PLoS Neglected Tropical Diseases: New Articles

PLoS Neglected Tropical Diseases Issue Image | Vol. 4(7) July 2010

2010-07-27T07:00:00Z

The helminth fluorescent bioassay: An objective tool for quantifying schistosome viability.

Confocal microscopy of Schistosoma mansoni schistosomula illustrates the ease by which dead (propidium iodide-positive, red individuals) and live (fluorescein diacetate-positive, green individuals) parasites can be distinguished using a helminth fluorescent bioassay (HFB) described by Peak et al. (doi:10.1371/journal.pntd.1000759). It is anticipated that the HFB will be useful in objectively measuring schistosome survival during immunological assays (antibody- or complement-mediated killing), RNAi investigations, and drug screening protocols.

Image Credit: Emily Peak

Mycobacterium ulcerans and Other Mycolactone-Producing Mycobacteria Should Be Considered a Single Species

2010-07-27T07:00:00Z

Asymmetric Wolbachia Segregation during Early Brugia malayi Embryogenesis Determines Its Distribution in Adult Host Tissues

2010-07-27T07:00:00Z

Author Summary

Filarial diseases affect over 150 million people in tropical countries. They are caused by parasitic nematodes like Brugia malayi that rely on their endosymbiont Wolbachia for their survival and fertility. These bacteria are a recognized drug target in the search for treatments killing adult worms. To understand the transmission of Wolbachia from the embryonic to adult stages, we developed new techniques to track these bacteria at the cellular and tissue levels. These techniques include immunofluorescence in whole mount adult tissues and embryos. We found that Wolbachia segregate asymetrically in specific cells, in a lineage-specific manner during early Brugia embryogenesis, and rely on cell fusion to subsequently populate the adult hypodermal chords. From the chords, the Wolbachia can be secreted in the secretory-excretory canal, suggesting that in addition to dead worms releasing the bacteria in the human body, living worms may also secrete Wolbachia, whose role in stimulating the immune system in filarial pathologies is now well established.

Development and Validation of a Quantitative, High-Throughput, Fluorescent-Based Bioassay to Detect Schistosoma Viability

2010-07-27T07:00:00Z

Author Summary

With only one effective drug, praziquantel, currently used to treat most worldwide cases of schistosomiasis, there exists a pressing need to identify alternative anthelmintics before the development of praziquantel-resistant schistosomes removes our ability to combat this neglected tropical disease. At present, the most widely adopted methodology used to identify promising new anti-schistosome compounds relies on time consuming and subjective microscopic examination of parasite viability in response to in vitro schistosome/compound co-culturing. In our continued effort to identify novel drug and vaccine targets, we detail a dual-fluorescence bioassay that can objectively be used for assessing Schistosoma mansoni schistosomula viability in a medium or high- throughput manner to suit either academic or industrial settings. The described methodology replaces subjectivity with sensitivity and provides an enabling technology useful for rapid in vitro screens of both natural and synthetic compound libraries. It is expected that results obtained from these quantifiable in vitro screens would prioritize the most effective anti-schistosomal compounds for follow-up in vivo experimentation. This highly-adaptable dual-fluorescence bioassay could be integrated with other methods for measuring schistosome phenotype and, together, be used to greatly accelerate our search for novel anthelmintics.

Neglected Tropical Diseases outside the Tropics

2010-07-27T07:00:00Z

Author Summary

Neglected Tropical Diseases (NTDs) have been targeted due to their prevalence and the burden of disease they cause globally, but there has been no significant focus in the literature on the subject of NTDs as a group in immigrants and travelers, and no specific studies on the emerging phenomenon of imported NTDs. We present the experience of a Tropical Medicine Unit in a major European city, over a 19-year period, describing and comparing NTDs diagnosed amongst immigrants, travelers and travelers visiting friends and relatives (VFRs). NTDs were diagnosed outside tropical areas and occurred more frequently in immigrants, followed by VFR travelers and then by other travelers. The main NTDs diagnosed in immigrants were onchocerciasis, Chagas disease and ascariasis; most frequent NTDs in travelers were schistosomiasis, onchocerciasis and ascariasis, and onchocerciasis and schistosomiasis in VFRs. Issues focusing on modes of transmission outside endemic areas and how eradication programs for some NTDs in endemic countries may have an impact in non-tropical Western countries by decreasing disease burden in immigrants, are addressed. Adherence to basic precautions such as safe consumption of food/water and protection against arthropod bites could help prevent many NTDs in travelers.

Rift Valley Fever Virus Seroprevalence in Human Rural Populations of Gabon

2010-07-27T07:00:00Z

Author Summary

Rift Valley fever (RVF) is a disease transmitted by a mosquito bite (Aedes). Humans can also be infected through direct contact with blood (aerosols) or tissues (placenta, stillborn) of infected animals. Although severe clinical cases can be observed, infection with RVF virus (RVFV) in humans in most cases causes a febrile illness without serious symptoms. In small ruminants RVFV mainly causes abortion and neonatal death. RVFV distribution has been poorly investigated in Central Africa. We conducted a large scale serological survey of RVF antibodies in rural populations in Gabon, involving 4,323 individuals from 212 randomly selected villages. The results showed an overall RVFV prevalence of 3.3%, with values of 2.9% in the forested zones, 2.2% in savannas and 8.3% in the lakes region. These findings strongly suggest for the first time the wide circulation of Rift valley fever virus in Gabon and the possible existence of a sylvan cycle of RVF virus in this country. The serological higher prevalence in the lake region suggests that this region is likely to have particular ecological conditions, especially mosquito vector species, favoring the circulation of this virus. In Gabon, human cases of RVF may occur but are either misdiagnosed or not reported.

A Curative Immune Profile One Week after Treatment of Indian Kala-Azar Patients Predicts Success with a Short-Course Liposomal Amphotericin B Therapy

2010-07-27T07:00:00Z

Author Summary

Visceral leishmaniasis (VL) is a potentially fatal disease without treatment, characterized by prolonged fever, enlargement of spleen and liver, anaemia and weight loss. Treatment for VL is difficult, as it requires prolonged and painful application of toxic drugs with adverse side effects. It is therefore important to develop alternative satisfactory therapies for VL. Herein, we report the efficacy of a new liposomal formulation of amphotericin-B, Fungisome, and the immunological changes that take place 1-week after treatment. Patients treated with 5 and 7.5 mg/kg (single-dose) and 10 mg/kg (5 mg/kg double-dose) of Fungisome showed 60%, 50% and 90% successful cure at 6-month posttreatment, respectively. Successfully cured patients showed reduced IL-12 and IL-10 levels in the plasma and two-fold or more increase in Th1 type-cytokines IFN-γ, IL-12 and TNF, and down-regulation of immunosuppressive factors IL-10 and TGF-β in the culture supernatants, 1-week after treatment independent of drug-dose. Insignificant decrease of plasma IL-12 and IL-10, negligible increase of Th1-cytokines, and persistence of IL-10, despite decrease in TGF-β in culture supernatants, correlated with relapse within 6-months of treatment. These interesting results pave the way for further testing of this drug as a new alternative in the chemotherapy of leishmaniasis.

Phylogeography of Recently Emerged DENV-2 in Southern Viet Nam

2010-07-27T07:00:00Z

Author Summary

Dengue virus (DENV) is the cause of the most common vector-borne viral disease of humans, and is at particularly high prevalence in parts of Southeast Asia. Most studies of DENV transmission have focused on very local or international movement patterns, and have not explored how DENV moves through an endemic region. To address this issue, we employed newly developed phylogeographic methods to study patterns of spatial spread in 168 full-length DENV-2 genome sequences collected during a hospital-based study in southern Viet Nam, focusing on the Asian I genotype that recently emerged in this region. This analysis revealed that the urban population of Ho Chi Minh City plays a central role in the dispersal of the virus, and that DENV in this city tends to move along a gradient of population density. In addition, human movement between urban and rural areas was the most likely explanation for the rapid diffusion of DENV across southern Viet Nam following its introduction into Ho Chi Minh City. After reaching more rural areas, some virus lineages were maintained there for a number of years. These results therefore indicate that virological surveillance is necessary in both urban and rural populations.

Randomised Controlled Double-Blind Non-Inferiority Trial of Two Antivenoms for Saw-Scaled or Carpet Viper (Echis ocellatus) Envenoming in Nigeria

2010-07-27T07:00:00Z

Author Summary

Snake bite threatens millions of poor rural folk throughout Africa. In Nigeria, as in many countries of sub-Saharan Africa, it takes a terrible toll on human life and limb. Over the years, the news for those exposed to snake bite has been generally bad: withdrawal of antivenom manufacturers, increasing cost and, most recently, the marketing of ineffective or fake antivenoms in the region. Our paper reports encouraging results achieved by two antivenoms created as a direct consequence of the present crisis in antivenom supply for Africa. They have been assessed in the most powerful trial ever attempted in this field. The trial showed that in people with non-clotting blood following carpet viper bite, the commonest cause of snake bite morbidity and mortality in the West African savannah, administration of the antivenoms- EchiTAb G and EchiTAb Plus-ICP led to permanent restoration of blood clotting in 76% and 83% of the patients within 6 hours, respectively. Generally mild early adverse reactions were recorded in 19% and 26%, respectively. Both antivenoms proved effective and acceptably safe and can be recommended for treating carpet viper envenoming in Nigeria.

The Global Atlas of Helminth Infection: Mapping the Way Forward in Neglected Tropical Disease Control

2010-07-27T07:00:00Z

Health Education through Analogies: Preparation of a Community for Clinical Trials of a Vaccine against Hookworm in an Endemic Area of Brazil

2010-07-20T07:00:00Z

Author Summary

Conducting clinical trials of new vaccines in rural, resource-limited areas can be challenging since the people living in these areas often have high levels of illiteracy, little experience with clinical research, and limited access to routine health care. Especially difficult is obtaining informed consent for participation in this type of research and ensuring that potential participants adequately understand the potential risks and benefits of participation. The researchers have been preparing a remote field site in the northeastern part of the state of Minas Gerais, Brazil, for clinical trials of experimental hookworm vaccines. A special educational video was designed based on the method of analogies to introduce new scientific concepts related to the researchers' work and to improve knowledge of hookworm, a disease that is highly prevalent in their community. A questionnaire was administered both before and after the video was shown to a group of adults at the field site, which demonstrated the effectiveness of the video in disseminating knowledge about hookworm infection and about the vaccine being developed. Therefore, even in a rural, resource-limited area, educational tools can be specially designed that significantly improve understanding and therefore the likelihood of obtaining truly informed consent for participation in clinical research.

The Jacob2 Lectin of the Entamoeba histolytica Cyst Wall Binds Chitin and Is Polymorphic

2010-07-20T07:00:00Z

Author Summary

For many years, we and others have used cysts of Entamoeba invadens (Ei), a reptilian parasite, to model the infectious and diagnostic cysts of the human pathogen Entamoeba histolytica (Eh). The Ei cyst wall is composed of chitin fibrils, as well as Jacob and Jessie lectins that have unique chitin-binding domains. Our recent results suggest a “wattle and daub” model of the Ei cyst wall, where the wattle or sticks (chitin fibrils bound by multivalent Jacob lectins) is constructed prior to the addition of the mortar or daub (self-aggregating Jessie3 lectins). Here we “humanize” the Ei model of the cyst wall with four findings. First, a recombinant Eh Jacob2 lectin, which has three predicted chitin-binding domains surrounding a large spacer domain, binds chitin beads. Second, polymorphisms in the spacer domain of EhJacob2 discriminate clinical isolates of Entamoeba. Third, chitinase, Jacob2 lectin, and Jessie3 lectin are present in cyst walls of clinical isolates of Entamoeba. Finally, numerous sera from patients infected with Entamoeba recognize recombinant Eh Jacob1 and Jessie3 lectins.

Single Nucleotide Polymorphism Typing of Mycobacterium ulcerans Reveals Focal Transmission of Buruli Ulcer in a Highly Endemic Region of Ghana

2010-07-20T07:00:00Z

Author Summary

Mycobacterium ulcerans causes a destructive skin disease known as Buruli ulcer (BU), which has been reported from more than 30 tropical or subtropical countries, with the highest prevalence in Western Africa. Due to the striking genetic monomorphism of African M. ulcerans populations, conventional genetic fingerprinting methods have largely failed to differentiate isolates coming from the same BU endemic area. Here we report a highly discriminatory fingerprinting method for M. ulcerans using a single nucleotide polymorphism-based genetic fine-typing technique. This method has enabled us for the first time to identify different M. ulcerans haplotypes within a BU endemic area. Linking the origins of M. ulcerans strains with the patients' residences unveiled the clustering of unique M. ulcerans haplotypes within the Densu river basin of Ghana. Results show, that haplotypes do not spread within a short time over the entire BU endemic region, but rather form independent focal transmission clusters.

High Rates of Homologous Recombination in the Mite Endosymbiont and Opportunistic Human Pathogen Orientia tsutsugamushi

2010-07-20T07:00:00Z

Author Summary

Scrub typhus, the rickettsial infectious disease caused by the obligate intracellular bacterium Orientia tsutsugamushi, is endemic across the Asia Pacific region. The bacterium is transmitted by the bite of larval stages of trombiculid mites (“chiggers”; Leptotrombidium spp.), which more typically feed on small rodents. Clinical features include fever, headache, myalgia, lymphadenopathy and an eschar at the site of the bite. Despite the importance of this pathogen, little is known of the population diversity or the role of homologous recombination in driving the microevolution of this species. Here, we describe the development and application of a multilocus sequence typing (MLST) scheme that can be applied directly to blood samples, and that was applied to 108 O. tsutsugamushi isolates. We found that this organism demonstrated a high rate of homologous recombination, a surprising finding given the intracellular life-style of this species. We also found that 25% of patients in our study were simultaneously infected with multiple sequence types, suggesting multiple infection caused by either multiple mite bites, or multiple strains co-existing within individual mites.

Evaluation of Chikungunya Diagnostic Assays: Differences in Sensitivity of Serology Assays in Two Independent Outbreaks

2010-07-20T07:00:00Z

Author Summary

Chikungunya is a mounting public health concern in many parts of the world. Definitive diagnosis is critical in differentiating the diseases, especially in dengue endemic areas. There are some commercial chikungunya kits and published molecular protocols available, but no comprehensive comparative evaluation of them was performed. Using sera collected in outbreaks caused by two variants of Chikungunya virus (A226 and 226V), we tested 2 commercial IgM tests (CTK lateral flow rapid test and EUROIMMUN IFA) alongside our in-house IgM assays (using both variants of the virus). Sensitivities of 2 published PCR protocols were also evaluated based on RNA standards derived from cell-cultured viruses. The commercial assays had different performances in each outbreak, with CTK's lateral flow test having the best performance in the first outbreak and EUROIMMUN IFA being more sensitive in the second outbreak. Use of the current circulating virus in a test assay improves sensitivity of the MAC-ELISAs. For PCR, a probe-based real time RT-PCR method was found to be 10 times more sensitive than the SYBR Green method. Despite this, the latter protocol is found to be more suitable and cost-effective for our diagnostic laboratory. This evaluation demonstrates the importance of appraisal of commercial kits and published protocols before application of a diagnostic tool in the clinical and operational setting.

Comparing Diagnostic Accuracy of Kato-Katz, Koga Agar Plate, Ether-Concentration, and FLOTAC for Schistosoma mansoni and Soil-Transmitted Helminths

2010-07-20T07:00:00Z

Author Summary

Infections with parasitic worms (e.g., Schistosoma mansoni, hookworm, roundworm, whipworm, and threadworm) are still widespread in the developing world. Accurate diagnosis is important for better patient management and for monitoring of deworming programs. Unfortunately, methods to detect parasite eggs or larvae in stool samples lack sensitivity, particularly when infection intensities are low. The most widely used method for the diagnosis of S. mansoni, hookworm, roundworm and whipworm in epidemiological surveys is the Kato-Katz technique. Recently, the FLOTAC technique has shown a higher sensitivity than the Kato-Katz method for the diagnosis of hookworm, roundworm and whipworm, but no data are available for S. mansoni. We compared the diagnostic accuracy of the FLOTAC with the Kato-Katz, ether-concentration and Koga agar plate techniques for S. mansoni and other parasitic worm infections using stool samples from 112 school children from Côte d'Ivoire. FLOTAC showed the highest sensitivity for S. mansoni diagnosis. Egg counts, however, were lower when using FLOTAC, an issue which needs further investigations. The FLOTAC, Kato-Katz and ether-concentration techniques failed to accurately detect threadworm larvae, and hence, the Koga agar plate remains the method of choice for this neglected parasite.

A Tractable Experimental Model for Study of Human and Animal Scabies

2010-07-20T07:00:00Z

Author Summary

Scabies, a neglected parasitic disease caused by the microscopic mite Sarcoptes scabiei, is a major driving force behind bacterial skin infections in tropical settings. Aboriginal and Torres Strait Islander peoples are nearly twenty times more likely to die from acute rheumatic fever and rheumatic heart disease than individuals from the wider Australian community. These conditions are caused by bacterial pathogens such as Group A streptococci, which have been linked to underlying scabies infestations. Community based initiatives to reduce scabies and associated disease have expanded, but have been threatened in recent years by emerging drug resistance. Critical biological questions surrounding scabies remain unanswered due to a lack of biomedical research. This has been due in part to a lack of either a suitable animal model or an in vitro culture system for scabies mites. The pig/mite model reported here will be a much needed resource for parasite material and will facilitate in vivo studies on host immune responses to scabies, including relations to associated bacterial pathogenesis, and more detailed studies of molecular evolution and host adaptation. It represents the missing tool to extrapolate emerging molecular data into an in vivo setting and may well allow the development of clinical interventions.

Emergence of the Asian 1 Genotype of Dengue Virus Serotype 2 in Viet Nam: In Vivo Fitness Advantage and Lineage Replacement in South-East Asia

2010-07-20T07:00:00Z

Author Summary

Dengue virus (DENV) is a mosquito transmitted RNA virus. One of the most characteristic patterns of DENV evolution is that viral lineages, including whole genotypes, are born and die-out on a regular basis. However, the precise cause of such lineage turnover is unclear. To address this issue we explored the genome-scale genetic diversity and evolution of dengue serotype 2 virus (DENV-2) in Viet Nam, a country with a high burden of dengue disease. We observed that DENV viruses assigned to the Asian 1 lineage were likely introduced into southern Viet Nam in the late 1990's (perhaps from Thailand) and subsequently displaced the resident Asian/American lineage serotype 2 viruses. A similar scenario seems to have occurred in Thailand and Cambodia, such that there appears to have been a region-wide proliferation of Asian 1 lineage viruses. Investigation of Vietnamese patients experiencing DENV-2 infection revealed that Asian 1 viruses also attain higher virus levels in the blood than viruses of the Asian/American lineage. This difference in virus titre is likely to have a profound impact on viral fitness by increasing the probability of mosquito transmission, and therein providing Asian 1 lineage viruses with a selective advantage.

The First Human Epitope Map of the Alphaviral E1 and E2 Proteins Reveals a New E2 Epitope with Significant Virus Neutralizing Activity

2010-07-13T07:00:00Z

Author Summary

Although the murine immune response to Venezuelan equine encephalitis virus (VEEV) is well-characterized, little is known about the human antibody response to VEEV. In this study we used phage display technology to isolate a panel of 11 VEEV-specfic Fabs from two human donors. Seven E2-specific and four E1-specific Fabs were identified and mapped to five E2 epitopes and three E1 epitopes. Two neutralizing Fabs were isolated, E2-specific F5 and E1-specific L1A7, although the neutralizing capacity of L1A7 was 300-fold lower than F5. F5 Fab was expressed as a complete IgG1 molecule, F5 native (n) IgG. Neutralization-escape VEEV variants for F5 nIgG were isolated and their structural genes were sequenced to determine the theoretical binding site of F5. Based on this sequence analysis as well as the ability of F5 to neutralize four neutralization-escape variants of anti-VEEV murine monoclonal antibodies (mapped to E2 amino acids 182–207), a unique neutralization domain on E2 was identified and mapped to E2 amino acids 115–119.

In Vitro and In Vivo High-Throughput Assays for the Testing of Anti-Trypanosoma cruzi Compounds

2010-07-13T07:00:00Z

Author Summary

The treatment of Trypanosoma cruzi infection (the cause of human Chagas disease) remains a significant challenge. Only two drugs, both with substantial toxicity, are available and the efficacy of these dugs is often questioned – in many cases due to the limitations of the methods for assessing efficacy rather than to true lack of efficacy. For these reasons relatively few individuals infected with T. cruzi actually have their infections treated. In this study, we report on innovative methods that will facilitate the discovery of new compounds for the treatment of T. cruzi infection and Chagas disease. Utilizing fluorescent and bioluminescent parasite lines, we have developed in vitro tests that are reproducible and facile and can be scaled for high-throughput screening of large compound libraries. We also validate an in vivo screening test that monitors parasite replication at the site of infection and determines the effectiveness of drug treatment in less than two weeks. More importantly, results in this rapid in vivo test show strong correlations with those obtained in long-term (e.g. 40 day or more) treatment assays. The results of this study remove one of the obstacles for identification of effective and safe compounds to treat Chagas disease.

Farm-Level Risk Factors for Fish-Borne Zoonotic Trematode Infection in Integrated Small-Scale Fish Farms in Northern Vietnam

2010-07-13T07:00:00Z

Background

Northern Vietnam is an endemic region for fish-borne zoonotic trematodes (FZT), including liver and intestinal flukes. Humans acquire the FZT infection by eating raw or inadequately cooked fish. The production of FZT-free fish in aquaculture is a key component in establishing a sustainable program to prevent and control the FZT transmission to humans. Interventions in aquaculture should be based on knowledge of the main risk factors associated with FZT transmission.

Methodology/Principal Findings

A longitudinal study was carried out from June 2006 to May 2007 in Nam Dinh province, Red River Delta to investigate the development and risk factors of FZT infections in freshwater cultured fish. A total of 3820 fish were sampled six times at two-month intervals from 96 fish farms. Logistic analysis with repeated measurements was used to evaluate potential risk factors based on information collected through questionnaire interviews with 61 fish farm owners. The results showed that the FZT infections significantly increased from first sampling in June to July 2006 (65%) to sixth sampling in April to May, 2007 (76%). The liver fluke, Clonorchis sinensis and different zoonotic intestinal flukes including Haplochis pumilio, H. taichui, H. yokogawai, Centrocestus formosanus and Procerovum varium were found in sampled fish. Duration of fish cultured (sampling times), mebendazole drug self-medication of household members, presence of snails in the pond, and feeding fish with green vegetation collected outside fish farms all had a significant effect on the development of FZT prevalence in the fish.

Conclusions/Significance

The FZT prevalence in fish increased by 11 percentage points during a one-year culture period and the risk factors for the development of infection were identified. Results also highlight that the young fish are already highly infected when stocked into the grow-out systems. This knowledge should be incorporated into control programs of FZT transmission in integrated small-scale aquaculture nursery and grow-out systems in Vietnam.

Kinetic Analysis of Ex Vivo Human Blood Infection by Leishmania

2010-07-13T07:00:00Z

Author Summary

Leishmania infection is transmitted to mammalian hosts by phlebotomine sand flies. During the vector's bloodmeal, promastigotes are inoculated into hemorrhagic spots in the skin or are delivered into the extracellular matrix of the dermis. In the first case, blood is involved in transmission; in the second, it apparently is not. This is important, as the cellular milieu of infection can be critical for induction of the anti-parasite immune response and the subsequent course of disease. In humans, there are few comprehensive studies of the initial stages of Leishmania transmission in blood. Using blood to mimic the skin hematoma, we carried out kinetic and quantitative analyses of the reaction with serum and blood components of promastigotes from two Leishmania species with different tropism. We describe the kinetics of the promastigote reaction pathway that leads to blood infection and provide quantitative data for the cell types infected in the first five minutes of leishmaniosis transmission.

Integrated Surveys of Neglected Tropical Diseases in Southern Sudan: How Much Do They Cost and Can They Be Refined?

2010-07-13T07:00:00Z

Author Summary

Control of neglected tropical diseases (NTDs) is suggested to be more cost-effective when drugs are co-administered through a single integrated delivery system rather than separate systems. An essential prerequisite for such efficiency gains is sufficient geographical overlap of the targeted diseases – lymphatic filariasis (LF), onchocerciasis, schistosomiasis, soil-transmitted helminth infection and trachoma. Lack of data on geographical NTD distribution currently hampers the implementation of integrated control in many African countries. To generate the required data quickly and efficiently, integrated surveys of several NTDs simultaneously have been recommended. However, experience with integrated surveys is limited and requires additional research on cost and effectiveness to inform improvements in methodology and to guide scale-up. Here we analyse costs of the first integrated NTD survey round in Southern Sudan, generating average costs per implementation unit surveyed. Cost estimates are presented for use of the existing survey method and for modified versions. Key cost drivers were survey consumables and personnel, both of which are recurrent costs. These inputs could be reduced or put to more efficient use by modifying sampling for LF. To generate comparable cost estimates and identify key cost drivers in other settings we provide detailed cost data and guidance on how to replicate this work.

Family Relationship, Water Contact and Occurrence of Buruli Ulcer in Benin

2010-07-13T07:00:00Z

Author Summary

Mycobacterium ulcerans disease (Buruli ulcer) is the most widespread mycobacterial disease in the world after leprosy and tuberculosis. How M. ulcerans is introduced into the skin of humans remains unclear, but it appears that individuals living in the same environment may have different susceptibilities. This case control study aims to determine whether frequent contacts with natural water sources, family relationship or the practice of consanguineous marriages are associated with the occurrence of Buruli ulcer (BU). The study involved 416 participants, of which 104 BU-confirmed cases and 312 age, gender and village of residence matched controls (persons who had no signs or symptoms of active or inactive BU). The results confirmed that contact with natural water sources is a risk factor. Furthermore, it suggests that a combination of genetic factors may constitute risk factors for the development of BU, possibly by influencing the type of immune response in the individual, and, consequently, the development of BU infection per se and its different clinical forms. These findings may be of major therapeutic interest.

Dengue Dynamics in Binh Thuan Province, Southern Vietnam: Periodicity, Synchronicity and Climate Variability

2010-07-13T07:00:00Z

Author Summary

Dengue has become a major international public health problem due to increasing geographic distribution and a transition from epidemic transmission with long inter-epidemic intervals to endemic transmission with seasonal fluctuation. Seasonal and multi-annual cycles in dengue incidence vary over time and space. We performed wavelet analyses on time series of monthly notified dengue cases in Binh Thuan province, southern Vietnam, from January 1994 to June 2009. We observed a continuous annual mode of oscillation with a non-stationary 2–3-year multi-annual cycle. We used phase differences to describe the spatio-temporal patterns which suggest that the seasonal wave of infection was either synchronous with all districts or moving away from Phan Thiet district, while the multi-annual wave of infection was moving towards Phan Thiet district. We also found a strong non-stationary association between ENSO indices and climate variables with dengue incidence. We provided insight in dengue population transmission dynamics over the past 14.5 years. Further studies on an extensive time series dataset are needed to test the hypothesis that epidemics emanate from larger cities in southern Vietnam.

A Virulent Wolbachia Infection Decreases the Viability of the Dengue Vector Aedes aegypti during Periods of Embryonic Quiescence

2010-07-13T07:00:00Z

Author Summary

A virulent strain of the vertically-inherited bacterium Wolbachia pipientis (wMelPop-CLA) from the vinegar fly Drosophila melanogaster has been established in the dengue vector Aedes aegypti as part of a biological strategy for dengue control. In this medically important disease vector, wMelPop-CLA infection shortens mosquito lifespan and effectively blocks dengue productivity within the mosquito – two powerful effects that could decrease the vectorial capacity of mosquito populations for transmission of dengue viruses. Here, we further characterize the phenotypic effects of wMelPop-CLA on several life-history traits of Ae. aegypti, and report that this infection influences the survival of this mosquito species during sustained periods of embryonic quiescence. From an applied perspective, we suggest that this novel phenotype may be a useful tool to reduce mosquito population size in regions where embryonic quiescence contributes towards survival of this species through seasonal changes in rainfall or temperature, and thus further reduce the probability of dengue transmission at the beginning of each wet season. This study also highlights key fitness parameters needed to accurately model invasion dynamics of this virulent Wolbachia strain.

Antiangiogenic and Antitumor Effects of Trypanosoma cruzi Calreticulin

2010-07-06T07:00:00Z

Author Summary

In Latin America, 18 million people are infected with Trypanosoma cruzi, a protozoan that causes Chagas' disease. Vertebrate calreticulins (CRTs) are multifunctional, intra- and extracellular calcium binding, chaperone proteins. Since human CRT (HuCRT) inhibits capillary growth (angiogenesis) and suppresses tumor growth, the presence of these functions in T. cruzi CRT (TcCRT) may have interesting consequences in the host/parasite interactions. Previously, we have cloned and expressed TcCRT and shown that, when translocated from the endoplasmic reticulum to the area of trypomastigote flagellum emergence, it promotes infectivity, inactivates the complement system, an innate defense arm and inhibits angiogenesis in the chorioallantoid chicken egg membrane. TcCRT inhibits angiogenesis, since it interferes with endothelial cell multiplication, migration and capillary morphogenesis in vitro, as well as angiogenesis in rat aortic rings. The parasite molecule also displays important antitumor effects. In these activities, TcCRT is more effective than the human counterpart. Perhaps, by virtue of its capacity to inhibit angiogenesis, TcCRT is anti-inflammatory, thus impairing the antiparasite immune response. The TcCRT antiangiogenic effect could also explain, at least partially, the in vivo antitumor effects reported herein and the reports proposing antitumor properties for T. cruzi infection.

Seasonal and Regional Dynamics of M. ulcerans Transmission in Environmental Context: Deciphering the Role of Water Bugs as Hosts and Vectors

2010-07-06T07:00:00Z

Author Summary

Buruli ulcer, caused by Mycobacterium ulcerans, is a devastating skin disease. Most cases of Buruli ulcer occur in poor rural communities. As a result, treatment is frequently sought too late and about 25% of those infected—particularly children—become permanently disabled. Outbreaks of Buruli ulcer have always been associated with swampy areas. However, the route(s) of bacillus transmission is (are) still unclear. This Mycobacterium species resides in water where it colonizes many ecological niches such as aquatic plants, herbivorous animals and predatory/carnivorous insects. For several years the role of water bugs as hosts and vectors of M. ulcerans was suspected and was demonstrated under laboratory conditions. The aim of this work was to further assess the role of water bugs as hosts and vectors of M. ulcerans in environmental context. This work identifies several water bug families as hosts of M. ulcerans in Buruli ulcer endemic area. The detection of bacilli in saliva of human biting insects provides further evidence for their role in M. ulcerans transmission. Interestingly, three of these insects are good flyers, and as such could participate in M. ulcerans dissemination.

Serological Studies of Neurologic Helminthic Infections in Rural Areas of Southwest Cameroon: Toxocariasis, Cysticercosis and Paragonimiasis

2010-07-06T07:00:00Z

Author Summary

A total of 188 people (168 and 20 with and without symptoms confirmed by clinicians, respectively, 84.6% under 20 years old) were selected on a voluntary basis in Cameroon. Soil transmitted helminthic infections were prevalent among persons surveyed as is common in developing countries, since eggs of Ascaris lumbricoides, Trichuris trichiura and hookworms were found from 56 (33.3%), 72 (42.8%) and 19 (11.3%) persons, respectively. Serological analyses revealed that 61 (36.3%), 25 (14.9%) and 2 (1.2%) persons were positive to the diagnostic antigens specific for toxocariasis, paragonimiasis and cysticercosis, respectively. Among 14 people with epilepsy, 5 persons were seropositive to the antigen of Toxocara and one of them was simultaneously positive to the antigens of Paragonimus. Serological confirmation of cysticercosis in two children is very important, and we suggest that further serologic surveys of cysticercosis be carried out in both children and adults in this area for the promotion of a better quality of life including control and early treatment.

Specific Humoral Immunity versus Polyclonal B Cell Activation in Trypanosoma cruzi Infection of Susceptible and Resistant Mice

2010-07-06T07:00:00Z

Author Summary

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects 10–12 million people in Latin America. Patent parasitemia develops during acute disease. During this phase, polyclonal B cell activation has been reported to generate high levels of serum antibody with low parasite specificity, and delayed protective humoral immunity, which is necessary to prevent the host from succumbing to infection. In this manuscript, data show that relatively resistant mice have improved parasite-specific humoral immunity and decreased polyclonal B cell activation compared to susceptible mice. Parasite-specific humoral immunity was associated with differential expansion of B cell subsets and T cells in the spleen, as well as with increased Th1 and decreased Th2 cytokine production. These data suggest that host susceptibility/genetic biases impact the development of humoral responses to infection. Th2 cytokines are generally associated with improved antibody responses. In the context of T. cruzi infection of susceptible mice, Th2 cytokines were associated with increased total antibody production concomitant with delayed pathogen-specific humoral immunity. This study highlights the need to consider the effect of host biases when investigating humoral immunity to any pathogen that has reported polyclonal B cell activation during infection.

Where Do We Go from Here? Prevalence of Trachoma Three Years after Stopping Mass Distribution of Antibiotics in the Regions of Kayes and Koulikoro, Mali

2010-07-06T07:00:00Z

Author Summary

Trachoma, a blinding bacterial disease, is targeted for elimination by 2020. To achieve the elimination target, the World Health Organization (WHO) recommends member states implement the SAFE strategy; surgery, mass administration of antibiotics, promotion of hygiene and facial cleanliness and water and sanitation as environmental improvements. We present results from evaluation surveys conducted in 2006 and 2009 from the regions of Kayes and Koulikoro, Mali. Prevalence of active trachoma in 2006 was below baseline intervention thresholds in all surveyed districts and the national program stopped antibiotic distribution. The prevalence of trachoma in 2009 remained well below levels in 1998. However, in 8 of 13 districts compared, the prevalence of active trachoma was higher in 2009 than 2006. Three years of antibiotic intervention did not equate in all districts to a sustained reduction of active trachoma. No surveillance activities were implemented after stopping interventions. Surgical interventions may have reduced the burden of blinding trachoma but there is an ongoing need for surgeries specifically targeting affected women. Four districts meet the WHO criteria for resuming district-wide mass antibiotic distribution. A community-by-community approach to elimination may be needed in other districts. The promotion of facial cleanliness and good hygiene behavior should be reintroduced.

Response to Treatment in a Prospective Cohort of Patients with Large Ulcerated Lesions Suspected to Be Buruli Ulcer (Mycobacterium ulcerans Disease)

2010-07-06T07:00:00Z

Author Summary

Buruli ulcer (BU) disease, a neglected devastating infection caused by Mycobacterium ulcerans, has a huge impact because of the massive necrotizing, disfiguring ulcers that may result if not treated. Therapeutic options are surgery, antibiotics or combinations of both. Since 2004, the World Health Organization has recommended the use of antibiotics (rifampicin and streptomycin) for the management of the disease. The effectiveness of this antibiotic treatment on advanced lesions is, however, not well documented. We evaluated this strategy on large ulcers clinically suspected to be BU, in a rural zone of the Democratic Republic of Congo, and also assessed the outcome of treatment based only on clinical diagnosis. All patients were treated with antibiotics for 12 weeks and surgery was performed after 4 weeks. BU was confirmed by laboratory tests in 67% of the patients indicating that the clinical diagnosis of ulcerated forms of BU may be more difficult than usually reported. Although delayed surgery seemed detrimental in some confirmed cases, it was possible to treat 92% of patients successfully with low recurrence rates (1.1%) by combining antibiotic treatment with surgery in a rural zone. However, the need for and the best time for surgery for large Buruli ulcers requires clarification.

Phase II Evaluation of Sensitivity and Specificity of PCR and NASBA Followed by Oligochromatography for Diagnosis of Human African Trypanosomiasis in Clinical Samples from D.R. Congo and Uganda

2010-07-06T07:00:00Z

Author Summary

Diagnosis plays a central role in the control of human African trypanosomiasis (HAT) whose mainstay in disease control is chemotherapy. However, accurate diagnosis is hampered by the absence of sensitive techniques for parasite detection. Without concentrating the blood, detection thresholds can be as high as 10,000 trypanosomes per milliliter of blood. The polymerase chain reaction (PCR) and nucleic acid sequence-based amplification (NASBA) are promising molecular diagnostics that generally yield high sensitivity and could improve case detection. Recently, these two tests were coupled to oligochromatography (OC) for simplified and standardized detection of amplified products, eliminating the need for electrophoresis. In this study, we evaluated the diagnostic accuracy of these two novel tests on blood specimens from HAT patients and healthy endemic controls from D.R. Congo and Uganda. Both tests exhibited good sensitivity and specificity compared to the current diagnostic tests and may be valuable tools for sensitive and specific parasite detection in clinical specimens. These standardized molecular test formats open avenues for improved case detection, particularly in epidemiological studies and in disease diagnosis at reference centres.

Comparison of Three Commercially Available Dengue NS1 Antigen Capture Assays for Acute Diagnosis of Dengue in Brazil

2010-07-06T07:00:00Z

Author Summary

Dengue is the one of the most prevalent arthropod-borne viral diseases in tropical regions of the world. Manifestations may vary from asymptomatic to potentially fatal complications. Laboratorial diagnosis is essential to diagnose dengue and differentiate it from other diseases. Dengue virus non-structural protein 1 (NS1) may be used as a marker of acute dengue virus infection. Our results, based in the comparison of three NS1 antigen capture assays available, have shown that this approach is reliable for the early diagnosis of dengue infections, especially in the first four days after the onset of the symptoms. A lower sensitivity was observed in DENV-3 cases. Serum positive by virus isolation were more often detected than those positive by RT-PCR by all three assays. Only the Platelia™ NS1 test showed a higher sensitivity in confirming primary infections than secondary ones. In conclusion, NS1 antigen capture commercial kits are useful for diagnosis of acute primary and secondary dengue infections and, in endemic countries where secondary infections are expected to occur, may be used in combination with MAC-ELISA to increase the overall sensitivity of both tests.