Should We Aim For Genetic Improvement In Host Resistance Or Tolerance To Infectious Disease

Recent advances in quantitative genetic and genomic studies have shed light on the important role of genetic control strategies for reducing disease risk and severity in livestock populations. There are two alternative host defence strategies to infectious pathogens that could be enhanced by genetic selection: improvement of host resistance versus improvement of host tolerance to infectious pathogens. Resistance refers to mechanisms that restrict the reproduction rate of a pathogen within a host, whilst tolerance mechanisms focus on minimising the damage that a pathogen inflicts on the host. Both strategies may have a similar impact on individual host fitness and performance, but can have contrasting effects on population performance and disease risk and severity. For example, improving host resistance may result in successful eradication of a disease from a livestock population, whereas disease eradication may be difficult if hosts are tolerant as these can harbour the pathogen without showing obvious or severe symptoms. On the other hand, it has been argued that increasing host resistance would fuel the arms race between host and pathogen and stimulate pathogen evolution towards higher virulence. Increasing tolerance, in contrast, imposes no or little selection pressure on the pathogen. Further, whereas disease resistance mechanisms may be specific to a particular pathogen (e.g. development of specific antibodies), tolerance mechanisms that repair damaged tissues are associated with the host rather than the pathogen, and are thus more likely to be generic to a range of pathogens. Hence, improving tolerance may be beneficial if individuals are exposed to a variety of pathogens or pathogen strains, and disease eradication has proven difficult. In contrast to evolutionary biology and plant breeding, animal breeding has only recently started to seriously consider a distinction between disease resistance and tolerance and their consequences. However, a deeper understanding of the underlying mechanisms and implications of improving either or both of the host defence mechanisms on future disease risk and severity is urgently needed by animal scientists, veterinarians and breeders to make informed decisions that help to maintain healthy livestock populations and guarantee food security. The topic ‘genetic improvement of disease resistance v tolerance’ would lend itself to research papers covering a variety of aspects that need to be considered, such as ‘how to obtain genetic parameter estimates and genomic breeding values related to disease resistance / tolerance’, ‘evidence for host genetic influence of resistance or tolerance’, ‘genetic, genomic and immunological understanding of resistance / tolerance mechanisms’, ‘epidemiological consequences of improving disease resistance / tolerance’. I believe that this research topic is both timely and relevant, and that sufficient knowledge is available across disciplines for composing valuable research / review articles that stimulate interest to a wide range of readers of Frontiers, and thus promote the growth of this journal.

The evolution of metazoans has been accompanied by new interfaces with the microbial environment that include biological barriers and surveillance by specialized cell types. Increasingly complex organisms require increased capacities to confront pathogens, achieved by co-evolution of recognition mechanisms and regulatory pathways. Two distinct but interactive forms of immunity have evolved. Innate immunity, shared by all metazoans, is traditionally viewed as simple and non-specific. Adaptive immunity possesses the capacity to anticipate new infectious challenges and recall previous exposures; the most well-understood example of such a system, exhibited by lymphocytes of vertebrates, is based on somatic gene alterations that generate extraordinary specificity in discrimination of molecular structures. Our understanding of immune phylogeny over the past decades has tried to reconcile immunity from a vertebrate standpoint. While informative, such approaches cannot completely address the complex nature of selective pressures brought to bear by the complex microbiota (including pathogens) that co-exist with all metazoans. In recent years, comparative studies (and new technologies) have broadened our concepts of immunity from a systems-wide perspective. Unexpected findings, e.g., genetic expansions of innate receptors, high levels of polymorphism, RNA-based forms of generating diversity, adaptive evolution and functional divergence of gene families and the recognition of novel mediators of adaptive immunity, prompt us to reconsider the very nature of immunity. Even fundamental paradigms as to how the jawed vertebrate adaptive immune system should be structured for “optimal” recognition potential have been disrupted more than once (e.g., the discovery of the multicluster organization and germline joining of immunoglobulin genes in sharks, gene conversion as a mechanism of somatic diversification, absence of IgM or MHC II in certain teleost fishes). Mechanistically, concepts of innate immune memory, often referred to as “trained memory,” have been realized further, with the development of new discoveries in studies of epigenetic regulation of somatic lineages. Immune systems innovate and adapt in a taxon-specific manner, driven by the complexity of interactions with microbial symbionts (commensals, mutualists and pathogens). Immune systems are shaped by selective forces that reflect consequences of dynamic interactions with microbial environments as well as a capacity for rapid change that can be facilitated by genomic instabilities. We have learned that characterizing receptors and receptor interactions is not necessarily the most significant component in understanding the evolution of immunity. Rather, such a subject needs to be understood from a more global perspective and will necessitate re-consideration of the physical barriers that afford protection and the developmental processes that create them. By far, the most significant paradigm shifts in our understanding of immunity and the infection process has been that microbes no longer are considered to be an automatic cause or consequence of illness, but rather integral components of normal physiology and homeostasis. Immune phylogeny has been shaped not only by an arms race with pathogens but also perhaps by mutualistic interactions with resident microbes. This Research Topic updates and extends the previous eBook on Changing Views of the Evolution of Immunity and contains peer-reviewed submissions of original research, reviews and opinions.

The new Animal Genetics and Disease 2017 conference committee organized a Research Topic for the proceedings of this inaugural conference. The meeting brought together specialists working on the interface between genomics, genetic engineering, and infectious disease, with the aims of improving animal and human health and welfare. This conference was funded by Advanced Courses and Scientific Conference at the Wellcome Genome Campus, Hinxton, UK. The conference will highlight breakthroughs in genomic technologies that are rapidly increasing our understanding of the fundamental role that host and pathogen genetics play in infections and epidemics. This Research Topic focuses on how infections spread and how they further affect the productivity of livestock systems and food supply chains. Thanks to technological advances, we now have the tools for real-time surveillance of zoonoses affecting wildlife, farm animals and animal-to-human disease transmission.

Introduces readers to key case studies that illustrate how theory and data can be integrated to understand wildlife disease ecology.

Fish Diseases: Prevention and Control Strategies provides essential information on disease prevention and treatment by the most experienced fish culturists in the industry. The book presents both traditional and novel methodologies of identifying and addressing fish disease risk, along with preventative and responsive insights to the challenges impacting fish production today. Both specific (vaccination) and non-specific (immunostimulation) approaches are explored, from maintaining optimal environmental conditions, to understanding how stressors in fish affect their immune system. Includes relevant information on government restrictions on drug usage in aquaculture to address the strict demand for fish products free of pollutants/antibiotics Presents best practices in fish farming to prevent disease and promote good health status and fish disease management Provides the most recent research on fish diseases prevention, the pathogens most studied, and options for methods of treatment

Genetically engineered (GE) crops were first introduced commercially in the 1990s. After two decades of production, some groups and individuals remain critical of the technology based on their concerns about possible adverse effects on human health, the environment, and ethical considerations. At the same time, others are concerned that the technology is not reaching its potential to improve human health and the environment because of stringent regulations and reduced public funding to develop products offering more benefits to society. While the debate about these and other questions related to the genetic engineering techniques of the first 20 years goes on, emerging genetic-engineering technologies are adding new complexities to the conversation. Genetically Engineered Crops builds on previous related Academies reports published between 1987 and 2010 by undertaking a retrospective examination of the purported positive and adverse effects of GE crops and to anticipate what emerging genetic-engineering technologies hold for the future. This report indicates where there are uncertainties about the economic, agronomic, health, safety, or other impacts of GE crops and food, and makes recommendations to fill gaps in safety assessments, increase regulatory clarity, and improve innovations in and access to GE technology.

The Second Autumn Course on Mathematical Ecology was held at the Intern ational Centre for Theoretical Physics in Trieste, Italy in November and December of 1986. During the four year period that had elapsed since the First Autumn Course on Mathematical Ecology, sufficient progress had been made in applied mathemat ical ecology to merit tilting the balance maintained between theoretical aspects and applications in the 1982 Course toward applications. The course format, while similar to that of the first Autumn Course on Mathematical Ecology, consequently focused upon applications of mathematical ecology. Current areas of application are almost as diverse as the spectrum covered by ecology. The topiys of this book reflect this diversity and were chosen because of perceived interest and utility to developing countries. Topical lectures began with foundational material mostly derived from Math ematical Ecology: An Introduction (a compilation of the lectures of the 1982 course published by Springer-Verlag in this series, Volume 17) and, when possible, progressed to the frontiers of research. In addition to the course lectures, workshops were arranged for small groups to supplement and enhance the learning experience. Other perspectives were provided through presentations by course participants and speakers at the associated Research Conference. Many of the research papers are in a companion volume, Mathematical Ecology: Proceedings Trieste 1986, published by World Scientific Press in 1988. This book is structured primarily by application area. Part II provides an introduction to mathematical and statistical applications in resource management.

Infectious diseases are the leading cause of death globally, particularly among children and young adults. The spread of new pathogens and the threat of antimicrobial resistance pose particular challenges in combating these diseases. Major Infectious Diseases identifies feasible, cost-effective packages of interventions and strategies across delivery platforms to prevent and treat HIV/AIDS, other sexually transmitted infections, tuberculosis, malaria, adult febrile illness, viral hepatitis, and neglected tropical diseases. The volume emphasizes the need to effectively address emerging antimicrobial resistance, strengthen health systems, and increase access to care. The attainable goals are to reduce incidence, develop innovative approaches, and optimize existing tools in resource-constrained settings.