Global distribution of outbreaks of water-associated infectious diseases

Background

Water plays an important role in the transmission of many infectious diseases, which pose a great burden on global public health. However, the global distribution of these water-associated infectious diseases and underlying factors remain largely unexplored.

Methods and Findings

Based on the Global Infectious Disease and Epidemiology Network (GIDEON), a global database including water-associated pathogens and diseases was developed. In this study, reported outbreak events associated with corresponding water-associated infectious diseases from 1991 to 2008 were extracted from the database. The location of each reported outbreak event was identified and geocoded into a GIS database. Also collected in the GIS database included geo-referenced socio-environmental information including population density (2000), annual accumulated temperature, surface water area, and average annual precipitation. Poisson models with Bayesian inference were developed to explore the association between these socio-environmental factors and distribution of the reported outbreak events. Based on model predictions a global relative risk map was generated. A total of 1,428 reported outbreak events were retrieved from the database. The analysis suggested that outbreaks of water-associated diseases are significantly correlated with socio-environmental factors. Population density is a significant risk factor for all categories of reported outbreaks of water-associated diseases; water-related diseases (e.g., vector-borne diseases) are associated with accumulated temperature; water-washed diseases (e.g., conjunctivitis) are inversely related to surface water area; both water-borne and water-related diseases are inversely related to average annual rainfall. Based on the model predictions, “hotspots” of risks for all categories of water-associated diseases were explored.

Conclusions

At the global scale, water-associated infectious diseases are significantly correlated with socio-environmental factors, impacting all regions which are affected disproportionately by different categories of water-associated infectious diseases.     

The book reopened on infectious diseases

Emerging infectious diseases represent a major challenge to human health worldwide. The risk of evolving new infectious pathogens has been intensifying due to urbanization, demographic changes, air travel, inappropriate use of antibiotics, and climate change. These pathogens can affect humans from urban centers to the remotest corners of the globe. Far from being a scourge of the past, infectious diseases are relevant for the world today.     

Patterns in the effects of infectious diseases on population growth

An infectious disease may reduce or even stop the exponential growth of a population. We consider two very simple models for microparasitic and macroparasitic diseases, respectively, and study how the effect depends on a contact parameter K. The results are presented as bifurcation diagrams involving several threshold values of . The precise form of the bifurcation diagram depends critically on a second parameter , measuring the influence of the disease on the fertility of the hosts. A striking outcome of the analysis is that for certain ranges of parameter values bistable behaviour occurs: either the population grows exponentially or it oscillates periodically with large amplitude.The work of this author was supported by a grant of the Deutsche Forschungsgemeinschaft (DFG)     

Role of oxidative stress in infectious diseases. A review

Oxidative stress plays a dual role in infections. Free radicals protect against invading microorganisms, and they can also cause tissue damage during the resulting inflammation. In the process of infection, there is generation of reactive species by myeloperoxidase, NADPH oxidase, and nitric oxide synthase. On the other hand, reactive species can be generated among others, by cytochrome P450, some metals, and xanthine oxidase. Some pathologies arising during infection can be attributed to oxidative stress and generation of reactive species in infection can even have fatal consequences. This article reviews the basic pathways in which reactive species can accumulate during infectious diseases and discusses the related health consequences.     

植物对环境应力刺激的生物学效应

植物生长在自然环境中由于其“不动性”而不可避免地要受到各种环境应力的刺激,应力－生长关系一直是生物学家和物理学家所关心的课题,是生物力学的灵魂。很多研究已经表明外界应力作用对植物的生长发育有着重要的影响。本综述了国内外关于应力对植物组织所引起的生物学效应,首先论述了环境应力所引起的宏观生物学效应,随后重点论述了环境应力所引起的生物学效应在细胞和分子水平上的研究,其中包括单个细胞的加载、电磁场、微     

Outside-host phage therapy as a biological control against environmental infectious diseases

Background

Environmentally growing pathogens present an increasing threat for human health, wildlife and food production. Treating the hosts with antibiotics or parasitic bacteriophages fail to eliminate diseases that grow also in the outside-host environment. However, bacteriophages could be utilized to suppress the pathogen population sizes in the outside-host environment in order to prevent disease outbreaks. Here, we introduce a novel epidemiological model to assess how the phage infections of the bacterial pathogens affect epidemiological dynamics of the environmentally growing pathogens. We assess whether the phage therapy in the outside-host environment could be utilized as a biological control method against these diseases. We also consider how phage-resistant competitors affect the outcome, a common problem in phage therapy. The models give predictions for the scenarios where the outside-host phage therapy will work and where it will fail to control the disease. Parameterization of the model is based on the fish columnaris disease that causes significant economic losses to aquaculture worldwide. However, the model is also suitable for other environmentally growing bacterial diseases.

Results

Transmission rates of the phage determine the success of infectious disease control, with high-transmission phage enabling the recovery of the host population that would in the absence of the phage go asymptotically extinct due to the disease. In the presence of outside-host bacterial competition between the pathogen and phage-resistant strain, the trade-off between the pathogen infectivity and the phage resistance determines phage therapy outcome from stable coexistence to local host extinction.

Conclusions

We propose that the success of phage therapy strongly depends on the underlying biology, such as the strength of trade-off between the pathogen infectivity and the phage-resistance, as well as on the rate that the phages infect the bacteria. Our results indicate that phage therapy can fail if there are phage-resistant bacteria and the trade-off between pathogen infectivity and phage resistance does not completely inhibit the pathogen infectivity. Also, the rate that the phages infect the bacteria should be sufficiently high for phage-therapy to succeed.

     

Seasonal and environmental effects on the blood hemoglobin concentrations of some Panamanian air-breathing fishes

Synopsis Interspecific differences in blood hemoglobin concentration ([Hb]) occur among air breathing fishes. However, the effect on [Hb] of factors such as air-breathing organ structure and blood circulation pattern, air breathing behavior, as well as season and environmental conditions have not been fully examined. [Hb] in seven Panamanian species of air-breathing freshwater teleost fishes were compared and were monitored for most species during the wet and dry seasons and in hypoxic laboratory conditions. Fishes studied were Ancistrus, Hypostomus, and Loricaria (Family Loricariidae); Hoplosternum (Callichthyidae); Synbranchus (Synbranchidae); Piabucina (Lebiasinidae); and Dormitator (Eleotridae). [Hb] in these species ranged from 4.8 to 14.6 g 100 ml^–1 (g%). Ancistrus, Hypostomus, and Dormitator significantly increased [Hb] during the dry season and, with Piabucina, also increased [Hb] when acclimated to hypoxia in the laboratory. An increase in [Hb] during the dry season may precondition facultative air breathers for habitat hypoxia (and the need to respire aerially) in the event this occurs. Intraspecific differences in both [Hb] and in red cell Hb-phosphate ratio, an index of oxygen affinity, were found in populations of Hypostomus and relate directly to differences in habitat oxygen level. In all species tested alterations in blood hematocrit (Hmct) and mean corpuscular hemoglobin concentration (MCHC) occurred only with correspondingly large net changes in blood [Hb]. The [Hb] of Loricaria, Synbranchus, and Hoplosternum was not affected by season or hypoxia and this may be due to behavioral and physiological adaptations that reduce the transbranchial loss of aerially-obtained oxygen or to a ventilatory mode that precludes this possibility.     

Role of passive immunotherapies in managing infectious outbreaks

The historical and current role of passive immunization in managing outbreaks of infectious diseases reviewed.     

Coupling effects on turning points of infectious diseases epidemics in scale-free networks

Background

Pandemic is a typical spreading phenomenon that can be observed in the human society and is dependent on the structure of the social network. The Susceptible-Infective-Recovered (SIR) model describes spreading phenomena using two spreading factors; contagiousness (β) and recovery rate (γ). Some network models are trying to reflect the social network, but the real structure is difficult to uncover.

Methods

We have developed a spreading phenomenon simulator that can input the epidemic parameters and network parameters and performed the experiment of disease propagation. The simulation result was analyzed to construct a new marker VRTP distribution. We also induced the VRTP formula for three of the network mathematical models.

Results

We suggest new marker VRTP (value of recovered on turning point) to describe the coupling between the SIR spreading and the Scale-free (SF) network and observe the aspects of the coupling effects with the various of spreading and network parameters. We also derive the analytic formulation of VRTP in the fully mixed model, the configuration model, and the degree-based model respectively in the mathematical function form for the insights on the relationship between experimental simulation and theoretical consideration.

Conclusions

We discover the coupling effect between SIR spreading and SF network through devising novel marker VRTP which reflects the shifting effect and relates to entropy.

     

Ontogenetic changes and environmental effects on ocular transmission in four species of coral reef fishes

Filtration by the humors, cornea and lens limits the spectrum of light available for vision as blocking compounds prevent some wavelengths from reaching photo-sensitive cells of the retina. The visual ecology of fishes is dependent upon factors changing with size and/or habitat. We predicted that ontogeny and habitat depth would affect ocular transmission for four fishes, Mulloidichthys flavolineatus, Parupeneus multifasciatus, Acanthurus triostegas, and Naso lituratus. We measured ocular transmission in specimens from a range of sizes (juvenile-adult) and capture depths (<3-37 m), and used the wavelength (nm) where transmission was reduced 50% as our comparative measure (T(50)). We modeled lens transmission varying pigment concentrations and pathlength, and compared predicted versus measured results. P. multifasciatus, M. flavolineatus, and N. lituratus showed a significant increase in short-wavelength blocking with size. A. triostegas were constant across sizes, and showed a slight but significant effect with depth. Comparisons of predicted versus observed transmission values suggest that pigment concentrations are held constant with age for all species, but species- and family-level differences emerge. The accumulation of blocking compounds in ocular tissues is a contributing means for balancing the costs and benefits of admitting short-wavelength radiation to the retina.     

The deepest vertebrate fossil and other arctolepid fishes*

A new genus and species of arctolepid arthrodire, Qataraspis deprofundis is based on an anterolateral plate recovered from a bore-hole in Qatar, Persian Gulf at a depth of nearly two and a half miles. It is compared with the corresponding plates of all known arctolepid arthrodires, particularly those referred to the undefined genus Kujdanoteiaspis Stensiö. The British species K. anglica is described in detail and referred to a new genus, Heightington-aspis, and a specimen from the Senni Beds of the Black Mountains is described as Ailuracantha dorsifelis gen. et sp. nov.     

The impact of genomics on discovering drugs against infectious diseases

Genomics is accelerating the progress in data generation and interpretation in the global analyses of components of cells, including the spectrum of lipids, RNA, metabolites, proteins, mutational phenotypes or DNA methylation sites. Integration of the knowledge generated by these diverse strategies is predicted to have a tremendous impact on approaches to rational drug discovery against infectious diseases.