1
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Bosco L, Yañez O, Schauer A, Maurer C, Cushman SA, Arlettaz R, Jacot A, Seuberlich T, Neumann P, Schläppi D. Landscape structure affects temporal dynamics in the bumble bee virome: Landscape heterogeneity supports colony resilience. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 946:174280. [PMID: 38942311 DOI: 10.1016/j.scitotenv.2024.174280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2024] [Revised: 06/23/2024] [Accepted: 06/23/2024] [Indexed: 06/30/2024]
Abstract
Virus spillovers from managed honey bees, Apis mellifera, are thought to contribute to the decline of wild pollinators, including bumble bees. However, data on the impact of such viruses on wild pollinators remain scarce, and the influence of landscape structure on virus dynamics is poorly understood. In this study, we deployed bumble bee colonies in an agricultural landscape and studied changes in the bumble bee virome during field placement under varying habitat composition and configuration using a multiscale analytical framework. We estimated prevalence of viruses and viral loads (i.e. number of viral genomic equivalent copies) in bumble bees before and after placing them in the field using next generation sequencing and quantitative PCR. The results show that viral loads and number of different viruses present increased during placement in the field and that the virus composition of the colonies shifted from an initial dominance of honey bee associated viruses to a higher number (in both viral loads and number of viruses present) of bumble bee associated viruses. Especially DWV-B, typical for honey bees, drastically decreased after the time in the field. Viral loads prior to placing colonies in the field showed no effect on colony development, suggesting low impacts of these viruses in field settings. Notably, we further demonstrate that increased habitat diversity results in a lower number of different viruses present in Bombus colonies, while colonies in areas with well-connected farmland patches decreased in their total viral load after field placement. Our results emphasize the importance of landscape heterogeneity and connectivity for wild pollinator health and that these influences predominate at fine spatial scales.
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Affiliation(s)
- Laura Bosco
- LUOMUS - Finnish Museum of Natural History, PL 17 - P.O. Box 17, 00014, University of Helsinki, Finland; Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland.
| | - Orlando Yañez
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, 3003 Bern, Switzerland.
| | - Alexandria Schauer
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, 3003 Bern, Switzerland.
| | - Corina Maurer
- Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland; Agroecology and Environment, Agroscope, Reckenholzstrasse 191, 8046 Zürich, Switzerland; Ecosystems Landscape Evolution, Institute of Terrestrial Ecosystems, Department of Environmental Systems Science, ETH Zürich, 8092 Zürich, Switzerland.
| | - Samuel A Cushman
- Wildlife Conservation Research Unit, Department of Biology, University of Oxford, Oxford, United Kingdom
| | - Raphaël Arlettaz
- Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland.
| | - Alain Jacot
- Division of Conservation Biology, Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland; Swiss Ornithological Institute, Regional Office Valais, 1950 Sion, Switzerland.
| | - Torsten Seuberlich
- Division of Neurological Sciences, University of Bern, Bern, Switzerland.
| | - Peter Neumann
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, 3003 Bern, Switzerland.
| | - Daniel Schläppi
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Schwarzenburgstrasse 161, 3003 Bern, Switzerland; School of Biological Sciences, University of Bristol, Life Science Building, 24 Tyndall Avenue, BS8 1TQ Bristol, United Kingdom.
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2
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Cressler CE, Adelman JS. Links between Innate and Adaptive Immunity Can Favor Evolutionary Persistence of Immunopathology. Integr Comp Biol 2024; 64:841-852. [PMID: 39030049 PMCID: PMC11428335 DOI: 10.1093/icb/icae105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/12/2024] [Accepted: 06/19/2024] [Indexed: 07/21/2024] Open
Abstract
Immunopathology, or the harm caused to an organism's own tissues during the activation of its immune system, carries substantial costs. Moreover, avoiding this self-harm may be an important mechanism underlying tolerance of infection, helping to reducing fitness costs without necessarily clearing parasites. Despite the apparent benefits of minimizing immunopathology, such damage persists across a range of host species. Prior work has explored a trade-off with resistance during a single infection as a potential driver of this persistence, with some collateral damage being unavoidable when killing parasites. Here, we present an additional trade-off that could favor the continued presence of immunopathology: robust immune responses during initial infection (e.g., innate immunity in vertebrates) can induce stronger memory (adaptive immunity), offering protection from future infections. We explore this possibility in an adaptive dynamics framework, using theoretical models parameterized from an ecologically relevant host-parasite system, house finches (Haemorhous mexicanus) infected with the bacterial pathogen, Mycoplasma gallisepticum. We find that some degree of immunopathology is often favored when immunopathology during first infection either reduces susceptibility to or enhances recovery from second infection. Further, interactions among factors like transmission rate, recovery rate, background mortality, and pathogen virulence also shape these evolutionary dynamics. Most notably, the evolutionary stability of investment in immunopathology is highly dependent upon the mechanism by which hosts achieve secondary protection (susceptibility vs. recovery), with the potential for abrupt evolutionary shifts between high and low investment under certain conditions. These results highlight the potential for immune memory to play an important role in the evolutionary persistence of immunopathology and the need for future empirical research to reveal the links between immunopathology during initial infections and longer-term immune protection.
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Affiliation(s)
- Clayton E Cressler
- School of Biological Sciences, The University of Nebraska, Lincoln, Lincoln, NE 68588, USA
| | - James S Adelman
- Department of Biological Sciences, The University of Memphis, Memphis, TN 39152, USA
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3
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Evensen C, White A, Boots M. Multispecies interactions and the community context of the evolution of virulence. Proc Biol Sci 2024; 291:20240991. [PMID: 39317313 PMCID: PMC11421928 DOI: 10.1098/rspb.2024.0991] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 07/19/2024] [Accepted: 08/19/2024] [Indexed: 09/26/2024] Open
Abstract
Pairwise host-parasite relationships are typically embedded in broader networks of ecological interactions, which have the potential to shape parasite evolutionary trajectories. Understanding this 'community context' of pathogen evolution is vital for wildlife, agricultural and human systems alike, as pathogens typically infect more than one host-and these hosts may have independent ecological relationships. Here, we introduce an eco-evolutionary model examining ecological feedback across a range of host-host interactions. Specifically, we analyse a model of the evolution of virulence of a parasite infecting two hosts exhibiting competitive, mutualistic or exploitative relationships. We first find that parasite specialism is necessary for inter-host interactions to impact parasite evolution. Furthermore, we find generally that increasing competition between hosts leads to higher shared parasite virulence while increasing mutualism leads to lower virulence. In exploitative host-host interactions, the particular form of parasite specialization is critical-for instance, specialization in terms of onward transmission, host tolerance or intra-host pathogen growth rate lead to distinct evolutionary outcomes under the same host-host interactions. Our work provides testable hypotheses for multi-host disease systems, predicts how changing interaction networks may impact virulence evolution and broadly demonstrates the importance of looking beyond pairwise relationships to understand evolution in realistic community contexts.
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Affiliation(s)
- Claire Evensen
- Department of Integrative Biology, University of California Berkeley, CA, USA
| | - Andrew White
- Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Edinburgh, UK
- Department of Mathematics, Heriot-Watt University, Edinburgh, UK
| | - Mike Boots
- Department of Integrative Biology, University of California Berkeley, CA, USA
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4
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Cressler CE, Metz DCG, Chang van Oordt DA, Graham AL. Immunological feedback loops generate parasite persistence thresholds that explain variation in infection duration. Proc Biol Sci 2024; 291:20240934. [PMID: 39317318 PMCID: PMC11421898 DOI: 10.1098/rspb.2024.0934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 07/24/2024] [Accepted: 08/06/2024] [Indexed: 09/26/2024] Open
Abstract
Infection duration affects individual host fitness and between-host transmission. Whether an infection is cleared or becomes chronic depends on the complex interaction between host immune responses and parasite growth. Empirical and theoretical studies have suggested that there are critical thresholds of parasite dose that can determine clearance versus chronicity, driven by the ability of the parasite to manipulate host immunity. However, the mammalian immune response is characterized by strong positive and negative feedback loops that could generate duration thresholds even in the absence of direct immunomodulation. Here, we derive and analyse a simple model for the interaction between T-cell subpopulations and parasite growth. We show that whether an infection is cleared or not is very sensitive to the initial immune state, parasite dose and strength of immunological feedbacks. In particular, chronic infections are possible even when parasites provoke a strong and effective immune response and lack any ability to immunomodulate. Our findings indicate that the initial immune state, which often goes unmeasured in empirical studies, is a critical determinant of infection duration. This work also has implications for epidemiological models, as it implies that infection duration will be highly variable among individuals, and dependent on each individual's infection history.
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Affiliation(s)
- Clayton E. Cressler
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Daniel C. G. Metz
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
| | | | - Andrea L. Graham
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, USA
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5
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Fieldman T. Evolutionary principles for modifying pathogen virulence. Crit Rev Microbiol 2024; 50:385-396. [PMID: 37146153 DOI: 10.1080/1040841x.2023.2203766] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/31/2023] [Accepted: 04/10/2023] [Indexed: 05/07/2023]
Abstract
Current methods for combatting infectious diseases are largely limited to the prevention of infection, enhancing host immunity (via vaccination), and administration of small molecules to slow the growth of or kill pathogens (e.g. antimicrobials). Beyond efforts to deter the rise of antimicrobial resistance, little consideration is given to pathogen evolution. Natural selection will favor different levels of virulence under different circumstances. Experimental studies and a wealth of theoretical work have identified many likely evolutionary determinants of virulence. Some of these, such as transmission dynamics, are amenable to modification by clinicians and public health practitioners. In this article, we provide a conceptual overview of virulence, followed by an analysis of modifiable evolutionary determinants of virulence including vaccinations, antibiotics, and transmission dynamics. Finally, we discuss both the importance and limitations of taking an evolutionary approach to reducing pathogen virulence.
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Affiliation(s)
- Tom Fieldman
- Clinical Microbiology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK
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6
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Poulin R, Salloum PM, Bennett J. Evolution of parasites in the Anthropocene: new pressures, new adaptive directions. Biol Rev Camb Philos Soc 2024. [PMID: 38984760 DOI: 10.1111/brv.13118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2024] [Revised: 06/27/2024] [Accepted: 07/02/2024] [Indexed: 07/11/2024]
Abstract
The Anthropocene is seeing the human footprint rapidly spreading to all of Earth's ecosystems. The fast-changing biotic and abiotic conditions experienced by all organisms are exerting new and strong selective pressures, and there is a growing list of examples of human-induced evolution in response to anthropogenic impacts. No organism is exempt from these novel selective pressures. Here, we synthesise current knowledge on human-induced evolution in eukaryotic parasites of animals, and present a multidisciplinary framework for its study and monitoring. Parasites generally have short generation times and huge fecundity, features that predispose them for rapid evolution. We begin by reviewing evidence that parasites often have substantial standing genetic variation, and examples of their rapid evolution both under conditions of livestock production and in serial passage experiments. We then present a two-step conceptual overview of the causal chain linking anthropogenic impacts to parasite evolution. First, we review the major anthropogenic factors impacting parasites, and identify the selective pressures they exert on parasites through increased mortality of either infective stages or adult parasites, or through changes in host density, quality or immunity. Second, we discuss what new phenotypic traits are likely to be favoured by the new selective pressures resulting from altered parasite mortality or host changes; we focus mostly on parasite virulence and basic life-history traits, as these most directly influence the transmission success of parasites and the pathology they induce. To illustrate the kinds of evolutionary changes in parasites anticipated in the Anthropocene, we present a few scenarios, either already documented or hypothetical but plausible, involving parasite taxa in livestock, aquaculture and natural systems. Finally, we offer several approaches for investigations and real-time monitoring of rapid, human-induced evolution in parasites, ranging from controlled experiments to the use of state-of-the-art genomic tools. The implications of fast-evolving parasites in the Anthropocene for disease emergence and the dynamics of infections in domestic animals and wildlife are concerning. Broader recognition that it is not only the conditions for parasite transmission that are changing, but the parasites themselves, is needed to meet better the challenges ahead.
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Affiliation(s)
- Robert Poulin
- Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand
| | - Priscila M Salloum
- Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand
| | - Jerusha Bennett
- Department of Zoology, University of Otago, P.O. Box 56, Dunedin, New Zealand
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7
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Klimov PB, He Q. Predicting host range expansion in parasitic mites using a global mammalian-acarine dataset. Nat Commun 2024; 15:5431. [PMID: 38926409 PMCID: PMC11208579 DOI: 10.1038/s41467-024-49515-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2023] [Accepted: 06/07/2024] [Indexed: 06/28/2024] Open
Abstract
Multi-host parasites pose greater health risks to wildlife, livestock, and humans than single-host parasites, yet our understanding of how ecological and biological factors influence a parasite's host range remains limited. Here, we assemble the largest and most complete dataset on permanently parasitic mammalian mites and build a predictive model assessing the probability of single-host parasites to become multi-hosts, while accounting for potentially unobserved host-parasite links and class imbalance. This model identifies statistically significant predictors related to parasites, hosts, climate, and habitat disturbance. The most important predictors include the parasite's contact level with the host immune system and two variables characterizing host phylogenetic similarity and spatial co-distribution. Our model reveals an overrepresentation of mites associated with Rodentia (rodents), Chiroptera (bats), and Carnivora in the multi-host risk group. This highlights both the potential vulnerability of these hosts to parasitic infestations and the risk of serving as reservoirs of parasites for new hosts. In addition, we find independent macroevolutionary evidence that supports our prediction of several single-host species of Notoedres, the bat skin parasites, to be in the multi-host risk group, demonstrating the forecasting potential of our model.
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Affiliation(s)
- Pavel B Klimov
- Lilly Hall of Life Sciences, Purdue University, 915 Mitch Daniels Blvd, West Lafayette, Indiana, 47907, USA.
| | - Qixin He
- Lilly Hall of Life Sciences, Purdue University, 915 Mitch Daniels Blvd, West Lafayette, Indiana, 47907, USA.
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8
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Surasinghe S, Kabengele K, Turner PE, Ogbunugafor CB. Evolutionary Invasion Analysis of Modern Epidemics Highlights the Context-Dependence of Virulence Evolution. Bull Math Biol 2024; 86:88. [PMID: 38877355 PMCID: PMC11178639 DOI: 10.1007/s11538-024-01313-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 05/25/2024] [Indexed: 06/16/2024]
Abstract
Models are often employed to integrate knowledge about epidemics across scales and simulate disease dynamics. While these approaches have played a central role in studying the mechanics underlying epidemics, we lack ways to reliably predict how the relationship between virulence (the harm to hosts caused by an infection) and transmission will evolve in certain virus-host contexts. In this study, we invoke evolutionary invasion analysis-a method used to identify the evolution of uninvadable strategies in dynamical systems-to examine how the virulence-transmission dichotomy can evolve in models of virus infections defined by different natural histories. We reveal peculiar patterns of virulence evolution between epidemics with different disease natural histories (SARS-CoV-2 and hepatitis C virus). We discuss the findings with regards to the public health implications of predicting virus evolution, and in broader theoretical canon involving virulence evolution in host-parasite systems.
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Affiliation(s)
- Sudam Surasinghe
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA
- Public Health Modeling Unit, Yale School of Public Health, New Haven, CT, 06510, USA
| | - Ketty Kabengele
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA
| | - Paul E Turner
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA
- Microbiology Program, Yale School of Medicine, New Haven, CT, 06510, USA
| | - C Brandon Ogbunugafor
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA.
- Public Health Modeling Unit, Yale School of Public Health, New Haven, CT, 06510, USA.
- Santa Fe Institute, Santa Fe, NM, 87501, USA.
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9
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Hector TE, Shocket MS, Sgrò CM, Hall MD. Acclimation to warmer temperatures can protect host populations from both further heat stress and the potential invasion of pathogens. GLOBAL CHANGE BIOLOGY 2024; 30:e17341. [PMID: 38837568 DOI: 10.1111/gcb.17341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 04/15/2024] [Accepted: 04/20/2024] [Indexed: 06/07/2024]
Abstract
Thermal acclimation can provide an essential buffer against heat stress for host populations, while acting simultaneously on various life-history traits that determine population growth. In turn, the ability of a pathogen to invade a host population is intimately linked to these changes via the supply of new susceptible hosts, as well as the impact of warming on its immediate infection dynamics. Acclimation therefore has consequences for hosts and pathogens that extend beyond simply coping with heat stress-governing both population growth trajectories and, as a result, an inherent propensity for a disease outbreak to occur. The impact of thermal acclimation on heat tolerances, however, is rarely considered simultaneously with metrics of both host and pathogen population growth, and ultimately fitness. Using the host Daphnia magna and its bacterial pathogen, we investigated how thermal acclimation impacts host and pathogen performance at both the individual and population scales. We first tested the effect of maternal and direct thermal acclimation on the life-history traits of infected and uninfected individuals, such as heat tolerance, fecundity, and lifespan, as well as pathogen infection success and spore production. We then predicted the effects of each acclimation treatment on rates of host and pathogen population increase by deriving a host's intrinsic growth rate (rm) and a pathogen's basic reproductive number (R0). We found that direct acclimation to warming enhanced a host's heat tolerance and rate of population growth, despite a decline in life-history traits such as lifetime fecundity and lifespan. In contrast, pathogen performance was consistently worse under warming, with within-host pathogen success, and ultimately the potential for disease spread, severely hampered at higher temperatures. Our results suggest that hosts could benefit more from warming than their pathogens, but only by linking multiple individual traits to population processes can the full impact of higher temperatures on host and pathogen population dynamics be realised.
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Affiliation(s)
| | - Marta S Shocket
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | - Carla M Sgrò
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
| | - Matthew D Hall
- School of Biological Sciences, Monash University, Melbourne, Victoria, Australia
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10
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Franz M, Regoes RR, Rolff J. How infection-triggered pathobionts influence virulence evolution. Philos Trans R Soc Lond B Biol Sci 2024; 379:20230067. [PMID: 38497269 PMCID: PMC10945393 DOI: 10.1098/rstb.2023.0067] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/28/2023] [Indexed: 03/19/2024] Open
Abstract
Host-pathogen interactions can be influenced by the host microbiota, as the microbiota can facilitate or prevent pathogen infections. In addition, members of the microbiota can become virulent. Such pathobionts can cause co-infections when a pathogen infection alters the host immune system and triggers dysbiosis. Here we performed a theoretical investigation of how pathobiont co-infections affect the evolution of pathogen virulence. We explored the possibility that the likelihood of pathobiont co-infection depends on the evolving virulence of the pathogen. We found that, in contrast to the expectation from classical theory, increased virulence is not always selected for. For an increasing likelihood of co-infection with increasing pathogen virulence, we found scenario-specific selection for either increased or decreased virulence. Evolutionary changes, however, in pathogen virulence do not always translate into similar changes in combined virulence of the pathogen and the pathobiont. Only in one of the scenarios where pathobiont co-infection is triggered above a specific virulence level we found a reduction in combined virulence. This was not the case when the probability of pathobiont co-infection linearly increased with pathogen virulence. Taken together, our study draws attention to the possibility that host-microbiota interactions can be both the driver and the target of pathogen evolution. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.
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Affiliation(s)
- Mathias Franz
- Institute of Biology, Freie Universität Berlin, Berlin 14195, Germany
| | - Roland R. Regoes
- Institute of Integrative Biology, ETH Zurich, Zurich 8092, Switzerland
| | - Jens Rolff
- Institute of Biology, Freie Universität Berlin, Berlin 14195, Germany
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11
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Buckingham LJ, Ashby B. Coevolution of Age-Structured Tolerance and Virulence. Bull Math Biol 2024; 86:62. [PMID: 38662120 PMCID: PMC11045647 DOI: 10.1007/s11538-024-01292-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 04/03/2024] [Indexed: 04/26/2024]
Abstract
Hosts can evolve a variety of defences against parasitism, including resistance (which prevents or reduces the spread of infection) and tolerance (which protects against virulence). Some organisms have evolved different levels of tolerance at different life-stages, which is likely to be the result of coevolution with pathogens, and yet it is currently unclear how coevolution drives patterns of age-specific tolerance. Here, we use a model of tolerance-virulence coevolution to investigate how age structure influences coevolutionary dynamics. Specifically, we explore how coevolution unfolds when tolerance and virulence (disease-induced mortality) are age-specific compared to when these traits are uniform across the host lifespan. We find that coevolutionary cycling is relatively common when host tolerance is age-specific, but cycling does not occur when tolerance is the same across all ages. We also find that age-structured tolerance can lead to selection for higher virulence in shorter-lived than in longer-lived hosts, whereas non-age-structured tolerance always leads virulence to increase with host lifespan. Our findings therefore suggest that age structure can have substantial qualitative impacts on host-pathogen coevolution.
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Affiliation(s)
- Lydia J Buckingham
- Department of Mathematical Sciences, University of Bath, Bath, UK.
- Milner Centre for Evolution, University of Bath, Bath, UK.
| | - Ben Ashby
- Department of Mathematical Sciences, University of Bath, Bath, UK
- Milner Centre for Evolution, University of Bath, Bath, UK
- Department of Mathematics, Simon Fraser University, Burnaby, BC, Canada
- Pacific Institute on Pathogens, Pandemics and Society, Burnaby, BC, Canada
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12
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Northrup GR, White A, Parratt SR, Rozins C, Laine AL, Boots M. The evolutionary dynamics of hyperparasites. J Theor Biol 2024; 582:111741. [PMID: 38280543 DOI: 10.1016/j.jtbi.2024.111741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 12/14/2023] [Accepted: 01/16/2024] [Indexed: 01/29/2024]
Abstract
Evolutionary theory has typically focused on pairwise interactions, such as those between hosts and parasites, with relatively little work having been carried out on more complex interactions including hyperparasites: parasites of parasites. Hyperparasites are common in nature, with the chestnut blight fungus virus CHV-1 a well-known natural example, but also notably include the phages of important human bacterial diseases. We build a general modeling framework for the evolution of hyperparasites that highlights the central role that the ability of a hyperparasite to be transmitted with its parasite plays in their evolution. A key result is that hyperparasites which transmit with their parasite hosts (hitchhike) will be selected for lower virulence, trending towards hypermutualism or hypercommensalism. We examine the impact on the evolution of hyperparasite systems of a wide range of host and parasite traits showing, for example, that high parasite virulence selects for higher hyperparasite virulence resulting in reductions in parasite virulence when hyperparasitized. Furthermore, we show that acute parasite infection will also select for increased hyperparasite virulence. Our results have implications for hyperparasite research, both as biocontrol agents and for their role in shaping community ecology and evolution and moreover emphasize the importance of understanding evolution in the context of multitrophic interactions.
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Affiliation(s)
- Graham R Northrup
- Center for Computational Biology, College of Engineering, University of California, Berkeley, CA, USA.
| | - Andy White
- Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Edinburgh, UK; Department of Mathematics, Heriot-Watt University, Edinburgh, UK
| | - Steven R Parratt
- Department of Ecology, Evolution and Behaviour, University of Liverpool, Liverpool, UK
| | - Carly Rozins
- Department of Science and Technology Studies, Division of Natural Science, York University, Toronto, Ontario, Canada
| | - Anna-Liisa Laine
- Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, University of Helsinki, Finland; Department of Evolutionary Biology and Environmental Studies, University of Zurich, Switzerland
| | - Mike Boots
- Department of Integrative Biology, University of California Berkeley, CA, USA; Center for Ecology and Conservation, College of Life and Environmental Sciences, University of Exeter, Penryn Campus, UK
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13
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Torstenson M, Shaw AK. Pathogen evolution following spillover from a resident to a migrant host population depends on interactions between host pace of life and tolerance to infection. J Anim Ecol 2024; 93:475-487. [PMID: 38462682 DOI: 10.1111/1365-2656.14075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 02/19/2024] [Indexed: 03/12/2024]
Abstract
Changes to migration routes and phenology create novel contact patterns among hosts and pathogens. These novel contact patterns can lead to pathogens spilling over between resident and migrant populations. Predicting the consequences of such pathogen spillover events requires understanding how pathogen evolution depends on host movement behaviour. Following spillover, pathogens may evolve changes in their transmission rate and virulence phenotypes because different strategies are favoured by resident and migrant host populations. There is conflict in current theoretical predictions about what those differences might be. Some theory predicts lower pathogen virulence and transmission rates in migrant populations because migrants have lower tolerance to infection. Other theoretical work predicts higher pathogen virulence and transmission rates in migrants because migrants have more contacts with susceptible hosts. We aim to understand how differences in tolerance to infection and host pace of life act together to determine the direction of pathogen evolution following pathogen spillover from a resident to a migrant population. We constructed a spatially implicit model in which we investigate how pathogen strategy changes following the addition of a migrant population. We investigate how differences in tolerance to infection and pace of life between residents and migrants determine the effect of spillover on pathogen evolution and host population size. When the paces of life of the migrant and resident hosts are equal, larger costs of infection in the migrants lead to lower pathogen transmission rate and virulence following spillover. When the tolerance to infection in migrant and resident populations is equal, faster migrant paces of life lead to increased transmission rate and virulence following spillover. However, the opposite can also occur: when the migrant population has lower tolerance to infection, faster migrant paces of life can lead to decreases in transmission rate and virulence. Predicting the outcomes of pathogen spillover requires accounting for both differences in tolerance to infection and pace of life between populations. It is also important to consider how movement patterns of populations affect host contact opportunities for pathogens. These results have implications for wildlife conservation, agriculture and human health.
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Affiliation(s)
- Martha Torstenson
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - Allison K Shaw
- Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, Minnesota, USA
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14
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Negus SS. An economon model of drug addiction. Psychopharmacology (Berl) 2024; 241:417-425. [PMID: 38277005 PMCID: PMC10884072 DOI: 10.1007/s00213-024-06535-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Accepted: 01/14/2024] [Indexed: 01/27/2024]
Abstract
The term "economon" (i:'ka.nə.muhn; plural: economa) is introduced here to describe an economic unit composed of two participants engaged in mutually reinforcing operant behavior. Economa are basic building blocks of transactional behavior that aggregate in social networks called economies. In a drug-addiction economon, operant behavior by one participant (the "supplier") provides an addictive drug as a reinforcer to the second participant (a "Person with Substance Use Disorder; PwSUD"). Reciprocal operant behavior by the PwSUD usually provides money as a reinforcer to the supplier. After defining the features of the drug-addiction economon, this article discusses its implications for (1) prevalence and virulence of drug addiction, (2) opportunities for drug-addiction research in general, (3) the "brain-disease model of addiction" in particular, and (4) factors that mitigate harm or promote risk of drug addiction. The economon model is intended to provide a novel perspective on the uniquely human disorder of drug addiction.
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Affiliation(s)
- S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, 410 N. 12 St, Richmond, VA, 23298, USA.
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15
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Kürschner T, Scherer C, Radchuk V, Blaum N, Kramer‐Schadt S. Resource asynchrony and landscape homogenization as drivers of virulence evolution: The case of a directly transmitted disease in a social host. Ecol Evol 2024; 14:e11065. [PMID: 38380064 PMCID: PMC10877554 DOI: 10.1002/ece3.11065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/22/2024] Open
Abstract
Throughout the last decades, the emergence of zoonotic diseases and the frequency of disease outbreaks have increased substantially, fuelled by habitat encroachment and vectors overlapping with more hosts due to global change. The virulence of pathogens is one key trait for successful invasion. In order to understand how global change drivers such as habitat homogenization and climate change drive pathogen virulence evolution, we adapted an established individual-based model of host-pathogen dynamics. Our model simulates a population of social hosts affected by a directly transmitted evolving pathogen in a dynamic landscape. Pathogen virulence evolution results in multiple strains in the model that differ in their transmission capability and lethality. We represent the effects of global change by simulating environmental changes both in time (resource asynchrony) and space (homogenization). We found an increase in pathogenic virulence and a shift in strain dominance with increasing landscape homogenization. Our model further indicated that lower virulence is dominant in fragmented landscapes, although pulses of highly virulent strains emerged under resource asynchrony. While all landscape scenarios favoured co-occurrence of low- and high-virulent strains, the high-virulence strains capitalized on the possibility for transmission when host density increased and were likely to become dominant. With asynchrony likely to occur more often due to global change, our model showed that a subsequent evolution towards lower virulence could lead to some diseases becoming endemic in their host populations.
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Affiliation(s)
- Tobias Kürschner
- Department of Ecological DynamicsLeibniz Institute for Zoo and Wildlife ResearchBerlinGermany
| | - Cédric Scherer
- Department of Ecological DynamicsLeibniz Institute for Zoo and Wildlife ResearchBerlinGermany
| | - Viktoriia Radchuk
- Department of Ecological DynamicsLeibniz Institute for Zoo and Wildlife ResearchBerlinGermany
| | - Niels Blaum
- Plant Ecology and Nature ConservationUniversity of PotsdamPotsdamGermany
| | - Stephanie Kramer‐Schadt
- Department of Ecological DynamicsLeibniz Institute for Zoo and Wildlife ResearchBerlinGermany
- Institute of EcologyTechnische Universität BerlinBerlinGermany
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16
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Doublet V, Oddie MAY, Mondet F, Forsgren E, Dahle B, Furuseth-Hansen E, Williams GR, De Smet L, Natsopoulou ME, Murray TE, Semberg E, Yañez O, de Graaf DC, Le Conte Y, Neumann P, Rimstad E, Paxton RJ, de Miranda JR. Shift in virus composition in honeybees ( Apis mellifera) following worldwide invasion by the parasitic mite and virus vector Varroa destructor. ROYAL SOCIETY OPEN SCIENCE 2024; 11:231529. [PMID: 38204792 PMCID: PMC10776227 DOI: 10.1098/rsos.231529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024]
Abstract
Invasive vectors can induce dramatic changes in disease epidemiology. While viral emergence following geographical range expansion of a vector is well known, the influence a vector can have at the level of the host's pathobiome is less well understood. Taking advantage of the formerly heterogeneous spatial distribution of the ectoparasitic mite Varroa destructor that acts as potent virus vector among honeybees Apis mellifera, we investigated the impact of its recent global spread on the viral community of honeybees in a retrospective study of historical samples. We hypothesized that the vector has had an effect on the epidemiology of several bee viruses, potentially altering their transmissibility and/or virulence, and consequently their prevalence, abundance, or both. To test this, we quantified the prevalence and loads of 14 viruses from honeybee samples collected in mite-free and mite-infested populations in four independent geographical regions. The presence of the mite dramatically increased the prevalence and load of deformed wing virus, a cause of unsustainably high colony losses. In addition, several other viruses became more prevalent or were found at higher load in mite-infested areas, including viruses not known to be actively varroa-transmitted, but which may increase opportunistically in varroa-parasitized bees.
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Affiliation(s)
- Vincent Doublet
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
- Institute for Biology, Martin Luther University Halle-Wittenberg, Halle (Saale) 061200, Germany
| | - Melissa A. Y. Oddie
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala 750 07, Sweden
- Norwegian Beekeepers Association, Kløfta 2040, Norway
| | - Fanny Mondet
- INRAE, UR 406 Abeilles et Environnement, Avignon 84914, France
| | - Eva Forsgren
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Bjørn Dahle
- Norwegian Beekeepers Association, Kløfta 2040, Norway
| | - Elisabeth Furuseth-Hansen
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Ås 1432, Norway
| | - Geoffrey R. Williams
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern 3097, Switzerland
- Entomology & Plant Pathology, Auburn University, Auburn, AL 36832, USA
| | - Lina De Smet
- Department of Biochemistry and Microbiology, Ghent University, Ghent 9000, Belgium
| | - Myrsini E. Natsopoulou
- Institute for Biology, Martin Luther University Halle-Wittenberg, Halle (Saale) 061200, Germany
| | - Tomás E. Murray
- Institute for Biology, Martin Luther University Halle-Wittenberg, Halle (Saale) 061200, Germany
| | - Emilia Semberg
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala 750 07, Sweden
| | - Orlando Yañez
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern 3097, Switzerland
| | - Dirk C. de Graaf
- Department of Biochemistry and Microbiology, Ghent University, Ghent 9000, Belgium
| | - Yves Le Conte
- INRAE, UR 406 Abeilles et Environnement, Avignon 84914, France
| | - Peter Neumann
- Institute of Bee Health, Vetsuisse Faculty, University of Bern, Bern 3097, Switzerland
| | - Espen Rimstad
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, Ås 1432, Norway
| | - Robert J. Paxton
- Institute for Biology, Martin Luther University Halle-Wittenberg, Halle (Saale) 061200, Germany
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, 04103, Germany
| | - Joachim R. de Miranda
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala 750 07, Sweden
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17
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O'Keeffe FE, Pendleton RC, Holland CV, Luijckx P. Increased virulence due to multiple infection in Daphnia leads to limited growth in 1 of 2 co-infecting microsporidian parasites. Parasitology 2024; 151:58-67. [PMID: 37981808 PMCID: PMC10941049 DOI: 10.1017/s0031182023001130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/21/2023]
Abstract
Recent outbreaks of various infectious diseases have highlighted the ever-present need to understand the drivers of the outbreak and spread of disease. Although much of the research investigating diseases focuses on single infections, natural systems are dominated by multiple infections. These infections may occur simultaneously, but are often acquired sequentially, which may alter the outcome of infection. Using waterfleas (Daphnia magna) as a model organism, we examined the outcome of sequential and simultaneous multiple infections with 2 microsporidian parasites (Ordospora colligata and Hamiltosporidium tvaerminnensis) in a fully factorial design with 9 treatments and 30 replicates. We found no differences between simultaneous and sequential infections. However, H. tvaerminnensis fitness was impeded by multiple infection due to increased host mortality, which gave H. tvaerminnensis less time to grow. Host fecundity was also reduced across all treatments, but animals infected with O. colligata at a younger age produced the fewest offspring. As H. tvaerminnensis is both horizontally and vertically transmitted, this reduction in offspring may have further reduced H. tvaerminnensis fitness in co-infected treatments. Our findings suggest that in natural populations where both species co-occur, H. tvaerminnensis may evolve to higher levels of virulence following frequent co-infection by O. colligata.
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Affiliation(s)
- Floriane E. O'Keeffe
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Rebecca C. Pendleton
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Celia V. Holland
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
| | - Pepijn Luijckx
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin, Ireland
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18
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Hite JL, Roos AMD. Pathogens stabilize or destabilize depending on host stage structure. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2023; 20:20378-20404. [PMID: 38124557 DOI: 10.3934/mbe.2023901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
A common assumption is that pathogens more readily destabilize their host populations, leading to an elevated risk of driving both the host and pathogen to extinction. This logic underlies many strategies in conservation biology and pest and disease management. Yet, the interplay between pathogens and population stability likely varies across contexts, depending on the environment and traits of both the hosts and pathogens. This context-dependence may be particularly important in natural consumer-host populations where size- and stage-structured competition for resources strongly modulates population stability. Few studies, however, have examined how the interplay between size and stage structure and infectious disease shapes the stability of host populations. Here, we extend previously developed size-dependent theory for consumer-resource interactions to examine how pathogens influence the stability of host populations across a range of contexts. Specifically, we integrate a size- and stage-structured consumer-resource model and a standard epidemiological model of a directly transmitted pathogen. The model reveals surprisingly rich dynamics, including sustained oscillations, multiple steady states, biomass overcompensation, and hydra effects. Moreover, these results highlight how the stage structure and density of host populations interact to either enhance or constrain disease outbreaks. Our results suggest that accounting for these cross-scale and bidirectional feedbacks can provide key insight into the structuring role of pathogens in natural ecosystems while also improving our ability to understand how interventions targeting one may impact the other.
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Affiliation(s)
- Jessica L Hite
- University of Wisconsin-Madison, Department of Pathobiological Sciences, School of Veterinary Medicine, Madison, Wisconsin, USA
| | - André M de Roos
- Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, the Netherlands; Santa Fe Institute, Santa Fe, NM 87501, USA
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19
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Wang Y, Gallagher LA, Andrade PA, Liu A, Humphreys IR, Turkarslan S, Cutler KJ, Arrieta-Ortiz ML, Li Y, Radey MC, McLean JS, Cong Q, Baker D, Baliga NS, Peterson SB, Mougous JD. Genetic manipulation of Patescibacteria provides mechanistic insights into microbial dark matter and the epibiotic lifestyle. Cell 2023; 186:4803-4817.e13. [PMID: 37683634 PMCID: PMC10633639 DOI: 10.1016/j.cell.2023.08.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 07/06/2023] [Accepted: 08/16/2023] [Indexed: 09/10/2023]
Abstract
Patescibacteria, also known as the candidate phyla radiation (CPR), are a diverse group of bacteria that constitute a disproportionately large fraction of microbial dark matter. Its few cultivated members, belonging mostly to Saccharibacteria, grow as epibionts on host Actinobacteria. Due to a lack of suitable tools, the genetic basis of this lifestyle and other unique features of Patescibacteira remain unexplored. Here, we show that Saccharibacteria exhibit natural competence, and we exploit this property for their genetic manipulation. Imaging of fluorescent protein-labeled Saccharibacteria provides high spatiotemporal resolution of phenomena accompanying epibiotic growth, and a transposon-insertion sequencing (Tn-seq) genome-wide screen reveals the contribution of enigmatic Saccharibacterial genes to growth on their hosts. Finally, we leverage metagenomic data to provide cutting-edge protein structure-based bioinformatic resources that support the strain Southlakia epibionticum and its corresponding host, Actinomyces israelii, as a model system for unlocking the molecular underpinnings of the epibiotic lifestyle.
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Affiliation(s)
- Yaxi Wang
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Larry A Gallagher
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Pia A Andrade
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Andi Liu
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Ian R Humphreys
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; Institute for Protein Design, University of Washington, Seattle, WA 98195, USA
| | | | - Kevin J Cutler
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | | | - Yaqiao Li
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA; Institute for Systems Biology, Seattle, WA 98109, USA
| | - Matthew C Radey
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Jeffrey S McLean
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA; Department of Periodontics, University of Washington, Seattle, WA 98195, USA
| | - Qian Cong
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA; Institute for Protein Design, University of Washington, Seattle, WA 98195, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98109, USA
| | | | - S Brook Peterson
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Joseph D Mougous
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA; Howard Hughes Medical Institute, University of Washington, Seattle, WA 98109, USA; Microbial Interactions and Microbiome Center, University of Washington, Seattle, WA 98195, USA.
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20
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O'Neill X, White A, Boots M. The evolution of parasite virulence under targeted culling and harvesting in wildlife and livestock. Evol Appl 2023; 16:1697-1707. [PMID: 38020874 PMCID: PMC10660816 DOI: 10.1111/eva.13594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 07/27/2023] [Accepted: 09/01/2023] [Indexed: 12/01/2023] Open
Abstract
There is a clear need to understand the effect of human intervention on the evolution of infectious disease. In particular, culling and harvesting of both wildlife and managed livestock populations are carried out in a wide range of management practices, and they have the potential to impact the evolution of a broad range of disease characteristics. Applying eco-evolutionary theory we show that once culling/harvesting becomes targeted on specific disease classes, the established result that culling selects for higher virulence is only found when sufficient infected individuals are culled. If susceptible or recovered individuals are targeted, selection for lower virulence can occur. An important implication of this result is that when culling to eradicate an infectious disease from a population, while it is optimal to target infected individuals, the consequent evolution can increase the basic reproductive ratio of the infection, R 0 , and make parasite eradication more difficult. We show that increases in evolved virulence due to the culling of infected individuals can lead to excess population decline when sustainably harvesting a population. In contrast, culling susceptible or recovered individuals can select for decreased virulence and a reduction in population decline through culling. The implications to the evolution of virulence are typically the same in wildlife populations, that are regulated by the parasite, and livestock populations, that have a constant population size where restocking balances the losses due to mortality. However, the well-known result that vertical transmission selects for lower virulence and transmission in wildlife populations is less marked in livestock populations for parasites that convey long-term immunity since restocking can enhance the density of the immune class. Our work emphasizes the importance of understanding the evolutionary consequences of intervention strategies and the different ecological feedbacks that can occur in wildlife and livestock populations.
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Affiliation(s)
- Xander O'Neill
- Department of MathematicsMaxwell Institute for Mathematical Sciences, Heriot‐Watt UniversityEdinburghUK
| | - Andy White
- Department of MathematicsMaxwell Institute for Mathematical Sciences, Heriot‐Watt UniversityEdinburghUK
| | - Mike Boots
- Department of Integrative BiologyUniversity of CaliforniaBerkeleyCaliforniaUSA
- Centre for Ecology and Conservation, BiosciencesUniversity of ExeterCornwallUK
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21
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Shillcock G, Úbeda F, Wild G. Vertical transmission does not always lead to benign pathogen-host associations. Evol Lett 2023; 7:305-314. [PMID: 37829501 PMCID: PMC10565904 DOI: 10.1093/evlett/qrad028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 06/04/2023] [Accepted: 06/08/2023] [Indexed: 10/14/2023] Open
Abstract
Understanding the capacity of pathogens to cause severe disease is of fundamental importance to human health and the preservation of biodiversity. Many of those pathogens are not only transmitted horizontally between unrelated hosts but also vertically between parents and their progeny. It is widely accepted that vertical transmission leads to the evolution of less virulent pathogens, but this idea stems from research that neglects the evolutionary response of hosts. Here, we use a game-theory model of coevolution between pathogen and host to show that vertical transmission does not always lead to more benign pathogens. We highlight scenarios in which vertical transmission results in pathogens exhibiting more virulence. However, we also predict that more benign outcomes are still possible (a) when generating new horizontal infections inflicts too much damage on hosts, (b) when clearing an infection is too costly for the host, and (c) when vertical transmission is promoted by a greater growth rate of the host population. Though our work offers a new perspective on the role of vertical transmission in pathogen-host systems, it does agree with previous experimental work.
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Affiliation(s)
| | - Francisco Úbeda
- Department of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, United Kingdom
| | - Geoff Wild
- Department of Mathematics, Western University, London, Canada
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22
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Alizon S. Predicting the virulence of future emerging zoonotic viruses. PLoS Biol 2023; 21:e3002286. [PMID: 37682826 PMCID: PMC10490851 DOI: 10.1371/journal.pbio.3002286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/10/2023] Open
Abstract
Would you rather kiss a platypus, a hedgehog, or a llama? According to a new study in this issue of PLOS Biology, the virulence of a zoonotic virus in humans depends on its reservoir host. Could physiology be the key to anticipating viral threats lethality?
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Affiliation(s)
- Samuel Alizon
- Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France
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23
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Zinck CB, Raveendram Thampy P, Uhlemann EME, Adam H, Wachter J, Suchan D, Cameron ADS, Rego ROM, Brisson D, Bouchard C, Ogden NH, Voordouw MJ. Variation among strains of Borrelia burgdorferi in host tissue abundance and lifetime transmission determine the population strain structure in nature. PLoS Pathog 2023; 19:e1011572. [PMID: 37607182 PMCID: PMC10473547 DOI: 10.1371/journal.ppat.1011572] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 09/01/2023] [Accepted: 07/23/2023] [Indexed: 08/24/2023] Open
Abstract
Pathogen life history theory assumes a positive relationship between pathogen load in host tissues and pathogen transmission. Empirical evidence for this relationship is surprisingly rare due to the difficulty of measuring transmission for many pathogens. The comparative method, where a common host is experimentally infected with a set of pathogen strains, is a powerful approach for investigating the relationships between pathogen load and transmission. The validity of such experimental estimates of strain-specific transmission is greatly enhanced if they can predict the pathogen population strain structure in nature. Borrelia burgdorferi is a multi-strain, tick-borne spirochete that causes Lyme disease in North America. This study used 11 field-collected strains of B. burgdorferi, a rodent host (Mus musculus, C3H/HeJ) and its tick vector (Ixodes scapularis) to determine the relationship between pathogen load in host tissues and lifetime host-to-tick transmission (HTT). Mice were experimentally infected via tick bite with 1 of 11 strains. Lifetime HTT was measured by infesting mice with I. scapularis larval ticks on 3 separate occasions. The prevalence and abundance of the strains in the mouse tissues and the ticks were determined by qPCR. We used published databases to obtain estimates of the frequencies of these strains in wild I. scapularis tick populations. Spirochete loads in ticks and lifetime HTT varied significantly among the 11 strains of B. burgdorferi. Strains with higher spirochete loads in the host tissues were more likely to infect feeding larval ticks, which molted into nymphal ticks that had a higher probability of B. burgdorferi infection (i.e., higher HTT). Our laboratory-based estimates of lifetime HTT were predictive of the frequencies of these strains in wild I. scapularis populations. For B. burgdorferi, the strains that establish high abundance in host tissues and that have high lifetime transmission are the strains that are most common in nature.
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Affiliation(s)
- Christopher B. Zinck
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Prasobh Raveendram Thampy
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Eva-Maria E. Uhlemann
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Hesham Adam
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Jenny Wachter
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Danae Suchan
- Institute for Microbial Systems and Society, Faculty of Science, University of Regina, Regina, Saskatchewan, Canada
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | - Andrew D. S. Cameron
- Institute for Microbial Systems and Society, Faculty of Science, University of Regina, Regina, Saskatchewan, Canada
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | - Ryan O. M. Rego
- Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovice, Czech Republic
- Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Dustin Brisson
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Catherine Bouchard
- Public Health Risk Sciences, National Microbiology Laboratory, Public Health Agency of Canada, St Hyacinthe, Quebec, Canada
- Groupe de recherche en épidémiologie des zoonoses et santé publique (GREZOSP), Faculté de Médecine Vétérinaire, Université de Montréal, Montreal, Canada
| | - Nicholas H. Ogden
- Public Health Risk Sciences, National Microbiology Laboratory, Public Health Agency of Canada, St Hyacinthe, Quebec, Canada
- Groupe de recherche en épidémiologie des zoonoses et santé publique (GREZOSP), Faculté de Médecine Vétérinaire, Université de Montréal, Montreal, Canada
- Centre de recherche en santé publique (CReSP), Université de Montréal, Montreal, QC, Canada
| | - Maarten J. Voordouw
- Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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24
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Isibor PO, Onwaeze OO, Kayode-Edwards II, Agbontaen DO, Ifebem-Ezima IAM, Bilewu O, Onuselogu C, Akinniyi AP, Obafemi YD, Oniha MI. Investigating and combatting the key drivers of viral zoonoses in Africa: an analysis of eight epidemics. BRAZ J BIOL 2023; 84:e270857. [PMID: 37531478 DOI: 10.1590/1519-6984.270857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 03/02/2023] [Indexed: 08/04/2023] Open
Abstract
Investigating the interplay of factors that result in a viral zoonotic outbreak is difficult, though it is increasingly important. As anthropogenic influences shift the delicate balance of ecosystems, new zoonoses emerge in humans. Sub-Saharan Africa is a notable hotspot for zoonotic disease due to abundant competent mammalian reservoir hosts. Furthermore, poverty, corruption, and an overreliance on natural resources play considerable roles in depleting biological resources, exacerbating the population's susceptibility. Unsurprisingly, viral zoonoses have emerged in Africa, including HIV/AIDS, Ebola, Avian influenza, Lassa fever, Zika, and Monkeypox. These diseases are among the principal causes of death in endemic areas. Though typically distinct in their manifestations, viral zoonoses are connected by underlying, definitive factors. This review summarises vital findings on viral zoonoses in Africa using nine notable case studies as a benchmark for future studies. We discuss the importance of ecological recuperation and protection as a central strategy to control zoonotic diseases. Emphasis was made on moderating key drivers of zoonotic diseases to forestall future pandemics. This is in conjunction with attempts to redirect efforts from reactive to pre-emptive through a multidisciplinary "one health" approach.
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Affiliation(s)
- P O Isibor
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - O O Onwaeze
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - I I Kayode-Edwards
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - D O Agbontaen
- University of South Wales, Department of Public Health, Pontypridd, United Kingdom
| | - I-A M Ifebem-Ezima
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - O Bilewu
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - C Onuselogu
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - A P Akinniyi
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - Y D Obafemi
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
| | - M I Oniha
- Covenant University, Department of Biological Sciences, Ota, Ogun State, Nigeria
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25
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Borer ET, Kendig AE, Holt RD. Feeding the fever: Complex host-pathogen dynamics along continuous resource gradients. Ecol Evol 2023; 13:e10315. [PMID: 37502304 PMCID: PMC10368943 DOI: 10.1002/ece3.10315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Accepted: 07/04/2023] [Indexed: 07/29/2023] Open
Abstract
Food has long been known to perform dual functions of nutrition and medicine, but mounting evidence suggests that complex host-pathogen dynamics can emerge along continuous resource gradients. Empirical examples of nonmonotonic responses of infection with increasing host resources (e.g., low prevalence at low and high resource supply but high prevalence at intermediate resources) have been documented across the tree of life, but these dynamics, when observed, often are interpreted as nonintuitive, idiosyncratic features of pathogen and host biology. Here, by developing generalized versions of existing models of resource dependence for within- and among-host infection dynamics, we provide a synthetic view of nonmonotonic infection dynamics. We demonstrate that where resources jointly impact two (or more) processes (e.g., growth, defense, transmission, mortality, predation), nonmonotonic infection dynamics, including alternative states, can emerge across a continuous resource supply gradient. We review the few empirical examples that concurrently measured resource effects on multiple rates and pair this with a wide range of examples in which resource dependence of multiple rates could generate nonmonotonic infection outcomes under realistic conditions. This review and generalized framework highlight the likely generality of such resource effects in natural systems and point to opportunities ripe for future empirical and theoretical work.
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Affiliation(s)
- Elizabeth T. Borer
- Department of Ecology, Evolution, and BehaviorUniversity of MinnesotaSaint PaulMinnesotaUSA
| | - Amy E. Kendig
- Agronomy DepartmentUniversity of FloridaGainesvilleFloridaUSA
- Minnesota Department of Natural ResourcesMinnesota Biological SurveySaint PaulMinnesotaUSA
| | - Robert D. Holt
- Department of BiologyUniversity of FloridaGainesvilleFloridaUSA
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26
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Lindsay RJ, Holder PJ, Talbot NJ, Gudelj I. Metabolic efficiency reshapes the seminal relationship between pathogen growth rate and virulence. Ecol Lett 2023; 26:896-907. [PMID: 37056166 PMCID: PMC10947253 DOI: 10.1111/ele.14218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 04/15/2023]
Abstract
A cornerstone of classical virulence evolution theories is the assumption that pathogen growth rate is positively correlated with virulence, the amount of damage pathogens inflict on their hosts. Such theories are key for incorporating evolutionary principles into sustainable disease management strategies. Yet, empirical evidence raises doubts over this central assumption underpinning classical theories, thus undermining their generality and predictive power. In this paper, we identify a key component missing from current theories which redefines the growth-virulence relationship in a way that is consistent with data. By modifying the activity of a single metabolic gene, we engineered strains of Magnaporthe oryzae with different nutrient acquisition and growth rates. We conducted in planta infection studies and uncovered an unexpected non-monotonic relationship between growth rate and virulence that is jointly shaped by how growth rate and metabolic efficiency interact. This novel mechanistic framework paves the way for a much-needed new suite of virulence evolution theories.
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Affiliation(s)
| | | | - Nicholas J. Talbot
- The Sainsbury LaboratoryUniversity of East Anglia, Norwich Research ParkNorwichUK
| | - Ivana Gudelj
- Biosciences and Living Systems InstituteUniversity of ExeterExeterUK
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27
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Al Naggar Y, Shafiey H, Paxton RJ. Transcriptomic Responses Underlying the High Virulence of Black Queen Cell Virus and Sacbrood Virus following a Change in Their Mode of Transmission in Honey Bees ( Apis mellifera). Viruses 2023; 15:1284. [PMID: 37376584 DOI: 10.3390/v15061284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 05/22/2023] [Accepted: 05/28/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND Over the last two decades, honey bees (Apis mellifera) have suffered high rates of colony losses that have been attributed to a variety of factors, chief among which are viral pathogens, such as deformed wing virus (DWV), whose virulence has increased because of vector-based transmission by the invasive, ectoparasitic varroa mite (Varroa destructor). A shift in the experimental mode of transmission of the black queen cell virus (BQCV) and sacbrood virus (SBV) from fecal/food-oral (direct horizontal) to vector-mediated (indirect horizontal) transmission also results in high virulence and viral titers in pupal and adult honey bees. Agricultural pesticides represent another factor that acts independently or in interaction with pathogens, and they are also thought to cause colony loss. Understanding the molecular mechanisms underlying the higher virulence following a vector-based mode of transmission provides deeper insight into honey bee colony losses, as does determining whether or not host-pathogen interactions are modulated by exposure to pesticides. METHODS Through an experimental design with controlled laboratory, we investigated the effects of the modes of transmission of BQCV and SBV (feeding vs. vector-mediated via injection) alone or in combination with chronic exposure to sublethal and field-realistic concentrations of flupyradifurone (FPF), a novel agricultural insecticide, on honey bee survival and transcription responses by using high-throughput RNA sequencing (RNA-seq) analysis. RESULTS Co-exposure to viruses via feeding (VF) or injection (VI) and FPF insecticide had no statistically significant interactive effect on their survival compared to, respectively, VF or VI treatments alone. Transcriptomic analysis revealed a distinct difference in the gene expression profiles of bees inoculated with viruses via injection (VI) and exposed to FPF insecticide (VI+FPF). The number of differentially expressed genes (DEGs) at log2 (fold-change) > 2.0 in VI bees (136 genes) or/and VI+FPF insecticide (282 genes) was very high compared to that of VF bees (8 genes) or the VF+FPF insecticide treatment (15 genes). Of these DEGs, the expression in VI and VI+FPF bees of some immune-related genes, such as those for antimicrobial peptides, Ago2, and Dicer, was induced. In short, several genes encoding odorant binding proteins, chemosensory proteins, odor receptors, honey bee venom peptides, and vitellogenin were downregulated in VI and VI+FPF bees. CONCLUSIONS Given the importance of these suppressed genes in honey bees' innate immunity, eicosanoid biosynthesis, and olfactory associative function, their inhibition because of the change in the mode of infection with BQCV and SBV to vector-mediated transmission (injection into haemocoel) could explain the high virulence observed in these viruses when they were experimentally injected into hosts. These changes may help explain why other viruses, such as DWV, represent such a threat to colony survival when transmitted by varroa mites.
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Affiliation(s)
- Yahya Al Naggar
- 1 General Zoology, Institute for Biology, Martin Luther University Halle-Wittenberg, Hoher Weg 8, 06120 Halle (Saale), Germany
- Zoology Department, Faculty of Science, Tanta University, Tanta 31527, Egypt
- Department of Community Ecology, UFZ-Helmholtz Centre for Environmental Research, Theodor-Lieser-Str. 4, 06120 Halle (Saale), Germany
| | - Hassan Shafiey
- 1 General Zoology, Institute for Biology, Martin Luther University Halle-Wittenberg, Hoher Weg 8, 06120 Halle (Saale), Germany
| | - Robert J Paxton
- 1 General Zoology, Institute for Biology, Martin Luther University Halle-Wittenberg, Hoher Weg 8, 06120 Halle (Saale), Germany
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28
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Čeirāns A, Pupins M, Kirjusina M, Gravele E, Mezaraupe L, Nekrasova O, Tytar V, Marushchak O, Garkajs A, Petrov I, Skute A, Georges JY, Theissinger K. Top-down and bottom-up effects and relationships with local environmental factors in the water frog-helminth systems in Latvia. Sci Rep 2023; 13:8621. [PMID: 37244932 DOI: 10.1038/s41598-023-35780-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 05/23/2023] [Indexed: 05/29/2023] Open
Abstract
Semi-aquatic European water frogs (Pelophylax spp.) harbour rich helminth infra-communities, whose effects on host population size in nature are poorly known. To study top-down and bottom-up effects, we conducted calling male water frog counts and parasitological investigations of helminths in waterbodies from different regions of Latvia, supplemented by descriptions of waterbody features and surrounding land use data. We performed a series of generalized linear model and zero-inflated negative binomial regressions to determine the best predictors for frog relative population size and helminth infra-communities. The highest-ranked (by Akaike information criterion correction, AICc) model explaining the water frog population size contained only waterbody variables, followed by the model containing only land use within 500 m, while the model containing helminth predictors had the lowest rank. Regarding helminth infection responses, the relative importance of the water frog population size varied from being non-significant (abundances of larval plagiorchiids and nematodes) to having a similar weight to waterbody features (abundances of larval diplostomids). In abundances of adult plagiorchiids and nematodes the best predictor was the host specimen size. Environmental factors had both direct effects from the habitat features (e.g., waterbody characteristics on frogs and diplostomids) and indirect effects through parasite-host interactions (impacts of anthropogenic habitats on frogs and helminths). Our study suggests the presence of synergy between top-down and bottom-up effects in the water frog-helminth system that creates a mutual dependence of frog and helminth population sizes and helps to balance helminth infections at a level that does not cause over-exploitation of the host resource.
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Affiliation(s)
- Andris Čeirāns
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia.
| | - Mihails Pupins
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Muza Kirjusina
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Evita Gravele
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Ligita Mezaraupe
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Oksana Nekrasova
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
- I. I. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Volodymyr Tytar
- I. I. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Oleksii Marushchak
- I. I. Schmalhausen Institute of Zoology of National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Alberts Garkajs
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Iurii Petrov
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | - Arturs Skute
- Department of Ecology, Institute of Life Sciences and Technologies, Daugavpils University, Daugavpils, Latvia
| | | | - Kathrin Theissinger
- LOEWE Center for Translational Biodiversity Genomics, TBG - Senckenberg Nature Research Institute, Frankfurt, Germany
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29
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Wang Y, Gallagher LA, Andrade PA, Liu A, Humphreys IR, Turkarslan S, Cutler KJ, Arrieta-Ortiz ML, Li Y, Radey MC, McLean JS, Cong Q, Baker D, Baliga NS, Peterson SB, Mougous JD. Genetic manipulation of candidate phyla radiation bacteria provides functional insights into microbial dark matter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.02.539146. [PMID: 37205512 PMCID: PMC10187176 DOI: 10.1101/2023.05.02.539146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The study of bacteria has yielded fundamental insights into cellular biology and physiology, biotechnological advances and many therapeutics. Yet due to a lack of suitable tools, the significant portion of bacterial diversity held within the candidate phyla radiation (CPR) remains inaccessible to such pursuits. Here we show that CPR bacteria belonging to the phylum Saccharibacteria exhibit natural competence. We exploit this property to develop methods for their genetic manipulation, including the insertion of heterologous sequences and the construction of targeted gene deletions. Imaging of fluorescent protein-labeled Saccharibacteria provides high spatiotemporal resolution of phenomena accompanying epibiotic growth and a transposon insertion sequencing genome-wide screen reveals the contribution of enigmatic Saccharibacterial genes to growth on their Actinobacteria hosts. Finally, we leverage metagenomic data to provide cutting-edge protein structure-based bioinformatic resources that support the strain Southlakia epibionticum and its corresponding host, Actinomyces israelii , as a model system for unlocking the molecular underpinnings of the epibiotic lifestyle.
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Affiliation(s)
- Yaxi Wang
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Larry A. Gallagher
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Pia A. Andrade
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Andi Liu
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Ian R. Humphreys
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
- Institute for Protein Design, Seattle, WA 98109, USA
| | | | - Kevin J. Cutler
- Department of Physics, University of Washington, Seattle, WA 98195, USA
| | | | - Yaqiao Li
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
- Institute for Systems Biology, Seattle, WA 98109, USA
| | - Matthew C. Radey
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Jeffrey S. McLean
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
- Department of Periodontics, University of Washington, Seattle, WA 98195, USA
| | - Qian Cong
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, WA 98109, USA
- Institute for Protein Design, Seattle, WA 98109, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
| | | | - S. Brook Peterson
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
| | - Joseph D. Mougous
- Department of Microbiology, University of Washington, Seattle, WA 98109, USA
- Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
- Microbial Interactions and Microbiome Center, University of Washington, Seattle, WA 98109, USA
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30
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Franz M, Armitage SAO, Rolff J, Regoes RR. Virulence decomposition for bifurcating infections. Proc Biol Sci 2023; 290:20230396. [PMID: 37161327 PMCID: PMC10170194 DOI: 10.1098/rspb.2023.0396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 04/06/2023] [Indexed: 05/11/2023] Open
Abstract
A fundamental goal in infection biology is to understand the emergence of variation in pathogen virulence-here defined as the decrease in host fitness caused by a pathogen. To uncover the sources of such variation, virulence can be decomposed into both host- and pathogen-associated components. However, decomposing virulence can be challenging owing to complex within-host pathogen dynamics such as bifurcating infections, which recently received increased empirical and theoretical attention. Bifurcating infections are characterized by the emergence of two distinct infection types: (i) terminal infections with high pathogen loads resulting in rapid host death, and (ii) persistent infections with lower loads and delayed host death. Here, we propose to use discrete mixture models to perform separate virulence decompositions for each infection type. Using this approach, we reanalysed a recently published experimental dataset on bacterial load and survival in Drosophila melanogaster. This analysis revealed several advantages of the new approach, most importantly the generation of a more comprehensive picture of the varying sources of virulence in different bacterial species. Beyond this application, our approach could provide valuable information for ground-truthing and improving theoretical models of within-host infection dynamics, which are developed to predict variation in infection outcome and pathogen virulence.
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Affiliation(s)
- Mathias Franz
- Institute of Biology, Freie Universität Berlin, D-14195 Berlin, Germany
| | | | - Jens Rolff
- Institute of Biology, Freie Universität Berlin, D-14195 Berlin, Germany
| | - Roland R. Regoes
- Institute of Integrative Biology, ETH Zurich, 8092 Zurich, Switzerland
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31
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Licon MH, Giuliano CJ, Chan AW, Chakladar S, Eberhard JN, Shallberg LA, Chandrasekaran S, Waldman BS, Koshy AA, Hunter CA, Lourido S. A positive feedback loop controls Toxoplasma chronic differentiation. Nat Microbiol 2023; 8:889-904. [PMID: 37081202 PMCID: PMC10520893 DOI: 10.1038/s41564-023-01358-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 03/07/2023] [Indexed: 04/22/2023]
Abstract
Successful infection strategies must balance pathogen amplification and persistence. In the obligate intracellular parasite Toxoplasma gondii this is accomplished through differentiation into dedicated cyst-forming chronic stages that avoid clearance by the host immune system. The transcription factor BFD1 is both necessary and sufficient for stage conversion; however, its regulation is not understood. In this study we examine five factors that are transcriptionally activated by BFD1. One of these is a cytosolic RNA-binding protein of the CCCH-type zinc-finger family, which we name bradyzoite formation deficient 2 (BFD2). Parasites lacking BFD2 fail to induce BFD1 and are consequently unable to fully differentiate in culture or in mice. BFD2 interacts with the BFD1 transcript under stress, and deletion of BFD2 reduces BFD1 protein levels but not messenger RNA abundance. The reciprocal effects on BFD2 transcription and BFD1 translation outline a positive feedback loop that enforces the chronic-stage gene-expression programme. Thus, our findings help explain how parasites both initiate and commit to chronic differentiation. This work provides new mechanistic insight into the regulation of T. gondii persistence, and can be exploited in the design of strategies to prevent and treat these key reservoirs of human infection.
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Affiliation(s)
| | - Christopher J Giuliano
- Whitehead Institute, Cambridge, MA, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Alex W Chan
- Whitehead Institute, Cambridge, MA, USA
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Sundeep Chakladar
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Julia N Eberhard
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Lindsey A Shallberg
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Benjamin S Waldman
- Whitehead Institute, Cambridge, MA, USA
- Department of Microbiology and Immunology, School of Medicine, Stanford University, Stanford, CA, USA
| | - Anita A Koshy
- BIO5 Institute, University of Arizona, Tucson, AZ, USA
- Department of Neurology, Department of Immunobiology, University of Arizona, Tucson, AZ, USA
| | - Christopher A Hunter
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Sebastian Lourido
- Whitehead Institute, Cambridge, MA, USA.
- Biology Department, Massachusetts Institute of Technology, Cambridge, MA, USA.
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32
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Hasik AZ, King KC, Hawlena H. Interspecific host competition and parasite virulence evolution. Biol Lett 2023; 19:20220553. [PMID: 37130550 PMCID: PMC10734695 DOI: 10.1098/rsbl.2022.0553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 04/17/2023] [Indexed: 05/04/2023] Open
Abstract
Virulence, the harm to hosts caused by parasite infection, can be selected for by several ecological factors acting synergistically or antagonistically. Here, we focus on the potential for interspecific host competition to shape virulence through such a network of effects. We first summarize how host natural mortality, body mass changes, population density and community diversity affect virulence evolution. We then introduce an initial conceptual framework highlighting how these host factors, which change during host competition, may drive virulence evolution via impacts on life-history trade-offs. We argue that the multi-faceted nature of both interspecific host competition and virulence evolution still requires consideration and experimentation to disentangle contrasting mechanisms. It also necessitates a differential treatment for parasites with various transmission strategies. However, such a comprehensive approach focusing on the role of interspecific host competition is essential to understand the processes driving the evolution of virulence in a tangled bank.
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Affiliation(s)
- Adam Z. Hasik
- Jacob Blaustein Center for
Scientific Cooperation, Ben-Gurion University of the
Negev, 8499000 Midreshet Ben-Gurion,
Israel
| | - Kayla C. King
- Department of Biology,
University of Oxford, 11a Mansfield Road,
Oxford OX1 3SZ, UK
| | - Hadas Hawlena
- Mitrani Department of Desert
Ecology, Swiss Institute for Dryland Environmental and Energy Research, The
Jacob Blaustein Institutes for Desert Research, Ben-Gurion
University of the Negev, 849900 Midreshet Ben-Gurion,
Israel
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33
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Hagen EH, Blackwell AD, Lightner AD, Sullivan RJ. Homo medicus: The transition to meat eating increased pathogen pressure and the use of pharmacological plants in Homo. AMERICAN JOURNAL OF BIOLOGICAL ANTHROPOLOGY 2023; 180:589-617. [PMID: 36815505 DOI: 10.1002/ajpa.24718] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 01/31/2023] [Accepted: 02/08/2023] [Indexed: 02/24/2023]
Abstract
The human lineage transitioned to a more carnivorous niche 2.6 mya and evolved a large body size and slower life history, which likely increased zoonotic pathogen pressure. Evidence for this increase includes increased zoonotic infections in modern hunter-gatherers and bushmeat hunters, exceptionally low stomach pH compared to other primates, and divergence in immune-related genes. These all point to change, and probably intensification, in the infectious disease environment of Homo compared to earlier hominins and other apes. At the same time, the brain, an organ in which immune responses are constrained, began to triple in size. We propose that the combination of increased zoonotic pathogen pressure and the challenges of defending a large brain and body from pathogens in a long-lived mammal, selected for intensification of the plant-based self-medication strategies already in place in apes and other primates. In support, there is evidence of medicinal plant use by hominins in the middle Paleolithic, and all cultures today have sophisticated, plant-based medical systems, add spices to food, and regularly consume psychoactive plant substances that are harmful to helminths and other pathogens. We propose that the computational challenges of discovering effective plant-based treatments, the consequent ability to consume more energy-rich animal foods, and the reduced reliance on energetically-costly immune responses helped select for increased cognitive abilities and unique exchange relationships in Homo. In the story of human evolution, which has long emphasized hunting skills, medical skills had an equal role to play.
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Affiliation(s)
- Edward H Hagen
- Department of Anthropology, Washington State University, Pullman, Washington, USA
| | - Aaron D Blackwell
- Department of Anthropology, Washington State University, Pullman, Washington, USA
| | - Aaron D Lightner
- Department of Anthropology, Washington State University, Pullman, Washington, USA
- Department of the Study of Religion, Aarhus University, Aarhus, Denmark
| | - Roger J Sullivan
- Department of Anthropology, California State University, Sacramento, California, USA
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34
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Kun Á, Hubai AG, Král A, Mokos J, Mikulecz BÁ, Radványi Á. Do pathogens always evolve to be less virulent? The virulence–transmission trade-off in light of the COVID-19 pandemic. Biol Futur 2023:10.1007/s42977-023-00159-2. [PMID: 37002448 PMCID: PMC10066022 DOI: 10.1007/s42977-023-00159-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Accepted: 03/09/2023] [Indexed: 04/03/2023]
Abstract
AbstractThe direction the evolution of virulence takes in connection with any pathogen is a long-standing question. Formerly, it was theorized that pathogens should always evolve to be less virulent. As observations were not in line with this theoretical outcome, new theories emerged, chief among them the transmission–virulence trade-off hypotheses, which predicts an intermediate level of virulence as the endpoint of evolution. At the moment, we are very much interested in the future evolution of COVID-19’s virulence. Here, we show that the disease does not fulfill all the assumptions of the hypothesis. In the case of COVID-19, a higher viral load does not mean a higher risk of death; immunity is not long-lasting; other hosts can act as reservoirs for the virus; and death as a consequence of viral infection does not shorten the infectious period. Consequently, we cannot predict the short- or long-term evolution of the virulence of COVID-19.
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35
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Heylen DJA, Kumsa B, Kimbita E, Frank MN, Muhanguzi D, Jongejan F, Adehan SB, Toure A, Aboagye-Antwi F, Ogo NI, Juleff N, Crafford D, Fourie J, Labuchange M, Madder M. Tick-borne pathogens and body condition of cattle in smallholder rural livestock production systems in East and West Africa. Parasit Vectors 2023; 16:117. [PMID: 36998091 PMCID: PMC10064580 DOI: 10.1186/s13071-023-05709-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2022] [Accepted: 02/18/2023] [Indexed: 04/01/2023] Open
Abstract
BACKGROUND The majority of the African population lives in rural areas where they heavily depend on crop and livestock production for their livelihoods. Given their socio-economic importance, we initiated a standardized multi-country (Benin, Burkina Faso, Ghana, Nigeria, Ethiopia Tanzania and Uganda) surveillance study to assess the current status of important tick-borne haemoparasites (TBHPs) of cattle. METHODS We assessed pathogen prevalences (Anaplasma marginale, Anaplasma centrale, Babesia bigemina, Babesia bovis, Ehrlichia ruminantium, and Theileria parva) in the blood of 6447 animals spread over fourteen districts (two districts per country). In addition, we screened for intrinsic (sex, weight, body condition) and extrinsic (husbandry, tick exposure) risk factors as predictors of infections with TBHPs. RESULTS There was a large macro-geographic variation observed in A. marginale, B. bigemina, B. bovis and E. ruminantium prevalences. Most correlated with the co-occurrence of their specific sets of vector-competent ticks. Highest numbers of infected cattle were found in Ghana and Benin, and lowest in Burkina Faso. While T. parva was seldomly found (Uganda only: 3.0%), A. marginale was found in each country with a prevalence of at least 40%. Babesia bovis infected individuals had lower body condition scores. Age (as estimated via body weight) was higher in A. marginale infected cattle, but was negatively correlated with B. bigemina and E. ruminantium prevalences. Ehrlichia ruminantium infection was more often found in males, and A. marginale more often in transhumance farming. High levels of co-infection, especially the combination A. marginale × B. bigemina, were observed in all countries, except for Uganda and Burkina Faso. Babesia bigemina was more or less often observed than expected by chance, when cattle were also co-infected with E. ruminantium or A. marginale, respectively. CONCLUSIONS Tick-borne pathogens of cattle are ubiquitous in African's smallholder cattle production systems. Our standardized study will help a wide range of stakeholders to provide recommendations for TBHP surveillance and prevention in cattle, especially for B. bovis which heavily impacts production and continues its spread over the African continent via the invasive Rhipicephalus microplus tick.
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Affiliation(s)
- Dieter J A Heylen
- Evolutionary Ecology Group, Department of Biology, University of Antwerp, Wilrijk, Belgium.
- Eco-Epidemiology Group, Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
- Interuniversity Institute for Biostatistics and Statistical Bioinformatics, Hasselt University, Diepenbeek, Belgium.
| | - Bersissa Kumsa
- Department of Parasitology, College of Veterinary Medicine and Agriculture, Addis Ababa University, Bishoftu, Ethiopia
| | - Elikira Kimbita
- Department of Veterinary Microbiology and Parasitology, College of Veterinary Medicine and Biomedical Sciences, Sokoine University of Agriculture, PO Box 3019, Morogoro, Tanzania
| | - Mwiine Nobert Frank
- Department of Bio-Molecular Resources and Bio-Laboratory Sciences (BBS), College of Veterinary Medicine, Makerere University, Kampala, Uganda
| | - Dennis Muhanguzi
- Department of Bio-Molecular Resources and Bio-Laboratory Sciences (BBS), College of Veterinary Medicine, Makerere University, Kampala, Uganda
| | - Frans Jongejan
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - Safiou Bienvenu Adehan
- Zootechnical, Veterinary and Halieutic Research Laboratory (LRZVH), National Institute of Agricultural Research (INRAB), 01 BP 884, Cotonou, Benin
| | - Alassane Toure
- Université Nangui Abrogoua, UFR Sciences de La Nature, 02 Bp 801, Abidjan 02, Côte d'Ivoire
| | - Fred Aboagye-Antwi
- Department of Animal Biology and Conservation Science, School of Biological Sciences, College of Basic and Applied Sciences, University of Ghana, Legon-Accra, Ghana
| | - Ndudim Isaac Ogo
- National Veterinary Research Institute, Vom, Plateau State, Nigeria
| | - Nick Juleff
- Bill & Melinda Gates Foundation, Seattle, WA, USA
| | - Dionne Crafford
- Clinvet International Pty (Ltd), 1479 Talmadge Hill South, Waverly, NY, 14892, USA
| | - Josephus Fourie
- Clinvet International Pty (Ltd), 1479 Talmadge Hill South, Waverly, NY, 14892, USA
| | | | - Maxime Madder
- Clinglobal, B03/04, The Tamarin Commercial Hub, Jacaranda Avenue, Tamarin, 90903, Mauritius
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Kennedy DA. Death is overrated: the potential role of detection in driving virulence evolution. Proc Biol Sci 2023; 290:20230117. [PMID: 36987649 PMCID: PMC10050922 DOI: 10.1098/rspb.2023.0117] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/03/2023] [Indexed: 03/30/2023] Open
Abstract
A common assumption in the evolution of virulence theory literature is that pathogens transmit better when they exploit their host more heavily, but by doing so, they impose a greater risk of killing their host, thus truncating infectious periods and reducing their own opportunities for transmission. Here, I derive an equation for the magnitude of this cost in terms of the infection fatality rate, and in doing so, I show that there are many cases where mortality costs are too small to plausibly constrain increases in host exploitation by pathogens. I propose that pathogen evolution may often be constrained by detection costs, whereby hosts alter their behaviour when infection is detectable, and thus reduce pathogen opportunities for onward transmission. I then derive an inequality to illustrate when mortality costs or detection costs impose stronger constraints on pathogen evolution, and I use empirical data from the literature to demonstrate that detection costs are frequently large in both human and animal populations. Finally, I give examples of how evolutionary predictions can change depending on whether costs of host exploitation are borne out through mortality or detection.
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Affiliation(s)
- David A. Kennedy
- Department of Biology, Center for Infectious Disease Dynamics, The Pennsylvania State University, University Park, PA, USA
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Zinner D, Paciência FMD, Roos C. Host-Parasite Coevolution in Primates. Life (Basel) 2023; 13:823. [PMID: 36983978 PMCID: PMC10058613 DOI: 10.3390/life13030823] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 01/26/2023] [Accepted: 03/15/2023] [Indexed: 03/30/2023] Open
Abstract
Organisms adapt to their environment through evolutionary processes. Environments consist of abiotic factors, but also of other organisms. In many cases, two or more species interact over generations and adapt in a reciprocal way to evolutionary changes in the respective other species. Such coevolutionary processes are found in mutualistic and antagonistic systems, such as predator-prey and host-parasite (including pathogens) relationships. Coevolution often results in an "arms race" between pathogens and hosts and can significantly affect the virulence of pathogens and thus the severity of infectious diseases, a process that we are currently witnessing with SARS-CoV-2. Furthermore, it can lead to co-speciation, resulting in congruent phylogenies of, e.g., the host and parasite. Monkeys and other primates are no exception. They are hosts to a large number of pathogens that have shaped not only the primate immune system but also various ecological and behavioral adaptions. These pathogens can cause severe diseases and most likely also infect multiple primate species, including humans. Here, we briefly review general aspects of the coevolutionary process in its strict sense and highlight the value of cophylogenetic analyses as an indicator for coevolution.
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Affiliation(s)
- Dietmar Zinner
- Cognitive Ethology Laboratory, German Primate Center, Leibniz Institute for Primate Research, 37077 Göttingen, Germany
- Department of Primate Cognition, Georg-August-University of Göttingen, 37077 Göttingen, Germany
- Leibniz Science Campus Primate Cognition, 37077 Göttingen, Germany
| | | | - Christian Roos
- Gene Bank of Primates and Primate Genetics Laboratory, German Primate Center, Leibniz Institute for Primate Research, 37077 Göttingen, Germany
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Guichard M, Dainat B, Dietemann V. Prospects, challenges and perspectives in harnessing natural selection to solve the ‘varroa problem’ of honey bees. Evol Appl 2023; 16:593-608. [PMID: 36969141 PMCID: PMC10035043 DOI: 10.1111/eva.13533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 02/24/2023] Open
Abstract
Honey bees, Apis mellifera, of European origin are major pollinators of crops and wild flora. Their endemic and exported populations are threatened by a variety of abiotic and biotic factors. Among the latter, the ectoparasitic mite Varroa destructor is the most important single cause behind colony mortality. The selection of mite resistance in honey bee populations has been deemed a more sustainable solution to its control than varroacidal treatments. Because natural selection has led to the survival of some European and African honey bee populations to V. destructor infestations, harnessing its principles has recently been highlighted as a more efficient way to provide honey bee lineages that survive infestations when compared with conventional selection on resistance traits against the parasite. However, the challenges and drawbacks of harnessing natural selection to solve the varroa problem have only been minimally addressed. We argue that failing to consider these issues could lead to counterproductive results, such as increased mite virulence, loss of genetic diversity reducing host resilience, population collapses or poor acceptance by beekeepers. Therefore, it appears timely to evaluate the prospects for the success of such programmes and the qualities of the populations obtained. After reviewing the approaches proposed in the literature and their outcomes, we consider their advantages and drawbacks and propose perspectives to overcome their limitations. In these considerations, we not only reflect on the theoretical aspects of host-parasite relationships but also on the currently largely neglected practical constraints, that is, the requirements for productive beekeeping, conservation or rewilding objectives. To optimize natural selection-based programmes towards these objectives, we suggest designs based on a combination of nature-driven phenotypic differentiation and human-directed selection of traits. Such a dual strategy aims at allowing field-realistic evolutionary approaches towards the survival of V. destructor infestations and the improvement of honey bee health.
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Affiliation(s)
| | | | - Vincent Dietemann
- Swiss Bee Research Centre Agroscope Bern Switzerland
- Department of Ecology and Evolution, Biophore, UNIL‐Sorge University of Lausanne Lausanne Switzerland
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Trejo-Meléndez VJ, Méndez-López TT, Contreras-Garduño J. The Coincidental Evolution of Virulence Partially Explains the Virulence in a Generalist Entomopathogenic. Acta Parasitol 2023:10.1007/s11686-023-00663-4. [PMID: 36806112 DOI: 10.1007/s11686-023-00663-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 01/16/2023] [Indexed: 02/23/2023]
Abstract
PURPOSE The parasites' virulence is labile after jumping to a new host species, and it might derivate in gaining virulence against a new host as a side effect of living in a non-host environment (coincidental evolution of virulence hypothesis). METHODS To test this hypothesis, we monitored the experimental evolution of the Rhabditis regina nematode for over 290 generations (4 years) in three environments (strains): (1) the natural host, Phyllophaga polyphylla, (2) an alternate host, Tenebrio molitor, and (3) saprophytic medium (beef; the food that may provide evidence for the coincidental evolution of virulence). Each strain was exposed to P. polyphylla, T. molitor, or Galleria mellonella. We compared the host survival and immune response (proPO, PO, and lytic activity) of infected versus uninfected hosts. RESULTS The saprophytic nematodes gained virulence only against G. mellonella. However, the P. polyphylla strain was more effective in killing P. polyphylla than T. molitor, and the T. molitor strain was more effective against T. molitor than P. polyphylla. Additionally, one dauer larva was sufficient to kill the hosts. Finally, the immune response did not differ between the challenged and control groups. CONCLUSION The coincidental evolution of virulence partially explains our results, but they might also support the short-sighted hypothesis. Additionally, we found evidence for immunomodulation because nematodes passed unnoticed to the immune response. It is crucial to analyze the virulence of entomopathogens from the point of view of the evolution of virulence to be aware of potential scenarios that might limit biological control.
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Affiliation(s)
- Víctor José Trejo-Meléndez
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Av. Ciudad Universitaria 3000, C.P. 04510, Coyoacán, CDMX, Mexico
- ENES, Unidad Morelia, UNAM. Antigua Carretera a Pátzcuaro No.8701. Col. Ex-Hacienda San José de la Huerta Código Postal 58190, Morelia, Michoacán, Mexico
| | - Texca T Méndez-López
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Av. Ciudad Universitaria 3000, C.P. 04510, Coyoacán, CDMX, Mexico
- ENES, Unidad Morelia, UNAM. Antigua Carretera a Pátzcuaro No.8701. Col. Ex-Hacienda San José de la Huerta Código Postal 58190, Morelia, Michoacán, Mexico
| | - Jorge Contreras-Garduño
- ENES, Unidad Morelia, UNAM. Antigua Carretera a Pátzcuaro No.8701. Col. Ex-Hacienda San José de la Huerta Código Postal 58190, Morelia, Michoacán, Mexico.
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Cooperative virulence via the collective action of secreted pathogen effectors. Nat Microbiol 2023; 8:640-650. [PMID: 36782026 DOI: 10.1038/s41564-023-01328-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 01/13/2023] [Indexed: 02/15/2023]
Abstract
Although virulence is typically attributed to single pathogenic strains, here we investigated whether effectors secreted by a population of non-virulent strains could function as public goods to enable the emergence of collective virulence. We disaggregated the 36 type III effectors of the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 into a 'metaclone' of 36 coisogenic strains, each carrying a single effector in an effectorless background. Each coisogenic strain was individually unfit, but the metaclone was collectively as virulent as the wild-type strain on Arabidopsis thaliana, suggesting that effectors can drive the emergence of cooperation-based virulence through their public action. We show that independently evolved effector suits can equally drive this cooperative behaviour by transferring the effector alleles native to the strain PmaES4326 into the conspecific but divergent strain PtoDC3000. Finally, we transferred the disaggregated PtoDC3000 effector arsenal into Pseudomonas fluorescens and show that their cooperative action was sufficient to convert this rhizosphere-inhabiting beneficial bacterium into a phyllosphere pathogen. These results emphasize the importance of microbial community interactions and expand the ecological scale at which disease may be attributed.
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41
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Wang M, Jiang W. Virulence evolution of
Toxoplasma gondii
within a multi‐host system. Evol Appl 2023; 16:721-737. [PMID: 36969145 PMCID: PMC10033858 DOI: 10.1111/eva.13530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 11/04/2022] [Accepted: 12/27/2022] [Indexed: 01/25/2023] Open
Abstract
Current research on the virulence evolution of Toxoplasma gondii is mainly conducted via experiments, and studies using mathematical models are still limited. Here, we constructed a complex cycle model of T. gondii in a multi-host system considering multiple transmission routes and cat-mouse interaction. Based on this model, we studied how the virulence of T. gondii evolves with the factors related to transmission routes and the regulation of infection on host behavior under an adaptive dynamics framework. The study shows that all factors that enhance the role of mice favored decreased virulence of T. gondii, except the decay rate of oocysts that led to different evolutionary trajectories under different vertical transmission. The same was true of the environmental infection rate of cats, whose effect was different under different vertical transmission. The effect of the regulation factor on the virulence evolution of T. gondii was the same as that of the inherent predation rate depending on its net effect on direct and vertical transmissions. The global sensitivity analysis on the evolutionary outcome suggests that changing the vertical infection rate and decay rate was most effective in regulating the virulence of T. gondii. Furthermore, the presence of coinfection would favor virulent T. gondii and make evolutionary bifurcation easy to occur. The results reveal that the virulence evolution of T. gondii had a compromise between adapting to different transmission routes and maintaining the cat-mouse interaction thereby leading to different evolutionary scenarios. This highlights the significance of evolutionary ecological feedback to evolution. In addition, the qualitative verification of T. gondii virulence evolution in different areas by the present framework will provide a new perspective for the study of evolution.
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Affiliation(s)
- Mengyue Wang
- Department of Mechanics Huazhong University of Science and Technology Wuhan China
- Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment Wuhan China
| | - Wen Jiang
- Department of Mechanics Huazhong University of Science and Technology Wuhan China
- Hubei Key Laboratory for Engineering Structural Analysis and Safety Assessment Wuhan China
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Dimitriu T, Souissi W, Morwool P, Darby A, Crickmore N, Raymond B. Selecting for infectivity across metapopulations can increase virulence in the social microbe
Bacillus thuringiensis. Evol Appl 2023; 16:705-720. [PMID: 36969139 PMCID: PMC10033855 DOI: 10.1111/eva.13529] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Accepted: 12/27/2022] [Indexed: 01/18/2023] Open
Abstract
Passage experiments that sequentially infect hosts with parasites have long been used to manipulate virulence. However, for many invertebrate pathogens, passage has been applied naively without a full theoretical understanding of how best to select for increased virulence and this has led to very mixed results. Understanding the evolution of virulence is complex because selection on parasites occurs across multiple spatial scales with potentially different conflicts operating on parasites with different life histories. For example, in social microbes, strong selection on replication rate within hosts can lead to cheating and loss of virulence, because investment in public goods virulence reduces replication rate. In this study, we tested how varying mutation supply and selection for infectivity or pathogen yield (population size in hosts) affected the evolution of virulence against resistant hosts in the specialist insect pathogen Bacillus thuringiensis, aiming to optimize methods for strain improvement against a difficult to kill insect target. We show that selection for infectivity using competition between subpopulations in a metapopulation prevents social cheating, acts to retain key virulence plasmids, and facilitates increased virulence. Increased virulence was associated with reduced efficiency of sporulation, and possible loss of function in putative regulatory genes but not with altered expression of the primary virulence factors. Selection in a metapopulation provides a broadly applicable tool for improving the efficacy of biocontrol agents. Moreover, a structured host population can facilitate artificial selection on infectivity, while selection on life-history traits such as faster replication or larger population sizes can reduce virulence in social microbes.
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Affiliation(s)
- Tatiana Dimitriu
- Centre for Ecology and Conservation University of Exeter Penryn UK
| | - Wided Souissi
- School of Life Sciences University of Sussex Brighton UK
| | - Peter Morwool
- Centre for Ecology and Conservation University of Exeter Penryn UK
| | - Alistair Darby
- Centre for Genomic Research, Institute of Integrative Biology University of Liverpool Liverpool UK
| | - Neil Crickmore
- School of Life Sciences University of Sussex Brighton UK
| | - Ben Raymond
- Centre for Ecology and Conservation University of Exeter Penryn UK
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Gatto NM, Freund D, Ogata P, Diaz L, Ibarrola A, Desai M, Aspelund T, Gluckstein D. Correlates of Coronavirus Disease 2019 Inpatient Mortality at a Southern California Community Hospital With a Predominantly Hispanic/Latino Adult Population. Open Forum Infect Dis 2023; 10:ofad011. [PMID: 36726553 PMCID: PMC9887269 DOI: 10.1093/ofid/ofad011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 12/06/2023] [Indexed: 01/11/2023] Open
Abstract
Background Studies of inpatient coronavirus disease 2019 (COVID-19) mortality risk factors have mainly used data from academic medical centers or large multihospital databases and have not examined populations with large proportions of Hispanic/Latino patients. In a retrospective cohort study of 4881 consecutive adult COVID-19 hospitalizations at a single community hospital in Los Angeles County with a majority Hispanic/Latino population, we evaluated factors associated with mortality. Methods Data on demographic characteristics, comorbidities, laboratory and clinical results, and COVID-19 therapeutics were abstracted from the electronic medical record. Cox proportional hazards regression modeled statistically significant, independently associated predictors of hospital mortality. Results Age ≥65 years (hazard ratio [HR] = 2.66; 95% confidence interval [CI] = 1.90-3.72), male sex (HR = 1.31; 95% CI = 1.07-1.60), renal disease (HR = 1.52; 95% CI = 1.18-1.95), cardiovascular disease (HR = 1.45; 95% CI = 1.18-1.78), neurological disease (HR = 1.84; 95% CI = 1.41-2.39), D-dimer ≥500 ng/mL (HR = 2.07; 95% CI = 1.43-3.0), and pulse oxygen level <88% (HR = 1.39; 95% CI = 1.13-1.71) were independently associated with increased mortality. Patient household with (1) multiple COVID-19 cases and (2) Asian, Black, or Hispanic compared with White non-Hispanic race/ethnicity were associated with reduced mortality. In hypoxic COVID-19 inpatients, remdesivir, tocilizumab, and convalescent plasma were associated with reduced mortality, and corticosteroid use was associated with increased mortality. Conclusions We corroborate several previously identified mortality risk factors and find evidence that the combination of factors associated with mortality differ between populations.
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Affiliation(s)
- Nicole M Gatto
- Correspondence: Nicole M. Gatto, MPH, PhD, Adjunct Research Assistant Professor Department of Population and Public Health Sciences Keck School of Medicine University of Southern California 1845 N Soto St, Los Angeles, CA 90032, USA ()
| | - Debbie Freund
- School of Community and Global Health, Claremont Graduate University, Claremont, California, USA,Department of Economic Sciences, Claremont Graduate University, Claremont, California, USA,Department of Health Policy and Management, Fielding School of Public Health, University of California Los Angeles, Los Angeles, California, USA
| | - Pamela Ogata
- School of Community and Global Health, Claremont Graduate University, Claremont, California, USA
| | - Lisa Diaz
- Pomona Valley Hospital and Medical Center, Pomona, California, USA
| | - Ace Ibarrola
- Pomona Valley Hospital and Medical Center, Pomona, California, USA
| | - Mamta Desai
- Pomona Valley Hospital and Medical Center, Pomona, California, USA
| | - Thor Aspelund
- Center for Public Health Sciences, University of Iceland, Reykjavik, Iceland
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Virulence evolution during a naturally occurring parasite outbreak. Evol Ecol 2023; 37:113-129. [PMID: 35431396 PMCID: PMC9002213 DOI: 10.1007/s10682-022-10169-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Revised: 02/27/2022] [Accepted: 03/03/2022] [Indexed: 11/22/2022]
Abstract
Virulence, the degree to which a pathogen harms its host, is an important but poorly understood aspect of host-pathogen interactions. Virulence is not static, instead depending on ecological context and potentially evolving rapidly. For instance, at the start of an epidemic, when susceptible hosts are plentiful, pathogens may evolve increased virulence if this maximizes their intrinsic growth rate. However, if host density declines during an epidemic, theory predicts evolution of reduced virulence. Although well-studied theoretically, there is still little empirical evidence for virulence evolution in epidemics, especially in natural settings with native host and pathogen species. Here, we used a combination of field observations and lab assays in the Daphnia-Pasteuria model system to look for evidence of virulence evolution in nature. We monitored a large, naturally occurring outbreak of Pasteuria ramosa in Daphnia dentifera, where infection prevalence peaked at ~ 40% of the population infected and host density declined precipitously during the outbreak. In controlled infections in the lab, lifespan and reproduction of infected hosts was lower than that of unexposed control hosts and of hosts that were exposed but not infected. We did not detect any significant changes in host resistance or parasite infectivity, nor did we find evidence for shifts in parasite virulence (quantified by host lifespan and number of clutches produced by hosts). However, over the epidemic, the parasite evolved to produce significantly fewer spores in infected hosts. While this finding was unexpected, it might reflect previously quantified tradeoffs: parasites in high mortality (e.g., high predation) environments shift from vegetative growth to spore production sooner in infections, reducing spore yield. Future studies that track evolution of parasite spore yield in more populations, and that link those changes with genetic changes and with predation rates, will yield better insight into the drivers of parasite evolution in the wild. Supplementary Information The online version contains supplementary material available at 10.1007/s10682-022-10169-6.
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Transmission of deformed wing virus between Varroa destructor foundresses, mite offspring and infested honey bees. Parasit Vectors 2022; 15:333. [PMID: 36151583 PMCID: PMC9502634 DOI: 10.1186/s13071-022-05463-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Accepted: 08/22/2022] [Indexed: 11/16/2022] Open
Abstract
Background Varroa destructor is the major ectoparasite of the western honey bee (Apis mellifera). Through both its parasitic life-cycle and its role as a vector of viral pathogens, it can cause major damage to honey bee colonies. The deformed wing virus (DWV) is the most common virus transmitted by this ectoparasite, and the mite is correlated to increased viral prevalence and viral loads in infested colonies. DWV variants A and B (DWV-A and DWV-B, respectively) are the two major DWV variants, and they differ both in their virulence and transmission dynamics. Methods We studied the transmission of DWV between bees, parasitic mites and their offspring by quantifying DWV loads in bees and mites collected in in vitro and in situ environments. In vitro, we artificially transmitted DWV-A to mites and quantified both DWV-A and DWV-B in mites and bees. In situ, we measured the natural presence of DWV-B in bees, mites and mites’ offspring. Results Bee and mite viral loads were correlated, and mites carrying both variants were associated with higher mortality of the infected host. Mite infestation increased the DWV-B loads and decreased the DWV-A loads in our laboratory conditions. In situ, viral quantification in the mite offspring showed that, after an initially non-infected egg stage, the DWV-B loads were more closely correlated with the foundress (mother) mites than with the bee hosts. Conclusions The association between mites and DWV-B was highlighted in this study. The parasitic history of a mite directly impacts its DWV infection potential during the rest of its life-cycle (in terms of variant and viral loads). Regarding the mite’s progeny, we hypothesize that the route of contamination is likely through the feeding site rather than by vertical transmission, although further studies are needed to confirm this hypothesis. Graphical Abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1186/s13071-022-05463-9.
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Sorci G, Faivre B. Age-dependent virulence of human pathogens. PLoS Pathog 2022; 18:e1010866. [PMID: 36137159 PMCID: PMC9531802 DOI: 10.1371/journal.ppat.1010866] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 10/04/2022] [Accepted: 09/08/2022] [Indexed: 11/19/2022] Open
Abstract
Host age is often evoked as an intrinsic factor aggravating the outcome of host-pathogen interactions. However, the shape of the relationship between age and infection-induced mortality might differ among pathogens, with specific clinical and ecological traits making some pathogens more likely to exert higher mortality in older hosts. Here, we used a large dataset on age-specific case fatality rate (CFR) of 28 human infectious diseases to investigate i) whether age is consistently associated to increased CFR, ii) whether pathogen characteristics might explain higher CFR in older adults. We found that, for most of the infectious diseases considered here, CFR slightly decreased during the first years of life and then steeply increased in older adults. Pathogens inducing diseases with long-lasting symptoms had the steepest increase of age-dependent CFR. Similarly, bacterial diseases and emerging viruses were associated with increasing mortality risk in the oldest age classes. On the contrary, we did not find evidence suggesting that systemic infections have steeper slopes between CFR and age; similarly, the relationship between age and CFR did not differ according to the pathogen transmission mode. Overall, our analysis shows that age is a key trait affecting infection-induced mortality rate in humans, and that the extent of the aggravating effect on older adults depends on some key traits, such as the duration of illness. Mortality due to infectious diseases varies tremendously among infectious agents, with some pathogens producing no mortality, and others being often associated with a fatal outcome. Such variability depends on characteristics of the pathogen, the host and the environment where hosts and pathogens interact. Age is one of the main host traits that accounts for differences in infection-induced mortality (with mortality being higher at the extremes of the age spectrum). Here, we used a large dataset on 28 human infectious diseases to explore the clinical and ecological traits that might account for differences in age-specific mortality risk. We found that pathogens producing long-lasting disease symptoms exert the highest mortality risk in the older adults. Similarly, emerging pathogens are also associated with higher mortality risk in the oldest age classes. These results confirm that age is a key trait affecting infection-induced mortality rate in humans, and show that the extent of the aggravating effect in older adults depends on some key traits, such as the duration of illness.
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Affiliation(s)
- Gabriele Sorci
- Biogéosciences, UMR 6282 CNRS, Université de Bourgogne Franche-Comté, Dijon, France
- * E-mail:
| | - Bruno Faivre
- Biogéosciences, UMR 6282 CNRS, Université de Bourgogne Franche-Comté, Dijon, France
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Alharbi W, Sandhu SK, Areshi M, Alotaibi A, Alfaidi M, Al-Qadhi G, Morozov AY. Revisiting implementation of multiple natural enemies in pest management. Sci Rep 2022; 12:15023. [PMID: 36056142 PMCID: PMC9440112 DOI: 10.1038/s41598-022-18120-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/05/2022] [Indexed: 11/23/2022] Open
Abstract
A major goal of biological control is the reduction and/or eradication of pests using various natural enemies, in particular, via deliberate infection of the target species by parasites. To enhance the biological control, a promising strategy seems to implement a multi-enemy assemblage rather than a single control agent. Although a large body of theoretical studies exists on co-infections in epidemiology and ecology, there is still a big gap in modelling outcomes of multi-enemy biological control. Here we theoretically investigate how the efficiency of biological control of a pest depends on the number of natural enemies used. We implement a combination of eco-epidemiological modelling and the Adaptive Dynamics game theory framework. We found that a progressive addition of parasite species increases the evolutionarily stable virulence of each parasite, and thus enhances the mortality of the target pest. However, using multiple enemies may have only a marginal effect on the success of biological control, or can even be counter-productive when the number of enemies is excessive. We found the possibility of evolutionary suicide, where one or several parasite species go extinct over the course of evolution. Finally, we demonstrate an interesting scenario of coexistence of multiple parasites at the edge of extinction.
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Affiliation(s)
- Weam Alharbi
- Department of Mathematics, Faculty of science, University of Tabuk, Tabuk, 71491, Saudi Arabia
| | - Simran K Sandhu
- School of Computing and Mathematical Sciences, University of Leicester, Leicester, LE1 7RH, UK
| | - Mounirah Areshi
- Department of Mathematics, Faculty of science, University of Tabuk, Tabuk, 71491, Saudi Arabia
| | - Abeer Alotaibi
- Department of Mathematics, Faculty of science, University of Tabuk, Tabuk, 71491, Saudi Arabia
| | - Mohammed Alfaidi
- Department of Biology, University College of Duba, University of Tabuk, Tabuk, 71491, Saudi Arabia
| | - Ghada Al-Qadhi
- Department of Mathematics, Faculty of science, University of Tabuk, Tabuk, 71491, Saudi Arabia
| | - Andrew Yu Morozov
- School of Computing and Mathematical Sciences, University of Leicester, Leicester, LE1 7RH, UK.
- Laboratory of Behaviour of Lower Vertebrates, Institute of Ecology and Evolution, Moscow, 119071, Russia.
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Abstract
Following the initiation of the unprecedented global vaccination campaign against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), attention has now turned to the potential impact of this large-scale intervention on the evolution of the virus. In this Essay, we summarize what is currently known about pathogen evolution in the context of immune priming (including vaccination) from research on other pathogen species, with an eye towards the future evolution of SARS-CoV-2.
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Affiliation(s)
- Troy Day
- Department of Mathematics and Statistics, Department of Biology, Queen’s University, Kingston, Ontario, Canada
| | - David A. Kennedy
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Andrew F. Read
- Department of Biology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Sylvain Gandon
- CEFE, CNRS, Univ Montpellier, EPHE, IRD, Montpellier, France
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49
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Prevalence of Intestinal Parasites in HIV/AIDS-Infected Patients Attending Clinics in Selected Areas of the Eastern Cape. MICROBIOLOGY RESEARCH 2022. [DOI: 10.3390/microbiolres13030040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Introduction: Intestinal parasites in HIV and AIDS patients increase the risk of gastroenteritis, adding to the complexity of the virus. According to the literature, their interactions are one of the factors leading to HIV replication and progression of AIDS in Africa. Chronic immunosuppression caused by HIV infection makes people vulnerable to parasitic infections, and this is associated with a CD4+ cell count of less than 100. The study describes the prevalence of intestinal parasites in patients attending HIV/AIDS clinics in certain areas of the Eastern Cape. Methods: A cross-sectional study was conducted among 600 patients from HIV/AIDS clinics in the Eastern Cape. Tambo Municipality and Amatole Municipality were the municipalities covered. These included the Ngangalizwe Community Clinic, Tsolo Gateway Clinic, Idutywa Health Centre, and Nqamakwe Health Centre. The stools of 600 participants were examined using direct wet saline/iodine embedding, formal ether concentration technique, and modified Ziehl–Neelsen methods. Results: The mean age of the study participants was 28.2 years. They were predominantly female (79.9%), mostly single (63.6%), and lived in rural (65.2%) and urban areas (34.8%). The prevalence of intestinal parasites was determined to be 30% (180/600) after screening 600 stool samples. The most frequently detected parasites were Ascaris lumbricoides (55.9%), Balantidium coli (15.1%), Entamoeba coli (11.3%), Diphyllobothrium latum (4.3%), Taenia species (3.8%), Schistosoma mansoni (1.6%), and Cryptosporidium spp. (1.6%). Males were affected more frequently (39.2%) than females (27.9%). The difference was statistically significant (p = 0.017). Among the identified intestinal parasites, A. lumbricoides, B. coli, and Taenia spp. were found at all four sites. Conclusion: This study has shed light on the high burden of intestinal parasites in HIV/AIDS patients in the Eastern Cape. Medication adherence, deworming, and sanitary hygiene practices are needed to enhance the control of infection in the affected communities and hence contribute to the control of the HIV pandemic.
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50
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Mitchell E, Graham AL, Úbeda F, Wild G. On maternity and the stronger immune response in women. Nat Commun 2022; 13:4858. [PMID: 35982048 PMCID: PMC9386672 DOI: 10.1038/s41467-022-32569-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 08/08/2022] [Indexed: 11/09/2022] Open
Abstract
Medical research reports that women often exhibit stronger immune responses than men, while pathogens tend to be more virulent in men. Current explanations cannot account for this pattern, creating an obstacle for our understanding of infectious-disease outcomes and the incidence of autoimmune diseases. We offer an alternative explanation that relies on a fundamental difference between the sexes: maternity and the opportunities it creates for transmission of pathogens from mother to child (vertical transmission). Our explanation relies on a mathematical model of the co-evolution of host immunocompetence and pathogen virulence. Here, we show that when there is sufficient vertical transmission co-evolution leads women to defend strongly against temperate pathogens and men to defend weakly against aggressive pathogens, in keeping with medical observations. From a more applied perspective, we argue that limiting vertical transmission of infections would alleviate the disproportionate incidence of autoimmune diseases in women over evolutionary time.
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Affiliation(s)
- Evan Mitchell
- Department of Mathematics, Western University, London, ON, N6A 5B7, Canada
| | - Andrea L Graham
- Department of Ecology & Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA
| | - Francisco Úbeda
- Department of Biological Sciences, Royal Holloway, University of London Egham, Surrey, TW20 0EX, United Kingdom.
| | - Geoff Wild
- Department of Mathematics, Western University, London, ON, N6A 5B7, Canada.
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