SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Pathogens and global health

25

Free-living amoebae (FLA) are potential reservoirs of Legionella in aquatic environments. However, the parasitic relationship between various Legionella and amoebae remains unclear. In this study, surface water samples were gathered from two rivers for evaluating parasitic Legionella. Warmer water temperature is critical to the existence of Legionella. This result suggests that amoebae may be helpful in maintaining Legionella in natural environments because warmer temperatures could enhance parasitisation of Legionella in amoebae. We next used immunomagnetic separation (IMS) to identify extracellular Legionella and remove most free Legionella before detecting the parasitic ones in selectively enriched amoebae. Legionella pneumophila was detected in all the approaches, confirming that the pathogen is a facultative amoebae parasite. By contrast, two obligate amoebae parasites, Legionella-like amoebal pathogens (LLAPs) 8 and 9, were detected only in enriched amoebae. However, several uncultured Legionella were detected only in the extracellular samples. Because the presence of potential hosts, namely Vermamoeba vermiformis, Acanthamoeba spp. and Naegleria gruberi, was confirmed in the samples that contained intracellular Legionella, uncultured Legionella may survive independently of amoebae. Immunomagnetic separation and amoebae enrichment may have referential value for detecting parasitic Legionella in surface waters.

Concepts: Immune system, Bacteria, Water, Symbiosis, Parasitism, Acanthamoeba, Surface water, Percolozoa

20

Policy prescriptions for combating dengue fever tend to focus on addressing environmental and social conditions of poverty. However, while poverty has long been considered a determinant of dengue, the research evidence for such a relationship is not well established. Results of a systematic review of the research literature designed to identify and assess the current state of the empirical evidence for the dengue-poverty link reveal a mixed story. Of 260 peer-reviewed articles referencing dengue-poverty relationships, only 12 English-language studies empirically assessed these relationships. Our analysis covering various social and economic conditions of poverty showed no clear associations with dengue rates. While nine of the 12 studies demonstrated some positive associations between measures of dengue and poverty (measured inconsistently through income, education, structural housing condition, overcrowding, and socioeconomic status), nine also presented null results and five with negative results. Of the five studies relating to access to water and sanitation, four reported null associations. Income and physical housing conditions were more consistently correlated with dengue outcomes than other poverty indicators. The small size of this sample, and the heterogeneity of measures and scales used to capture conditions of poverty, make it difficult to assess the strength and consistency of associations between various poverty indicators and dengue outcomes. At present, the global body of eligible English-language peer-reviewed literature investigating dengue-poverty relationships is too small to support a definitive relationship. We conclude that more research, particularly using standardized measures of both outcomes and indicators, is needed to support evidence-informed policies and approaches.

Concepts: Scientific method, Economics, Academic publishing, Empiricism, Empirical, Peer review, Fever, Empirical research

5

In zones of violent conflict in the tropics, social disruption leads to elevated child mortality, of which malaria is the leading cause. Understanding the social determinants of malaria transmission may be helpful to optimize malaria control efforts. We conducted a cross-sectional study of healthy children aged 2 months to 5 years attending well-child and/or immunization visits in the Democratic Republic of Congo (DRC). Six hundred and forty-seven children were tested for malaria antigenemia by rapid diagnostic test and the accompanying parent or legal guardian simultaneously completed a survey questionnaire related to demographics, socioeconomic status, maternal education, as well as bednet use and recent febrile illness. We examined the associations between variables using multivariable logistic regression analysis, chi-squared statistic, Fisher’s exact test, and Spearman’s rank correlation, as appropriate. One hundred and twenty-three out of the 647 (19%) children in the study tested positive for malaria. Higher levels of maternal education were associated with a lower risk of malaria in their children. The prevalence of malaria in children of mothers with no education, primary school, and beyond primary was 41/138 (30%), 41/241 (17%), and 39/262 (15%), respectively (p = 0.001). In a multivariable logistic regression model adjusting for the effect of a child’s age and study site, the following remained significant predictors of malaria antigenemia: maternal education, number of children under five per household, and HIV serostatus. Higher maternal education, through several putative causal pathways, was associated with lower malaria prevalence among children in the DRC. Our findings suggest that maternal education might be an effective ‘social vaccine’ against malaria in the DRC and globally.

Concepts: Logistic regression, Statistical tests, Statistics, Malaria, Spearman's rank correlation coefficient, Non-parametric statistics, Democratic Republic of the Congo, United Nations

1

Lassa fever (LF) is increasingly recognized by global health institutions as an important rodent-borne disease with severe impacts on some of West Africa’s poorest communities. However, our knowledge of LF ecology, epidemiology and distribution is limited, which presents barriers to both short-term disease forecasting and prediction of long-term impacts of environmental change on Lassa virus (LASV) zoonotic transmission dynamics. Here, we synthesize current knowledge to show that extrapolations from past research have produced an incomplete picture of the incidence and distribution of LF, with negative consequences for policy planning, medical treatment and management interventions. Although the recent increase in LF case reports is likely due to improved surveillance, recent studies suggest that future socio-ecological changes in West Africa may drive increases in LF burden. Future research should focus on the geographical distribution and disease burden of LF, in order to improve its integration into public policy and disease control strategies.

Concepts: Medicine, Epidemiology, Africa, Future, Forecasting, Viral hemorrhagic fever, Zoonosis, Lassa fever

1

Zika virus (ZIKV) is an emerging Flavivirus that have recently caused an outbreak in Brazil and rapid spread in several countries. In this study, the consequences of ZIKV evolution on protein recognition by the host immune system have been analyzed. Evolutionary analysis was combined with homology modeling and T-B cells epitope predictions. Two separate clades, the African one with the Uganda sequence, as the most probable ancestor, and the second one containing all the most recent sequences from the equatorial belt were identified. Brazilian strains clustered all together and closely related to the French Polynesia isolates. A strong presence of a negatively selected site in the envelope gene (Env) protein was evidenced, suggesting a probable purging of deleterious polymorphisms in functionally important genes. Our results show relative conservancy of ZIKV sequences when envelope and other non-structural proteins (NS3 and NS5) are analyzed by homology modeling. However, some regions within the consensus sequence of NS5 protein and to a lesser extent in the envelope protein, show localized high mutation frequency corresponding to a considerable alteration in protein stability. In terms of viral immune escape, envelope protein is under a higher selective pressure than NS5 and NS3 proteins for HLA class I and II molecules. Moreover, envelope mutations that are not strictly related to T-cell immune responses are mostly located on the surface of the protein in putative B-cell epitopes, suggesting an important contribution of B cells in the immune response as well.

Concepts: Immune system, Antibody, DNA, Protein, Evolution, Adaptive immune system, Antigen, Epitope

1

As the most recent outbreak of Ebola virus disease (EVD) in West Africa continues to grow since its initial recognition as a Public Health Emergency of International Concern, an unanswered question is what is the cost of a case of Ebola? Understanding this cost will help decision makers better understand the impact of each case of EVD, benchmark this against that of other diseases, prioritize which cases may require response, and begin to estimate the cost of Ebola outbreaks. To date, the scientific literature has not characterized this cost per case. Therefore, we developed a mathematical model to estimate the cost of an EVD case from the provider and societal perspectives in the three most affected countries of Guinea, Liberia, and Sierra Leone. Our model estimates the total societal cost of an EVD case with full recovery ranges from $480 to $912, while that of an EVD case not surviving ranges from $5929 to $18 929, varying by age and country. Therefore, as of 10 December 2014, the estimated total societal costs of all reported EVD cases in these three countries range from $82 to potentially over $356 million.

Concepts: Mathematics, Nigeria, West Africa, Ebola, Liberia, Sierra Leone, Economic Community of West African States, Guinea

1

It is hypothesized that animals living in polluted environments possess antimicrobials to counter pathogenic microbes. The fact that snakes feed on germ-infested rodents suggests that they encounter pathogenic microbes and likely possess antimicrobials. The venom is used only to paralyze the rodent, but the ability of snakes to counter potential infections in the gut due to disease-ridden rodents requires robust action of the immune system against a broad range of pathogens. To test this hypothesis, crude lysates of different organs of Naja naja karachiensis (black cobra) were tested for antimicrobial properties. The antimicrobial activities of extracts were tested against selected bacterial pathogens (neuropathogenic Escherichia coli K1, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Streptococcus pneumonia), protist (Acanthamoeba castellanii), and filamentous fungus (Fusarium solani). The findings revealed that plasma and various organ extracts of N. n. karachiensis exhibited antimicrobial activity against E. coli K1, MRSA, P. aeruginosa, S. pneumoniae, A. castellanii, and F. solani in a concentration-dependent manner. The results of this study are promising for the development of new antimicrobials.

Concepts: Immune system, Bacteria, Gut flora, Microbiology, Pneumonia, Staphylococcus aureus, Antibiotic resistance, Pseudomonas aeruginosa

0

Schistosomiasis is a parasitic infection that has evolved together with the humankind. Evidence in ancient Egyptian medical papyri or Assyrian medical texts reported signs and symptoms that could resemble schistosomiasis; similarly, some biblical passages describe an epidemic (depicted as a ‘curse’) that has been hypothesized to be associated with schistosomiasis' spread in Mesopotamia. In the modern era, Theodor Maximilian Bilharz and Patrick Manson (the ‘father of tropical medicine’) gave an impetus to the knowledge about the parasite and its spread until the present time, when immunoassays and molecular biology on mummies allowed retracing important milestones regarding schistosomiasis' evolution. Schistosomiasis affects more than 200 millions of people worldwide and it is an emblem of how hard it is to prevent, control and treat neglected tropical diseases. Our work reviews the history of schistosomiasis with regard to human infections.

0

Eastern Europe (EE) has been severely affected by mosquito-borne viruses (moboviruses). In this review, we summarize the epidemiology of moboviruses, with particular attention to West Nile virus (WNV). The study of WNV human cases in EE between 2010 and 2016, revealed that the epidemiology of WNV in EE is complex with the combination of introduction of different WNV strains from lineages 1 and 2, and the establishment of endemic cycles. We found a positive correlation between the risk of WNV re-emergence in an area and the number of human cases reported in the previous year. We also report the main ecological and biological characteristics of the key mosquito species vectors of moboviruses. Recent expansion of invasive mosquito species in EE, mainly Aedes albopictus but also Aedes aegypti and Culex quinquefasciatus, may result in new scenarios with an increased risk of transmission of moboviruses. Main gaps of knowledge in relation to moboviruses and their vectors in EE are identified. Understanding the epidemiology of moboviruses in EE is essential for the improvement of their surveillance and the control of the diseases they cause.

0

Governance is a broader and more flexible concept than statute-driven regulations as it incorporates components outside the latter’s remit. Considerations of governance are critical in the development of emerging biotechnologies such as gene drive organisms. These have been proposed or are being developed to address public and environmental health issues not addressed easily by conventional means. Here, we consider how the concept of governance differs from statute-driven regulation with reference to the role each may play in the development of gene drive organisms. First, we discuss existing statute-based regulatory systems. Second, we consider whether novel risks or different concerns derive from gene drive organisms, concentrating on characteristics that contribute to public health or environmental risk and uncertainties that may affect risk perceptions. Third, we consider public engagement, outlining how existing statute-driven regulatory systems and other governance mechanisms may provide opportunities for constructive interactions. Finally, we provide some observations that may help address science- and values-based concerns in a governance space larger than that of statute-driven regulatory systems.