Host Range and Emerging and Reemerging Pathogens

Centre for Infectious Diseases, University of Edinburgh, Edinburgh, United Kingdom.
Emerging infectious diseases (Impact Factor: 6.75). 01/2006; 11(12):1842-7. DOI: 10.3201/eid1112.050997
Source: PubMed


An updated literature survey identified 1,407 recognized species of human pathogen, 58% of which are zoonotic. Of the total, 177 are regarded as emerging or reemerging. Zoonotic pathogens are twice as likely to be in this category as are nonzoonotic pathogens. Emerging and reemerging pathogens are not strongly associated with particular types of nonhuman hosts, but they are most likely to have the broadest host ranges. Emerging and reemerging zoonoses are associated with a wide range of drivers, but changes in land use and agriculture and demographic and societal changes are most commonly cited. However, although zoonotic pathogens do represent the most likely source of emerging and reemerging infectious disease, only a small minority have proved capable of causing major epidemics in the human population.

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    • "With over 1,400 human pathogens and 100's estimated yet to be discovered55565758, plus interactions between pathogens [31], there is ample scope for an infectious aetiology behind the step-like events, and the unexplained portion of the increase in medical admissions. "

    Full-text · Article · Jan 2016
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    • "Collectively, these pathways capture nearly all the ways in which pathogens and the diseases they cause can change in the human population. These seven pathways have been used predominantly to identify emergence, but have been overlooked in macroscale analyses of EIDs [18] [19] [21]. Neglect of the pathways used to designate diseases as emerging has left some important questions unanswered . "
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    ABSTRACT: Microbial infections are as old as the hosts they sicken, but interest in the emergence of pathogens and the diseases they cause has been accelerating rapidly. The term 'emerging infectious disease' was coined in the mid-1900s to describe changes in disease dynamics in the modern era. Both the term and the phenomena it is meant to characterize have evolved and diversified over time, leading to inconsistencies and confusion. Here, we review the evolution of the term 'emerging infectious disease' (EID) in the literature as applied to human hosts. We examine the pathways (e.g., speciation or strain differentiation in the causative agent vs. rapid geographic expansion of an existing pathogen) by which diseases emerge. We propose a new framework for disease and pathogen emergence to improve prioritization. And we illustrate how the operational definition of an EID affects conclusions concerning the pathways by which diseases emerge and the ecological and socioeconomic drivers that elicit emergence. As EIDs appear to be increasing globally, and resources for science level off or decline , the research community is pushed to prioritize its focus on the most threatening diseases, riskiest potential pathogens, and the places they occur. The working definition of emerging infectious diseases and pathogens plays a crucial role in prioritization, but we argue that the current definitions may be impeding these efforts. We propose a new framework for classifying pathogens and diseases as " emerging " that distinguishes EIDs from emerging pathogens and novel potential pathogens. We suggest prioritization of: 1) EIDs for adaptation and mitigation, 2) emerging pathogens for preventive measures, and 3) novel potential pathogens for intensive surveillance.
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    • "This observation reveals that a parasite's good performance at one step of the infection sequence cannot be used to predict its ability to spread in a host population. (Woolhouse & Gowtage-Sequeria 2005;Schmid-Hempel 2011). Our approach could be applied in other systems that allow the experimental study of host populations. "
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    ABSTRACT: Parasites often have a smaller geographic distribution than their hosts. Common garden infection trials can untangle the role that historical contingencies, ecological conditions and the genetic constitution of local host populations play in limiting parasite geographic range: however, infection trials usually overestimate the range of hosts in which a parasite could naturally persist. This study overcomes that problem by using multi-generation, long-term persistence experiments. We study the microsporidian parasite Hamiltosporidium tvaerminnensis in monoclonal populations of Daphnia magna from 43widely spread sites. The parasite persisted well in hosts collected from its natural geographic range, but demonstrated long-term persistence in only a few host genotypes outside this range. Genetic distance between hosts from the parasite's origin site and newly tested host populations correlated negatively with parasite persistence. Furthermore, the parasite persisted only in host populations from habitats with a high likelihood of drying up in summer, although we excluded environmental variation in our experiments. Together, our results suggest that host genetic factors play the dominant role in explaining the limited geographic range of parasites, and that these genetic differences covary with geographic distance and the habitat type the host is adapted to. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    No preview · Article · Jul 2015 · Journal of Animal Ecology
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