Jennifer Keiser

Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at risk

An estimated 779 million people are at risk of schistosomiasis, of whom 106 million (13.6%) live in irrigation schemes or in close proximity to large dam reservoirs. We identified 58 studies that examined the relation between water resources development projects and schistosomiasis, primarily in African settings. We present a systematic literature review and meta-analysis with the following objectives: (1) to update at-risk populations of schistosomiasis and number of people infected in endemic countries, and (2) to quantify the risk of water resources development and management on schistosomiasis. Using 35 datasets from 24 African studies, our meta-analysis showed pooled random risk ratios of 2.4 and 2.6 for urinary and intestinal schistosomiasis, respectively, among people living adjacent to dam reservoirs. The risk ratio estimate for studies evaluating the effect of irrigation on urinary schistosomiasis was in the range 0.02-7.3 (summary estimate 1.1) and that on intestinal schistosomiasis in the range 0.49-23.0 (summary estimate 4.7). Geographic stratification showed important spatial differences, idiosyncratic to the type of water resources development. We conclude that the development and management of water resources is an important risk factor for schistosomiasis, and hence strategies to mitigate negative effects should become integral parts in the planning, implementation, and operation of future water projects.

Efficacy of Current Drugs Against Soil-Transmitted Helminth Infections: Systematic Review and Meta-analysis

CONTEXT More than a quarter of the human population is likely infected with soil-transmitted helminths (Ascaris lumbricoides, hookworm, and Trichuris trichiura) in highly endemic areas. Preventive chemotherapy is the mainstay of control, but only 4 drugs are available: albendazole, mebendazole, levamisole, and pyrantel pamoate. OBJECTIVE To assess the efficacy of single-dose oral albendazole, mebendazole, levamisole, and pyrantel pamoate against A lumbricoides, hookworm, and T trichiura infections. DATA SOURCES A systematic search of PubMed, ISI Web of Science, ScienceDirect, the World Health Organization library database, and the Cochrane Central Register of Controlled Trials (1960 to August 2007). STUDY SELECTION From 168 studies, 20 randomized controlled trials were included. DATA EXTRACTION AND DATA SYNTHESIS Information on study year and country, sample size, age of study population, mean infection intensity before treatment, diagnostic method used, time between evaluations before and after treatment, cure rate (the percentage of individuals who became helminth egg negative following treatment with an anthelminthic drug), egg reduction rate, adverse events, and trial quality was extracted. Relative risk, including a 95% confidence interval (CI), was used to measure the effect of the drugs on the risk of infection prevalence with a random-effects model. RESULTS Single-dose oral albendazole, mebendazole, and pyrantel pamoate for infection with A lumbricoides resulted in cure rates of 88% (95% CI, 79%-93%; 557 patients), 95% (95% CI, 91%-97%; 309 patients), and 88% (95% CI, 79%-93%; 131 patients), respectively. Cure rates for infection with T trichiura following treatment with single-dose oral albendazole and mebendazole were 28% (95% CI, 13%-39%; 735 patients) and 36% (95% CI, 16%-51%; 685 patients), respectively. The efficacy of single-dose oral albendazole, mebendazole, and pyrantel pamoate against hookworm infections was 72% (95% CI, 59%-81%; 742 patients), 15% (95% CI, 1%-27%; 853 patients), and 31% (95% CI, 19%-42%; 152 patients), respectively. No pooled relative risks could be calculated for pyrantel pamoate against T trichiura and levamisole for any of the parasites investigated. CONCLUSIONS Single-dose oral albendazole, mebendazole, and pyrantel pamoate show high cure rates against A lumbricoides. For hookworm infection, albendazole was more efficacious than mebendazole and pyrantel pamoate. Treatment of T trichiura with single oral doses of current anthelminthics is unsatisfactory. New anthelminthics are urgently needed.

Emerging foodborne trematodiasis.

Foodborne trematodiasis is emerging because of increased aquaculture.

The Global Burden of Disease Study 2010: Interpretation and Implications for the Neglected Tropical Diseases

The publication of the Global Burden of Disease Study 2010 (GBD 2010) and the accompanying collection of Lancet articles in December 2012 provided the most comprehensive attempt to quantify the burden of almost 300 diseases, injuries, and risk factors, including neglected tropical diseases (NTDs) [1]–[3]. The disability-adjusted life year (DALY), the metric used in the GBD 2010, is a tool which may be used to assess and compare the relative impact of a number of diseases locally and globally [4]–[6]. Table 1 lists the major NTDs as defined by the World Health Organization (WHO) [7] and their estimated DALYs [1]. With a few exceptions, most of the NTDs currently listed by the WHO [7] or those on the expanded list from PLOS Neglected Tropical Diseases [8] are disablers rather than killers, so the DALY estimates represent one of the few metrics available that could fully embrace the chronic effects of these infections. Table 1 Estimated DALYs (in millions) of the NTDs from the Global Burden of Disease Study 2010. Disease DALYs from GBD 2010 (numbers in parentheses indicate 95% confidence intervals) [1] NTDs 26.06 (20.30–35.12) Intestinal nematode infections 5.19 (2.98–8.81) Hookworm disease 3.23 (1.70–5.73) Ascariasis 1.32 (0.71–2.35) Trichuriasis 0.64 (0.35–1.06) Leishmaniasis 3.32 (2.18–4.90) Schistosomiasis 3.31 (1.70–6.26) Lymphatic filariasis 2.78 (1.8–4.00) Food-borne trematodiases 1.88 (0.70–4.84) Rabies 1.46 ((0.85–2.66) Dengue 0.83 (0.34–1.41) African trypanosomiasis 0.56 (0.08–1.77) Chagas disease 0.55 (0.27–1.05) Cysticercosis 0.50 (0.38–0.66) Onchocerciasis 0.49 (0.36–0.66) Trachoma 0.33 (0.24–0.44) Echinococcosis 0.14 (0.07–0.29) Yellow fever <0.001 Other NTDs * 4.72 (3.53–6.35) Open in a separate window * Relapsing fevers, typhus fever, spotted fever, Q fever, other rickettsioses, other mosquito-borne viral fevers, unspecified arthropod-borne viral fever, arenaviral haemorrhagic fever, toxoplasmosis, unspecified protozoal disease, taeniasis, diphyllobothriasis and sparganosis, other cestode infections, dracunculiasis, trichinellosis, strongyloidiasis, enterobiasis, and other helminthiases. Even DALYs, however, do not tell the complete story of the harmful effects from NTDs. Some of the specific and potential shortcomings of GBD 2010 have been highlighted elsewhere [9]. Furthermore, DALYs measure only direct health loss and, for example, do not consider the economic impact of the NTDs that results from detrimental effects on school attendance and child development, agriculture (especially from zoonotic NTDs), and overall economic productivity [10], [11]. Nor do DALYs account for direct costs of treatment, surveillance, and prevention measures. Yet, economic impact has emerged as an essential feature of the NTDs, which may trap people in a cycle of poverty and disease [10]–[12]. Additional aspects not considered by the DALY metrics are the important elements of social stigma for many of the NTDs and the spillover effects to family and community members [13], [14], loss of tourism [15], and health system overload (e.g., during dengue outbreaks). Ultimately NTD control and elimination efforts could produce social and economic benefits not necessarily reflected in the DALY metrics, especially among the most affected poor communities [11].

Food-Borne Trematodiases

SUMMARY An estimated 750 million people are at risk of infections with food-borne trematodes, which comprise liver flukes (Clonorchis sinensis, Fasciola gigantica, Fasciola hepatica, Opisthorchis felineus, and Opisthorchis viverrini), lung flukes (Paragonimus spp.), and intestinal flukes (e.g., Echinostoma spp., Fasciolopsis buski, and the heterophyids). Food-borne trematodiases pose a significant public health and economic problem, yet these diseases are often neglected. In this review, we summarize the taxonomy, morphology, and life cycle of food-borne trematodes. Estimates of the at-risk population and number of infections, geographic distribution, history, and ecological features of the major food-borne trematodes are reviewed. We summarize clinical manifestations, patterns of infection, and current means of diagnosis, treatment, and other control options. The changing epidemiological pattern and the rapid growth of aquaculture and food distribution networks are highlighted, as these developments might be associated with an elevated risk of transmission of food-borne trematodiases. Current research needs are emphasized.

Past, present, and future of Japanese encephalitis.

JE is increasing in some areas (due to population growth and intensified rice irrigation) but declining in others.

Schistosomiasis and soil-transmitted helminthiasis: common drugs for treatment and control.

Schistosomiasis is a disease caused by parasitic trematode worms (schistosomes) that currently affects 200 million people living in tropical and subtropical environments. It is a chronic disease and the latest estimates for sub-Saharan Africa are that it kills > 200,000 people every year. Soil-transmitted helminthiasis (STH) is caused by intestinal nematodes. More than 2 billion people are infected worldwide and the disease burden might approach that of malaria. Recognising the enormous public health significance of schistosomiasis and STH, particularly among the poor, and in view of readily available drugs that are safe, efficacious and inexpensive, the World Health Assembly recently set forth a resolution for a combined approach for morbidity control of both diseases. This review briefly summarises the geographical distribution, life cycle and global burden of schistosomiasis and STH. The current arsenal of drugs available for morbidity control, including discovery, chemistry, pharmacological properties and aspects of therapeutic efficacy and adverse events in clinical human use is then discussed. The emphasis is on praziquantel, oxamniquine and artemisinin derivatives (against schistosomes) and albendazole, mebendazole, levamisole, pyrantel pamoate and other compounds (against intestinal nematodes). The experience gained with combination chemotherapy in schistosomiasis and STH is briefly discussed. Finally, current research needs and the critical importance for development of novel anthelmintic drugs, so that chemotherapy can continue to serve as the backbone of integrated and sustainable control of schistosomiasis and STH, is highlighted.

Effect of Sanitation on Soil-Transmitted Helminth Infection: Systematic Review and Meta-Analysis

A systematic review and meta-analysis by Kathrin Ziegelbauer and colleagues finds that sanitation is associated with a reduced risk of transmission of helminthiases to humans.

Global burden of human food-borne trematodiasis: a systematic review and meta-analysis

BACKGROUND Food-borne trematodiases are a group of neglected tropical diseases caused by liver, lung, and intestinal parasitic fluke infections. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD 2010 study) and a WHO initiative, we assessed the global burden of human food-borne trematodiasis, as expressed in disability-adjusted life years (DALYs) for the year 2005. METHODS We systematically searched electronic databases for reports about human food-borne trematodiasis without language restriction, between Jan 1, 1980, and Dec 31, 2008. We used a broad search strategy with a combination of search terms and parasite and disease names. The initial search results were then screened on the basis of title, abstract, and, finally, full text. Relevant quantitative and qualitative data on human prevalence, morbidity, and mortality of food-borne trematodiasis were extracted. On the basis of available information on pathological and clinical appearance, we developed simplified disease models and did meta-analyses on the proportions and odds ratios of specified sequelae and estimated the global burden of human food-borne trematodiasis. FINDINGS We screened 33,921 articles and identified 181 eligible studies containing quantitative information for inclusion in the meta-analyses. About 56·2 million people were infected with food-borne trematodes in 2005: 7·9 million had severe sequelae and 7158 died, most from cholangiocarcinoma and cerebral infection. Taken together, we estimate that the global burden of food-borne trematodiasis was 665,352 DALYs (lower estimate 479,496 DALYs; upper estimate 859,051 DALYs). Furthermore, knowledge gaps in crucial epidemiological disease parameters and methodological features for estimating the global burden of parasitic diseases that are characterised by highly focal spatial occurrence and scarce and patchy information were highlighted. INTERPRETATION Despite making conservative estimates, we found that food-borne trematodiases are an important cluster of neglected diseases. FUNDING Swiss National Science Foundation; Institute for Health Metrics and Evaluation.

Reducing the burden of malaria in different eco-epidemiological settings with environmental management: a systematic review

The public health and economic significance of malaria is enormous, and its control remains a great challenge. Many established malaria control methods are hampered by drug resistance and insecticide-resistant vectors. Malaria control measures built around environmental management are non-toxic, cost-effective, and sustainable. However, there has been no comprehensive review of the literature or meta-analysis examining the effect of these interventions. We therefore did a systematic literature review and identified 40 studies that emphasised environmental management interventions and reported clinical malaria variables as outcome measures. Of these 40 studies, environmental modification (measures aiming to create a permanent or long-lasting effect on land, water, or vegetation to reduce vector habitats--eg, the installation and maintenance of drains) was the central feature in 27 studies, environmental manipulation (methods creating temporary unfavourable conditions for the vector--eg, water or vegetation management) in four, and nine quantified the effect of modifications of human habitation. Most of the studies (n=34, 85%) were implemented before the Global Malaria Eradication Campaign (1955-69), which mainly relied on indoor residual spraying with dichlorodiphenyltrichloroethane (DDT). In 16 studies that applied environmental modification and in eight studies on modification of human habitation, the risk ratio of malaria was reduced by 88.0% (95% CI 81.7-92.1) and 79.5% (95% CI 67.4-87.2), respectively. We conclude that malaria control programmes that emphasise environmental management are highly effective in reducing morbidity and mortality. Lessons learned from these past successful programmes can inspire sound and sustainable malaria control approaches and strategies.