Aedes aegypti is the urban vector of dengue viruses worldwide. While climate influences the geographical distribution of this mosquito species, other factors also determine the suitability of the physical environment for this mosquito. Importantly, the close association of Ae. aegypti with humans and the domestic environment allows this species to persist in regions that may otherwise be unsuitable based on climatic factors alone. This review highlights the need to incorporate the impact of the urban environment in attempts to model the potential distribution of Ae. aegypti and briefly discuss the potential for future technology to aid management and control of this widespread vector species.
There is strong evidence to suggest that climate change has, and will continue to affect the occurrence, distribution and prevalence of livestock diseases in Great Britain (GB). This paper reviews how climate change could affect livestock diseases in GB. Factors influenced by climate change and that could affect livestock diseases include the molecular biology of the pathogen itself; vectors (if any); farming practice and land use; zoological and environmental factors; and the establishment of new microenvironments and microclimates. The interaction of these factors is an important consideration in forecasting how livestock diseases may be affected. Risk assessments should focus on looking for combinations of factors that may be directly affected by climate change, or that may be indirectly affected through changes in human activity, such as land use (e.g. deforestation), transport and movement of animals, intensity of livestock farming and habitat change. A risk assessment framework is proposed, based on modules that accommodate these factors. This framework could be used to screen for the emergence of unexpected disease events.
The flavivirus genus includes viruses with a remarkable ability to produce disease on a large scale. The expansion and increased endemicity of dengue and West Nile viruses in the Americas exemplifies their medical and epidemiological importance. The rapid detection of virus infection and induction of the innate antiviral response are crucial to determining the outcome of infection. The intracellular pathogen receptors RIG-I and MDA5 play a central role in detecting flavivirus infections and initiating a robust antiviral response. Yet, these viruses are still capable of producing acute illness in humans. It is now clear that flaviviruses utilize a variety of mechanisms to modulate the interferon response. The non-structural proteins of the various flaviviruses reduce expression of interferon dependent genes by blocking phosphorylation, enhancing degradation or down-regulating expression of major components of the JAK/STAT pathway. Recent studies indicate that interferon modulation is an important factor in the development of severe flaviviral illness. This suggests that an increased understanding of viral-host interactions will facilitate the development of novel therapeutics to treat these viral infections and improved biological models to study flavivirus pathogenesis.
Infectious diseases have for centuries ranked with wars and famine as major challenges to human progress and survival. They remain among the leading causes of death and disability worldwide. Against a constant background of established infections, epidemics of new and old infectious diseases periodically emerge, greatly magnifying the global burden of infections. Studies of these emerging infections reveal the evolutionary properties of pathogenic microorganisms and the dynamic relationships between microorganisms, their hosts and the environment.
Emerging infections (EIs) can be defined as “infections that have newly appeared in a population or have existed previously but are rapidly increasing in incidence or geographic range”. EIs have shaped the course of human history and have caused incalculable misery and death. In 1981, a new disease – acquired immune deficiency syndrome (AIDS) – was first recognized. As a global killer, AIDS now threatens to surpass the Black Death of the fourteenth century and the 1918–1920 influenza pandemic, each of which killed at least 50 million people. Of the newly emerging and re-emerging/resurging diseases that have followed the appearance of AIDS, some have been minor curiosities, such as the 2003 cases of monkeypox imported into the United States, whereas others, such as severe acute respiratory syndrome (SARS), which emerged in the same year, have had a worldwide impact. The 2001 anthrax bioterrorist attack in the United States falls into a third category: deliberately emerging diseases. EIs can be expected to remain a considerable challenge for the foreseeable future. Emergence results from dynamic interactions between rapidly evolving infectious agents and changes in the environment and in host behaviour that provide such agents with favourable new ecological niches. This review examines the nature and scope of emerging and re-emerging microbial threats and considers methods for their control.
Traditional lab tests for disease diagnosis can be too expensive and cumbersome for the regions most in need. George Whitesides’ ingenious answer is a foolproof tool that can be manufactured at virtually zero cost, as shown in this video:
Coldwater and tropical fish are the third most popular pet in the UK after cats and dogs. Over 3 million homeowners have a pond in their garden and many of these are stocked with fish, some of which, like koi carp, are very expensive. As Keith Way describes in this article in Microbiology Today (pdf) a whole host of viruses are in the environment just waiting to infect them with harmful diseases:
With the discovery of non-filterable disease agents, or viruses, in the late 19th century there came a greater realization of the role that viruses may play in infectious diseases of fish. However, the breakthrough for fish virology came with the general developments in virological techniques that blossomed in the 1950s and 60s. In particular, visualization of viruses by electron microscopy, improvements in protein and nucleic acid analysis and, most significantly, the isolation of viruses on continuous (immortal) fish cell lines. At the same time, aquaculture around the world developed in the 1960s and 70s, and farming of fish and fish-keeping rapidly increased. With these developments and, more recently, the global increase in trade in ornamental fish there has been an increase in new diseases and the emergence of serious virus diseases. Viruses that have caused serious but isolated disease outbreaks in cyprinid species and some ictalurid (catfish) species, and may affect coldwater ornamental fish, include aquareoviruses, coronaviruses, poxviruses and iridoviruses. More serious disease epidemics in ornamental species have been caused by rhabdoviruses and herpesviruses.
Climate change is incontestably a phenomenon of global causes and impacts. However, as the contribution of different regions and countries to climate change differs, so do the impacts. This paper examines the current and potential impact of climate change on infectious diseases in regions that could not be more different: the Arctic and the tropics. Despite obvious differences in environmental and socio-economic contexts, there are commonalities between these areas, both in the mechanisms through which climate change influences disease transmission and in the adaptation responses health systems can and should mount. The authors consider five main common characteristics and requirements, respectively, regarding climate-sensitive infectious diseases:
Exposure to new patterns of climate-sensitive infectious diseases.
Disease surveillance and early warning systems.
Health system preparedness.
Enhanced global efforts towards developing drugs and vaccines.
Staphylococcus aureus is the main cause of purulent infection in humans. S. aureus has the potential for local as well as disseminated infection and can cause lesions in all tissues and anatomical sites. Infections can be either acquired in the community or in association with health care. The position of S. aureus as one of the most important human pathogens is largely due to its virulence potential and ubiquitous occurrence as a coloniser in humans, domestic animals, and livestock. Between 25% and 35% of healthy human individuals carry S. aureus on the skin or mucous membranes. Any injury that compromises epithelial integrity, trauma, medical or surgical interventions, as well as viral infections, can lead to tissue invasion. It is assumed that severity and outcome depend largely on the virulence of the introduced strain and the immune repertoire of the host. Occasionally, S. aureus acquires enhanced virulence and antimicrobial resistance through horizontal DNA transfer and maintains these mobile genetic elements in a predominantly clonal genomic background. Thus, clones of S. aureus are relatively stable and mainly diversify by the accumulation of single nucleotide substitutions in the absence of frequent interstrain recombination. It is therefore possible to discern different clones and clonal lineages by molecular typing. This method allows several important observations to be made regarding the evolution, epidemiology, and spread of clones with particular public health importance, such as hospital-, community- , and livestock-associated methicillin-resistant S. aureus (MRSA).
A new study finds that methicillin-resistant S. aureus (MRSA), responsible for several difficult-to-treat infections including blood poisoning and pneumonia and a particular problem in hospitals, occurs in distinct geographical clusters across Europe, indicating that MRSA is being diffused by patients moving between hospitals rather than spreading freely in the community. The study used an interactive Web tool to map different strains of the Staphylococcus aureus bacterium across the continent. MRSA infections have become more prevalent in hospitals over the past ten years, and information about its geographical distribution could help us to understand how it spreads and how to control it.
Since 2006 a large group of collaborators in 450 European hospitals located in 26 different countries collected both MRSA and methicillin-sensitive S. aureus (MSSA) isolates from infected patients. National laboratories identified specific strains of S. aureus by molecular typing and entered this information into a Web-based mapping application which is publicly available. The results show that strains of MRSA tend to cluster within regional borders and, in several instances, were associated with individual hospitals. This suggests that MRSA is mainly spread by patients who are repeatedly admitted to different hospitals. Control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful.
Geographic Distribution of Staphylococcus aureus Causing Invasive Infections in Europe: A Molecular-Epidemiological Analysis. PLoS Med 7(1): e1000215 doi:10.1371/journal.pmed.1000215: Staphylococcus aureus is one of the most important human pathogens and methicillin-resistant variants (MRSAs) are a major cause of hospital and community-acquired infection. We aimed to map the geographic distribution of the dominant clones that cause invasive infections in Europe. In each country, staphylococcal reference laboratories secured the participation of a sufficient number of hospital laboratories to achieve national geo-demographic representation. Participating laboratories collected successive methicillin-susceptible (MSSA) and MRSA isolates from patients with invasive S. aureus infection using an agreed protocol. All isolates were sent to the respective national reference laboratories and characterised by quality-controlled sequence typing of the variable region of the staphylococcal spa gene (spa typing), and data were uploaded to a central database. Relevant genetic and phenotypic information was assembled for interactive interrogation by a purpose-built Web-based mapping application. Between September 2006 and February 2007, 357 laboratories serving 450 hospitals in 26 countries collected 2,890 MSSA and MRSA isolates from patients with invasive S. aureus infection. A wide geographical distribution of spa types was found with some prevalent in all European countries. MSSA were more diverse than MRSA. Genetic diversity of MRSA differed considerably between countries with dominant MRSA spa types forming distinctive geographical clusters. We provide evidence that a network approach consisting of decentralised typing and visualisation of aggregated data using an interactive mapping tool can provide important information on the dynamics of MRSA populations such as early signalling of emerging strains, cross border spread, and importation by travel. In contrast to MSSA, MRSA spa types have a predominantly regional distribution in Europe. This finding is indicative of the selection and spread of a limited number of clones within health care networks, suggesting that control efforts aimed at interrupting the spread within and between health care institutions may not only be feasible but ultimately successful and should therefore be strongly encouraged.
Even before I wrote my online notes about Bornaviruses over 10 years ago, this group of viruses was always a bit of a mystery. Considerable controversy still surrounds the role of these viruses in human pathogenesis, so it is of great interest that a report has just been published in Nature describing how Bornavirus-like sequences have been repeatedly incorporated into the genome during mammalian evolution. BDV infection might create a source of mutation in infected individuals, which allows a testable hypothesis for the alleged, but still controversial, causative association of BDV infection with certain psychiatric disorders, such as schizophrenia and mood disorders.
Endogenous non-retroviral RNA virus elements in mammalian genomes. Nature 463, 84, (2010). doi:10.1038/nature08695
Retroviruses are the only group of viruses known to have left a fossil record, in the form of endogenous proviruses, and approximately 8% of the human genome is made up of these elements. Although many other viruses, including non-retroviral RNA viruses, are known to generate DNA forms of their own genomes during replication, none has been found as DNA in the germline of animals. Bornaviruses, a genus of non-segmented, negative-sense RNA virus, are unique among RNA viruses in that they establish persistent infection in the cell nucleus. Here we show that elements homologous to the nucleoprotein (N) gene of bornavirus exist in the genomes of several mammalian species, including humans, non-human primates, rodents and elephants. These sequences have been designated endogenous Borna-like N (EBLN) elements. Some of the primate EBLNs contain an intact open reading frame (ORF) and are expressed as mRNA. Phylogenetic analyses showed that EBLNs seem to have been generated by different insertional events in each specific animal family. Furthermore, the EBLN of a ground squirrel was formed by a recent integration event, whereas those in primates must have been formed more than 40 million years ago. We also show that the N mRNA of a current mammalian bornavirus, Borna disease virus (BDV), can form EBLN-like elements in the genomes of persistently infected cultured cells. Our results provide the first evidence for endogenization of non-retroviral virus-derived elements in mammalian genomes and give novel insights not only into generation of endogenous elements, but also into a role of bornavirus as a source of genetic novelty in its host.
Aedes aegypti is the urban vector of dengue viruses worldwide. While climate influences the geographical distribution of this mosquito species, other factors also determine the suitability of the physical environment for this mosquito. Importantly, the close association of Ae. aegypti with humans and the domestic environment allows this species to persist in regions that may otherwise be unsuitable based on climatic factors alone. This review highlights the need to incorporate the impact of the urban environment in attempts to model the potential distribution of Ae. aegypti and briefly discuss the potential for future technology to aid management and control of this widespread vector species.
