Special Issue "Population Ecology, Epidemiology, and Control of Neglected Tropical Diseases"

A special issue of Tropical Medicine and Infectious Disease (ISSN 2414-6366).

Deadline for manuscript submissions: closed (31 July 2017).

Special Issue Editors

Guest Editor
Prof. Dr. Edwin Michael

Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, 46556, USA
Website | E-Mail
Interests: epidemiology; population biology
Guest Editor
Assist. Prof. Dr. Anuj Mubayi

School of Human Evolution and Social Change, Simon A. Levin Mathematical Computational Modeling Science Center, Arizona State University, Tempe, Arizona, USA
Website | E-Mail
Interests: mathematical epidemiology; quantitative social sciences

Special Issue Information

Dear Colleagues,

In 2012, the World Health Organization (WHO) laid out a roadmap for achieving the control, local elimination or reduction of disease burdens to low levels of ten major Neglected Tropical Diseases (NTDs) by the year 2020, primarily using mass drug treatments. Despite impressive progress made against these NTDs since large-scale treatment programmes began in endemic countries, critical challenges and barriers have emerged that need urgent addressing if the laudable goals set above by the WHO for these NTDs are to be successfully met.

The ecological challenges to control or local elimination primarily includes changes to population dynamics as elimination nears, reflecting a range of factors from critical slowing down, roles of spatial heterogeneities and emergence of “hotspots” in transmission, community connectivity and host/vector movements, effects of changes in host exposure intensity and immunity, impact of asymptomatics, changed biting behaviours of vectors, and possibility of genetic changes in both parasites and vectors to drugs and insecticides. The impact of multiparasitism and cormorbidity effects on parasite response to interventions are other emerging themes.

On the intervention side, key challenges include how best to increase collaboration and integration across strategic health sectors, including sanitation, education and nutrition. A recognized need is also how to design programmes that are sustainable over the long-term.

This Special Issue is dedicated to exploring and discussing these complexities in parasite population ecology, epidemiology and control that arise as control or elimination goals near. Topics may include modelling work highlighting features of transmission regimes as control/elimination nears and system trajectories or responses that may be expected of particular ecologies and pathologies of infection, including population genetics, and approaches to their management; use of spatial technologies and methodologies in disease mapping, clustering and control; systems biology and molecular approaches to investigating the parasite-host interface and for drug discovery; field entomological studies highlighting changed vector ecologies and impacts on interventions; immunological studies of host responses under conditions of interventions; advances in diagnostic tool development suited to investigating population dynamics at near control/elimination stages; epidemiological studies of the impacts of integrated control combining various health-related sectors; the role and outcome of multiparasitism in NTD control; development and application of surveillance systems for decision making; and social science investigations of past or ongoing studies for learning, designing, and implementing sustainable NTD programmes.

Prof. Dr. Edwin Michael
Assist. Prof. Dr. Anuj Mubayi
Guest Editors

Manuscript Submission Information

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Keywords

  • Parasite population ecology and epidemiology
  • Modelling neglected tropical diseases
  • Elimination dynamics
  • Parasite population genetics
  • Parasite systems biology
  • Spatial epidemiology and mapping hotspots
  • Vector ecology
  • Host-parasite immunology
  • Parasite diagnostics
  • Multiparasitism
  • Integrated control
  • Social science studies
  • Sustainable control

Published Papers (8 papers)

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Research

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Open AccessArticle
A Comparative Assessment of Epidemiologically Different Cutaneous Leishmaniasis Outbreaks in Madrid, Spain and Tolima, Colombia: An Estimation of the Reproduction Number via a Mathematical Model
Trop. Med. Infect. Dis. 2018, 3(2), 43; https://doi.org/10.3390/tropicalmed3020043
Received: 12 December 2017 / Revised: 2 April 2018 / Accepted: 10 April 2018 / Published: 19 April 2018
Cited by 1 | PDF Full-text (4312 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Leishmaniasis is a neglected tropical disease caused by the Leishmania parasite and transmitted by the Phlebotominae subfamily of sandflies, which infects humans and other mammals. Clinical manifestations of the disease include cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL) and visceral leishmaniasis (VL) with a [...] Read more.
Leishmaniasis is a neglected tropical disease caused by the Leishmania parasite and transmitted by the Phlebotominae subfamily of sandflies, which infects humans and other mammals. Clinical manifestations of the disease include cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL) and visceral leishmaniasis (VL) with a majority (more than three-quarters) of worldwide cases being CL. There are a number of risk factors for CL, such as the presence of multiple reservoirs, the movement of individuals, inequality, and social determinants of health. However, studies related to the role of these factors in the dynamics of CL have been limited. In this work, we (i) develop and analyze a vector-borne epidemic model to study the dynamics of CL in two ecologically distinct CL-affected regions—Madrid, Spain and Tolima, Colombia; (ii) derived three different methods for the estimation of model parameters by reducing the dimension of the systems; (iii) estimated reproduction numbers for the 2010 outbreak in Madrid and the 2016 outbreak in Tolima; and (iv) compared the transmission potential of the two economically-different regions and provided different epidemiological metrics that can be derived (and used for evaluating an outbreak), once R0 is known and additional data are available. On average, Spain has reported only a few hundred CL cases annually, but in the course of the outbreak during 2009–2012, a much higher number of cases than expected were reported and that too in the single city of Madrid. Cases in humans were accompanied by sharp increase in infections among domestic dogs, the natural reservoir of CL. On the other hand, CL has reemerged in Colombia primarily during the last decade, because of the frequent movement of military personnel to domestic regions from forested areas, where they have increased exposure to vectors. In 2016, Tolima saw an unexpectedly high number of cases leading to two successive outbreaks. On comparing, we estimated reproduction number of the Madrid outbreak to be 3.1 (with range of 2.8–3.9), which was much higher than reproduction number estimates of the Tolima first outbreak 1.2 (with range of 1.1–1.3), and the estimate for the second outbreak in Tolima of 1.019 (with range of 1.018–1.021). This suggests that the epidemic outbreak in Madrid was much more severe than the Tolima outbreak, even though Madrid was economically better-off compared to Tolima. It indicates a potential relationship between urban development and increasing health disparities. Full article
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Open AccessArticle
Biosocial Determinants of Persistent Schistosomiasis among Schoolchildren in Tanzania despite Repeated Treatment
Trop. Med. Infect. Dis. 2017, 2(4), 61; https://doi.org/10.3390/tropicalmed2040061
Received: 15 September 2017 / Revised: 21 November 2017 / Accepted: 23 November 2017 / Published: 4 December 2017
Cited by 1 | PDF Full-text (1761 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Schistosomiasis is a parasitic disease endemic to Tanzania and other countries of the global south, which is currently being addressed through preventive chemotherapy campaigns. However, there is growing recognition that chemotherapy strategies will need to be supplemented to sustainably control and eventually eliminate [...] Read more.
Schistosomiasis is a parasitic disease endemic to Tanzania and other countries of the global south, which is currently being addressed through preventive chemotherapy campaigns. However, there is growing recognition that chemotherapy strategies will need to be supplemented to sustainably control and eventually eliminate the disease. There remains a need to understand the factors contributing to continued transmission in order to ensure the effective configuration and implementation of supplemented programs. We conducted a cross-sectional questionnaire, to evaluate the biosocial determinants facilitating the persistence of schistosomiasis, among 1704 Tanzanian schoolchildren residing in two districts undergoing a preventive chemotherapeutic program: Rufiji and Mkuranga. A meta-analysis was carried out to select the diagnostic questions that provided a likelihood for predicting infection status. We found that self-reported schistosomiasis continues to persist among the schoolchildren, despite multiple rounds of drug administration.Using mixed effects logistic regression modeling, we found biosocial factors, including gender, socio-economic status, and water, sanitation, and hygiene (WASH)-related variables, were associated with this continued schistosomiasis presence. These findings highlight the significant role that social factors may play in the persistence of disease transmission despite multiple treatments, and support the need not only for including integrated technical measures, such as WASH, but also addressing issues of poverty and gender when designing effective and sustainable schistosomiasis control programs. Full article
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Open AccessArticle
Polisye Kont Moustik: A Culturally Competent Approach to Larval Source Reduction in the Context of Lymphatic Filariasis and Malaria Elimination in Haiti
Trop. Med. Infect. Dis. 2017, 2(3), 39; https://doi.org/10.3390/tropicalmed2030039
Received: 25 July 2017 / Revised: 12 August 2017 / Accepted: 13 August 2017 / Published: 18 August 2017
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Abstract
Community engagement has become an increasingly important focus of global health programs. Arbovirus emergence in the Americas (Zika and chikungunya virues), and global goals for malaria and lymphatic filariasis elimination, mean that community-based mosquito control has taken on a new salience. But how [...] Read more.
Community engagement has become an increasingly important focus of global health programs. Arbovirus emergence in the Americas (Zika and chikungunya virues), and global goals for malaria and lymphatic filariasis elimination, mean that community-based mosquito control has taken on a new salience. But how should mosquito control initiatives be designed and implemented in ways that best engage local people? What are the challenges and trade-offs of different strategies, not only for effectiveness but also for scale-up? In this paper, we describe the social and political dynamics of a pilot study in a small town in northern Haiti. With the aim of developing a culturally-competent approach to larval source management (LSM), our pilot project combined larval surveillance with environmental management, social engagement, community education, and larvicide application. Orientated around a network of ‘Mosquito Police’ (Polisye Kont Moustik, in Haitian Creole), our approach integrated elements of formative research, social learning, and community participation. Here, we reflect on the challenges we encountered in the field, from larval mapping, staff management, education and behavior change, engagement with formal and informal leaders, and community-based environmental cleanup. We discuss how these programmatic efforts were influenced and shaped by a complex range of social, cultural, political, and economic realities, and conclude by discussing the implications of our community-based approach for the elimination of lymphatic filariasis and malaria, and other vector-borne diseases, in Haiti. Full article
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Review

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Open AccessReview
The Interdependence between Schistosome Transmission and Protective Immunity
Trop. Med. Infect. Dis. 2017, 2(3), 42; https://doi.org/10.3390/tropicalmed2030042
Received: 17 July 2017 / Revised: 2 August 2017 / Accepted: 8 August 2017 / Published: 23 August 2017
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Abstract
Mass drug administration (MDA) for control of schistosomiasis is likely to affect transmission dynamics through a combination of passive vaccination and reduction of local transmission intensity. This is indicated in phenomenological models of immunity and the impact of MDA, yet immunity parameters in [...] Read more.
Mass drug administration (MDA) for control of schistosomiasis is likely to affect transmission dynamics through a combination of passive vaccination and reduction of local transmission intensity. This is indicated in phenomenological models of immunity and the impact of MDA, yet immunity parameters in these models are not validated by empirical data that reflects protective immunity to reinfection. There is significant empirical evidence supporting the role of IgE in acquired protective immunity. This is proposed to be a form of delayed concomitant immunity, driven at least in part by protective IgE responses to the tegument allergen-like (TAL) family of proteins. Specific questions have arisen from modeling studies regarding the strength and duration of the protective immune response. At present, field studies have not been specifically designed to address these questions. There is therefore a need for field studies that are explicitly designed to capture epidemiological effects of acquired immunity to elucidate these immunological interactions. In doing so, it is important to address the discourse between theoretical modelers and immuno-epidemiologists and develop mechanistic models that empirically define immunity parameters. This is of increasing significance in a climate of potential changing transmission dynamics following long-term implementation of MDA. Full article
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Open AccessReview
Neglected Tropical Diseases: Epidemiology and Global Burden
Trop. Med. Infect. Dis. 2017, 2(3), 36; https://doi.org/10.3390/tropicalmed2030036
Received: 21 June 2017 / Revised: 19 July 2017 / Accepted: 2 August 2017 / Published: 5 August 2017
Cited by 10 | PDF Full-text (661 KB) | HTML Full-text | XML Full-text
Abstract
More than a billion people—one-sixth of the world’s population, mostly in developing countries—are infected with one or more of the neglected tropical diseases (NTDs). Several national and international programs (e.g., the World Health Organization’s Global NTD Programs, the Centers for Disease Control and [...] Read more.
More than a billion people—one-sixth of the world’s population, mostly in developing countries—are infected with one or more of the neglected tropical diseases (NTDs). Several national and international programs (e.g., the World Health Organization’s Global NTD Programs, the Centers for Disease Control and Prevention’s Global NTD Program, the United States Global Health Initiative, the United States Agency for International Development’s NTD Program, and others) are focusing on NTDs, and fighting to control or eliminate them. This review identifies the risk factors of major NTDs, and describes the global burden of the diseases in terms of disability-adjusted life years (DALYs). Full article
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Other

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Open AccessProtocol
The COUNTDOWN Study Protocol for Expansion of Mass Drug Administration Strategies against Schistosomiasis and Soil-Transmitted Helminthiasis in Ghana
Trop. Med. Infect. Dis. 2018, 3(1), 10; https://doi.org/10.3390/tropicalmed3010010
Received: 25 October 2017 / Revised: 3 January 2018 / Accepted: 4 January 2018 / Published: 22 January 2018
Cited by 2 | PDF Full-text (848 KB) | HTML Full-text | XML Full-text
Abstract
(1) Background: Current international policy for schistosomiasis and soil-transmitted helminthiasis (STH) control emphasises mass administration of deworming drugs in school-based programmes. However, this approach is insufficient to control the transmission of these diseases, and their burden in non-school cohorts is recognised, albeit under-researched. [...] Read more.
(1) Background: Current international policy for schistosomiasis and soil-transmitted helminthiasis (STH) control emphasises mass administration of deworming drugs in school-based programmes. However, this approach is insufficient to control the transmission of these diseases, and their burden in non-school cohorts is recognised, albeit under-researched. This research will investigate the feasibility and acceptability of expanding access to praziquantel (PZQ) against schistosomiasis, and albendazole (ALB) against STH, to communities in selected transmission settings in Ghana. (2) Methods: A three-site longitudinal study will be implemented to investigate the effectiveness of expanding treatment strategies for PZQ and ALB to community members. In the context of community mass drug administration (to preschool children, school non-attending children, and adults, including pregnant women), the intervention will be assessed in a random sample of community members, at baseline with follow-up at 6, 12, and 18 months. In each community, 658 participants will be enrolled, and 314 followed up at each time point. The primary outcome measure is the prevalence of infection of Schistosoma haematobium and/or S. mansoni at study endpoint, as assessed by longitudinal surveys. Secondary outcomes are to quantify the infection of schistosomiasis and STH infections in non-treated cohorts, reductions in prevalence of STH, and intensity of schistosomiasis and STH, and treatment coverage. Nested within this study will be qualitative, cost-benefit, and cost-effectiveness evaluations that will explore accessibility, feasibility, and economic impact of expanded treatment from different complementary perspectives. (3) Discussion: Using a multidisciplinary approach, this study will generate evidence for improved availability, acceptability, affordability, and accessibility to deworming drugs against schistosomiasis and STH to individuals and communities in Ghana. This is likely to have considerable research, programmatic, and political value to contribute evidence for national programme policy development within Ghana, and, more broadly, World Health Organization policy development. Full article
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Open AccessCommentary
Control of Tungiasis in Absence of a Roadmap: Grassroots and Global Approaches
Trop. Med. Infect. Dis. 2017, 2(3), 33; https://doi.org/10.3390/tropicalmed2030033
Received: 28 June 2017 / Revised: 20 July 2017 / Accepted: 23 July 2017 / Published: 27 July 2017
Cited by 3 | PDF Full-text (9386 KB) | HTML Full-text | XML Full-text
Abstract
Tungiasis is a tropical skin disease caused by the sand flea Tunga penetrans. It inflicts misery upon tens of millions of people, mostly children, across Central and South America and sub-Saharan Africa, and yet there is no globally accepted roadmap for its [...] Read more.
Tungiasis is a tropical skin disease caused by the sand flea Tunga penetrans. It inflicts misery upon tens of millions of people, mostly children, across Central and South America and sub-Saharan Africa, and yet there is no globally accepted roadmap for its control. Here we review how research in the last 15 years has developed control methods and report on new grassroots and digital mapping approaches. Treatment is now possible with a two-component dimethicone, used for the treatment of headlice in Europe, Asia and Canada, but not yet available in most tungiasis-endemic areas. Prevention is possible through the daily use of repellents based on coconut oil. A Kenyan coastal community has successfully controlled tungiasis using a neem and coconut oil mix produced locally to treat cases, combined with spraying floors with neem solution and distributing closed shoes. Development of affordable hard floor technology is underway, although not yet widely available, but is a priority to control off-host stages in the floors of homes. A new web-based digital mapping application will enable researchers and health officials to collaborate, share data and map the prevalence of tungiasis. We conclude that tungiasis can be controlled through a multi-disciplinary, One Health approach. Full article
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Open AccessPerspective
Monitoring the Path to the Elimination of Infectious Diseases
Trop. Med. Infect. Dis. 2017, 2(3), 20; https://doi.org/10.3390/tropicalmed2030020
Received: 2 March 2017 / Revised: 17 June 2017 / Accepted: 21 June 2017 / Published: 26 June 2017
Cited by 3 | PDF Full-text (1280 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
During the endgame of elimination programs, parasite populations may exhibit dynamical phenomena not typical of endemic disease. Particularly, monitoring programs for tracking infection prevalence may be hampered by overall rarity, the sporadic and unpredictable timing and location of outbreaks, and under-reporting. A particularly [...] Read more.
During the endgame of elimination programs, parasite populations may exhibit dynamical phenomena not typical of endemic disease. Particularly, monitoring programs for tracking infection prevalence may be hampered by overall rarity, the sporadic and unpredictable timing and location of outbreaks, and under-reporting. A particularly important problem for monitoring is determining the distance that must be covered to achieve the elimination threshold at an effective reproduction number less than one. In this perspective, we suggest that this problem may be overcome by measuring critical slowing down. Critical slowing down is a phenomenon exhibited by nonlinear dynamical systems in the vicinity of a critical threshold. In infectious disease dynamics, critical slowing down is expressed as an increase in the coefficient of variation and other properties of the fluctuations in the number of cases. In simulations, we show the coefficient of variation to be insensitive to under-reporting error and therefore a robust measurement of the approach to elimination. Additionally, we show that there is an inevitable delay between the time at which the effective reproduction number is reduced to below one and complete elimination is achieved. We urge that monitoring programs include dynamical properties such as critical slowing down in their metrics for measuring achievement and avoid withdrawing control activities prematurely. Full article
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