Exploring the Potential of Natural Products as Antiparasitic Agents for Neglected Tropical Diseases

Recent developments in the use of natural product-based molecules as antiparasitic agents for Malaria, leishmaniasis (LE), Chagas disease (CD), and Human African trypanosomiasis (HAT) are reviewed. The role of diverse plants in developing bioactive species is discussed in addition to analyzing the structural diversity of natural products as active agents and the diverse biological applications in CD, HAT, LE, and Malaria. This review focuses on medicinal chemistry, emphasizing the structural characteristics of natural molecules as bioactive agents against parasitic infections caused by Leishmania, Trypanosoma, and Plasmodium parasites.

Multiple-bead assay for the differential serodiagnosis of neglected human cestodiases: Neurocysticercosis and cystic echinococcosis

BACKGROUND

Neurocysticercosis (NCC), and cystic echinococcosis (CE) are two neglected diseases caused by cestodes, co-endemic in many areas of the world. Imaging studies and serological tests are used in the diagnosis of both parasitic diseases, but cross-reactions may confound the results of the latter. The novel multiplex bead-based assay with recombinant antigens has been reported to increases the diagnostic accuracy of serological techniques.

METHODOLOGY

We set-up an immunoassay based on the multiplex bead-based platform (MBA), using the rT24H (against Cysticercus cellulosae, causing cysticercosis) and r2B2t (against Echinococcus granulosus sensu lato, causing CE) recombinant antigens, for simultaneous and differential diagnosis of these infections. The antigens were tested on 356 sera from 151 patients with CE, 126 patients with NCC, and 79 individuals negative for both diseases. Specificity was calculated including sera from healthy donors, other neurological diseases and the respective NCC or CE sera counterpart. The diagnostic accuracy of this assay was compared with two commercial ELISA tests, Novalisa and Ridascreen, widely used in the routine diagnosis of cysticercosis and CE, respectively.

MAIN FINDINGS

For the diagnosis of NCC, sensitivity ranged from 57.94-63.49% for the rT24H-MBA, and 40.48-46.03% for Novalisa ELISA depending on exclusion or inclusion of sera having equivocal results on ELISA from the analysis; specificities ranged from 90.87-91.30% and 70.43-76.96%, respectively. AUC values of the ROC curve were 0.783 (rT24H) and 0.619 (Novalisa) (p-value < 0.001). For the diagnosis of CE, the sensitivity of the r2B2t-MBA ranged from 68.87-69.77% and of Ridascreen ELISA from 50.00-57.62%; specificities from 92.47-92.68% and from 74.15-80.98%, respectively. AUC values were 0.717 and 0.760, respectively.

CONCLUSIONS/SIGNIFICANCE

Overall, the recombinant antigens tested with the bead-based technology showed better diagnostic accuracy than the commercial assays, particularly for the diagnosis of NCC. The possibility of testing the same serum sample simultaneously for the presence of antibodies against both antigens is an added value particularly in seroprevalence studies for cysticercosis linked to control programs in endemic areas where these two parasites coexist.

ASCVac-1, a Multi-Peptide Chimeric Vaccine, Protects Mice Against Ascaris suum Infection

Control of human ascariasis, the most prevalent neglected tropical disease globally affecting 450 million people, mostly relies on mass drug administration of anthelmintics. However, chemotherapy alone is not efficient due to the high re-infection rate for people who live in the endemic area. The development of a vaccine that reduces the intensity of infection and maintains lower morbidity should be the primary target for infection control. Previously, our group demonstrated that immunization with crude Ascaris antigens in mice induced an IgG-mediated protective response with significant worm reduction. Here, we aimed to develop a multipeptide chimera vaccine based on conserved B-cell epitopes predicted from 17 common helminth proteomes using a bioinformatics algorithm. More than 480 B-cell epitopes were identified that are conserved in all 17 helminths. The Ascaris-specific epitopes were selected based on their reactivity to the pooled sera of mice immunized with Ascaris crude antigens or infected three times with A. suum infective eggs. The top 35 peptides with the strongest reactivity to Ascaris immune serum were selected to construct a chimeric antigen connected in sequence based on conformation. This chimera, called ASCVac-1, was produced as a soluble recombinant protein in an Escherichia coli expression system and, formulated with MPLA, was used to immunize mice. Mice immunized with ASCVac-1/MPLA showed around 50% reduced larvae production in the lungs after being challenged with A. suum infective eggs, along with significantly reduced inflammation and lung tissue/function damage. The reduced parasite count and pathology in infected lungs were associated with strong Th2 immune responses characterized by the high titers of antigen-specific IgG and its subclasses (IgG1, IgG2a, and IgG3) in the sera and significantly increased IL-4, IL-5, IL-13 levels in lung tissues. The reduced IL-33 titers and stimulated eosinophils were also observed in lung tissues and may also contribute to the ASCVac-1-induced protection. Taken together, the preclinical trial with ASCVac-1 chimera in a mouse model demonstrated its significant vaccine efficacy associated with strong IgG-based Th2 responses, without IgE induction, thus reducing the risk of an allergic response. All results suggest that the multiepitope-based ASCVac-1 chimera is a promising vaccine candidate against Ascaris sp. infections.

A hidden deadly venomous insect: First eco-epidemiological assessment and risk mapping of lonomism in Argentina

BACKGROUND

Envenomation by the South American Lonomia saturniid caterpillars, named lonomism, constitutes an emerging and somewhat neglected public health issue in Argentina and neighboring countries. Considering that there is an intricate relationship between environment and human health in such cases, this study aimed to analyze the eco-epidemiological profile of 40 accidents and 33 occurrences of Lonomia spp. in Misiones (Argentina) between January 2014 and May 2020.

METHODOLOGY/PRINCIPAL FINDINGS

We described the eco-epidemiological variables and characterized the abiotic scenario of such cases. Additionally, we obtained a density map that shows the punctual intensity of Lonomia records throughout Misiones. Most of the accidents occurred in the Department of Guaraní and involved male victims younger than 20 years old. The accidental/occasional occurrence of Lonomia spp. (considering both adult and caterpillar stages together) was significantly higher in the rural area, whereas only adult specimens were found in urban areas. We determined that the presence of this insect in Misiones is positively related to higher temperatures and solar radiation, and larger precipitation and evapotranspiration throughout the year.

CONCLUSION/SIGNIFICANCE

This study represents an initial step towards the global understanding of lonomism as a public health problem in Argentina. It provides a map of the risk level for this envenomation in Misiones, which could help authorities address public health policy efforts to implement sustainable strategies for prevention and response to this threat in Northeastern Argentina and neighboring regions.

Comparison of Plasmodium ovale curtisi and Plasmodium ovale wallikeri infections by a meta-analysis approach

Malaria caused by Plasmodium ovale species is considered a neglected tropical disease with limited information about its characteristics. It also remains unclear whether the two distinct species P. ovale curtisi and P. ovale wallikeri exhibit differences in their prevalence, geographic distribution, clinical characteristics, or laboratory parameters. Therefore, this study was conducted to clarify these differences to support global malaria control and eradication programs. Studies reporting the occurrence of P. ovale curtisi and P. ovale wallikeri were explored in databases. Differences in proportion, clinical data, and laboratory parameters between the two species were estimated using a random-effects model and expressed as pooled odds ratios (ORs), mean difference (MD), or standardized MD depending on the types of extracted data. The difference in geographical distribution was visualized by mapping the origin of the two species. A total of 1453 P. ovale cases extracted from 35 studies were included in the meta-analysis. The p-value in the meta-analyses provided evidence favoring a real difference between P. ovale curtisi malaria cases (809/1453, 55.7%) and P. ovale wallikeri malaria cases (644/1453, 44.3%) (p: 0.01, OR 1.61, 95% CI 0.71-3.63, I2: 77%). Subgroup analyses established evidence favoring a real difference between P. ovale curtisi and P. ovale wallikeri malaria cases among the imported cases (p: 0.02, 1135 cases). The p value in the meta-analyses provided evidence favoring a real difference in the mean latency period between P. ovale curtisi (289 cases) and P. ovale wallikeri malaria (266 cases) (p: 0.03, MD: 27.59, 95% CI 1.99-53.2, I2: 94%), total leukocyte count (p < 0.0001, MD: 840, 95% CI 610-1070, I2: 0%, two studies) and platelet count (p < 0.0001, MD: 44,750, 95% CI 2900-60,500, I2: 32%, three studies). Four continents were found to have reports of P. ovale spp., among which Africa had the highest number of reports for both P. ovale spp. in its 37 countries, with a global proportion of 94.46%, and an almost equal distribution of both P. ovale spp., where P. ovale curtisi and P. ovale wallikeri reflected 53.09% and 46.90% of the continent's proportion, respectively. This is the first systematic review and meta-analysis to demonstrate the differences in the characteristics of the two distinct P. ovale species. Malaria caused by P. ovale curtisi was found in higher proportions among imported cases and had longer latency periods, higher platelet counts, and higher total leukocyte counts than malaria caused by P. ovale wallikeri. Further studies with a larger sample size are required to confirm the differences or similarities between these two species to promote malaria control and effective eradication programs.

Loop-Mediated Isothermal Amplification as Point-of-Care Diagnosis for Neglected Parasitic Infections

The World Health Organisation (WHO) has placed twenty diseases into a group known as neglected tropical diseases (NTDs), twelve of them being parasitic diseases: Chagas’ disease, cysticercosis/taeniasis, echinococcosis, food-borne trematodiasis, human African trypanosomiasis (sleeping sickness), leishmaniasis, lymphatic filariasis, onchocerciasis (river blindness), schistosomiasis, soil-transmitted helminthiasis (ascariasis, hookworm, trichuriasis), guinea-worm and scabies. Such diseases affect millions of people in developing countries where one of the main problems concerning the control of these diseases is diagnosis-based due to the most affected areas usually being far from laboratories having suitable infrastructure and/or being equipped with sophisticated equipment. Advances have been made during the last two decades regarding standardising and introducing techniques enabling diagnoses to be made in remote places, i.e., the loop-mediated isothermal amplification (LAMP) technique. This technique’s advantages include being able to perform it using simple equipment, diagnosis made directly in the field, low cost of each test and the technique’s high specificity. Using this technique could thus contribute toward neglected parasite infection (NPI) control and eradication programmes. This review describes the advances made to date regarding LAMP tests, as it has been found that even though several studies have been conducted concerning most NPI, information is scarce for others.

The complex health seeking pathway of a human African trypanosomiasis patient in Côte d'Ivoire underlines the need of setting up passive surveillance systems

Background

Significant efforts to control human African trypanosomiasis (HAT) over the two past decades have resulted in drastic decrease of its prevalence in Côte d’Ivoire. In this context, passive surveillance, integrated in the national health system and based on clinical suspicion, was reinforced. We describe here the health-seeking pathway of a girl who was the first HAT patient diagnosed through this strategy in August 2017.

Methods

After definitive diagnosis of this patient, epidemiological investigations were carried out into the clinical evolution and the health and therapeutic itinerary of the patient before diagnosis.

Results

At the time of diagnosis, the patient was positive in both serological and molecular tests and trypanosomes were detected in blood and cerebrospinal fluid. She suffered from important neurological disorders. The first disease symptoms had appeared three years earlier, and the patient had visited several public and private peripheral health care centres and hospitals in different cities. The failure to diagnose HAT for such a long time caused significant health deterioration and was an important financial burden for the family.

Conclusion

This description illustrates the complexity of detecting the last HAT cases due to complex diagnosis and the progressive disinterest and unawareness by both health professionals and the population. It confirms the need of implementing passive surveillance in combination with continued sensitization and health staff training.

Human African trypanosomiasis (HAT) or sleeping sickness is a parasitic disease caused by Trypanosoma brucei that is transmitted by tsetse flies. In 2012, HAT was included in the World Health Organization roadmap for the control of neglected tropical diseases with the objective of elimination as a public health problem by 2020. In Côte d’Ivoire, HAT prevalence has dropped sharply the last decade. A passive HAT surveillance was therefore integrated in the national health system, which allowed to detect a first patient in 2017. This article describes the complex health seeking pathway and suffering before diagnosis of this patient, an 11 years old girl, and illustrates the challenge when health agents and population no longer consider HAT as a threat in an elimination context. Our results show the need to install a solid surveillance system, in combination with continued sensitization and repeated health staff training.

Feasibility of community-based control of tsetse: A pilot project using Tiny Targets in the Democratic Republic of Congo

Gambiense Human African Trypanosomiasis (g-HAT) is a neglected tropical disease caused by trypanosomes transmitted by tsetse flies. 70% of cases in 2019 (604/863) occurred in the Democratic Republic of Congo (DRC). The national programme for g-HAT elimination in DRC includes a large-scale deployment of Tiny Targets which attract and kill tsetse. This intervention is directed by vector-control specialists with small teams, moving in canoes, deploying Tiny Targets along riverbanks where tsetse concentrate. While the targets are deployed in communal areas, and the method is cheap and easy-to-use, local people have little involvement. This study aimed to evaluate if a community-led vector control programme was feasible in the context of DRC's g-HAT elimination programme. In 2017, a community-led intervention was implemented in three villages in the Kwilu province of DRC. This intervention was evaluated through an Action Research with qualitative data collected through 21 focus group discussions and 289 hours of observation. Also the geographical location and quality of each Tiny Targets were collected (total number deployed = 2429). This research revealed that community-based approach largely worked: people were motivated and proactive, showed a good application of the acquired knowledge resulting in an effective deployment of Tiny Targets. In addition, our study provided evidence that acceptability of the targets by the community can improve deployment quality by reducing target loss and damage. The approach was feasible in places where canoe-based teams could not reach. Against these advantages, a community-based approach was time-consuming and had to adapt to the seasonal and daily rhythms of the community. A community-based approach for tsetse control is technically feasible and recommended but limits to the speed and scale of the approach restraints its application as a standalone strategy in a large-scale national programme aiming to eliminate g-HAT in a short timeframe.

Cystic echinococcosis in the Eastern Mediterranean region: Neglected and prevailing!

Cystic echinococcosis (CE) is distributed worldwide, extending from China to the Middle East and from Mediterranean countries to the sub-Saharan Africa and South America. According to WHO, one million people around the world are suffering from CE with an estimated burden of 183,573 DALYs. The annual monetary burden of the disease due to treatment costs and CE-related livestock losses has been estimated at US$ 3 billion. CE is endemic in all countries within the WHO Eastern Mediterranean Regional Office (EMRO). The region, which includes most of the Middle East and North Africa, is one of the most ancient foci of the domestic cycle of CE and is recognized as one of the major hotspots of CE. There are 22 countries in the EMRO, where about 688 million people are living at risk of CE. In many EMRO countries, little is known about CE epidemiology and transmission. WHO included echinococcosis in a list of 17 neglected tropical diseases (NTDs) and 12 neglected zoonotic diseases (NZDs). Accordingly, different regional offices of WHO organized several initiatives for CE control and prevention. WHO’s Western Pacific regional office considered echinococcosis as one of the region’s major health topics, and several preventive measures have been implemented in the American region with the support of Pan American Health Organization (PAHO) in Argentina, Peru, Uruguay, and Chile. Although CE is endemic in all 22 EMRO countries, surprisingly, CE is absent from the health topics list of diseases and conditions in this region. Therefore, CE clearly requires further attention in the WHO EMRO agenda, and the need for elaboration of specific measures for CE control is becoming apparent in EMRO countries, where substantial collaborations among the member states and WHO EMRO is of paramount importance. Major topics of collaborative activities include training programs and health communication on different aspects of CE control, analysis of CE burden, national and international surveillance and disease registry systems, technical support to promote epidemiological studies for collecting baseline data, cost–benefit analysis of control interventions, and intersectoral cooperation among the agriculture, veterinary, medical, and health sectors.

Efficacy and safety assessment of different dosage of benznidazol for the treatment of Chagas disease in chronic phase in adults (MULTIBENZ study): study protocol for a multicenter randomized Phase II non-inferiority clinical trial

BACKGROUND

Chagas disease (CD) continues to be a neglected infectious disease with one of the largest burdens globally. Despite the modest cure rates in adult chronic patients and its safety profile, benznidazole (BNZ) is still the drug of choice. Its current recommended dose is based on nonrandomized studies, and efficacy and safety of the optimal dose of BNZ have been scarcely analyzed in clinical trials.

METHODS/DESIGN

MULTIBENZ is a phase II, randomized, noninferiority, double-blind, multicenter international clinical trial. A total of 240 patients with Trypanosoma CD in the chronic phase will be recruited in four different countries (Argentina, Brazil, Colombia, and Spain). Patients will be randomized to receive BNZ 150 mg/day for 60 days, 400 mg/day for 15 days, or 300 mg/day for 60 days (comparator arm). The primary outcome is the efficacy of three different BNZ therapeutic schemes in terms of dose and duration. Efficacy will be assessed according to the proportion of patients with sustained parasitic load suppression in peripheral blood measured by polymerase chain reaction. The secondary outcomes are related to pharmacokinetics and drug tolerability. The follow-up will be 12 months from randomization to end of study participation. Recruitment was started in April 2018.

CONCLUSION

This is a clinical trial conducted for the assessment of different dose schemes of BNZ compared with the standard treatment regimen for the treatment of CD in the chronic phase. MULTIBENZ may help to clarify which is the most adequate BNZ regimen in terms of efficacy and safety, predicated on sustained parasitic load suppression in peripheral blood.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03191162. Registered on 19 June 2017.

Epidemiological characteristics of hepatic echinococcosis, concurrent cerebral echinococcosis, and pulmonary echinococcosis in Ganzi County, Sichuan Province, China

Human echinococcosis has become a major public health problem in most parts of the world. The objective of this article was to study the demographics of patients with hepatic echinococcosis in Ganzi County to elucidate the main risk factors, as well as to report the concurrent prevalence of cerebral echinococcosis and pulmonary echinococcosis.We recruited 195 patients with hepatic echinococcosis from the Datongma area of Ganzi County from January 2018 to November 2018. The patients' demographics, living environments, supported medical resources, knowledge of echinococcosis prevention and control, and hygienic practices were investigated and analyzed. The prevalence of cerebral echinococcosis and pulmonary echinococcosis were also investigated.The data were analyzed to identify risk factors for human echinococcosis. Our analysis showed that the herding Tibetan population within the 20 to 60 age group, and females, in particular, were at the highest risk of human echinococcosis infection. Having stray dogs around habitations and intimate activities with dogs and livestock were also behavioral risk factors. People with poor health literacy and low educational qualifications had possible risks of infection. In terms of hygiene, not using tap water as the drinking water source and lack of medical staff were significantly correlated with echinococcosis prevalence. Four patients were diagnosed with cerebral echinococcosis. Among them, 1 patient had both cerebral echinococcosis and pulmonary echinococcosis.Possible high-risk factors for echinococcosis were being female, herding population, in the 20 to 60 age group, having stray dogs around habitations, having activities with dogs and livestock, having poor health literacy, having low educational qualifications, and not using tap water as a drinking water source. The detection rate for brain echinococcosis in patients with hepatic echinococcosis was high (2.05%). Effective preventive strategies should be implemented in epidemic areas. Head CT scans should be applied for early detection of cerebral echinococcosis to carry out the treatment.

Screening Marine Natural Products for New Drug Leads against Trypanosomatids and Malaria

Neglected Tropical Diseases (NTD) represent a serious threat to humans, especially for those living in poor or developing countries. Almost one-sixth of the world population is at risk of suffering from these diseases and many thousands die because of NTDs, to which we should add the sanitary, labor and social issues that hinder the economic development of these countries. Protozoan-borne diseases are responsible for more than one million deaths every year. Visceral leishmaniasis, Chagas disease or sleeping sickness are among the most lethal NTDs. Despite not being considered an NTD by the World Health Organization (WHO), malaria must be added to this sinister group. Malaria, caused by the apicomplexan parasite Plasmodium falciparum, is responsible for thousands of deaths each year. The treatment of this disease has been losing effectiveness year after year. Many of the medicines currently in use are obsolete due to their gradual loss of efficacy, their intrinsic toxicity and the emergence of drug resistance or a lack of adherence to treatment. Therefore, there is an urgent and global need for new drugs. Despite this, the scant interest shown by most of the stakeholders involved in the pharmaceutical industry makes our present therapeutic arsenal scarce, and until recently, the search for new drugs has not been seriously addressed. The sources of new drugs for these and other pathologies include natural products, synthetic molecules or repurposing drugs. The most frequent sources of natural products are microorganisms, e.g., bacteria, fungi, yeasts, algae and plants, which are able to synthesize many drugs that are currently in use (e.g. antimicrobials, antitumor, immunosuppressants, etc.). The marine environment is another well-established source of bioactive natural products, with recent applications against parasites, bacteria and other pathogens which affect humans and animals. Drug discovery techniques have rapidly advanced since the beginning of the millennium. The combination of novel techniques that include the genetic modification of pathogens, bioimaging and robotics has given rise to the standardization of High-Performance Screening platforms in the discovery of drugs. These advancements have accelerated the discovery of new chemical entities with antiparasitic effects. This review presents critical updates regarding the use of High-Throughput Screening (HTS) in the discovery of drugs for NTDs transmitted by protozoa, including malaria, and its application in the discovery of new drugs of marine origin.

Parasite associations predict infection risk: incorporating co-infections in predictive models for neglected tropical diseases

BACKGROUND

Schistosomiasis and infection by soil-transmitted helminths are some of the world's most prevalent neglected tropical diseases. Infection by more than one parasite (co-infection) is common and can contribute to clinical morbidity in children. Geostatistical analyses of parasite infection data are key for developing mass drug administration strategies, yet most methods ignore co-infections when estimating risk. Infection status for multiple parasites can act as a useful proxy for data-poor individual-level or environmental risk factors while avoiding regression dilution bias. Conditional random fields (CRF) is a multivariate graphical network method that opens new doors in parasite risk mapping by (i) predicting co-infections with high accuracy; (ii) isolating associations among parasites; and (iii) quantifying how these associations change across landscapes.

METHODS

We built a spatial CRF to estimate infection risks for Ascaris lumbricoides, Trichuris trichiura, hookworms (Ancylostoma duodenale and Necator americanus) and Schistosoma mansoni using data from a national survey of Rwandan schoolchildren. We used an ensemble learning approach to generate spatial predictions by simulating from the CRF's posterior distribution with a multivariate boosted regression tree that captured non-linear relationships between predictors and covariance in infection risks. This CRF ensemble was compared against single parasite gradient boosted machines to assess each model's performance and prediction uncertainty.

RESULTS

Parasite co-infections were common, with 19.57% of children infected with at least two parasites. The CRF ensemble achieved higher predictive power than single-parasite models by improving estimates of co-infection prevalence at the individual level and classifying schools into World Health Organization treatment categories with greater accuracy. The CRF uncovered important environmental and demographic predictors of parasite infection probabilities. Yet even after capturing demographic and environmental risk factors, the presences or absences of other parasites were strong predictors of individual-level infection risk. Spatial predictions delineated high-risk regions in need of anthelminthic treatment interventions, including areas with higher than expected co-infection prevalence.

CONCLUSIONS

Monitoring studies routinely screen for multiple parasites, yet statistical models generally ignore this multivariate data when assessing risk factors and designing treatment guidelines. Multivariate approaches can be instrumental in the global effort to reduce and eventually eliminate neglected helminth infections in developing countries.

Potent and selective inhibitors for M32 metallocarboxypeptidases identified from high-throughput screening of anti-kinetoplastid chemical boxes

Enzymes of the M32 family are Zn-dependent metallocarboxypeptidases (MCPs) widely distributed among prokaryotic organisms and just a few eukaryotes including Trypanosoma brucei and Trypanosoma cruzi, the causative agents of sleeping sickness and Chagas disease, respectively. These enzymes are absent in humans and several functions have been proposed for trypanosomatid M32 MCPs. However, no synthetic inhibitors have been reported so far for these enzymes. Here, we present the identification of a set of inhibitors for TcMCP-1 and TbMCP-1 (two trypanosomatid M32 enzymes sharing 71% protein sequence identity) from the GlaxoSmithKline HAT and CHAGAS chemical boxes; two collections grouping 404 compounds with high antiparasitic potency, drug-likeness, structural diversity and scientific novelty. For this purpose, we adapted continuous fluorescent enzymatic assays to a medium-throughput format and carried out the screening of both collections, followed by the construction of dose-response curves for the most promising hits. As a result, 30 micromolar-range inhibitors were discovered for one or both enzymes. The best hit, TCMDC-143620, showed sub-micromolar affinity for TcMCP-1, inhibited TbMCP-1 in the low micromolar range and was inactive against angiotensin I-converting enzyme (ACE), a potential mammalian off-target structurally related to M32 MCPs. This is the first inhibitor reported for this family of MCPs and considering its potency and specificity, TCMDC-143620 seems to be a promissory starting point to develop more specific and potent chemical tools targeting M32 MCPs from trypanosomatid parasites.

Progress on the development of rapid diagnostic tests for foodborne neglected zoonotic helminthiases: A systematic review

BACKGROUND

Foodborne Neglected Zoonotic Helminths (FNZH) are parasites of both economic and public health importance. They include Taenia solium, Echinococcus granulosus sensu lato, Echinococcus multilocularis and Foodborne trematodes (FBT). FNZH are earmarked for major interventions for control, elimination and eradication. This systematic review highlights the progress towards development of rapid tests for the diagnosis of FNZH since 2010 when they were listed as neglected tropical diseases.

METHODOLOGY

A systematic search was conducted in three databases, World of Science, Embase and PubMed using the same search phrase. The search produced 480 hits. Three studies from back referencing were included. Only 22 of these met the inclusion criteria. Data was extracted from these and presented qualitatively.

RESULTS

Twenty-five rapid diagnostic tests were found to have been developed since 2010, eight for diagnosis of T. solium infections, eight for echinococcosis and nine for FBT infections. The rapid tests for diagnosing T. solium infections included six antibody detecting and two antigen detecting tests. They constitute a combination among them, with some tests providing qualitative, others quantitative results. Similarly, seven out of the eight rapid tests developed for Echinococcus infections were antibody detecting tests save for one loop mediated isothermal amplification test. All of them were qualitative tests. For FBT infections, nine rapid tests were described; two antibody and one nucleic acid detecting test for diagnosis of Fascioliasis; three nucleic acid detecting tests for Opisthorchiasis; one antibody detecting test for Paragonimiasis; and for Clonorchiasis, one antibody and one nucleic acid detecting test. The FBT infection rapid tests were all qualitative in nature. Most of these tests have not undergone field evaluation in endemic areas where they will be used most.

CONCLUSION

This review describes the development and evaluation of rapid diagnostic tests, while highlighting the need for in depth validations of the tools to determine how well they can perform in endemic areas.

Assessing the nonhuman primate reservoir of Schistosoma mansoni in Africa: a systematic review

BACKGROUND

Reports of natural infections of Schistosoma mansoni in a number of species of nonhuman primates (NHPs) in Africa, coupled with the substantial overlap of NHP habitats and human schistosomiasis endemic areas, has led to concerns about the role of NHPs in the transmission of human schistosomiasis. We conducted a systematic review of the literature to describe the current scope of knowledge for Africa, for the NHP species implicated, their geographical distribution, infection rates with S. mansoni, and to discuss the implications for public health and conservation.

MAIN TEXT

A systematic search of the literature was performed using PubMed, Web of Science, Google Scholar, the World Health Organization (WHO) library database, World Cat, and ScienceDirect without any language restriction. Studies examining S. mansoni infection of any African NHP species were included. Study types, primate species, their geographical distribution, and parasite diagnostic techniques reported in the studies were qualitatively summarized. Data for species with sample sizes ≥10 were included in the meta-analysis. We assessed the reported infection rate, and used a random-effects model to estimate the summary infection rates and 95% confidence intervals (CIs). We assessed heterogeneity among studies using the I2 statistics. Twenty-nine publications, from 1960 to 2018, were identified and included in the review. The studies examined a total of 2962 primates belonging to 22 species in 11 genera across ten countries (Cameroon, Eritrea, Ethiopia, Gabon, Kenya, Nigeria, Senegal, Tanzania, Uganda, and Zimbabwe), and S. mansoni infections were found in nine species of five genera in all countries. When we excluded studies with sample sizes < 10, data from 24 studies on 11 species of primates in three genera in ten countries remained in the meta-analysis. The overall pooled estimate of infection rate was 10% (95% CI: 6-16%) with high heterogeneity (I2 = 94.77%) across countries and species/genera. Among the three genera, Pan had the highest infection rate of 15% (95% CI: 0-55%), followed by Papio at 11% (95% CI: 6-18%), and Cercopithecus at 5% (95% CI: 0-14%). The association between NHP and human infections was positive, but not significant, due to low study sample matches and high variation.

CONCLUSIONS

Our findings suggest that S. mansoni infection rate is high in African NHPs, with substantial heterogeneities across species/genera and countries in Africa. Given the evidence for potential spillover and spillback of S. mansoni between African NHPs and humans, further research is urgently needed to understand ecology and mechanisms of transmission of the parasite between NHP and human hosts, in order to inform control strategies of this important neglected tropical disease.

Genetic characterization of Echinococcus species in eastern Ethiopia

Cystic echinococcosis (CE) is a neglected zoonotic disease with considerable economic and public health burden worldwide, particularly affecting developing countries like Ethiopia. To initiate effective prevention and control of CE, comprehensive data on the local lifecycles of the various species/genotypes of Echinococcus are needed. In the present study, conducted in eastern Ethiopia, a total of 1106 livestock animals were examined at three slaughterhouses, which resulted in combined prevalence of morphologically and molecularly confirmed CE of 8.4% (75/891) in cattle, 1.1% (1/95) in sheep, 0.0% (0/95) in goats and 12.0% (3/25) in camels. All cystic lesions recovered during post mortem examination were assessed for cyst condition and underwent molecular characterization by PCR and sequencing of a 1081 bp fragment of the mitochondrial cox1 gene. A total of 175 cysts belonged to E. granulosus s.s. (n = 165), E. ortleppi (n = 6) and E. canadensis G6/7 (n = 4). Of all examined cysts, only 14 were fertile and contained protoscoleces, all from the lungs of cattle: 5 were E. granulosus s.s., 6 E. ortleppi and 3 E. canadensis G6/7. In sheep, only one sterile liver cyst of E. granulosus s.s. was found, while in camels seven sterile or caseated/calcified cysts of E. granulosus s.s. and E. canadensis G6/7 were found in liver and lungs. In conclusion, the prevalence of CE was rather low compared to other regions of Ethiopia, and, based on the number of fertile cysts, three Echinococcus spp. contributed almost equally to transmission. Cattle seem to be, epidemiologically, the most important livestock species. Our data provide a substantial basis for more detailed investigations of the transmission dynamics of CE in the study area.

Multi-locus characterization and phylogenetic inference of Leishmania spp. in snakes from Northwest China

BACKGROUND

Leishmaniasis caused by protozoan parasite Leishmania is a neglected disease which is endemic in the northwest of China. Reptiles were considered to be the potential reservoir hosts for mammalian Leishmaniasis, and Leishmania had been detected in lizards from the epidemic area in the northwest of China. To date, few studies are focused on the natural infection of snakes with Leishmania.

METHODS

In this study, 15 snakes captured from 10 endemic foci in the northwest of China were detected Leishmania spp. on the base of mitochondrial cytochrome b, heat shock protein 70 gene and ribosomal internal transcribed spacer 1 regions, and identified with phylogenetic and network analyses.

RESULT

In total, Leishmania gene was found in 7 snakes. The phylogenetic inference trees and network analysis suggests that the species identification was confirmed as Leishmania donovani, L. turanica and L. (Sauroleishmania) sp.

CONCLUSION

Our work is the first time to investigate the natural Leishmania spp. infection of snakes in the northwest of China. Mammalian Leishmania (L. donovani and L. turanica) was discovered in snakes and the reptilian Leishmania (Sauroleishmania sp.) was closely related to the clinical strains both prompt the importance of snakes in the disease cycle. To indicate the epidemiological involvement of snakes, a wide sample size in epidemic area and the pathogenic features of reptilian Leishmania promastigotes are recommended in the future research.

Histone deacetylase enzymes as potential drug targets of Neglected Tropical Diseases caused by cestodes

Cestode parasites cause neglected diseases, such as echinococcosis and cysticercosis, which represent a significant problem in human and animal health. Benzimidazoles and praziquantel are the only available drugs for chemotherapy and it is therefore important to identify new alternative drugs against cestode parasites. Histone deacetylases (HDACs) are validated drug targets for the treatment of cancer and other diseases, including neglected diseases. However, knowledge of HDACs in cestodes is very scarce. In this work, we investigated cestode HDACs as potential drug targets to develop new therapies against neglected diseases caused by cestodes. Here we showed the full repertoire of HDAC coding genes in several members of the class Cestoda. Between 6 and 7 zinc-dependent HDAC coding genes were identified in the genomes of species from Echinococcus, Taenia, Mesocestoides and Hymenolepis genera. We classified them as Class I and II HDACs and analyzed their transcriptional expression levels throughout developmental stages of Echinococcus spp. We confirmed for the first time the complete HDAC8 nucleotide sequences from Echinococcus canadensis G7 and Mesocestoides corti. Homology models for these proteins showed particular structural features which differentiate them from HDAC8 from Homo sapiens. Furthermore, we showed that Trichostatin A (TSA), a pan-HDAC inhibitor, decreases the viability of M. corti, alters its tegument and morphology and produces an increment of the total amount of acetylated proteins, including acetylated histone H4. These results suggest that HDAC from cestodes are functional and might play important roles on survival and development. The particular structural features observed in cestode HDAC8 proteins suggest that these enzymes could be selectively targeted. This report provides the basis for further studies on cestode HDAC enzymes and for discovery of new HDAC inhibitors for the treatment of neglected diseases caused by cestode parasites.

Association between IL1 gene polymorphism and human African trypanosomiasis in populations of sleeping sickness foci of southern Cameroon

BACKGROUND

Human African Trypanosomiasis (HAT) is a neglected tropical disease caused by infections due to Trypanosoma brucei subspecies. In addition to the well-established environmental and behavioural risks of becoming infected, there is evidence for a genetic component to the response to trypanosome infection. We undertook a candidate gene case-control study to investigate genetic associations further.

METHODOLOGY

We genotyped one polymorphism in each of seven genes (IL1A, IL1RN, IL4RN, IL6, HP, HPR, and HLA-G) in 73 cases and 250 controls collected from 19 ethno-linguistic subgroups stratified into three major ethno-linguistic groups, 2 pooled ethno-linguistic groups and 11 ethno-linguistic subgroups from three Cameroonian HAT foci. The seven polymorphic loci tested consisted of three SNPs, three variable numbers of tandem repeat (VNTR) and one INDEL.

RESULTS

We found that the genotype (TT) and minor allele (T) of IL1A gene as well as the genotype 1A3A of IL1RN were associated with an increased risk of getting Trypanosoma brucei gambiense and develop HAT when all data were analysed together and also when stratified by the three major ethno-linguistic groups, 2 pooled ethno-linguistic subgroups and 11 ethno-linguistic subgroups.

CONCLUSION

This study revealed that one SNP rs1800794 of IL1A and one VNTR rs2234663 of IL1RN were associated with the increased risk to be infected by Trypanosoma brucei gambiense and develop sleeping sickness in southern Cameroon. The minor allele T and the genotype TT of SNP rs1800794 in IL1A as well as the genotype 1A3A of IL1RN rs2234663 VNTR seem to increase the risk of getting Trypanosoma brucei gambiense infections and develop sleeping sickness in southern Cameroon.

Cutaneous leishmaniasis and co-morbid major depressive disorder: A systematic review with burden estimates

Background

Major depressive disorder (MDD) associated with chronic neglected tropical diseases (NTDs) has been identified as a significant and overlooked contributor to overall disease burden. Cutaneous leishmaniasis (CL) is one of the most prevalent and stigmatising NTDs, with an incidence of around 1 million new cases of active CL infection annually. However, the characteristic residual scarring (inactive CL) following almost all cases of active CL has only recently been recognised as part of the CL disease spectrum due to its lasting psychosocial impact.

Methods and findings

We performed a multi-language systematic review of the psychosocial impact of active and inactive CL. We estimated inactive CL (iCL) prevalence for the first time using reported WHO active CL (aCL) incidence data that were adjusted for life expectancy and underreporting. We then quantified the disability (YLD) burden of co-morbid MDD in CL using MDD disability weights at three severity levels. Overall, we identified 29 studies of CL psychological impact from 5 WHO regions, representing 11 of the 50 highest burden countries for CL. We conservatively calculated the disability burden of co-morbid MDD in CL to be 1.9 million YLDs, which equalled the overall (DALY) disease burden (assuming no excess mortality in depressed CL patients). Thus, upon inclusion of co-morbid MDD alone in both active and inactive CL, the DALY burden was seven times higher than the latest 2016 Global Burden of Disease study estimates, which notably omitted both psychological impact and inactive CL.

Conclusions

Failure to include co-morbid MDD and the lasting sequelae of chronic NTDs, as exemplified by CL, leads to large underestimates of overall disease burden.

Cutaneous leishmaniasis is a highly prevalent vector-borne disease affecting large parts of Latin America and the Middle East, as well as parts of Northern Africa. There are several types of Cutaneous leishmaniasis, almost all of which have an active phase characterized by a disfiguring lesion (typically on exposed parts of the body), which then becomes a permanent scar (the inactive phase). We recently published an article highlighting the impact of the inactive scarring phase of CL on affected individuals, which is associated with high levels of stigma. Nevertheless, this aspect of the disease is not considered in its own right when calculating the overall disease burden by the Global Burden of Disease (GBD) Studies. In this article we estimate the prevalence of depression (major depressive disorder) in cutaneous leishmaniasis, in both the active and inactive forms. We then show the contribution of inactive CL to the overall disease burden estimates when included, which is due to the large psychological impact it has on those affected by it. We also highlight the importance of further similar efforts for other NTDs which have a chronic course, and which are also not sufficiently included in disease burden calculations at present.

Epidemiological situation of yaws in the Americas: A systematic review in the context of a regional elimination goal

BACKGROUND

Yaws is targeted for eradication by 2020 in the WHA66.12 resolution of the World Health Assembly. The objective of this study was to describe the occurrence of yaws in the Americas and to contribute to the compilation of evidence based on published data to undertake the certification of yaws eradication.

METHODOLOGY

A systematic review of the epidemiological situation of yaws in the Americas was performed by searching in MEDLINE, Embase, LILACS, SCOPUS, Web of Science, DARE and Cochrane Database of Systematic Reviews. Experts on the topic were consulted, and institutional WHO/PAHO library databases were reviewed.

PRINCIPAL FINDINGS

Seventy-five full-text articles published between 1839 and 2012 met the inclusion criteria. Haiti and Jamaica were the two countries with the highest number of papers (14.7% and 12.0%, respectively). Three-quarters of the studies were conducted before 1970. Thirty-three countries reported yaws case count or prevalence data. The largest foci in the history were described in Brazil and Haiti. The most recent cases reported were recorded in eight countries: Suriname, Guyana, Colombia, Haiti, Martinique, Dominica, Trinidad and Tobago, and Brazil. Gaps in information and heterogeneity were detected in the methodologies used and outcome reporting, making cross-national and chronological comparisons difficult.

CONCLUSIONS

The lack of recent yaws publications may reflect, in the best-case scenario, the interruption of yaws transmission. It should be possible to reach the eradication goal in the region of the Americas, but it is necessary to collect more information. We suggest updating the epidemiological status of yaws, especially in two countries that need to assess ongoing transmission. Twenty-four countries need to demonstrate the interruption of transmission and declare its status of yaws endemicity, and sixteen countries should declare if they are yaws-free. It is necessary to formally verify the achievement of this goal in Ecuador.

Population genetic structure and geographical variation in Neotricula aperta (Gastropoda: Pomatiopsidae), the snail intermediate host of Schistosoma mekongi (Digenea: Schistosomatidae)

Background

Neotricula aperta is the snail-intermediate host of the parasitic blood-fluke Schistosoma mekongi which causes Mekong schistosomiasis in Cambodia and the Lao PDR. Despite numerous phylogenetic studies only one DNA-sequence based population-genetic study of N. aperta had been published, and the origin, structure and persistence of N. aperta were poorly understood. Consequently, a phylogenetic and population genetic study was performed, with addition of new data to pre-existing DNA-sequences for N. aperta from remote and inaccessible habitats, including one new taxon from Laos and 505 bp of additional DNA-sequence for all sampled taxa,.

Principal findings

Spatial Principal Component Analysis revealed the presence of significant spatial-genetic clustering. Genetic-distance-based clustering indicated four populations with near perfect match to a priori defined ecogeographical regions. Spring-dwelling taxa were found to form an ecological isolate relative to other N. aperta. The poor dispersal capabilities suggested by spatial-genetic analyses were confirmed by Bayesian inference of migration rates. Population divergence time estimation implied a mid-Miocene colonisation of the present range, with immediate and rapid radiation in each ecogeographical region. Estimated effective population sizes were large (120–310 thousand).

Conclusions

The strong spatial-genetic structure confirmed the poor dispersal capabilities of N. aperta—suggesting human-mediated reintroduction of disease to controlled areas as the primary reason for control failure. The isolation of the spring-dwelling taxa and ecogeographical structure suggests adaptation of sub-populations to different habitats; the epidemiological significance of this needs investigation. The large effective population sizes indicate that the high population densities observed in surveyed habitats are also present in inaccessible areas; affording great potential for recrudescence driven by animal-reservoir transmission in remote streams. Mid-Miocene colonisation implies heterochronous evolution of these snails and associated schistosomes and suggests against coevolution of snail and parasite. Heterochronicity favours ecological factors as shapers of host-parasite specificity and greater potential for escape from schistosomiasis control through host-switching.

The disease Mekong schistosomiasis poses a threat to the health of about 1.5 million people living near the Mekong river and its tributaries in Cambodia and Laos. It is a water-borne parasite transmitted by direct contact with water in which freshwater snails of the species Neotricula aperta live. Control of the snails is an effective approach to control of the parasite; however, because many suitable habitats for N. aperta occur in remote and inaccessible areas, knowledge of N. aperta population sizes and interconnectivity is insufficient for the design of effective snail control interventions. Although much of the region is difficult to survey by conventional means, population genetics can be used to estimate population structure and total size from small samples of accessible populations. The study added to existing data-sets, to give more population samples and longer DNA-sequences, together with improved analytical approaches to provide a better overview of N. aperta. The findings suggest that N. aperta in different kinds of habitats are also genetically different, with very low levels of migration between them; this genetic clustering is greater than expected from spatial distance alone. Further work is needed to determine if these different clusters vary in ability to transmit the parasite. The overall population size estimates were very large; thus suggesting that high snail population densities observed in accessible habitats are also characteristic of inaccessible populations—parasites are therefore more likely to return after disease control by immigration from remote areas. Finally, the timing of evolutionary events for snails and parasites was found to differ; this implies that the parasite may not be as strongly restricted to one species of snail as originally thought, which has implications for avoidance of parasite control by host-switching.

Integrated seroprevalence-based assessment of Wuchereria bancrofti and Onchocerca volvulus in two lymphatic filariasis evaluation units of Mali with the SD Bioline Onchocerciasis/LF IgG4 Rapid Test

BACKGROUND

Mali has become increasingly interested in the evaluation of transmission of both Wuchereria bancrofti and Onchocerca volvulus as prevalences of both infections move toward their respective elimination targets. The SD Bioline Onchocerciasis/LF IgG4 Rapid Test was used in 2 evaluation units (EU) to assess its performance as an integrated surveillance tool for elimination of lymphatic filariasis (LF) and onchocerciasis.

METHODOLOGY/PRINCIPAL FINDINGS

A cross sectional survey with SD Bioline Onchocerciasis/LF IgG4 Rapid Test was piggy-backed onto a transmission assessment survey (TAS) (using the immunochromatographic card test (ICT) Binax Filariasis Now test for filarial adult circulating antigen (CFA) detection) for LF in Mali among 6-7 year old children in 2016 as part of the TAS in two EUs namely Kadiolo-Kolondieba in the region of Sikasso and Bafoulabe -Kita-Oussoubidiagna-Yelimane in the region of Kayes. In the EU of Kadiolo- Kolondieba, of the 1,625 children tested, the overall prevalence of W. bancrofti CFA was 0.62% (10/1,625) [CI = 0.31-1.09]; while that of IgG4 to Wb123 was 0.19% (3/1,600) [CI = 0.04-0.50]. The number of positives tested with the two tests were statistically comparable (p = 0.09). In the EU of Bafoulabe-Kita-Oussoubidiagna-Yelimane, an overall prevalence of W. bancrofti CFA was 0% (0/1,700) and that of Wb123 IgG4 antibody was 0.06% (1/1,700), with no statistically significant difference between the two rates (p = 0.99). In the EU of Kadiolo- Kolondieba, the prevalence of Ov16-specific IgG4 was 0.19% (3/1,600) [CI = 0.04-0.50]. All 3 positives were in the previously O. volvulus-hyperendemic district of Kolondieba. In the EU of Bafoulabe-Kita-Oussoubidiagna-Yelimane, an overall prevalence of Ov16-specific IgG4 was 0.18% (3/1,700) [CI = 0.04-0.47]. These 3 Ov16 IgG4 positives were from previously O.volvulus-mesoendemic district of Kita.

CONCLUSIONS/SIGNIFICANCE

The SD Bioline Onchocerciasis/LF IgG4 Rapid test appears to be a good tool for integrated exposure measures of LF and onchocerciasis in co-endemic areas.

Mini-review on CRISPR-Cas9 and its potential applications to help controlling neglected tropical diseases caused by Trypanosomatidae

The CRISPR-Cas system, which was originally identified as a prokaryotic defense mechanism, is increasingly being used for the functional study of genes. This technology, which is simple, inexpensive and efficient, has aroused a lot of enthusiasm in the scientific community since its discovery, and every month many publications emanate from very different communities reporting on the use of CRISPR-Cas9. Currently, there are no vaccines to control neglected tropical diseases (NTDs) caused by Trypanosomatidae, particularly Human African Trypanosomiasis (HAT) and Animal African Trypanosomoses (AAT), and treatments are cumbersome and sometimes not effective enough. CRISPR-Cas9 has the potential to functionally analyze new target molecules that could be used for therapeutic and vaccine purposes. In this review, after briefly describing CRIPSR-Cas9 history and how it works, different applications on diseases, especially on parasitic diseases, are reviewed. We then focus the review on the use of CRISPR-Cas9 editing on Trypanosomatidae parasites, the causative agents of NTDs, which are still a terrible burden for human populations in tropical regions, and their vectors.

Cysteine proteases during larval migration and development of helminths in their final host

Neglected tropical diseases caused by metazoan parasites are major public health concerns, and therefore, new methods for their control and elimination are needed. Research over the last 25 years has revealed the vital contribution of cysteine proteases to invasion of and migration by (larval) helminth parasites through host tissues, in addition to their roles in embryogenesis, molting, egg hatching, and yolk degradation. Their central function to maintaining parasite survival in the host has made them prime intervention targets for novel drugs and vaccines. This review focuses on those helminth cysteine proteases that have been functionally characterized during the varied early stages of development in the human host and embryogenesis.

Canine filariasis in the Amazon: Species diversity and epidemiology of these emergent and neglected zoonoses

Dirofilaria immitis and Acanthocheilonema reconditum are common parasites in dogs but have also been reported parasitizing humans. The differential diagnosis and epidemiological evaluation of these zoonoses are important to the development of efficient public health policies and control strategies. The purpose of this study was to carry out an epidemiological survey by using molecular methods for the specific identification of filarid parasites of domestic dogs in the Marajó mesoregion, State of Pará (PA), Brazil. A total of 418 canine blood samples from Marajó mesoregion (Northern Brazil) were collected, submitted to DNA extraction, polymerase chain reaction (PCR) with “pan filarial” primer, subsequent sequencing and sequence analysis using BLASTn software comparison with previously deposited sequences in GenBank. After that, a phylogenetic analysis by Maximum Parsimony was performed to aid the specific diagnosis. The obtained sequences showed the occurrence of 9 (2.15%) dogs infected with D. immitis and 30 (7.18%) by A. reconditum, with a confidence interval of 95%, there were no cases of co-infection. We observed that male dogs were more likely to D. immits and A. reconditum infection. However, age was not significant to both infections. This study reports for the first time the occurrence of A. reconditum in the northern region of Brazil and confirmed the presence of D. immitis in the Marajó mesoregion.

Cutaneous Leishmaniasis in the Metropolitan City of Multan, Pakistan, a Neglected Tropical Disease

Cutaneous leishmaniasis is a vector-borne infection caused by flagellated parasitic protozoans in the genus Leishmania. Promastigotes are the infective stage, which are transmitted by the bite of female sand flies of the genera Phlebotomus or Lutzomyia. Three clinical forms of Leishmania infection are recognized in humans, and they are caused by different Leishmania species. They are cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (ML), and visceral leishmaniasis (VL). Up to 2 million cases of leishmaniasis are reported annually worldwide. In Pakistan, CL is widely distributed in endemic areas. In the current study, a survey was conducted to investigate the occurrence of CL in an endemic area of the metropolitan city of Multan, Pakistan. The material for diagnosis of CL was obtained from 461 patients from 239 clinical laboratories and health care centers in Multan. Of these patients, 42.9% (198 of 461) having positive findings of amastigotes in Giemsa stained tissue impression smears. The distribution of CL skin lesions was highly variable. Most patients (76.2%) had a single lesion. Most CL lesions were found on a single hand (23.7%). The prevalence of two CL lesions per patient was 21.7%, while three or more positive CL lesions were observed in 2.0% of patients. The 198 CL-positive patients ranged in age 10-40 yr old, 101 were males, and 97 were females. Logistic regression analysis of leishmaniasis versus age and gender showed that both the age and gender had a significant (P < 0.05) effect on the occurrence of infection. Outbreaks of CL were reported in 14 of the 68 Union Councils of Multan.

Cystic echinococcosis in animals and humans of Maharashtra State, India

Echinococcosis/hydatidosis which is a neglected parasitic zoonosis in the developing country like India. The study was conducted during April, 2010 to March, 2017 to determine the prevalence among slaughtered food animals, dogs and human. The samples were collected from the various slaughterhouses situated in different regions of Maharashtra state. A total of 9464 cattle (male), 3661 buffalo, 47189 sheep, 33350 goats and 13579 pigs were scientifically examined during PM inspection at different slaughterhouses. The study revealed that the prevalence of disease in cattle (3.00%) was highest followed by buffalo (2.05%), pig (1.28%), sheep (0.09%) and goat (0.01%), by PM examination. The average estimated economic losses (direct and indirect) due to hydatidosis were Rs. 8,65,83,566 in cattle, Rs. 44,33,93,900 in buffalo, Rs. 7,24,50,615 in sheep, Rs. 1,88,29,359 in goat and Rs. 5,20,49,081 in pigs. Dog faecal samples analyzed and showed the prevalence of echinococcosis as 4.34% (19/438) by sedimentation method and positive samples were confirmed by PCR assay, whereas in high risk human, 11.09% sera samples were found to be positive for echinococcosis. However, based on data collection for seven years, 58 patients were found to be surgically operated for hydatid cyst removal. The results of the present study indicated that cystic echinococcosis/hydatidosis is prevalent in both human and animal population in study areas which attracts serious attention from veterinary and public health authority to reduce economic burden and in designing appropriate strategy for prevention and control of disease.

Repurposing as a strategy for the discovery of new anti-leishmanials: the-state-of-the-art

Leishmaniasis is a vector-borne neglected tropical disease caused by protozoan parasites of the genus Leishmania for which there is a paucity of effective viable non-toxic drugs. There are 1·3 million new cases each year causing considerable socio-economic hardship, best measured in 2·4 million disability adjusted life years, with greatest impact on the poorest communities, which means that desperately needed new antileishmanial treatments have to be both affordable and accessible. Established medicines with cheaper and faster development times may hold the cure for this neglected tropical disease. This concept of using old drugs for new diseases may not be novel but, with the ambitious target of controlling or eradicating tropical diseases by 2020, this strategy is still an important one. In this review, we will explore the current state-of-the-art of drug repurposing strategies in the search for new treatments for leishmaniasis.

Evaluating Healthcare Claims for Neurocysticercosis by Using All-Payer All-Claims Data, Oregon, 2010-2013

To characterize the frequency of neurocysticercosis, associated diagnostic codes, and place of infection, we searched Oregon's All Payer All-Claims dataset for 2010-2013. Twice as many cases were found by searching inpatient and outpatient data than by inpatient data alone. Studies relying exclusively on inpatient data underestimate frequency and miss less severe disease.

Neglected tropical diseases in Brazilian children and adolescents: data analysis from 2009 to 2013

BACKGROUND

Neglected tropical diseases (NTDs) prevail in conditions of poverty and contribute to the maintenance of social inequality. Out of the NTDs prioritized by the Brazilian Ministry of Health, four parasitic infections require mandatory notification: acute Chagas disease, leishmaniasis, malaria, and schistosomiasis. Data on the behaviour of these NTDs in the young population are currently limited. This study seeks to analyse the epidemiological aspects of these parasitic infections in children and adolescents in Brazil.

METHODS

A retrospective exploratory ecological study was conducted. A spatial analysis of the cases reported between 2009 and 2013 in individuals aged between 0 and 19 years that were notified through the Health Notification Aggravation Information System (SINAN) was performed.

RESULTS

In total, 64,567 cases of cutaneous and visceral leishmaniasis, malaria, schistosomiasis, and acute Chagas disease were recorded in the SINAN database, representing a rate of 20.15 cases per 100,000 inhabitants. The average age of the cases was 12.2 years and 62.32% were male. Four hundred and three deaths related to these obligatorily reported parasites were recorded, indicating a case fatality rate of 0.62%. Visceral leishmaniasis and acute Chagas disease had the highest rates of lethality. A heterogeneous spatial distribution of the studied parasites was observed.

CONCLUSIONS

The number of cases and the lethality rate described in this study show that these diseases still represent a serious problem for public health in Brazil. This points to the need to encourage new research and the reformulation of social, economic, and public health policies aimed at ensuring better health and living conditions for all individuals, especially those among the populations considered vulnerable, as is the case of the young.

The cost-effectiveness of an eradication programme in the end game: Evidence from guinea worm disease

Background

Of the three diseases targeted for eradication by WHO, two are so-called Neglected Tropical Diseases (NTDs)–guinea worm disease (GWD) and yaws. The Guinea Worm Eradication Programme (GWEP) is in its final stages, with only 25 reported in 2016. However, global eradication still requires certification by WHO of the absence of transmission in all countries. We analyze the cost-effectiveness of the GWEP in the end game, when the number of cases is lower and the cost per case is higher than at any other time. Ours is the first economic evaluation of the GWEP since a World Bank study in 1997.

Methods

Using data from the GWEP, we estimate the cost of the implementation, pre-certification and certification stages. We model cost-effectiveness in the period 1986–2030. We compare the GWEP to two alternative scenarios: doing nothing (no intervention since 1986) and control (only surveillance and outbreak response during 2016–2030). We report the cost per case averted, cost per disability adjusted life year (DALY) averted and cost per at-risk life year averted. We assess cost-effectiveness against a threshold of about one half GDP per capita (less than US$ 500 in low income countries). All costs are expressed in US$ of 2015.

Results

The GWEP cost an estimated US$ 11 (95% uncertainty interval, 4.70–12.49) per case averted in the period 1986–2030. The pre-certification and certification phases can cost as much as US$ 0.0041 and US$ 0.0015 per capita per year. The cost per DALY averted by the GWEP relative to doing nothing is estimated at US$ 222 (118–372) in 1986–2030. The GWEP is probably more cost-effective than control by the year 2030. The GWEP is certainly more cost-effective than control if willingness to pay for one year of life lived without the risk of GWD exceeds US$ 0.10.

Discussion

Even if economic costs are two times as high as the financial costs estimated for the period to 2020, the GWEP will still be cost-effective relative to doing nothing. Whether the GWEP turns out to be the most cost-effective alternative in the period beyond 2015 depends on the time horizon. When framed in terms of the number of years of life lived without the risk of GWD, a case can be made more easily for finishing the end game, including certification of the absence of transmission.

Of the three diseases targeted for eradication by WHO, two are Neglected Tropical Diseases (NTDs)–guinea worm disease and yaws. The decision to pursue eradication of these diseases was based, in part, on economic arguments made at a time when case numbers were high. There is, in fact, little published evidence of the cost and cost-effectiveness of an eradication programme in the end game, when the number of cases is lower and the cost per case is higher than at any other time. The Guinea Worm Eradication Programme (GWEP) is in its final stages, with only 25 cases reported in 2016. Ours is the first economic evaluation of the GWEP since a World Bank study in 1997. For the first time for any eradication programme, we document the full cost of certifying the absence of transmission in all countries with a history of the disease. We analyze the cost-effectiveness of the GWEP to find that it remains highly cost-effective in spite of high costs in the end game. These results will be of interest to funders of guinea worm disease and yaws eradication, but also to policy makers considering eradication of other NTDs.

Histological assessment of granulomas in natural and experimental Schistosoma mansoni infections using whole slide imaging

The pathology of schistosomiasis mansoni, a neglected tropical disease of great clinical and socioeconomic importance, results from the parasite eggs that become trapped in host tissues, particularly in the liver and intestines. Continuous antigenic stimulation from these eggs leads to recruitment of inflammatory cells to the sites of infection with formation of periovular granulomas. These complex structures have variable size and composition and are the most striking histopathological feature of schistosomiasis mansoni. However, evaluation of granulomas by conventional microscopy methods is time-consuming and limited, especially in large-scale studies. Here, we used high resolution Whole Slide Imaging (WSI), which allows fast scanning of entire histological slides, and multiple morphometric evaluations, to assess the granulomatous response elicited in target organs (liver, small and large intestines) of two models of schistosomiasis mansoni. One of the advantages of WSI, also termed virtual microscopy, is that it generates images that simultaneously offer high resolution and a wide field of observation. By using a model of natural (Nectomys squamipes, a wild reservoir captured from endemic areas in Brazil) and experimental (Swiss mouse) infection with Schistosoma mansoni, we provided the first detailed WSI characterization of granulomas and other pathological aspects. WSI and quantitative analyses enabled a fast and reliable assessment of the number, evolutional types, frequency and areas of granulomas and inflammatory infiltrates and revealed that target organs are differentially impacted by inflammatory responses in the natural and experimental infections. Remarkably, high-resolution analysis of individual eosinophils, key cells elicited by this helminthic infection, showed a great difference in eosinophil numbers between the two infections. Moreover, features such as the intestinal egg path and confluent granulomas were uncovered. Thus, WSI may be a suitable tool for detailed and precise histological analysis of granulomas and other pathological aspects for clinical and research studies of schistosomiasis.

A cross-sectional survey of soil-transmitted helminthiases in two Myanmar villages receiving mass drug administration: epidemiology of infection with a focus on adults

BACKGROUND

Soil-transmitted helminths (STH) are still highly prevalent in southeast Asia. The country of Myanmar has had ongoing mass drug administration (MDA) programmes since 2003 in an attempt to control STH and reduce STH-related morbidities. Whilst the MDA programmes have reported high nationwide coverage, there have been no epidemiological surveys that included measurements from adults. This paper details three cross-sectional surveys that took place over the course of a year in two villages endemic for STH and receiving MDA in lower Myanmar.

RESULTS

At baseline, 27.81% of participants were infected with at least one type of STH. The most prevalent STH was Trichuris trichiura (18.12%) followed by hookworm (8.71%) and Ascaris lumbricoides (5.34%). Most infections were of low intensity, measured by eggs per gram of faeces (EPG). Gender stratification revealed that A. lumbricoides prevalence was significantly higher in females, whereas hookworm prevalence was significantly higher in males. The distribution of EPG in the study sample was highly overdispersed, suggesting that most people release few eggs whereas a few people release many eggs. Adults harbour a major proportion of the overall STH burden; 65.15% of STH infections were harboured by adults.

CONCLUSIONS

STH infection remains at medium prevalence in the study villages despite past and recent MDA. Recorded prevalence of STH in school-aged children has not substantially decreased since the last monitoring and evaluation activities in Myanmar in 2013. Analyses suggest that adults are a major contributor to the total STH prevalence and EPG burden, probably perpetuating transmission.

The causal relationship between neurocysticercosis infection and the development of epilepsy - a systematic review

BACKGROUND

Neurocysticercosis (NCC) is a parasitic infection of the human central nervous system, the most common form of which involves infection of the brain parenchyma with the larval form of the Taenia solium tapeworm. A causal relationship between such an NCC infection and the development of epilepsy in infected individuals is acknowledged, in part supported by high levels of comorbidity in endemic countries worldwide.

METHODS

This study undertook a systematic review and critical analysis of the NCC-epilepsy relationship with the primary objective of quantifying the risk of developing epilepsy following NCC infection. A secondary aim was to analyse the proportions of NCC-associated epilepsy within different populations. Significant emphasis was placed on the importance of neuroimaging (CT or MRI) availability and use of clear guidelines for epilepsy diagnosis, in order to avoid overestimations of prevalence rates of either condition; a limitation identified in several previous studies.

RESULTS

A common odds ratio of 2.76 was identified from meta-analysis of case-control studies, indicating that an individual infected with NCC has almost a three times higher risk of developing epilepsy than an uninfected individual. Furthermore, meta-analysis of studies identified a common proportion of 31.54% of epilepsy cases associated with NCC infection which suggests that amongst epileptic populations in at risk countries, approximately one-third may be associated with NCC infection.

CONCLUSION

A significant finding was the lack of good clinical data to enable accurate determination of a causal relationship. Even studies that were included had noticeable limitations, including a general lack of consistency in diagnostics, and lack of accurate epidemiological data. This review highlights a need for consistency in research in this field. In the absence of reliable estimates of its global burden, NCC will remain of low priority in the eyes of funding agencies - a truly neglected disease.

The Role of Spatial Statistics in the Control and Elimination of Neglected Tropical Diseases in Sub-Saharan Africa: A Focus on Human African Trypanosomiasis, Schistosomiasis and Lymphatic Filariasis

Disease control and elimination programmes can benefit greatly from accurate information on the spatial variability of disease risk, particularly when risk is highly spatially heterogeneous. Due to advances in statistical methodology, coupled with the increased availability of geospatial technology, this information is becoming increasingly accessible. In this chapter we describe recent advancements in spatial methods associated with the analysis of disease data measured at the point-level and demonstrate their application to the control and elimination of neglected tropical diseases (NTDs). We further provide information on spatially referenced data sources and software that can be used to create NTD risk maps, concentrating on those that can be freely obtained. Examples relating to three NTDs affecting populations in sub-Saharan Africa are presented throughout the chapter, i.e., human African trypanosomiasis, schistosomiasis and lymphatic filariasis. These three diseases, with differing routes of transmission, control methods and level of spatial heterogeneity, demonstrate the flexibility and applicability of the methods described.

Longitudinal Study of Transmission in Households with Visceral Leishmaniasis, Asymptomatic Infections and PKDL in Highly Endemic Villages in Bihar, India

Background

Visceral Leishmaniasis (VL) is a neglected tropical disease that afflicts some of the poorest populations in the world including people living in the Bihar state of India. Due to efforts from local governments, NGOs and international organizations, the number of VL cases has declined in recent years. Despite this progress, the reservoir for transmission remains to be clearly defined since it is unknown what role post kala-azar dermal leishmaniasis (PKDL) and asymptomatic infections play in transmission. This information is vital to establish effective surveillance and monitoring to sustainably eliminate VL.

Methodology/Principal Findings

We performed a longitudinal study over a 24-month period to examine VL transmission and seroconversion in households with VL, PKDL and asymptomatic infections in the Saran and Muzaffarpur districts of Bihar. During the initial screening of 5,144 people in 16 highly endemic villages, 195 cases of recently treated VL, 116 healthy rK39 positive cases and 31 PKDL cases were identified. Approximately half of the rK39-positive healthy cases identified during the initial 6-month screening period were from households (HHs) where a VL case had been identified. During the 18-month follow-up period, seroconversion of family members in the HHs with VL cases, PKDL cases, and rK39-positive individuals was similar to control HHs. Therefore, seroconversion was highest in HHs closest to the time of VL disease of a household member and there was no evidence of higher transmission in households with PKDL or healthy rK39-positive HHs. Moreover, within the PKDL HHs, (the initial 31 PKDL cases plus an additional 66 PKDL cases), there were no cases of VL identified during the initial screen or the 18-month follow-up. Notably, 23% of the PKDL cases had no prior history of VL suggesting that infection resulting directly in PKDL is more common than previously estimated.

Conclusions/Significance

These observations argue that acute VL cases represent the major reservoir for transmission in these villages and early identification and treatment of VL cases should remain a priority for VL elimination. We were unable to obtain evidence that transmission occurs in HHs with a PKDL case.

Visceral leishmaniasis (also known as kala-azar) caused by infection with L. donovani is a deadly parasitic disease that afflicts some of world’s poorest populations, including the people of the northern Bihar State of India. Once transmitted to a human by an infected sandfly, the L. donovani parasite migrates from the site of the sandfly bite throughout the reticuloendothelial system, resulting in high levels of infection in the spleen, liver and bone marrow that eventually lead to organ failure and death if not treated effectively. India, Nepal and Bangladesh are currently engaged in a program to eliminate visceral leishmaniasis, principally through early case detection, treatment and vector control. As humans are the only reservoir for L. donovani, it is necessary to understand how the disease is transmitted and specifically what role acute visceral leishmaniasis (VL) cases, asymptomatic infections and post kala-azar dermal leishmaniasis (PKDL) cases play in transmission. We therefore performed a study to determine seroconversion for antibodies against the L. donovani rK39 antigen as a surrogate for transmission in households with VL cases, asymptomatic infections and PKDL cases in 16 highly endemic villages over a 2-year period in Bihar, India. We observed that most transmission occurred in the VL households and further that it occurred closest to the time of acute disease. We were unable to confirm that transmission occurred in the households with either asymptomatic infections or PKDL cases. These observations argue that active surveillance to diagnose and treat VL cases as soon as possible to reduce transmission should remain a priority for VL elimination.

Activation of Bicyclic Nitro-drugs by a Novel Nitroreductase (NTR2) in Leishmania

Drug discovery pipelines for the “neglected diseases” are now heavily populated with nitroheterocyclic compounds. Recently, the bicyclic nitro-compounds (R)-PA-824, DNDI-VL-2098 and delamanid have been identified as potential candidates for the treatment of visceral leishmaniasis. Using a combination of quantitative proteomics and whole genome sequencing of susceptible and drug-resistant parasites we identified a putative NAD(P)H oxidase as the activating nitroreductase (NTR2). Whole genome sequencing revealed that deletion of a single cytosine in the gene for NTR2 that is likely to result in the expression of a non-functional truncated protein. Susceptibility of leishmania was restored by reintroduction of the wild-type gene into the resistant line, which was accompanied by the ability to metabolise these compounds. Overexpression of NTR2 in wild-type parasites rendered cells hyper-sensitive to bicyclic nitro-compounds, but only marginally to the monocyclic nitro-drugs, nifurtimox and fexinidazole sulfone, known to be activated by a mitochondrial oxygen-insensitive nitroreductase (NTR1). Conversely, a double knockout NTR2 null cell line was completely resistant to bicyclic nitro-compounds and only marginally resistant to nifurtimox. Sensitivity was fully restored on expression of NTR2 in the null background. Thus, NTR2 is necessary and sufficient for activation of these bicyclic nitro-drugs. Recombinant NTR2 was capable of reducing bicyclic nitro-compounds in the same rank order as drug sensitivity in vitro. These findings may aid the future development of better, novel anti-leishmanial drugs. Moreover, the discovery of anti-leishmanial nitro-drugs with independent modes of activation and independent mechanisms of resistance alleviates many of the concerns over the continued development of these compound series.

Visceral leishmaniasis (kala-azar) is a serious vector borne disease afflicting people, particularly in parts of Asia, Africa and Latin America. There are approximately 400,000 new cases and an estimated 40,000 deaths each year, making it the second biggest parasitic killer after malaria. We recently discovered that delamanid–an oral nitro-drug used for the treatment of tuberculosis–shows promise for the treatment of leishmaniasis with potential to provide a much needed alternative to the current unsatisfactory anti-leishmanial drugs. Understanding how a drug works is important for selecting the most appropriate partner drugs to be used to increase efficacy and decrease toxicity in patients, to minimise the risk of drug resistance emerging and in designing second generation drugs. Using a combination of biochemical and genetic approaches we have discovered a novel nitroreductase (NTR2) that is necessary and sufficient for the anti-leishmanial activity of delamanid and related experimental drugs containing a nitro-group attached to two fused rings. This enzyme is responsible for activating bicyclic nitro-compounds to form toxic products that kill the parasite. In contrast, the previously identified nitroreductase (NTR1), which specifically activates monocyclic drugs, is not involved in this process. This knowledge can be applied to develop novel treatments for this disease.

Increasing use and accessibility of anti parasitic drugs for migrants with neglected diseases at a time of migratory emergency

This work focused on Schistosoma spp. as a potential agent of gross haematuria in non endemic areas. This change in epidemiology is mainly due to recent migratory flows. Moreover it emphasized the needfor cultural action (aimed at Urologists, Dermatologists, General Practitioners and Emergency Medicine doctors) to provide the elements for a correct and timely diagnosis. But the most important issue raised by this paper is the call for a fast track supply of drugs (usually not available in Italy) to field operators for treating tropical diseases.