Use In Endemic Countries Research Articles

A Stakeholder Analysis of Schistosomiasis Diagnostic Landscape in South-West Nigeria: Insights for Diagnostics Co-creation.

Background: Schistosomiasis, one of the neglected tropical diseases, is a water-based parasitic disease of public health importance. Currently, tests for Schistosoma haematobium infection either demonstrate poor specificity, are expensive or too laborious for use in endemic countries, creating a need for more sensitive, cheaper, and easy to use devices for the diagnosis of schistosomiasis. To ensure engagement during the process of device development; and effective acceptance and use after the introduction of diagnostics devices for S. haematobium, there is a need to involve stakeholders with varying power, interest, and stakes in device co-creation, as well as those relevant for later use situation in the diagnostic landscape. The main goal of this study is to identify and analyze relevant stakeholders for co-creation using a power-interest matrix.Materials and Methods: The study was based on an action research methodology using a case study approach. A contextual inquiry approach consisting of 2 stages: stakeholder identification and interview; and stakeholder analysis was used. The field part of the study was carried out in Oyo State, Nigeria using a multistage cluster purposive sampling technique based on the category of stakeholders to be interviewed predicated on the organizational structure within the state and communities. A mix of qualitative research techniques was used. Identified themes related to power and interest were mapped and analyzed.Results: We identified 17 characteristics of stakeholders across 7 categories of stakeholders important for schistosomiasis diagnostics. Most of the stakeholders were important for both the co-creation and adoption phase of the device development for diagnostics. However, not all stakeholders were relevant to co-creation. Key Stakeholders relevant for diagnostics co-creation demonstrated significant social power, organization power, and legitimate power bases. Most of the stakeholders showed significant interest in the device to be created.Discussion: The power and interest of these stakeholders reveal some insight into how each stakeholder may be engaged for both co-creation and device usage. The involvement of relevant actors who will also be important for co-creation and implementation, will simplify the engagement process for the critical stakeholders, increase the ability to manage the process, and increase diagnostic device acceptability.

A single dose of African horse sickness virus (AHSV) VP2 based vaccines provides complete clinical protection in a mouse model

African horse sickness is a severe, often fatal, arboviral disease of equids. The control of African horse sickness virus (AHSV) in endemic countries is based currently on the use of live attenuated vaccines despite some biosafety concerns derived from its biological properties. Thus, experimental vaccination platforms have been developed over the years in order to avoid the biosafety concerns associated with the use of attenuated vaccines.Various studies showed that baculovirus-expressed AHSV-VP2 or modified Vaccinia Ankara virus expressing AHSV-VP2 (MVA-VP2) induced virus neutralising antibodies and protective immunity in small animals and horses.AHSV is an antigenically diverse pathogen and immunity against AHS is serotype-specific. Therefore, AHS vaccines for use in endemic countries need to induce an immune response capable of protecting against all existing serotypes. For this reason, current live attenuated vaccines are administered as polyvalent preparations comprising combinations of AHSV attenuated strains of different serotypes.Previous studies have shown that it is possible to induce cross-reactive virus neutralising antibodies against different serotypes of AHSV by using polyvalent vaccines comprising combinations of either different serotype-specific VP2 proteins, or MVA-VP2 viruses. However, these strategies could be difficult to implement if induction of protective immunity is highly dependent on using a two-dose vaccination regime for each serotype the vaccine intends to protect against.In our study, we have tested the protective capacity of MVA-VP2 and baculovirus-expressed VP2 vaccines when a single dose was used. Groups of interferon alpha receptor knock-out mice were inoculated with either MVA-VP2 or baculovirus-expressed VP2 vaccines using one dose or the standard two-dose vaccination regime. After vaccination, all four vaccinated groups were challenged with AHSV and clinical responses, lethality and viraemia compared between the groups. Our results show that complete clinical protection was achieved after a single vaccination with either MVA-VP2 or baculovirus sub-unit VP2 vaccines.

Highly targeted cholera vaccination campaigns in urban setting are feasible: The experience in Kalemie, Democratic Republic of Congo.

IntroductionOral cholera vaccines are primarily recommended by the World Health Organization for cholera control in endemic countries. However, the number of cholera vaccines currently produced is very limited and examples of OCV use in endemic countries, and especially in urban settings, are scarce. A vaccination campaign was organized by Médecins Sans Frontières and the Ministry of Health in a highly endemic area in the Democratic Republic of Congo. This study aims to describe the vaccine coverage achieved with this highly targeted vaccination campaign and the acceptability among the vaccinated communities.Methods and findingsWe performed a cross-sectional survey using random spatial sampling. The study population included individuals one year old and above, eligible for vaccination, and residing in the areas targeted for vaccination in the city of Kalemie. Data sources were household interviews with verification by vaccination card. In total 2,488 people were included in the survey. Overall, 81.9% (95%CI: 77.9–85.3) of the target population received at least one dose of vaccine. The vaccine coverage with two doses was 67.2% (95%CI: 61.9–72.0) among the target population. The vaccine coverage was higher during the first round (74.0, 95%CI: 69.3–78.3) than during the second round of vaccination (69.1%, 95%CI: 63.9–74.0). Vaccination coverage was lower in male adults. The main reason for non-vaccination was to be absent during the campaign. No severe adverse events were notified during the interviews.ConclusionsCholera vaccination campaigns using highly targeted strategies are feasible in urban settings. High vaccination coverage can be obtained using door to door vaccination. However, alternative strategies should be considered to reach non-vaccinated populations like male adults and also in order to improve the efficiency of the interventions.

Development and Validation of a PCR-ELISA for the Diagnosis of Symptomatic and Asymptomatic Infection by Leishmania (Leishmania) infantum.

A kDNA PCR enzyme-linked immunosorbent assay (kDNA PCR-ELISA) for the diagnosis of human visceral leishmaniasis (HVL) was developed. The detection limit of the reaction, precision measurements, and cut-off of the kDNA PCR-ELISA were defined in a proof-of-concept phase. A reference strain of Leishmania (Leishmania) infantum and a bank of 14 peripheral blood samples from immunocompetent patients with VL were characterized using techniques considered gold standards, and 11 blood samples obtained from healthy individuals of an endemic area were also assessed. Phase II evaluation determined the performance of the assay in peripheral blood samples from 105 patients with VL (adults and children), 25 patients with Leishmania/HIV coinfection, 40 healthy individuals, and 33 asymptomatic individuals living in endemic areas. The kDNA PCR-ELISA exhibited satisfactory precision, with a detection limit of 0.07 fg of DNA from L. (L.) infantum and 1 parasite/mL blood. The overall sensitivity of the assay for all groups studied was 100% (95% confidence interval [CI]: 97.1–100%), and the specificity was 95% (95% CI: 83.5–98.6%). The kDNA PCR-ELISA was shown to be a useful tool for VL symptomatic and asymptomatic individuals diagnosis and its use in endemic countries may help monitor control interventions.

Use of Malachite Green-Loop Mediated Isothermal Amplification for Detection of Plasmodium spp. Parasites.

Malaria elimination efforts are hampered by the lack of sensitive tools to detect infections with low-level parasitemia, usually below the threshold of standard diagnostic methods, microscopy and rapid diagnostic tests. Isothermal nucleic acid amplification assays such as the loop-mediated isothermal amplification (LAMP), are well suited for field use as they do not require thermal cyclers to run the test. However, the use of specialized equipment, as described by many groups, reduces the versatility of the LAMP technique as a simple tool for use in endemic countries. In this study, the use of the malachite green (MG) dye, as a visual endpoint readout, together with a simple mini heat block was evaluated for the detection of malaria parasites. The assay was performed for 1 hour at 63°C and the results scored by 3 independent human readers. The limit of detection of the assay was determined using well-quantified Plasmodium spp. infected reference samples and its utility in testing clinical samples was determined using 190 pre-treatment specimens submitted for reference diagnosis of imported malaria in the United States. Use of a simplified boil and spin methods of DNA extraction from whole blood and filter paper was also investigated. We demonstrate the accurate and sensitive detection of malaria parasites using this assay with a detection limit ranging between 1–8 parasites/μL, supporting its applicability for the detection of infections with low parasite burden. This assay is compatible with the use of a simple boil and spin sample preparation method from both whole blood and filter papers without a loss of sensitivity. The MG-LAMP assay described here has great potential to extend the reach of molecular tools to settings where they are needed.

The Parasitological, Immunological, and Molecular Diagnosis of Human Taeniasis with Special Emphasis on Taenia solium Taeniasis

Human neurocysticercosis, caused by the larval stage of the tapeworm Taenia solium, is an important neurological disorder reported as a major cause of epilepsy. An important risk factor for neurocysticercosis is the presence of human T. solium carriers who, upon open defecation, disseminate tapeworm eggs, which are infective to both humans and pigs. In the latter, infection also results in cysticercosis, with associated health and economic consequences. Control of T. solium therefore depends greatly on accurate detection and treatment of carriers. However, the currently available direct diagnostic tests depend on detection, in feces, of either parasite stages or parasite antigens and genetic material. The former are low cost but lack adequate sensitivity and specificity; the latter are too expensive to be routinely utilized in endemic communities. Indirect tests based on antibody detection may only show exposure and not active infection. An ideal diagnostic test should be one that is low cost and is able to quickly and reliably detect tapeworm carriers so that appropriate treatment can be prescribed in order to eliminate the source of infection. Such a test remains elusive. Efforts should, therefore, be directed at formulation of a test that is not only sensitive and specific but also affordable for use in endemic countries.

Immune mechanisms in malaria: new insights in vaccine development

Early data emerging from the first phase 3 trial of a malaria vaccine are raising hopes that a licensed vaccine will soon be available for use in endemic countries, but given the relatively low efficacy of the vaccine, this needs to be seen as a major step forward on the road to a malaria vaccine rather than as arrival at the final destination. The focus for vaccine developers now moves to the next generation of malaria vaccines, but it is not yet clear what characteristics these new vaccines should have or how they can be evaluated. Here we briefly review the epidemiological and immunological requirements for malaria vaccines and the recent history of malaria vaccine development and then put forward a manifesto for future research in this area. We argue that rational design of more effective malaria vaccines will be accelerated by a better understanding of the immune effector mechanisms involved in parasite regulation, control and elimination.

Real-Time Fluorescence Loop Mediated Isothermal Amplification for the Diagnosis of Malaria

BackgroundMolecular diagnostic methods can complement existing tools to improve the diagnosis of malaria. However, they require good laboratory infrastructure thereby restricting their use to reference laboratories and research studies. Therefore, adopting molecular tools for routine use in malaria endemic countries will require simpler molecular platforms. The recently developed loop-mediated isothermal amplification (LAMP) method is relatively simple and can be improved for better use in endemic countries. In this study, we attempted to improve this method for malaria diagnosis by using a simple and portable device capable of performing both the amplification and detection (by fluorescence) of LAMP in one platform. We refer to this as the RealAmp method.Methodology and Significant FindingsPublished genus-specific primers were used to test the utility of this method. DNA derived from different species of malaria parasites was used for the initial characterization. Clinical samples of P. falciparum were used to determine the sensitivity and specificity of this system compared to microscopy and a nested PCR method. Additionally, directly boiled parasite preparations were compared with a conventional DNA isolation method. The RealAmp method was found to be simple and allowed real-time detection of DNA amplification. The time to amplification varied but was generally less than 60 minutes. All human-infecting Plasmodium species were detected. The sensitivity and specificity of RealAmp in detecting P. falciparum was 96.7% and 91.7% respectively, compared to microscopy and 98.9% and 100% respectively, compared to a standard nested PCR method. In addition, this method consistently detected P. falciparum from directly boiled blood samples.ConclusionThis RealAmp method has great potential as a field usable molecular tool for diagnosis of malaria. This tool can provide an alternative to conventional PCR based diagnostic methods for field use in clinical and operational programs.

Treatment of visceral leishmaniasis

The Leishmania donovani complex includes L. chagasi and L. infantum, and causes visceral leishmaniasis (VL), a disseminated and potentially fatal form of leishmaniasis. The treatment options for VL are limited. Pentavalent antimonials (Sbv) are the first-line treatment options worldwide except for in Europe and Sbv-unresponsive regions of India. Amphotericin B deoxycholate is the drug of choice in India, as are its lipid formulations in Europe. However, liposomal amphotericin B (AmBisome®, Gilead Sciences, Inc.) is the best antileishmanial formulation, but its prohibitive cost limits its use in endemic countries. Preferential pricing of AmBisome for patients with VL may provide hope for these underprivileged patients. Oral miltefosine and paromomycin are the other drugs that have been recently developed. Limited therapeutic options, the potential for development of resistance and serious toxicity associated with antileishmanial drugs necessitates a change in the treatment policy. A shift from monotherapy to multi-drug combinations of short courses delivered at no or affordable cost, through directly observed therapy, seems to be the only way to develop the treatment of this disease.

Schistosomiasis epidemiology and control: how did we get here and where should we go?

Although a disease of great antiquity, scientific studies of schistosomiasis began only 150 years ago. The complete life-cycle was not described until just before the First World War, making it possible at last to plan proper community control programmes. Inadequate tools prevented their effective implementation until well after the Second World War when new tools became available, thanks to the newly formed World Health Organization. Molluscicides spearheaded control programmes until the late 1970s but were then replaced by the newly developed, safe drugs still used today. Whatever the method used, the initial goal of eradication was, in the light of experience and cost, gradually replaced by less ambitious targets; first to stop transmission and then to reduce morbidity. The most successful programmes combined several methods to minimise reinfection after chemotherapy. Comparisons between different programmes are difficult without using appropriate, standardised diagnostic techniques and the correct epidemiological measurements. Some examples will be presented, mainly from our studies on Schistosoma mansoni in Kenya. Drug resistance on a scale comparable with malaria has not occurred in schistosomiasis but the likely withdrawal of all drugs except praziquantel leaves its control extremely vulnerable to this potential problem. An effective, affordable vaccine for use in endemic countries is unlikely to be ready for at least 5 years, and developing strategies for its use could take a further decade or more, judging from experience with drugs and molluscicides. In the interim, by analogy with malaria, the most cost-effective approach would the use of drugs combined with other methods to stop transmission, including molluscicides. The cost of molluscicides needs to be reduced and fears allayed about their supposedly adverse ecological effects.

The ICT Filariasis Test: A rapid-format antigen test for diagnosis of bancroftian filariasis

Antigen testing is now recognized as the method of choice for detection of Wuchereria bancrofti infections. Unlike tests that detect microfilariae, antigen tests can be performed with blood collected during the day or night. However, existing enzyme-linked immunosorbent assay (ELISA) tests for filarial antigenemia are difficult to perform in the field, and this has limited their use in endemic countries. In this article, Gary Weil, Patrick Lammie and Niggi Weiss review their experience with a new rapid-format filarial antigen test. They found that the ICT card test was very easy to perform and that it was comparable with ELISA for the detection of filarial antigen in sera from people with microfilaremia. The introduction now of an antigen test suitable for use in the field is especially timely, in that it may facilitate implementation of new strategies proposed by the World Health Organization for control and elimination of lymphatic filariasis.