Incorporating a rapid-impact package for neglected tropical diseases with programs for HIV/AIDS, tuberculosis, and malaria

Fishing for anti-leishmania drugs: principles and problems

To date, there are no vaccines against any of the major parasitic diseases including leishmaniasis, and chemotherapy is the main weapon in our arsenal. Current drugs are toxic and expensive, and are losing their effectiveness due to parasite resistance. The availability of the genome sequence of two species of Leishmania, Leishmania major and Leishmania infantum, as well as that of Trypanosoma brucei and Trypanosoma cruzi should provide a cornucopia of potential new drug targets. Their exploitation will require a multi-disciplinary approach that includes protein structure and function and high throughput screening of random and directed chemical libraries, followed by in vivo testing in animals and humans. We outline the opportunities that are made possible by recent technologies, and potential problems that need to be overcome.

Below the belt: new insights into potential complications of HIV-1/schistosome coinfections

PURPOSE OF REVIEW

Areas of the world with high endemnicity for helminth parasites overlap with those regions that have a seemingly disproportionate prevalence of HIV/AIDS. This has fueled speculation that potential pathological interactions between these infectious agents may accelerate disease progression. The proximity of many helminth infections to gastrointestinal mucosal sites combined with the recent discovery that acute HIV-1 infection causes early and massive depletion of CD4+ T cells in the gut furthers the potential pathological significance of co-infection. In this review, the 'gut wrenching' consequences of schistosome infection on HIV disease progression that may ensue during coinfection are considered.

RECENT FINDINGS

Massive depletion of CD4+ T cells in the gut during acute HIV-1 infection suggests that in addition to the administration of highly active antiretroviral therapy, limiting viral infection of susceptible cells in the gut after initial exposure may offer the best opportunity for slowing disease progression. In addition to memory T cells, mast cells, which are present in the intestinal lamina propria and upregulated in the gut during schistosome infection, have been recently described as an inducible reservoir of persistent HIV-1 infection.

SUMMARY

Schistosome infections create immune environments that may accelerate HIV disease progression. Their impact on highly active antiretroviral therapy should be considered.

The challenges of Chagas Disease-- grim outlook or glimmer of hope

The authors discuss the key challenges that undermine the control of Chagas disease and that must be urgently addressed to ensure long-term, sustainable control.

Epidemiology of plasmodium-helminth co-infection in Africa: populations at risk, potential impact on anemia, and prospects for combining control

Human co-infection with Plasmodium falciparum and helminths is ubiquitous throughout Africa, although its public health significance remains a topic for which there are many unknowns. In this review, we adopted an empirical approach to studying the geography and epidemiology of co-infection and associations between patterns of co-infection and hemoglobin in different age groups. Analysis highlights the extensive geographic overlap between P. falciparum and the major human helminth infections in Africa, with the population at coincident risk of infection greatest for hookworm. Age infection profiles indicate that school-age children are at the highest risk of co-infection, and re-analysis of existing data suggests that co-infection with P. falciparum and hookworm has an additive impact on hemoglobin, exacerbating anemia-related malarial disease burden. We suggest that both school-age children and pregnant women--groups which have the highest risk of anemia--would benefit from an integrated approach to malaria and helminth control.

Target assessment for antiparasitic drug discovery

Drug discovery is a high-risk, expensive and lengthy process taking at least 12 years and costing upwards of US$500 million per drug to reach the clinic. For neglected diseases, the drug discovery process is driven by medical need and guided by pre-defined target product profiles. Assessment and prioritisation of the most promising targets for entry into screening programmes is crucial for maximising the chances of success. Here, we describe criteria used in our drug discovery unit for target assessment and introduce the 'traffic-light' system as a prioritisation and management tool. We hope this brief review will stimulate basic scientists to acquire additional information necessary for drug discovery.

Neglected patients with a neglected disease? A qualitative study of lymphatic filariasis

BACKGROUND

Lymphatic filariasis (LF) is a so-called neglected tropical disease, currently overshadowed by higher-profile efforts to address malaria, tuberculosis, and HIV/AIDS. Despite recent successes in arresting transmission, some 40 million people who already have the disease have been largely neglected. This study aims to increase understanding of how this vulnerable, neglected group can be helped.

METHODS

We used purposive sampling to select 60 men and women with filarial lymphoedema (45 with filarial elephantiasis and 15 men with filarial hydrocoele) from the south of Sri Lanka in 2004-2005. Participants were selected to give a balance of men and women and poor and nonpoor, and a range of stages of the disease. Participants' experiences and the consequences of their disease for the household were explored with in-depth qualitative, semistructured interviews.

FINDINGS

LF was extremely debilitating to participants over long periods of time. The stigma attached to the condition caused social isolation and emotional distress, and delayed diagnosis and treatment, resulting in undue advancement of the disease. Free treatment services at government clinics were avoided because the participants' condition would be identifiable in public. Loss of income due to the condition was reported by all households in the sample, not just the poorest. Households that were already on low incomes were pushed into near destitution, from which it was almost impossible to escape. Affected members of low-income households also had less opportunity to obtain appropriate treatment from distant clinics, and had living and working conditions that made hygiene and compliance difficult.

SIGNIFICANCE

This highly vulnerable category of patients has low visibility, thus becoming marginalized and forgotten. With an estimated 300,000 total cases of elephantiasis and/or oedema in Sri Lanka, and around 300,000 men with filarial hydrocoele, the affected households will need help and support for many years to come. These individuals should be specially targeted for identification, outreach, and care. The global strategy for elimination is aimed at the cessation of transmission, but there will remain some 40 million individuals with clinical manifestations whose needs and problems are illustrated in this study.

Bayesian risk maps for Schistosoma mansoni and hookworm mono-infections in a setting where both parasites co-exist

There is growing interest in the use of Bayesian geostatistical models for predicting the spatial distribution of parasitic infections, including hookworm, Schistosoma mansoni and co-infections with both parasites. The aim of this study was to predict the spatial distribution of mono-infections with either hookworm or S. mansoni in a setting where both parasites co-exist. School-based cross-sectional parasitological and questionnaire surveys were carried out in 57 rural schools in the Man region, western Côte d'Ivoire. A single stool specimen was obtained from each schoolchild attending grades 3-5. Stool specimens were processed by the Kato-Katz technique and an ether concentration method and examined for the presence of hookworm and S. mansoni eggs. The combined results from the two diagnostic approaches were considered for the infection status of each child. Demographic data (i.e. age and sex) were obtained from readily available school registries. Each child's socio-economic status was estimated, using the questionnaire data following a household-based asset approach. Environmental data were extracted from satellite imagery. The different data sources were incorporated into a geographical information system. Finally, a Bayesian spatial multinomial regression model was constructed and the spatial patterns of S. mansoni and hookworm mono-infections were investigated using Bayesian kriging. Our approach facilitated the production of smooth risk maps for hookworm and S. mansoni mono-infections that can be utilized for targeting control interventions. We argue that in settings where S. mansoni and hookworm co-exist and control efforts are under way, there is a need for both mono- and co-infection risk maps to enhance the cost-effectiveness of control programmes.

Occurrence of Strongyloides stercoralis in Yunnan Province, China, and comparison of diagnostic methods

BACKGROUND

Strongyloides stercoralis is a neglected soil-transmitted helminth species, and there is a lack of parasitologic and epidemiologic data pertaining to this parasite in China and elsewhere. We studied the local occurrence of S. stercoralis in a village in Yunnan province, China, and comparatively assessed the performance of different diagnostic methods.

METHODOLOGY/PRINCIPAL FINDINGS

Multiple stool samples from a random population sample were subjected to the Kato-Katz method, an ether-concentration technique, the Koga agar plate method, and the Baermann technique. Among 180 participants who submitted at least 2 stool samples, we found a S. stercoralis prevalence of 11.7%. Males had a significantly higher prevalence than females (18.3% versus 6.1%, p = 0.011), and infections were absent in individuals <15 years of age. Infections were only detected by the Baermann (highest sensitivity) and the Koga agar plate method, but neither with the Kato-Katz nor an ether-concentration technique. The examination of 3 stool samples rather than a single one resulted in the detection of 62% and 100% more infections when employing the Koga agar plate and the Baermann technique, respectively. The use of a mathematical model revealed a 'true' S. stercoralis prevalence in the current setting of up to 16.3%.

CONCLUSIONS/SIGNIFICANCE

We conclude that S. stercoralis is endemic in the southern part of Yunnan province and that differential diagnosis and integrated control of intestinal helminth infections needs more pointed emphasis in rural China.

FLOTAC: a new sensitive technique for the diagnosis of hookworm infections in humans

Hookworms infect more than 10% of the world's population, but current diagnostic tools have drawbacks. Our objective was to compare the diagnostic performance of three methods (Kato-Katz, ether concentration and FLOTAC techniques) for hookworm diagnosis. Stool samples were obtained from 102 schoolchildren in Côte d'Ivoire. First, a duplicate 41.7mg Kato-Katz thick smear was prepared. Next, a small portion of stool (mean weight 1.8g) was preserved in sodium acetate-acetic acid-formalin and forwarded to a European laboratory. These samples were split in three parts, one processed by an ether concentration technique and two by the FLOTAC technique. All samples were examined by experienced technicians for hookworm eggs using light microscopy. The observed hookworm prevalences as assessed by the FLOTAC, Kato-Katz and ether concentration techniques were 65.7%, 51.0% and 28.4%, respectively. Considering the combined results as the diagnostic 'gold' standard, the FLOTAC technique had a sensitivity of 88.2% compared with 68.4% for the Kato-Katz and 38.2% for the ether concentration techniques. The Kato-Katz method resulted in a significantly higher mean number of eggs per gram of stool (155.8 EPG) compared with the FLOTAC (37.7 EPG) and ether concentration (5.7 EPG) methods. The FLOTAC method shows promise as an important new tool for individual hookworm diagnosis and for rigorous monitoring of helminth control programmes. [Clinical Trial No. ISRCTN21782274].

Recent progress in integrated neglected tropical disease control

Three years have passed since the publication of the first of a series of policy papers, which first highlighted the under-appreciated global burden of the neglected tropical diseases (NTDs) and then outlined a rationale for linking vertical control strategies for the seven most prevalent NTDs in a cost-effective pro-poor package of preventive chemotherapy. Since then, global advocacy for these conditions has increased and, with it, new funds for scale-up of integrated NTD control in sub-Saharan Africa. Recent speeches by the Director General of the World Health Organization at regional meetings have referred to NTDs as important global health priorities (www.who.int/dg/speeches/2007). Outlined here is a summary of the recent progress in global efforts to integrate NTD control, with an emphasis on the challenges that lie ahead.

Comparing models for early warning systems of neglected tropical diseases

Background

Early warning systems (EWS) are management tools to predict the occurrence of epidemics of infectious diseases. While climate-based EWS have been developed for malaria, no standard protocol to evaluate and compare EWS has been proposed. Additionally, there are several neglected tropical diseases whose transmission is sensitive to environmental conditions, for which no EWS have been proposed, though they represent a large burden for the affected populations.

Methodology/Principal Findings

In the present paper, an overview of the available linear and non-linear tools to predict seasonal time series of diseases is presented. Also, a general methodology to compare and evaluate models for prediction is presented and illustrated using American cutaneous leishmaniasis, a neglected tropical disease, as an example. The comparison of the different models using the predictive R² for forecasts of “out-of-fit” data (data that has not been used to fit the models) shows that for the several linear and non-linear models tested, the best results were obtained for seasonal autoregressive (SAR) models that incorporate climatic covariates. An additional bootstrapping experiment shows that the relationship of the disease time series with the climatic covariates is strong and consistent for the SAR modeling approach. While the autoregressive part of the model is not significant, the exogenous forcing due to climate is always statistically significant. Prediction accuracy can vary from 50% to over 80% for disease burden at time scales of one year or shorter.

Conclusions/Significance

This study illustrates a protocol for the development of EWS that includes three main steps: (i) the fitting of different models using several methodologies, (ii) the comparison of models based on the predictability of “out-of-fit” data, and (iii) the assessment of the robustness of the relationship between the disease and the variables in the model selected as best with an objective criterion.

Early Warning Systems (EWS) are management tools to predict the occurrence of epidemics. They are based on the dependence of a given infectious disease on environmental variables. Although several neglected tropical diseases are sensitive to the effect of climate, our ability to predict their dynamics has been barely studied. In this paper, we use several models to determine if the relationship between cases and climatic variability is robust—that is, not simply an artifact of model choice. We propose that EWS should be based on results from several models that are to be compared in terms of their ability to predict future number of cases. We use a specific metric for this comparison known as the predictive R², which measures the accuracy of the predictions. For example, an R² of 1 indicates perfect accuracy for predictions that perfectly match observed cases. For cutaneous leishmaniasis, R² values range from 72% to77%, well above predictions using mean seasonal values (64%). We emphasize that predictability should be evaluated with observations that have not been used to fit the model. Finally, we argue that EWS should incorporate climatic variables that are known to have a consistent relationship with the number of observed cases.

Bridges to sustainable tropical health

Ensuring sustainable health in the tropics will require bridge building between communities that currently have a limited track record of interaction. It will also require new organizational innovation if much of the negative health consequences of large-scale economic development projects are to be equitably mitigated, if not prevented. We focus attention on three specific contexts: (i) forging linkages between the engineering and health communities to implement clean water and sanitation on a broad scale to prevent reworming, after the current deworming-only programs, of people by diverse intestinal parasites; (ii) building integrated human and animal disease surveillance infrastructure and technical capacity in tropical countries on the reporting and scientific evidence requirements of the sanitary and phytosanitary agreement under the World Trade Organization; and (iii) developing an independent and equitable organizational structure for health impact assessments as well as monitoring and mitigation of health consequences of economic development projects. Effective global disease surveillance and timely early warning of new outbreaks will require a far closer integration of veterinary and human medicine than heretofore. Many of the necessary surveillance components exist within separate animal- and human-oriented organizations. The challenge is to build the necessary bridges between them.

Helminth infections and risk factor analysis among residents in Eryuan county, Yunnan province, China

Whilst infections with soil-transmitted helminths are common across China, the public-health significance of Schistosoma japonicum and food-borne helminths is more focalized. Only few studies have investigated the local epidemiology of helminth infections in rural China, including risk factor analysis. We collected stool and blood samples from 3220 individuals, aged 5-88 years, from 35 randomly selected villages in Eryuan county, Yunnan province, China. Stool samples were subjected to the Kato-Katz technique and examined for helminth eggs. Blood samples were tested for Trichinella spp., S. japonicum and cysticerci-specific antibodies. Data on individual and family-level risk factors were collected using questionnaires. The prevalence of Ascaris lumbricoides, Taenia spp., Trichuris trichiura and hookworms was 15.4%, 3.5%, 1.7% and 0.3%, respectively. The seroprevalence of Trichinella spp. was 58.8% and that of cysticercosis 18.5%. The egg positivity rate of S. japonicum in the 13 known endemic villages was 2.7%, and the corresponding seroprevalence was 49.5%. We observed a strong spatial heterogeneity in the families' economic status. S. japonicum infections were more prevalent among the Han than Bai nationality (odds ratio (OR)=3.77, 95% confidence interval (CI)=1.97-7.23) and tobacco growers (OR=3.66, 95% CI=1.77-7.60) and was only found at elevations below 2150 m above sea level. A. lumbricoides and Taenia spp. infections were more prevalent at altitudes above 2150 m when compared to lower settings (OR=1.51, 95% CI=1.24-1.84 and OR=5.32, 95% CI=3.42-8.28, respectively). The opposite was found for T. trichiura (OR=0.31, 95% CI=0.14-0.70). Our findings can guide the design and spatial targeting of control interventions against helminth infections in Eryuan county.

Activity of artemether and OZ78 against triclabendazole-resistant Fasciola hepatica

Triclabendazole is the drug of choice against Fasciola hepatica infections in humans and animals. However, parasite resistance against triclabendazole is spreading in the veterinary field, and there are no drugs of comparable activity currently available for the treatment and control of fascioliasis. We investigated the efficacy of single oral doses of artemether and OZ78 against adult triclabendazole-resistant F. hepatica harboured in rats, and compared the results with triclabendazole administered at two different doses. Single oral doses of 100 mg/kg OZ78 and 200 mg/kg artemether resulted in worm burden reductions of 100%. Whereas a single 10 mg/kg dose of triclabendazole achieved a worm burden reduction of only 4.0%, a five-fold higher dose yielded a significant worm burden reduction of 60.9%. However, the lower dose of triclabendazole administered to rats harbouring a triclabendazole-sensitive F. hepatica isolate resulted in a worm burden reduction of 95.3%. Our findings confirm that artemether and OZ78 possess good fasciocidal properties, even against a triclabendazole-resistant F. hepatica isolate, and hence these drugs might become useful in areas where triclabendazole resistance is common.

Prevalence, intensity and associated morbidity of Schistosoma japonicum infection in the Dongting Lake region, China

OBJECTIVE

To determine the prevalence and intensity of Schistosoma japonicum infection and associated morbidity, and to estimate the infected human and buffalo populations in the Dongting Lake region, Hunan province, China.

METHODS

We used data from the third national schistosomiasis periodic epidemiological survey (PES) of 2004. These included 47 144 human serological and 7205 stool examinations, 3893 clinical examinations and questionnaire surveys, and 874 buffalo stool examinations, carried out in 47 villages in Hunan province. Serological examinations were performed using the enzyme linked immunosorbent assay technique and human stool samples were examined by the Kato-Katz method. Stools from buffaloes and other domestic animals were examined for schistosome infection by the miracidial hatching test.

FINDINGS

Sero-prevalence was 11.9% (range: 1.3-34.9% at the village level), and the rate of egg-positive stools was estimated at 1.9% (0-10.9%) for the same population. The prevalence of infection among buffaloes was 9.5% (0-66.7%). Extrapolating to the entire population of the Dongting Lake region, an estimated 73 225 people and 13 973 buffaloes were infected. Most frequently reported symptoms were abdominal pain (6.2%) and bloody stools (2.7%). More than half of the clinically examined people reported having had at least one prior antischistosomal treatment.

CONCLUSION

There was a significant reduction in the number of humans infected with S. japonicum since the previous national PES carried out in 1995, partially explained by large-scale chemotherapy campaigns. However, a near-stable number of buffalo infections suggest continuing human re-infection, which may lead to future increases in human prevalence.

Parasites, people and policy: infectious diseases and the Millennium Development Goals

Here, I briefly review past history and present patterns in the interactions between parasites (defined broadly to include viruses and bacteria along with protozoan, helminth and arthropod parasites) and human populations in developed and developing countries. Against this background, I offer thoughts on current public health initiatives at national and international levels, with particular reference to the Millennium Development Goals. The news is both good and bad: mortality and morbidity from infectious diseases in the developing world are significantly lower than they were 50 years ago, but we should and could be doing better, particularly in relation to neglected tropical diseases.

Neglected tropical diseases in Uganda: the prospect and challenge of integrated control

So-called ‘neglected tropical diseases’ (NTDs) are becoming less neglected, with increasing political and financial commitments to their control. These recent developments were preceded by substantial advocacy for integrated control of different NTDs, on the premise that integration is both feasible and cost-effective. Although the approach is intuitively attractive, there are few countrywide experiences to confirm or refute this assertion. Using the example of Uganda, this article reviews the geographical and epidemiological bases for integration and assesses the potential opportunities for, and operational challenges of, integrating existing control activities for several of these diseases under an umbrella vertical programme.

Parasitological impact of 2-year preventive chemotherapy on schistosomiasis and soil-transmitted helminthiasis in Uganda

BACKGROUND

Schistosomiasis and soil-transmitted helminthiasis (STH) are among the neglected tropical diseases in Africa. A national control program for these diseases was initiated in Uganda during March 2003. Annual treatment with praziquantel and albendazole was given to schoolchildren in endemic areas and to adults in selected communities where local prevalence of Schistosoma mansoni in schoolchildren was high.

METHODS

The impact of the treatment program was monitored through cohorts of schoolchildren and adults. Their infection status with S. mansoni and STH was determined by parasitological examinations at baseline and at annual follow-ups. The prevalence and intensity of S. mansoni and STH before and after treatment were analyzed.

RESULTS

Two rounds of treatment significantly reduced the prevalence of S. mansoni infection in schoolchildren across three regions in the country from 33.4-49.3% to 9.7-29.6%, and intensity of infection from 105.7-386.8 eggs per gram of faeces (epg) to 11.6-84.1 epg. The prevalence of hookworm infection was reduced from 41.2-57.9% to 5.5-16.1%, and intensity of infection from 186.9-416.8 epg to 3.7-36.9 epg. The proportion of children with heavy S. mansoni infection was significantly reduced from 15% (95% CI 13.4-16.8%) to 2.3% (95% CI 1.6-3.0%). In adults, significant reduction in the prevalence and intensity of S. mansoni and hookworm infections was also observed. More importantly, the prevalence and intensity of both S. mansoni and hookworm infections in the cohorts of newly-recruited 6-year-olds who had never previously received treatment decreased significantly over 2 years: 34.9% (95% CI 31.9-37.8%) to 22.6% (95% CI 19.9-25.2%) and 171.1 epg (95% CI 141.5-200.7) to 72.0 epg (95% CI 50.9-93.1) for S. mansoni; and 48.4% (95% CI 45.4-51.5) to 15.9% (95% CI 13.6-18.2) and 232.7 epg (95% CI 188.4-276.9) to 51.4 epg (95% CI 33.4-69.5) for hookworms, suggesting a general decline in environmental transmission levels.

CONCLUSION

Annual anthelminthic treatment delivered to schoolchildren and to adults at high risk in Uganda can significantly reduce the prevalence and intensity of infection for schistosomiasis and STH, and potentially also significantly reduce levels of environmental transmission of infection.

Chagas disease: an impediment in achieving the Millennium Development Goals in Latin America

BACKGROUND

Achieving sustainable economic and social growth through advances in health is crucial in Latin America within the framework of the United Nations Millennium Development Goals.

DISCUSSION

Health-related Millennium Development Goals need to incorporate a multidimensional approach addressing the specific epidemiologic profile for each region of the globe. In this regard, addressing the cycle of destitution and suffering associated with infection with Trypanosoma cruzi, the causal agent of Chagas disease of American trypanosomiasis, will play a key role to enable the most impoverished populations in Latin America the opportunity to achieve their full potential. Most cases of Chagas disease occur among forgotten populations because these diseases persist exclusively in the poorest and the most marginalized communities in Latin America.

SUMMARY

Addressing the cycle of destitution and suffering associated with T. cruzi infection will contribute to improve the health of the most impoverished populations in Latin America and will ultimately grant them with the opportunity to achieve their full economic potential.

Lysophospholipase from the human blood fluke, Schistosoma japonicum

BACKGROUND

Given the unusual nature of the schistosome surface (a highly unusual lipid bi-layer) and the central role of the schistosome tegument in host-parasite relations, an enhanced understanding of the lipid biochemistry of the schistosome surface can be expected to provide new insights into schistosome pathogenesis and lead to new interventions.

METHODS

Bioinformatics approaches including three-dimensional homology modeling, along with recombinant expression, dimensional gel electrophoresis, immunoblotting, and Southern hybridizations were employed to characterize a novel lysophospholipase gene transcript from Schistosoma japonicum.

RESULTS

A transcript encoding a small form lysophospholipase from the egg stage of S. japonicum was isolated as an expressed sequence tag (EST). The deduced polypeptide included 227 amino acid residues, shared identity with lysophospholipases of Schistosoma mansoni and Rattus norvegicus, and esterase A of Pseudomonas fluorescens, appeared to belong to the abhydrolase_2 family of phospholipases and carboxylesterases, and was structurally related to the alpha/beta-hydrolases (pfam00561). The S. japonicum enzyme exhibited the GXSXG consensus active site characteristic of serine proteases, esterases, and lipases, and included the catalytic triad motif of Ser-Asp-His residues characteristic of serine hydrolases. Three-dimensional structural predictions accomplished using the coordinates of human acyl protein thioesterase and P. fluorescens esterase indicated that the putative catalytic triad formed by these three residues was located at the alpha/beta-hydrolase fold characteristic of the lipases and esterases. Soluble S. japonicum lysophospholipase was expressed in Escherichia coli as a recombinant enzyme of approximately 26kDa and employed to raise a mono-specific antiserum. Immunoblot analysis revealed a single 23-kDa band in both membrane-associated and soluble tissue fractions of adult schistosomes. Southern hybridization and bioinformatics analyses indicated the likely presence of allelic-specific polymorphisms and/or two copies of the lysophospholipase gene in the S. japonicum genome.

CONCLUSIONS

A small form lysophospholipase has been characterized from the human schistosome, S. japonicum. The availability of the recombinant S. japonicum lysophospholipase should facilitate further characterization of the enzyme, including its substrate and inhibition profiles and its potential as an interventional target. Schistosome lysophospholipase may represent a new target for anti-schistosomal chemotherapy given that metrifonate, which targets the related enzyme acetylcholinesterase, is an effective and safe medicine for treatment of urinary schistosomiasis.

Neglected diseases, civil conflicts, and the right to health

Neglected diseases remain one of the largest causes of disease and mortality. In addition to the difficulties in provision of appropriate drugs for specific diseases, many other factors contribute to the prevalence of such diseases and the difficulties in reducing their burden. We address the role that poor governance and politically motivated oppression have on the epidemiology of neglected diseases. We give case examples including filariasis in eastern Burma and vector-borne diseases (Chagas' disease, leishmaniasis, and yellow fever) in Colombia, we show the links between systematic human rights violations and the effects of infectious disease on health. We also discuss the role of researchers in advocating for and researching within oppressed populations.

Chemotherapy of schistosomiasis: present and future

Schistosomiasis is a chronic parasitic disease in tropical and subtropical regions and is associated with a variety of clinical syndromes that may lead to severe morbidity. Over the past 25 years, therapy and control of schistosomiasis has come to rely heavily on one drug, praziquantel (PZQ). This reliance is of concern should widespread treatment failure arise, particularly as measures are being undertaken to increase PZQ's availability. This review summarizes the use, possible modes of action and limitations of PZQ, and recent attempts to derive synthetic analogs. Alternative artemisinin-based chemotherapies that have shown applicability in certain disease settings are also similarly examined. Looking forward, the review highlights some of the more experimental anti-schistosomals being evaluated (e.g. the trioxolanes), including those where knowledge of the parasite target (e.g. cysteine proteases and hemozoin formation) is more defined.

Anaemia: a useful indicator of neglected disease burden and control

The authors argue that one way of evaluating the effectiveness of an intervention aimed at controlling neglected tropical diseases would be to assess its impact on anemia prevalence.

Human benefits of animal interventions for zoonosis control

Although industrialized countries have been able to contain recent outbreaks of zoonotic diseases, many resource-limited and transitioning countries have not been able to react adequately. The key for controlling zoonoses such as rabies, echinococcosis, and brucellosis is to focus on the animal reservoir. In this respect, ministries of health question whether the public health sector really benefits from interventions for livestock. Cross-sectoral assessments of interventions such as mass vaccination for brucellosis in Mongolia or vaccination of dogs for rabies in Chad consider human and animal health sectors from a societal economic perspective. Combining the total societal benefits, the intervention in the animal sector saves money and provides the economic argument, which opens new approaches for the control of zoonoses in resource-limited countries through contributions from multiple sectors.

Risk factors for Schistosoma mansoni and hookworm in urban farming communities in western Côte d'Ivoire

OBJECTIVES

To identify risk factors for Schistosoma mansoni and hookworm infections in urban farming communities, and to investigate small-scale spatial patterns of infection prevalence.

METHODS

A cross-sectional survey was carried out in 113 farming households (586 individuals) and 21 non-farming households (130 individuals) from six agricultural zones in the town of Man, western Côte d'Ivoire. Heads of households were interviewed on common agricultural activities, land and water use, education attainment, socioeconomic status and sanitation facilities. Household members provided stool specimens that were processed by the Kato-Katz technique and a formol-ether concentration method and diagnosed for S. mansoni, hookworms and other soil-transmitted helminths and intestinal protozoa. Bayesian statistics were employed for spatial analyses.

RESULTS

The prevalences of S. mansoni and hookworm in farming households were 51.4% and 24.7%, respectively. Risk factors for a S. mansoni infection comprised living in close proximity to the Kô River, water contact with irrigation wells and ponds and low education attainment. Living in zones of smallholder irrigated rice plots or large rice perimeters, using water from domestic wells, and low socioeconomic status were risk factors for a hookworm infection. We found significant spatial heterogeneity between agricultural zones, with the highest infection prevalences of S. mansoni and hookworm in the zone where there was a large rice perimeter.

CONCLUSIONS

In this urban setting, both S. mansoni and hookworm infections were related to specific agricultural activities. Health education and active participation of urban farmers for the control of schistosomiasis and soil-transmitted helminthiasis is recommended.

Single nucleotide polymorphism (SNP) markers for benzimidazole resistance in veterinary nematodes

Resistance to the benzimidazole class of anthelmintics in nematodes of veterinary importance has a long history. Research into the mechanisms responsible for this resistance is subsequently at a more advanced stage than for other classes of anthelmintics. The principal mechanism of resistance to benzimidazoles is likely to involve changes in the primary structure of β-tubulins, the building blocks of microtubules. Specifically, point mutations in the β-tubulin isotype 1 gene leading to amino acid substitutions in codons 167, 198, and 200 of the protein have been associated with resistance in nematodes. These single nucleotide polymorphisms offer a means of detecting the presence of resistance within populations. In this mini-review, we focus on the prevalence and importance of these polymorphisms in three groups of nematodes: trichostrongylids, cyathostomins, and hookworms. A brief overview of existing strategies for genotyping single nucleotide polymorphisms is also presented. The CARS initiative hopes to exploit these known polymorphisms to further our understanding of the phenomenon of BZ resistance.

piggyBac transposon mediated transgenesis of the human blood fluke, Schistosoma mansoni

The transposon piggyBac from the genome of the cabbage looper moth Trichoplusia ni has been observed in the laboratory to jump into the genomes of key model and pathogenic eukaryote organisms including mosquitoes, planarians, human and other mammalian cells, and the malaria parasite Plasmodium falciparum. Introduction of exogenous transposons into schistosomes has not been reported but transposon-mediated transgenesis of schistosomes might supersede current methods for functional genomics of this important human pathogen. In the present study we examined whether the piggyBac transposon could deliver reporter transgenes into the genome of Schistosoma mansoni parasites. A piggyBac donor plasmid modified to encode firefly luciferase under control of schistosome gene promoters was introduced along with 7-methylguanosine capped RNAs encoding piggyBac transposase into cultured schistosomula by square wave electroporation. The activity of the helper transposase mRNA was confirmed by Southern hybridization analysis of genomic DNA from the transformed schistosomes, and hybridization signals indicated that the piggyBac transposon had integrated into numerous sites within the parasite chromosomes. piggyBac integrations were recovered by retrotransposon-anchored PCR, revealing characteristic piggyBac TTAA footprints in the vicinity of the endogenous schistosome retrotransposons Boudicca, SR1, and SR2. This is the first report of chromosomal integration of a transgene and somatic transgenesis of this important human pathogen, in this instance accomplished by mobilization of the piggyBac transposon.

Proteomic analysis of Schistosoma mansoni egg secretions

Schistosomiasis remains a largely neglected, global health problem. The morbid pathology of the disease stems from the host's inflammatory response to parasite eggs trapped in host tissues. Long term host/parasite survival is dependent upon the successful modulation of the acute pathological response, which is induced by egg antigens. In this study, using Multidimensional Protein Identification Technology, we identified the Schistosoma mansoni egg secretome consisting of 188 proteins. Notably we identified proteins involved in redox balance, molecular chaperoning and protein folding, development and signaling, scavenging and metabolic pathways, immune response modulation, and 32 novel, previously uncharacterized schistosome proteins. We localized a subset of previously characterized schistosome proteins identified in egg secretions in this study, to the surface of live S. mansoni eggs using the circumoval precipitin reaction. The identification of proteins actively secreted by live schistosome eggs provides important new information for understanding immune modulation and the pathology of schistosomiasis.

Parasitic nematodes - from genomes to control

The diseases caused by parasitic nematodes in domestic and companion animals are major factors that decrease production and quality of the agricultural products. Methods available for the control of the parasitic nematode infections are mainly based on chemical treatment, non-chemical management practices, immune modulation and biological control. However, even with integrated pest management that frequently combines these approaches, the effective and long-lasting control strategies are hampered by the persistent exposure of host animals to environmental stages of parasites, the incomplete protective response of the host and acquisition of anthelmintic resistance by an increasing number of parasitic nematodes. Therefore, the challenges to improve control of parasitic nematode infections are multi-fold and no single category of information will meet them all. However, new information, such as nematode genomics, functional genomics and proteomics, can strengthen basic and applied biological research aimed to develop improvements. In this review we will, summarize existing control strategies of nematode infections and discuss ongoing developments in nematode genomics. Genomics approaches offer a growing and fundamental base of information, which when coupled with downstream functional genomics and proteomics can accelerate progress towards developing more efficient and sustainable control programs.

Thioredoxin glutathione reductase from Schistosoma mansoni: an essential parasite enzyme and a key drug target

BACKGROUND

Schistosomiasis--infection with helminth parasites in the genus Schistosoma, including S. mansoni--is a widespread, devastating tropical disease affecting more than 200 million people. No vaccine is available, and praziquantel, the only drug extensively utilized, is currently administered more than 100 million people yearly. Because praziquantel resistance may develop it is essential to identify novel drug targets. Our goal was to investigate the potential of a unique, selenium-containing parasite enzyme thioredoxin glutathione reductase (TGR) as a drug target.

METHODS AND FINDINGS

Using RNA interference we found that TGR is essential for parasite survival; after silencing of TGR expression, in vitro parasites died within 4 d. We also found that auranofin is an efficient inhibitor of pure TGR (Ki = 10 nM), able to kill parasites rapidly in culture at physiological concentrations (5 microM), and able to partially cure infected mice (worm burden reductions of ~60%). Furthermore, two previously used antischistosomal compounds inhibited TGR activity, suggesting that TGR is a key target during therapy with those compounds.

CONCLUSIONS

Collectively, our results indicate that parasite TGR meets all the major criteria to be a key target for antischistosomal chemotherapy. To our knowledge this is the first validation of a Schistosoma drug target using a convergence of both genetic and biochemical approaches.

Transmission consequences of coinfection: cytokines writ large?

Coinfection of a host by multiple parasite species is commonly observed and recent epidemiological work indicates that coinfection can enhance parasite transmission. This article proposes an immunoepidemiological framework to understand how within-host interactions during coinfection might affect between-host transmission. Cytokines, immune signalling molecules with a fundamental role in the amplification of antiparasitic effector mechanisms, provide a useful way to simplify immunological complexity for this endeavour--focusing on cytokines offers analytical tractability without sacrificing realism. Testable predictions about the epidemiological consequences of coinfection are generated by this conceptual framework.

Assessment of the age-specific disability weight of chronic schistosomiasis japonica

OBJECTIVE

To estimate the age-specific disability weight of chronic schistosomiasis japonica in China.

METHODS

Between October 2004 and January 2005, residents from two schistosome-endemic counties were screened for Schistosoma japonicum infection using an enzyme-linked immunosorbent assay. Disability and morbidity were assessed in seropositive individuals using the European quality of life questionnaire with an additional cognitive dimension (known as the "EQ-5D plus") and ultrasonography. The age-specific disability weight of chronic schistosomiasis was estimated based on participants self-rated health scores on the visual analogue scale of the questionnaire; the relationships between health status, morbidity and disability weight were explored using multilevel regression models.

FINDINGS

Of 2843 seropositive individuals, 1419 (49.9%) were classified as having chronic schistosomiasis. Hepatomegaly was found in 76.3% (1082/1419); hepatic fibrosis was found in 73.3% (1040/1419); and splenomegaly was found in 18.6% (264/1419). Diarrhoea was the most common self-reported symptom (46.0%; 653/1419), followed by abdominal pain (32.6%; 463/1419), impaired capacity to work or study (30.7%; 436/1419), and blood in the stool (11.1%; 157/1419). More than half of the respondents reported impairments in at least one dimension of the EQ-5D plus questionnaire, particularly pain or discomfort (47.9%; 675/1410) and anxiety or depression (39.4%; 555/1410). The overall disability weight was 0.191, and age-specific weights ranged from 0.095 among those aged 5-14 years to 0.246 among those aged > 60 years. Multilevel regression models indicated that the disability weight was significantly associated with the participants sex, grade of hepatic fibrosis, the presence of hepatomegaly, abdominal pain, blood in the stool, impaired capacity to work or study, and cognition.

CONCLUSION

The disability weight attributable to chronic schistosomiasis japonica is high and increases with age. Our findings call for a reappraisal of the disability weights due to chronic schistosomiasis mansoni and schistosomiasis haematobia as well as a re-estimation of the global burden of schistosomiasis.

A Bayesian approach to estimate the age-specific prevalence of Schistosoma mansoni and implications for schistosomiasis control

Models that accurately estimate the age-specific infection prevalence of Schistosoma mansoni can be useful for schistosomiasis control programmes, particularly with regard to whether mass drug administration or selected treatment should be employed. We developed a Bayesian formulation of an immigration-death model that has been previously proposed, which used maximum likelihood inference for estimating the age-specific S. mansoni prevalence in a dataset from Egypt. For comparative purposes, we first applied the Bayesian formulation of the immigration-death model to the dataset from Egypt. We further analysed data obtained from a cross-sectional parasitological survey that determined the infection prevalence of S. mansoni among 447 individuals in a village in Côte d'Ivoire. Three consecutive stool samples were collected from each participant and analysed by the Kato-Katz technique. In the Côte d'Ivoire study, the observed S. mansoni infection prevalence was 41.6% and varied with age. The immigration-death model was able to correctly predict 50% of the observed age group-specific point prevalences. The model presented here can be utilized to estimate S. mansoni community infection prevalences, which in turn helps in the strategic planning of schistosomiasis control.

Micronutrient supplements for children after deworming

The availability of a few inexpensive, single-dose drugs to treat soil-transmitted helminths and schistosomiasis offers the potential to reduce a considerable burden of acute disease, especially among children in sub-Saharan Africa. These treatments are being promoted as "rapid impact interventions". However, if helminth infections cause underweight, stunting, anaemia, and impaired mental development in children, how will removing worms alone lead to recovery without treating the underlying deficits that have been caused or made worse by helminth disease? Energy, protein, and micronutrients are required by children who are underweight or who have stunted growth; children who are anaemic will require iron and other micronutrients for haemopoiesis; and children who have lost education will need remedial teaching. Treating neglected worm diseases is an essential first step to good health, but anthelmintic drugs need to be integrated with simple and inexpensive nutritional interventions such as micronutrient supplements to promote recovery and have a rapid effect.

Profiling Schistosoma mansoni development using serial analysis of gene expression (SAGE)

Despite the widespread use of chemotherapy and other control strategies over the past 50years, transmission rates for schistosomiasis have changed little. Regardless of the approach used, future control efforts will require a more complete understanding of fundamental parasite biology. Schistosomes undergo complex development involving an alteration of parasite generations within a mammalian and freshwater molluscan host in the completion of its lifecycle. Little is known about factors controlling schistosome development, but understanding these processes may facilitate the discovery of new control methods. Therefore, our goal in this study is to determine global developmentally regulated and stage-specific gene expression in Schistosoma mansoni using serial analysis of gene expression (SAGE). We present a preliminary analysis of genes expressed during development and sexual differentiation in the mammalian host and during early larval development in the snail host. A number of novel, differentially expressed genes have been identified, both within and between the different developmental stages found in the mammalian and snail hosts.

Manipulating the manipulators: advances in parasitic helminth transgenesis and RNAi

Because tropical medicine and parasitology research has moved into the postgenomic era, an enormous amount of gene sequence information for parasitic helminths is now accumulating. These sequences undoubtedly hold information that can be used for new interventions and control. However, to exploit the new resource, methods for gene manipulation and transformation of parasitic worms are needed. Until recently, gene manipulation approaches had not been seriously addressed. This situation is now changing in response to the availability of genome sequences and other advances. In this article, we review advances in the transgenesis and gene silencing of parasitic worms.

Prodrugs for the treatment of neglected diseases

Recently, World Health Organization (WHO) and Medicins San Frontieres (MSF) proposed a classification of diseases as global, neglected and extremely neglected. Global diseases, such as cancer, cardiovascular and mental (CNS) diseases represent the targets of the majority of the R&D efforts of pharmaceutical companies. Neglected diseases affect millions of people in the world yet existing drug therapy is limited and often inappropriate. Furthermore, extremely neglected diseases affect people living under miserable conditions who barely have access to the bare necessities for survival. Most of these diseases are excluded from the goals of the R&D programs in the pharmaceutical industry and therefore fall outside the pharmaceutical market. About 14 million people,mainly in developing countries, die each year from infectious diseases. From 1975 to 1999,1393 new drugs were approved yet only 1% were for the treatment of neglected diseases[3]. These numbers have not changed until now, so in those countries there is an urgent need for the design and synthesis of new drugs and in this area the prodrug approach is a very interesting field. It provides, among other effects, activity improvements and toxicity decreases for current and new drugs, improving market availability. It is worth noting that it is essential in drug design to save time and money, and prodrug approaches can be considered of high interest in this respect. The present review covers 20 years of research on the design of prodrugs for the treatment of neglected and extremely neglected diseases such as Chagas' disease (American trypanosomiasis), sleeping sickness (African trypanosomiasis), malaria, sickle cell disease, tuberculosis, leishmaniasis and schistosomiasis.

Schistosomiasis: challenges for control, treatment and drug resistance

PURPOSE OF REVIEW

Schistosomiasis is a parasitic disease that has recently attracted increased focus and funding for control. Despite shifts in global health policy towards the implementation of mass chemotherapeutic control programmes at the national scale in sub-Saharan Africa, however, many challenges still exist.

RECENT FINDINGS

Publications reviewed for this article cover: the development of treatment strategies; the planning, implementation and impact of control programmes; the re-evaluation of the burden of schistosomiasis; improved tools for control; new drugs; the safety of treatment during pregnancy; and the development of resistance against praziquantel.

SUMMARY

The morbidity due to schistosomiasis has been shown to be greater than was previously thought. The reduction in morbidity of schistosomiasis by control programmes has been demonstrated, while new tools include a validated dose pole for delivering the correct treatment, geographical information systems mapping for determining high-risk areas, and Lot Quality Assurance Sampling for determining treatment strategies at the local level. Sustainability and future funding are issues to be addressed. Despite some positive results, myrrh is apparently ineffective against schistosomiasis, but fortunately no resistance to praziquantel has developed. We predict the impact of schistosomiasis control will be a healthier generation of children within 5 years.

In vitro and in vivo activities of synthetic trioxolanes against major human schistosome species

Schistosomiasis is a parasitic disease that remains of considerable public health significance in tropical and subtropical environments. Since the mainstay of schistosomiasis control is chemotherapy with a single drug, praziquantel, drug resistance is a concern. Here, we present new data on the antischistosomal properties of representative synthetic 1,2,4-trioxolanes (OZs). Exposure of adult Schistosoma mansoni for 24 h to a medium containing 20 mug/ml OZ209 reduced worm motor activity, induced tegumental alterations, and killed worms within 72 h. While exposure of S. mansoni to OZ78 had no apparent effect, addition of hemin reduced worm motor activity and caused tegumental damage. Administration of single 200-mg/kg of body weight oral doses of OZ78, OZ209, and OZ288 to mice harboring a juvenile S. mansoni infection resulted in worm burden reductions of 82.0 to 95.4%. In the adult infection model in mice, single 400-mg/kg doses of these compounds resulted in a maximum total worm burden reduction of 52.2%. High worm burden reductions (71.7 to 86.5%) were observed after administration of single 200-mg/kg doses of OZ78 and OZ288 to hamsters infected with either juvenile or adult S. mansoni. A single 200-mg/kg dose of OZ78 to hamsters infected with adult Schistosoma japonicum resulted in total and female worm burden reductions of 94.2 to 100%. Our results, along with the low toxicity, metabolic stability, and good pharmacokinetic properties of the OZs, indicate the potential for the development of novel broad-spectrum antischistosomal OZ drug candidates.

Ascaris, co-infection and allergy: the importance of analysis based on immunological variables rather than egg excretion

The ratio of Ascaris seropositivity to the presence of eggs in the faeces was 2.44 in children residing near Cape Town, South Africa. Similar and larger ratios have previously been described for children and women living in the city. The new finding strengthens the concept that when helminthic infections occur together with non-helminthic diseases, an analysis of the interaction must include the use of disease-related immunological variables and not be based only on egg excretion status. One of the reasons is that many egg-negative people who live where helminthiasis is highly endemic are immunologically activated as a result of transitory non-patent or intermittent patent infection by Ascaris and/or other worms.

Prevention, control, and elimination of neglected diseases in the Americas: pathways to integrated, inter-programmatic, inter-sectoral action for health and development

Background

In the Latin America and Caribbean region over 210 million people live below the poverty line. These impoverished and marginalized populations are heavily burdened with neglected communicable diseases. These diseases continue to enact a toll, not only on families and communities, but on the economically constrained countries themselves.

Discussion

As national public health priorities, neglected communicable diseases typically maintain a low profile and are often left out when public health agendas are formulated. While many of the neglected diseases do not directly cause high rates of mortality, they contribute to an enormous rate of morbidity and a drastic reduction in income for the most poverty-stricken families and communities. The persistence of this "vicious cycle" between poverty and poor health demonstrates the importance of linking the activities of the health sector with those of other sectors such as education, housing, water and sanitation, labor, public works, transportation, agriculture, industry, and economic development.

Summary

The purpose of this paper is three fold. First, it focuses on a need for integrated "pro-poor" approaches and policies to be developed in order to more adequately address the multi-faceted nature of neglected diseases. This represents a move away from traditional disease-centered approaches to a holistic approach that looks at the overarching causes and mechanisms that influence the health and well being of communities. The second objective of the paper outlines the need for a specific strategy for addressing these diseases and offers several programmatic entry points in the context of broad public health measures involving multiple sectors. Finally, the paper presents several current Pan American Health Organization and other institutional initiatives that already document the importance of integrated, inter-programmatic, and inter-sectoral approaches. They provide the framework for a renewed effort toward the efficient use of resources and the development of a comprehensive integrated solution to neglected communicable diseases found in the context of poverty, and tailored to the needs of local communities.