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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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Hector TE, Gehman ALM, King KC. Infection burdens and virulence under heat stress: ecological and evolutionary considerations. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220018. [PMID: 36744570 PMCID: PMC9900716 DOI: 10.1098/rstb.2022.0018] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
As a result of global change, hosts and parasites (including pathogens) are experiencing shifts in their thermal environment. Despite the importance of heat stress tolerance for host population persistence, infection by parasites can impair a host's ability to cope with heat. Host-parasite eco-evolutionary dynamics will be affected if infection reduces host performance during heating. Theory predicts that within-host parasite burden (replication rate or number of infecting parasites per host), a key component of parasite fitness, should correlate positively with virulence-the harm caused to hosts during infection. Surprisingly, however, the relationship between within-host parasite burden and virulence during heating is often weak. Here, we describe the current evidence for the link between within-host parasite burden and host heat stress tolerance. We consider the biology of host-parasite systems that may explain the weak or absent link between these two important host and parasite traits during hot conditions. The processes that mediate the relationship between parasite burden and host fitness will be fundamental in ecological and evolutionary responses of host and parasites in a warming world. This article is part of the theme issue 'Infectious disease ecology and evolution in a changing world'.
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Affiliation(s)
- T. E. Hector
- Department of Biology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
| | - A.-L. M. Gehman
- Hakai Institute, End of Kwakshua Channel, Calvert Island, BC Canada, V0N 1M0,Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, BC Canada, V6T 1Z4
| | - K. C. King
- Department of Biology, University of Oxford, Oxford, Oxfordshire OX1 3SZ, UK
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3
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The effect of climate variability in the efficacy of the entomopathogenic fungus Metarhizium acridum against the desert locust Schistocerca gregaria. Sci Rep 2022; 12:7535. [PMID: 35534636 PMCID: PMC9085851 DOI: 10.1038/s41598-022-11424-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 04/21/2022] [Indexed: 11/08/2022] Open
Abstract
Despite substantial efforts to control locusts they remain periodically a major burden in Africa, causing severe yield loss and hence loss of food and income. Distribution maps indicating the value of the basic reproduction number R0 was used to identify areas where an insect pest can be controlled by a natural enemy. A dynamic process-based mathematical model integrating essential features of a natural enemy and its interaction with the pest is used to generate R0 risk maps for insect pest outbreaks, using desert locust and the entomopathogenic fungus Metarhizium acridum (Synn. Metarhizium anisoliae var. acridum) as a case study. This approach provides a tool for evaluating the impact of climatic variables such as temperature and relative humidity and mapping spatial variability on the efficacy of M. acridum as a biocontrol agent against desert locust invasion in Africa. Applications of M. acridum against desert locust in a few selected African countries including Morocco, Kenya, Mali, and Mauritania through monthly spatial projection of R0 maps for the prevailing climatic condition are illustrated. By combining mathematical modeling with a geographic information system in a spatiotemporal projection as we do in this study, the field implementation of microbial control against locust in an integrated pest management system may be improved. Finally, the practical utility of this model provides insights that may improve the timing of pesticide application in a selected area where efficacy is highly expected.
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Stewart Merrill TE, Rapti Z, Cáceres CE. Host Controls of Within-Host Disease Dynamics: Insight from an Invertebrate System. Am Nat 2021; 198:317-332. [PMID: 34403315 DOI: 10.1086/715355] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractWithin-host processes (representing the entry, establishment, growth, and development of a parasite inside its host) may play a key role in parasite transmission but remain challenging to observe and quantify. We develop a general model for measuring host defenses and within-host disease dynamics. Our stochastic model breaks the infection process down into the stages of parasite exposure, entry, and establishment and provides associated probabilities for a host's ability to resist infections with barriers and clear internal infections. We tested our model on Daphnia dentifera and the parasitic fungus Metschnikowia bicuspidata and found that when faced with identical levels of parasite exposure, Daphnia patent (transmitting) infections depended on the strength of internal clearance. Applying a Gillespie algorithm to the model-estimated probabilities allowed us to visualize within-host dynamics, within which signatures of host defense could be clearly observed. We also found that early within-host stages were the most vulnerable to internal clearance, suggesting that hosts have a limited window during which recovery can occur. Our study demonstrates how pairing longitudinal infection data with a simple model can reveal new insight into within-host dynamics and mechanisms of host defense. Our model and methodological approach may be a powerful tool for exploring these properties in understudied host-parasite interactions.
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Temperate and chronic virus competition leads to low lysogen frequency. J Theor Biol 2021; 523:110710. [PMID: 33839160 DOI: 10.1016/j.jtbi.2021.110710] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 04/04/2021] [Accepted: 04/05/2021] [Indexed: 11/23/2022]
Abstract
The canonical bacteriophage is obligately lytic: the virus infects a bacterium and hijacks cell functions to produce large numbers of new viruses which burst from the cell. These viruses are well-studied, but there exist a wide range of coexisting virus lifestyles that are less understood. Temperate viruses exhibit both a lytic cycle and a latent (lysogenic) cycle, in which viral genomes are integrated into the bacterial host. Meanwhile, chronic (persistent) viruses use cell functions to produce more viruses without killing the cell; chronic viruses may also exhibit a latent stage in addition to the productive stage. Here, we study the ecology of these competing viral strategies. We demonstrate the conditions under which each strategy is dominant, which aids in control of human bacterial infections using viruses. We find that low lysogen frequencies provide competitive advantages for both virus types; however, chronic viruses maximize steady state density by eliminating lysogeny entirely, while temperate viruses exhibit a non-zero 'sweet spot' lysogen frequency. Viral steady state density maximization leads to coexistence of temperate and chronic viruses, explaining the presence of multiple viral strategies in natural environments.
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Djouda BS, Ndjomatchoua FT, Moukam Kakmeni FM, Tchawoua C, Tonnang HEZ. Understanding biological control with entomopathogenic fungi-Insights from a stochastic pest-pathogen model. CHAOS (WOODBURY, N.Y.) 2021; 31:023126. [PMID: 33653067 DOI: 10.1063/5.0019971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 01/27/2021] [Indexed: 06/12/2023]
Abstract
In this study, an individual-based model is proposed to investigate the effect of demographic stochasticity on biological control using entomopathogenic fungi. The model is formulated as a continuous time Markov process, which is then decomposed into a deterministic dynamics using stochastic corrections and system size expansion. The stability and bifurcation analysis shows that the system dynamic is strongly affected by the contagion rate and the basic reproduction number. However, sensitivity analysis of the extinction probability shows that the persistence of a biological control agent depends to the proportion of spores collected from insect cadavers as well as their ability to be reactivated and infect insects. When considering the migration of each species within a set of patches, the dispersion relation shows a Hopf-damped Turing mode for a threshold contagion rate. A large size population led to a spatial and temporal resonant stochasticity and also induces an amplification effect on power spectrum density.
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Affiliation(s)
- Byliole S Djouda
- Laboratory of Mechanics, Materials and Structures, Research and Postgraduate Training Unit for Physics and Applications, Postgraduate School of Science, Technology and Geosciences, Department of Physics, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Ngoa Ekelle, Yaoundé, Cameroon
| | - Frank T Ndjomatchoua
- Sustainable Impact Platform, Adaptive Agronomy and Pest Ecology Cluster, International Rice Research Institute (IRRI), DAPO Box 7777-1301, Metro Manila, Philippines
| | - F M Moukam Kakmeni
- Complex Systems and Theoretical Biology Group, Laboratory of Research on Advanced Materials and Nonlinear Science (LaRAMaNS), Department of Physics, Faculty of Science, University of Buéa, P.O. Box 63, Buéa, Cameroon
| | - Clément Tchawoua
- Laboratory of Mechanics, Materials and Structures, Research and Postgraduate Training Unit for Physics and Applications, Postgraduate School of Science, Technology and Geosciences, Department of Physics, Faculty of Science, University of Yaoundé 1, P.O. Box 812, Ngoa Ekelle, Yaoundé, Cameroon
| | - Henri E Z Tonnang
- International Institute of Tropical Agriculture (IITA), 08 BP 0932 Tri Postal Abomey Calavi, Cotonou, Benin
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Strauss AT, Shoemaker LG, Seabloom EW, Borer ET. Cross‐scale dynamics in community and disease ecology: relative timescales shape the community ecology of pathogens. Ecology 2019; 100:e02836. [DOI: 10.1002/ecy.2836] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2019] [Revised: 05/15/2019] [Accepted: 06/25/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Alexander T. Strauss
- Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul Minnesota 55108 USA
| | - Lauren G. Shoemaker
- Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul Minnesota 55108 USA
| | - Eric W. Seabloom
- Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul Minnesota 55108 USA
| | - Elizabeth T. Borer
- Department of Ecology, Evolution, and Behavior University of Minnesota St. Paul Minnesota 55108 USA
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Rapti Z, Stewart Merrill TE, Mueller-Brennan B, Kavouras JH, Cáceres CE. Indirect effects in a planktonic disease system. Theor Popul Biol 2019; 130:132-142. [PMID: 31319041 DOI: 10.1016/j.tpb.2019.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 07/09/2019] [Accepted: 07/10/2019] [Indexed: 11/16/2022]
Abstract
Indirect effects, both density- and trait-mediated, have been known to act in tandem with direct effects in the interactions of numerous species. They have been shown to affect populations embedded in competitive and mutualistic networks alike. In this work, we introduce a four-dimensional system of ordinary differential equations and investigate the interplay between direct density-effects and density- and trait-mediated indirect effects that take place in a yeast parasite-zooplankton host-incompetent competitor system embedded in a food web which also includes resources and predators. Among our main findings is the demonstration that indirect effects cause qualitative and quantitative changes almost indistinguishable from direct effects and the corroboration through our analysis of the fact that the effects of direct and indirect mechanisms cannot be disentangled. Our results underpin the conclusions of past studies calling for comprehensive models that incorporate both direct and indirect effects to better describe field data.
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Affiliation(s)
- Zoi Rapti
- Department of Mathematics, University of Illinois at Urbana-Champaign, 1409 W. Green St., Urbana, IL 61801, USA.
| | - Tara E Stewart Merrill
- Program in Ecology, Evolution and Conservation Biology, School of Integrative Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL 61801, USA
| | - Bridget Mueller-Brennan
- Department of Mathematics, University of Illinois at Urbana-Champaign, 1409 W. Green St., Urbana, IL 61801, USA
| | - Jerry H Kavouras
- Department of Biology, Lewis University, Romeoville, IL 60446, USA
| | - Carla E Cáceres
- Department of Evolution, Ecology and Behavior, School of Integrative Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Ave., Urbana, IL 61801, USA
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