debe ser reconocida como otro componente de un programa integral de salud y de derechos humanos para las mujeres y las niñas de África, junto con el VIH y el cáncer de cuello uterino. Cada una de estas tres enfermedades tiene una intervención preventiva específica y comprobada: la terapia antirretroviral y la profilaxis previa a la exposición para el VIH; la vacuna contra el virus del papiloma humano para el cáncer de cuello uterino; y el tratamiento con praziquantel para la esquistosomiasis genital femenina. Se analiza cómo el control de la esquistosomiasis genital femenina se puede integrar con la atención del VIH y el cáncer de cuello uterino. Ese programa formará parte de un marco más amplio de salud y de derechos sexuales y reproductivos, de empoderamiento de la mujer y de justicia social en África. Los enfoques integrados que unen múltiples programas de salud pública tienen el potencial de ampliar o crear oportunidades para llegar a más niñas y mujeres a lo largo de sus vidas. Se describe a grandes rasgos un programa de investigación operacional pragmático que tiene el potencial de optimizar la implementación conjunta de una serie de medidas que respondan a las necesidades específicas de las niñas y de las mujeres.

Reflections on the decade of the neglected tropical diseases.

Neglected tropical diseases (NTDs) are a group of diseases that disproportionately affect the poorest of the poor. While for years attention has focused on single diseases within this group, efforts during the past decade have resulted in their being grouped together to highlight that they are fundamentally diseases of neglected populations. The formation of a World Health Organization department to address these diseases consolidated the efforts of the many stakeholders involved. In the past decade, focus has shifted from the Millennium Development Goals (MDGs), where NTDs are not mentioned, to the Sustainable Development Goals (SDGs), where NTDs are not only mentioned, but clear indicators are provided to measure progress. It has also been a decade where many NTD programmes have scaled up rapidly thanks to work by affected countries through their master plans, the commitment of partners and the unprecedented donations of pharmaceutical manufacturers. This decade has also seen the scaling down of programmes and acknowledgement of the elimination of some diseases in several countries. Given the successes to date, the challenges identified over the past decade and the opportunities of the coming decade, the NTD Programme at the WHO is working with partners and stakeholders to prepare the new NTD roadmap for 2021 to 2030. The focus is on three major paradigm shifts: a change of orientation from process to impact, a change in technical focus from diseases to delivery platforms and a change from an external-based agenda and funding to a more country-led and funded implementation within health systems. This article reviews the past decade and offers a glimpse of what the future might hold for NTDs as a litmus test of SDG achievements.

Transformation of World Health Organization's management practice and workforce to fit the priorities of African countries.

INTRODUCTION: The WHO Regional Office for Africa developed an evidence-based tool, called the Dalberg tool to guide the functional review and restructuring of the workforce and management of the country offices to better fit the health priorities of Member States. METHODS: The Dalberg tool was used in conjunction with a series of consultations and dialogues to review twenty-two countries have undergone the functional review. Results: the "core functions" in WHO country offices (WCOs) were identified. These are health coordination, strengthening of health systems, generation of evidence and strategic information management, and preparedness against health emergencies. RESULTS: In order to standardize country office functions, categorization of countries was undertaken, based on specific criteria, such as health system performance towards Universal Health Coverage (UHC), health emergencies, burden of communicable and non-communicable diseases, subnational presence and national population size. CONCLUSION: Following the functional review, the staff is now better aligned with country and organizational priorities. For example, the functional review has taken into consideration: (i) the ongoing polio transition planning; (ii) the implementation of the WHO emergency programme in countries; (iii) the investment case for strengthening routine immunization in Africa; and (iv) regional flagship programmes, such as adolescent health and UHC. The delivery of the core functions above will require the hiring of additional capacities and expertise in most country offices if deemed fit-for-purpose.

Lymphatic filariasis transmission in Rufiji District, southeastern Tanzania: infection status of the human population and mosquito vectors after twelve rounds of mass drug administration.

BACKGROUND: Control of lymphatic filariasis (LF) in most of the sub-Saharan African countries is based on annual mass drug administration (MDA) using a combination of ivermectin and albendazole. Monitoring the impact of this intervention is crucial for measuring the success of the LF elimination programmes. This study assessed the status of LF infection in Rufiji district, southeastern Tanzania after twelve rounds of MDA. METHODS: Community members aged between 10 and 79 years were examined for Wuchereria bancrofti circulating filarial antigens (CFA) using immunochromatographic test cards (ICTs) and antigen-positive individuals were screened for microfilaraemia. All study participants were examined for clinical manifestation of LF and interviewed for drug uptake during MDA rounds. Filarial mosquito vectors were collected indoor and outdoor and examined for infection with W. bancrofti using a microscope and quantitative real-time polymerase chain reaction (qPCR) techniques. RESULTS: Out of 854 participants tested, nine (1.1%) were positive for CFA and one (0.1%) was found to be microfilaraemic. The prevalence of hydrocele and elephantiasis was 4.8% and 2.9%, respectively. Surveyed drug uptake rates were high, with 70.5% of the respondents reporting having swallowed the drugs in the 2014 MDA round (about seven months before this study). Further, 82.7% of the respondents reported having swallowed the drugs at least once since the inception of MDA programme in 2000. Of the 1054 filarial vectors caught indoors and dissected to detect W. bancrofti infection none was found to be infected. Moreover, analysis by qPCR of 1092 pools of gravid Culex quinquefasciatus collected outdoors resulted in an estimated infection rate of 0.1%. None of the filarial vectors tested with qPCR were found to be infective. CONCLUSION: Analysis of indices of LF infection in the human population and filarial mosquito vectors indicated a substantial decline in the prevalence of LF and other transmission indices, suggesting that local transmission was extremely low if occurring at all in the study areas. We, therefore, recommend a formal transmission assessment survey (TAS) to be conducted in the study areas to make an informed decision on whether Rufiji District satisfied WHO criteria for stopping MDA.

Proceedings of the first African Health Forum: effective partnerships and intersectoral collaborations are critical for attainment of Universal Health Coverage in Africa.

BACKGROUND: Universal Health Coverage (UHC)is central to the health Sustainable Development Goals(SDG). Working towards UHC is a powerful mechanism for achieving the right to health and promoting human development which is a priority area of focus for the World Health Organization WHO. As a result, the WHO Regional Office for Africa convened the first-ever Africa Health Forum, co- hosted by the government of Rwanda in Kigali in June 2017 with the theme "Putting People First: The Road to Universal Health Coverage in Africa". The Forum aimed to strengthen and forge new partnerships, align priorities and galvanize commitment to advance the health agenda in Africa in order to attain UHC and the SDGs. This paper reports the proceedings and conclusions of the forum. METHODS: The forum was attended by over 800 participants. It employed moderated panel and public discussions, and side events with political leaders, policy makers and technicians from ministries of health and finance, United Nations agencies, the private sector, the academia, philanthropic foundations, youth, women and non-governmental organizations drawn from within and outside the Region. CONCLUSIONS: The commitment to achieve UHC was a collective expression of the belief that all people should have access to the health services they need without risk of financial hardship. The attainment of UHC will require a significant paradigm shift, including development of new partnerships especially public-private partnerships in selected areas with limited government resources, intersectoral collaboration to engage in interventions that affect health but are outside the purview of the ministries in charge of health and identification of public health issues where knowledge gaps exist as research priorities. The deliberations of the Forum culminated into a "Call-to-Action" - Putting People First: The Road to Universal Health Coverage in Africa, which pledged a renewed determination for Member States, in partnership with the private Sector, WHO, other UN Agencies and partners to support the attainment of the SDGs and UHC. There was agreement that immediate action was required to implement the call-to-action, and that the African Regional Office of WHO should develop a plan to rapidly operationalize the outcomes of the meeting.

Trends of Plasmodium falciparum prevalence in two communities of Muheza district North-eastern Tanzania: correlation between parasite prevalence, malaria interventions and rainfall in the context of re-emergence of malaria after two decades of progressively declining transmission.

BACKGROUND: Although the recent decline of malaria burden in some African countries has been attributed to a scale-up of interventions, such as bed nets (insecticide-treated bed nets, ITNs/long-lasting insecticidal nets, LLINs), the contribution of other factors to these changes has not been rigorously assessed. This study assessed the trends of Plasmodium falciparum prevalence in Magoda (1992-2017) and Mpapayu (1998-2017) villages of Muheza district, North-eastern Tanzania, in relation to changes in the levels of different interventions and rainfall patterns. METHODS: Individuals aged 0-19 years were recruited in cross-sectional surveys to determine the prevalence of P. falciparum infections in relation to different malaria interventions deployed, particularly bed nets and anti-malarial drugs. Trends and patterns of rainfall in Muheza for 35 years (from 1981 to 2016) were assessed to determine changes in the amount and pattern of rainfall and their possible impacts on P. falciparum prevalence besides of those ascribed to interventions. RESULTS: High prevalence (84-54%) was reported between 1992 and 2000 in Magoda, and 1998 and 2000 in Mpapayu, but it declined sharply from 2001 to 2004 (from 52.0 to 25.0%), followed by a progressive decline between 2008 and 2012 (to ≤ 7% in both villages). However, the prevalence increased significantly from 2013 to 2016 reaching ≥ 20.0% in 2016 (both villages), but declined in the two villages to ≤ 13% in 2017. Overall and age specific P. falciparum prevalence decreased in both villages over the years but with a peak prevalence shifting from children aged 5-9 years to those aged 10-19 years from 2008 onwards. Bed net coverage increased from < 4% in 1998 to > 98% in 2001 and was ≥ 85.0% in 2004 in both villages; followed by fluctuations with coverage ranging from 35.0 to ≤ 98% between 2008 and 2017. The 12-month weighted anomaly standardized precipitation index showed a marked rainfall deficit in 1990-1996 and 1999-2010 coinciding with declining prevalence and despite relatively high bed net coverage from 2000. From 1992, the risk of infection decreased steadily up to 2013 when the lowest risk was observed (RR = 0.07; 95% CI 0.06-0.08, P < 0.001), but it was significantly higher during periods with positive rainfall anomalies (RR = 2.79; 95% CI 2.23-3.50, P < 0.001). The risk was lower among individuals not owning bed nets compared to those with nets (RR = 1.35; 95% CI 1.22-1.49, P < 0.001). CONCLUSIONS: A decline in prevalence up to 2012 and resurgence thereafter was likely associated with changes in monthly rainfall, offset against changing malaria interventions. A sustained surveillance covering multiple factors needs to be undertaken and climate must be taken into consideration when relating control interventions to malaria prevalence.

Deployment and use of mobile phone technology for real-time reporting of fever cases and malaria treatment failure in areas of declining malaria transmission in Muheza district north-eastern Tanzania.

BACKGROUND: Early detection of febrile illnesses at community level is essential for improved malaria case management and control. Currently, mobile phone-based technology has been commonly used to collect and transfer health information and services in different settings. This study assessed the applicability of mobile phone-based technology in real-time reporting of fever cases and management of malaria by village health workers (VHWs) in north-eastern Tanzania. METHODS: The community mobile phone-based disease surveillance and treatment for malaria (ComDSTM) platform, combined with mobile phones and web applications, was developed and implemented in three villages and one dispensary in Muheza district from November 2013 to October 2014. A baseline census was conducted in May 2013. The data were uploaded on a web-based database and updated during follow-up home visits by VHWs. Active and passive case detection (ACD, PCD) of febrile cases were done by VHWs and cases found positive by malaria rapid diagnostic test (RDT) were given the first dose of artemether-lumefantrine (AL) at the dispensary. Each patient was visited at home by VHWs daily for the first 3 days to supervise intake of anti-malarial and on day 7 to monitor the recovery process. The data were captured and transmitted to the database using mobile phones. RESULTS: The baseline population in the three villages was 2934 in 678 households. A total of 1907 febrile cases were recorded by VHWs and 1828 (95.9%) were captured using mobile phones. At the dispensary, 1778 (93.2%) febrile cases were registered and of these, 84.2% were captured through PCD. Positivity rates were 48.2 and 45.8% by RDT and microscopy, respectively. Nine cases had treatment failure reported on day 7 post-treatment and adherence to treatment was 98%. One patient with severe febrile illness was referred to Muheza district hospital. CONCLUSION: The study showed that mobile phone-based technology can be successfully used by VHWs in surveillance and timely reporting of fever episodes and monitoring of treatment failure in remote areas. Further optimization and scaling-up will be required to utilize the tools for improved malaria case management and drug resistance surveillance.

Applying a mobile survey tool for assessing lymphatic filariasis morbidity in Mtwara Municipal Council of Tanzania.

BACKGROUND: A number of methods have been used to estimate lymphatic filariasis (LF) morbidity, including: routine programmatic data, cluster random surveys and the "town crier" method. Currently, few accurate data exist on the global LF morbidity burden in Tanzania. We aimed to estimate prevalence of lymphedema and hydrocele in Mtwara Municipal Council using mobile phone based survey. METHODS: A cross-sectional survey was conducted among adults of Mtwara Municipal council with access to mobile phones. A sample size of at least 384 completed surveys was required to estimate prevalence of lymphedema (both males and females) and hydrocele (males only) morbidity of 50% within a 5% error margin given a 5% level of significance and 95% confidence level. Eligible mobile phone users received a short message text (SMS) requesting consent to participate in the survey. A total of 10 questions were administered via interactive SMS through the GeoPoll, a survey platform developed by Mobile Accord (www.geopoll.com). RESULTS: The survey was completed over a period of 4 days. A total of 8,759 surveys were sent to mobile phone subscribers of whom 1,330 (15.2%) opted-in to complete the survey. A total of 492 (37.0% of those opted-in, 384 male and 108 female) people completed the survey. Lymphedema and hydrocele signs were reported by 20.9% (95% CI, 17.4-24.8) and 20.6% (95% CI, 16.6-25.0) of respondents, respectively. Majority of hydrocele patients (59.5%) and 46.6% of lymphedema patients reported having sought treatment. The proportion of patients reporting similar symptoms among friends and relatives was 66.0% and 70.9% for lymphedema and hydrocele, respectively. CONCLUSIONS: The findings suggest that mobile phone based surveys are a practical approach of undertaking morbidity surveys. While further surveys are needed to verify the findings, this approach can be expected to encourage identification of lymphedema and hydrocele morbidity at community level and provide evidence where further morbidity surveys are warranted.

Lymphatic filariasis elimination efforts in Rufiji, southeastern Tanzania: decline in circulating filarial antigen prevalence in young school children after twelve rounds of mass drug administration and utilization of long-lasting insecticide-treated nets.

BACKGROUND: Lymphatic filariasis (LF) is a parasitic infection transmitted by mosquito vectors, and in Sub-Saharan Africa it is caused by the nematode Wuchereria bancrofti. The disease has been targeted for global elimination with the annual mass drug administration (MDA) strategy. Vector control is known to play an important complementary role to MDA in reducing the transmission of LF. The effects of an MDA and insecticide-treated net intervention implemented in an endemic area of southeastern Tanzania are reported here. METHODS: A cross-sectional study assessing W. bancrofti circulating filarial antigen (CFA) was conducted in five primary schools in five different villages. Standard one pupils aged 6-9 years were screened for CFA using immunochromatographic test cards (ICT), with a total of 413 screened in 2012 and 659 in 2015. Just after CFA testing, the children were interviewed on their participation in the MDA campaign. Moreover, 246 heads of households in 2012 and 868 in 2015 were interviewed on their participation in MDA and utilization of long-lasting insecticide-treated nets (LLINs). RESULTS: The prevalence of CFA for the 413 children tested in 2012 was 14.3%, while it was 0.0% for the 659 children tested in 2015. The Tanzanian National Lymphatic Filariasis Elimination Programme reported annual treatment coverage for Rufiji District ranging from 54.3% to 94.0% during the years 2002-2014. The surveyed treatment was 51.6% in 2011 and 57.4% in 2014. With regard to LLINs, possession and utilization increased from 63.4% and 59.2%, respectively, in 2012, to 92.5% and 75.4%, respectively, in 2015. CONCLUSIONS: The findings suggest that 12 rounds of MDA complemented with vector control through the use of insecticide-treated nets resulted in a marked reduction in W. bancrofti CFA in young school children.

Progress of Trachoma Mapping in Mainland Tanzania: Results of Baseline Surveys from 2012 to 2014.

PURPOSE: Following surveys in 2004-2006 in 50 high-risk districts of mainland Tanzania, trachoma was still suspected to be widespread elsewhere. We report on baseline surveys undertaken from 2012 to 2014. METHODS: A total of 31 districts were surveyed. In 2012 and 2013, 12 at-risk districts were selected based on proximity to known trachoma endemic districts, while in 2014, trachoma rapid assessments were undertaken, and 19 of 55 districts prioritized for baseline surveys. A multi-stage cluster random sampling methodology was applied whereby 20 villages (clusters) and 36 households per cluster were surveyed. Eligible participants, children aged 1-9 years and people aged 15 years and older, were examined for trachoma using the World Health Organization simplified grading system. RESULTS: A total of 23,171 households were surveyed and 104,959 participants (92.3% of those enumerated) examined for trachoma signs. A total of 44,511 children aged 1-9 years and 65,255 people aged 15 years and older were examined for trachomatous inflammation-follicular (TF) and trichiasis, respectively. Prevalence of TF varied by district, ranging from 0.0% (95% confidence interval, CI 0.0-0.1%) in Mbinga to 11.8% (95% CI 6.8-16.5%) in Chunya. Trichiasis prevalence was lowest in Urambo (0.03%, 95% CI 0.00-0.24%) and highest in Kibaha (1.08%, 95% CI 0.74-1.43%). CONCLUSION: Only three districts qualified for mass drug administration with azithromycin. Trichiasis is still a public health problem in many districts, thus community-based trichiasis surgery should be considered to prevent blindness due to trachoma. These findings will facilitate achievement of trachoma elimination objectives.

Correction: Prevalence of Lymphatic Filariasis and Treatment Effectiveness of Albendazole/ Ivermectin in Individuals with HIV Co-infection in Southwest-Tanzania.

[This corrects the article DOI: 10.1371/journal.pntd.0004618.].