Should we aim for genetic improvement in host resistance or tolerance to infectious disease?
Andrea B. Doeschl-Wilson,
The Roslin Institute and R(D)SVS of the University of Edinburgh, United Kingdom
Newcastle University, United Kingdom
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.