Nilanthi de Silva

The Global Burden of Snakebite: A Literature Analysis and Modelling Based on Regional Estimates of Envenoming and Deaths

Background Envenoming resulting from snakebites is an important public health problem in many tropical and subtropical countries. Few attempts have been made to quantify the burden, and recent estimates all suffer from the lack of an objective and reproducible methodology. In an attempt to provide an accurate, up-to-date estimate of the scale of the global problem, we developed a new method to estimate the disease burden due to snakebites. Methods and Findings The global estimates were based on regional estimates that were, in turn, derived from data available for countries within a defined region. Three main strategies were used to obtain primary data: electronic searching for publications on snakebite, extraction of relevant country-specific mortality data from databases maintained by United Nations organizations, and identification of grey literature by discussion with key informants. Countries were grouped into 21 distinct geographic regions that are as epidemiologically homogenous as possible, in line with the Global Burden of Disease 2005 study (Global Burden Project of the World Bank). Incidence rates for envenoming were extracted from publications and used to estimate the number of envenomings for individual countries; if no data were available for a particular country, the lowest incidence rate within a neighbouring country was used. Where death registration data were reliable, reported deaths from snakebite were used; in other countries, deaths were estimated on the basis of observed mortality rates and the at-risk population. We estimate that, globally, at least 421,000 envenomings and 20,000 deaths occur each year due to snakebite. These figures may be as high as 1,841,000 envenomings and 94,000 deaths. Based on the fact that envenoming occurs in about one in every four snakebites, between 1.2 million and 5.5 million snakebites could occur annually. Conclusions Snakebites cause considerable morbidity and mortality worldwide. The highest burden exists in South Asia, Southeast Asia, and sub-Saharan Africa.

A review and meta-analysis of the impact of intestinal worms on child growth and nutrition

More than a half of the worlds population are infected with one or more species of intestinal worms of which the nematodes Ascaris lumbricoides, Trichuris trichiura and the hookworms are the most common and important in terms of child health. This paper: (1) introduces the main species of intestinal worms with particular attention to intestinal nematodes; (2) examines how such worms may affect child growth and nutrition; (3) reviews the biological and epidemiological factors that influence the effects that worms can have on the growth and nutrition of children; (4) considers the many factors that can affect the impact of treatment with anthelmintic drugs; (5) presents the results of a meta-analysis of studies of the effect of treating worm infections on child growth and nutrition; (6) discusses the results in terms of what is reasonable to expect that deworming alone can achieve; (7) describes some important characteristics of an ideal study of the effects of deworming; and (8) comments on the implications for programmes of recommendations concerning mass deworming.

World Health Organization Global Estimates and Regional Comparisons of the Burden of Foodborne Disease in 2010

Illness and death from diseases caused by contaminated food are a constant threat to public health and a significant impediment to socio-economic development worldwide. To measure the global and regional burden of foodborne disease (FBD), the World Health Organization (WHO) established the Foodborne Disease Burden Epidemiology Reference Group (FERG), which here reports their first estimates of the incidence, mortality, and disease burden due to 31 foodborne hazards. We find that the global burden of FBD is comparable to those of the major infectious diseases, HIV/AIDS, malaria and tuberculosis. The most frequent causes of foodborne illness were diarrheal disease agents, particularly norovirus and Campylobacter spp. Diarrheal disease agents, especially non-typhoidal Salmonella enterica, were also responsible for the majority of deaths due to FBD. Other major causes of FBD deaths were Salmonella Typhi, Taenia solium and hepatitis A virus. The global burden of FBD caused by the 31 hazards in 2010 was 33 million Disability Adjusted Life Years (DALYs); children under five years old bore 40% of this burden. The 14 subregions, defined on the basis of child and adult mortality, had considerably different burdens of FBD, with the greatest falling on the subregions in Africa, followed by the subregions in South-East Asia and the Eastern Mediterranean D subregion. Some hazards, such as non-typhoidal S. enterica, were important causes of FBD in all regions of the world, whereas others, such as certain parasitic helminths, were highly localised. Thus, the burden of FBD is borne particularly by children under five years old–although they represent only 9% of the global population–and people living in low-income regions of the world. These estimates are conservative, i.e., underestimates rather than overestimates; further studies are needed to address the data gaps and limitations of the study. Nevertheless, all stakeholders can contribute to improvements in food safety throughout the food chain by incorporating these estimates into policy development at national and international levels.

Unresolved issues in anthelmintic pharmacology for helminthiases of humans.

Helminth infections are an important constraint on the health and development of poor children and adults. Anthelmintic treatment programmes provide a safe and effective response, and increasing numbers of people are benefitting from these public health initiatives. Despite decades of clinical experience with anthelmintics for the treatment of human infections, relatively little is known about their clinical pharmacology. All of the drugs were developed initially in response to the considerable market for veterinary anthelmintics in high- and middle-income countries. In contrast, the greatest burden caused by these infections in humans is in resource-poor settings and as a result there has been insufficient commercial incentive to support studies on how these drugs work in humans, and how they should best be used in control programmes. The advent of mass drug administration programmes for the control of schistosomiasis, lymphatic filariasis, onchocerciasis and soil-transmitted helminthiases in humans increases the urgency to better understand and better monitor drug resistance, and to broaden the currently very narrow range of available anthelmintics. This provides fresh impetus for developing a comprehensive research platform designed to improve our understanding of these important drugs, in order to bring the scientific knowledge base supporting their use to a standard equivalent to that of drugs commonly used in developed countries. Furthermore, a better understanding of their clinical pharmacology will enable improved therapy and could contribute to the discovery of new products.

World Health Organization Estimates of the Global and Regional Disease Burden of 11 Foodborne Parasitic Diseases, 2010: A Data Synthesis.

Background Foodborne diseases are globally important, resulting in considerable morbidity and mortality. Parasitic diseases often result in high burdens of disease in low and middle income countries and are frequently transmitted to humans via contaminated food. This study presents the first estimates of the global and regional human disease burden of 10 helminth diseases and toxoplasmosis that may be attributed to contaminated food. Methods and Findings Data were abstracted from 16 systematic reviews or similar studies published between 2010 and 2015; from 5 disease data bases accessed in 2015; and from 79 reports, 73 of which have been published since 2000, 4 published between 1995 and 2000 and 2 published in 1986 and 1981. These included reports from national surveillance systems, journal articles, and national estimates of foodborne diseases. These data were used to estimate the number of infections, sequelae, deaths, and Disability Adjusted Life Years (DALYs), by age and region for 2010. These parasitic diseases, resulted in 48.4 million cases (95% Uncertainty intervals [UI] of 43.4–79.0 million) and 59,724 (95% UI 48,017–83,616) deaths annually resulting in 8.78 million (95% UI 7.62–12.51 million) DALYs. We estimated that 48% (95% UI 38%-56%) of cases of these parasitic diseases were foodborne, resulting in 76% (95% UI 65%-81%) of the DALYs attributable to these diseases. Overall, foodborne parasitic disease, excluding enteric protozoa, caused an estimated 23.2 million (95% UI 18.2–38.1 million) cases and 45,927 (95% UI 34,763–59,933) deaths annually resulting in an estimated 6.64 million (95% UI 5.61–8.41 million) DALYs. Foodborne Ascaris infection (12.3 million cases, 95% UI 8.29–22.0 million) and foodborne toxoplasmosis (10.3 million cases, 95% UI 7.40–14.9 million) were the most common foodborne parasitic diseases. Human cysticercosis with 2.78 million DALYs (95% UI 2.14–3.61 million), foodborne trematodosis with 2.02 million DALYs (95% UI 1.65–2.48 million) and foodborne toxoplasmosis with 825,000 DALYs (95% UI 561,000–1.26 million) resulted in the highest burdens in terms of DALYs, mainly due to years lived with disability. Foodborne enteric protozoa, reported elsewhere, resulted in an additional 67.2 million illnesses or 492,000 DALYs. Major limitations of our study include often substantial data gaps that had to be filled by imputation and suffer from the uncertainties that surround such models. Due to resource limitations it was also not possible to consider all potentially foodborne parasites (for example Trypanosoma cruzi). Conclusions Parasites are frequently transmitted to humans through contaminated food. These estimates represent an important step forward in understanding the impact of foodborne diseases globally and regionally. The disease burden due to most foodborne parasites is highly focal and results in significant morbidity and mortality among vulnerable populations.

WHO Initiative to Estimate the Global Burden of Foodborne Diseases

Abstract Background The public health impact of foodborne diseases globally is unknown. The WHO Initiative to Estimate the Global Burden of Foodborne Diseases was launched out of the need to fill this data gap. It is anticipated that this effort will enable policy makers and other stakeholders to set appropriate, evidence-informed priorities in the area of food safety. Methods The Initiative aims to provide estimates on the global burden of foodborne diseases by age, sex, and region; strengthen country capacity for conducting burden of foodborne disease assessments in parallel with food safety policy analyses; increase awareness and commitment among Member States for the implementation of food safety policy and standards; and encourage countries to use burden of foodborne disease estimates for cost-effectiveness analyses of prevention, intervention, and control measures. To estimate the global burden (expressed in disability-adjusted life-years), the Foodborne Disease Burden Epidemiology Reference Group (FERG) focused on the contamination of food with enteric and parasitic pathogens, chemicals, and toxins. Findings Study findings will provide the technical background and challenges of assessing the burden of foodborne diseases, based on national and international studies. Systematic reviews to support estimates of the incidence and mortality of food-related diseases are being completed. Results will be used to update and refine global burden estimates for relevant food-related hazards, in the context of other international burden of disease studies. It is recognised that exposure to such hazards may also occur through other pathways including the environment (eg, water, air) and by direct transmission (eg, human-to-human and animal-to-human). Structured expert elicitation will be used to provide the basis for attribution of incidence and burden to food, and estimation of the most important food sources. Interpretation Estimating the global burden of foodborne diseases is highly complex because of the diversity of hazards that can be transmitted by food, the multitude of health outcomes they cause, and complex transmission pathways. WHO is planning to present a global estimate for the first time in 2014. Funding WHO.

The global burden of foodborne parasitic diseases: an update.

Foodborne diseases (FBDs) are a major cause of morbidity and mortality in the human population. Accurate information on the burden of FBDs is needed to inform policy makers and allocate appropriate resources for food safety control and intervention. Consequently, in 2006 the WHO launched an initiative to estimate the global burden of FBDs in terms of Disability Adjusted Life Years (DALYs). This review gives an update of the progress on evaluating the burden of foodborne parasitic diseases that has been generated by this study. Results to date indicate that parasitic diseases that can be transmitted through food make a substantial contribution to the global burden of disease.

Child and Adolescent Health and Development: Realizing Neglected Potential

It seems that society and the common legal definition have got it about right: it takes some 21 years for a human being to reach adulthood. The evidence shows a particular need to invest in the crucial development period from conception to age two (the first 1,000 days) and also during critical phases over the next 7,000 days. Just as babies are not merely small people—they need special and different types of care from the rest of us— so growing children and adolescents are not merely short adults; they, too, have critical phases of development that need specific interventions. Ensuring that life’s journey begins right is essential, but it is now clear that we also need support to guide our development up to our 21st birthday if everyone is to have the opportunity to realize their potential. Our thesis is that research and action on child health and development should evolve from a narrow emphasis on the first 1,000 days to holistic concern over the first 8,000 days; from an age-siloed approach to an approach that embraces the needs across the life cycle. To begin researching and encouraging action, this volume, Child and Adolescent Health and Development, explores the health and development needs of the 5 to 21 year age group and presents evidence for a package of investments to address priority health needs, expanding on other recent work in this area, such as the Lancet Commission on Adolescent Health and Wellbeing (Patton, Sawyer, and others 2016). Given new evidence on the strong connection between a child’s education and health, we argue that modest investments in the health of this age group are essential to attain the maximum benefit from investments in schooling for this age group, such as those proposed by the recent International Commission on Financing Global Education Opportunity (2016). This volume shares contributors to both commissions and complements an earlier volume, Reproductive, Maternal, Newborn, and Child Health, which focuses on health in the group of children under age 5 years. There is a surprising lack of consistency in the language used to describe the phases of childhood, perhaps reflecting the historically narrow focus on the early years. The neglect of children ages 5 to 9 years in particular is reflected in the absence of a commonly reflected name for this age group. Figure 1.1 illustrates the nomenclature used in this volume, which we have sought to align with the definitions and use outlined in the 2016 Lancet Commission on Adolescent Health and Wellbeing. The editors of this volume built upon the commission’s definitions to include additional terms that are relevant to the broader age range considered here, including middle childhood to reflect the age range between 5 and 9 years. The editors also refer to children and adolescents between ages 5 and 14 years as “school-age,” since in lowand lower-middleincome countries these are the majority of children in

Soil-transmitted helminth infections among plantation sector schoolchildren in Sri Lanka: prevalence after ten years of preventive chemotherapy.

Background The plantation sector in Sri Lanka lags behind the rest of the country in terms of living conditions and health. In 1992, a sector-wide survey of children aged 3–12 years and women of reproductive age showed >90% prevalence of soil-transmitted helminth infections. Biannual mass de-worming targeting children aged 3–18 years started in 1994 and was continued until 2005. The present study was carried out to assess the status of infection four years after cessation of mass de-worming. Methods/Findings A school-based cross-sectional survey was carried out. Faecal samples from approximately 20 children from each of 114 schools in five districts were examined using the modified Kato-Katz technique. Data regarding the school, the childs family and household sanitation were recorded after inspection of schools and households. Multivariate analysis was carried out using logistic regression, to identify risk factors for infection. Faecal samples were obtained from 1890 children. In 4/5 districts, >20% were infected with one or more helminth species. Overall combined prevalence was 29.0%; 11.6% had infections of moderate-heavy intensity. The commonest infection was Ascaris lumbricoides, present in all five districts, as was Trichuris trichiura. Hookworm was not detected in two districts. Multivariate analysis identified low altitude and maternal under-education as risk factors for all three infections. Poor household sanitation was identified as a risk factor for A. lumbricoides and hookworm, but not T. trichiura infections. Conclusions/Significance The results indicate that regular mass de-worming of plantation sector children should be resumed along with more emphasis on better sanitation and health education. They show that even after 10 years of mass chemotherapy, prevalence can bounce back after cessation of preventive chemotherapy, if the initial force of transmission is strong and other long-term control measures are not concomitantly implemented.

Using the prevalence of individual species of intestinal nematode worms to estimate the combined prevalence of any species.

Objectives To assess if a probabilistic model could be used to estimate the combined prevalence of infection with any species of intestinal nematode worm when only the separate prevalence of each species is reported, and to estimate the extent to which simply taking the highest individual species prevalence underestimates the combined prevalence. Methods Data were extracted from community surveys that reported both the proportion infected with individual species and the combined proportion infected, for a minimum sample of 100 individuals. The predicted combined proportion infected was calculated based on the assumption that the probability of infection with one species was independent of infection with another species, so the probability of combined infections was multiplicative. Findings Thirty-three reports describing 63 data sets from surveys conducted in 20 countries were identified. A strong correlation was found between the observed and predicted combined proportion infected (r = 0.996, P<0.001). When the observed and predicted values were plotted against each other, a small correction of the predicted combined prevalence by dividing by a factor of 1.06 achieved a near perfect correlation between the two sets of values. The difference between the single highest species prevalence and the observed combined prevalence was on average 7% or smaller at a prevalence of ≤40%, but at prevalences of 40–80%, the difference was about 12%. Conclusions A simple probabilistic model of combined infection with a small correction factor is proposed as a novel method to estimate the number of individuals that would benefit from mass deworming when data are reported only for separate species.