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Sauer EL, Connelly C, Perrine W, Love AC, DuRant SE. Male pathology regardless of behaviour drives transmission in an avian host-pathogen system. J Anim Ecol 2024; 93:36-44. [PMID: 38044497 DOI: 10.1111/1365-2656.14026] [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: 12/20/2022] [Accepted: 10/04/2023] [Indexed: 12/05/2023]
Abstract
Host sex is an important source of heterogeneity in the severity of epidemics. Pinpointing the mechanisms causing this heterogeneity can be difficult because differences in behaviour among sexes (e.g. greater territorial aggression in males) can bias exposure risk, obfuscating the role of immune function, which can lead to differences in pathology, in driving differential susceptibility between sexes. Thus, sex-biased transmission driven by differences in immune function independent of behaviour is poorly understood, especially in non-mammalian systems. Here we examine the previously unexplored potential for male-biased pathology to affect transmission using an avian host-pathogen system. We employ a sex-dependent multistate transmission model parameterized with isolated, individual-based experimental exposures of domestic canaries and experimental transmission data of house finches. The experiment revealed that male birds have shorter incubation periods, longer recovery periods, higher pathogen burdens and greater disease pathology than females. Our model revealed that male-biased pathology led to epidemic size rapidly increasing with the proportion of male birds, with a nearly 10-fold increase in total epidemic size from an all-female to an all-male simulation. Our results demonstrate that female-biased resistance, independent of male behaviour, can drive sex-dependent transmission in wildlife, indicating that sex-based differences in immune function, not just differences in exposure risk, can shape epidemic dynamics.
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Affiliation(s)
- Erin L Sauer
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
| | - Chloe Connelly
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
| | - Weston Perrine
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
| | - Ashely C Love
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
- Ecology and Evolutionary Biology, University of Connecticut, Storrs, Connecticut, USA
| | - Sarah E DuRant
- Department of Biological Sciences, University of Arkansas, Fayetteville, Arkansas, USA
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2
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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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3
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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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4
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O’Keeffe KR, Wheeler BT, Mitchell CE. A Microbial Mutualist Within Host Individuals Increases Parasite Transmission Between Host Individuals: Evidence From a Field Mesocosm Experiment. Front Microbiol 2022; 13:824211. [PMID: 35531289 PMCID: PMC9069011 DOI: 10.3389/fmicb.2022.824211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 03/21/2022] [Indexed: 11/21/2022] Open
Abstract
The interactions among host-associated microbes and parasites can have clear consequences for disease susceptibility and progression within host individuals. Yet, empirical evidence for how these interactions impact parasite transmission between host individuals remains scarce. We address this scarcity by using a field mesocosm experiment to investigate the interaction between a systemic fungal endophyte, Epichloë coenophiala, and a fungal parasite, Rhizoctonia solani, in leaves of a grass host, tall fescue (Lolium arundinaceum). Specifically, we investigated how this interaction impacted transmission of the parasite under field conditions in replicated experimental host populations. Epichloë-inoculated populations tended to have greater disease prevalence over time, though this difference had weak statistical support. More clearly, Epichloë-inoculated populations experienced higher peak parasite prevalences than Epichloë-free populations. Epichloë conferred a benefit in growth; Epichloë-inoculated populations had greater aboveground biomass than Epichloë-free populations. Using biomass as a proxy, host density was correlated with peak parasite prevalence, but Epichloë still increased peak parasite prevalence after controlling for the effect of biomass. Together, these results suggest that within-host microbial interactions can impact disease at the population level. Further, while Epichloë is clearly a mutualist of tall fescue, it may not be a defensive mutualist in relation to Rhizoctonia solani.
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Affiliation(s)
- Kayleigh R. O’Keeffe
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Department of Biology, University of Pennsylvania, Philadelphia, PA, United States
- *Correspondence: Kayleigh R. O’Keeffe,
| | - Brandon T. Wheeler
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Department of Biology, Western Carolina University, Cullowhee, NC, United States
| | - Charles E. Mitchell
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Environment, Ecology and Energy Program, University of North Carolina, Chapel Hill, NC, United States
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5
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Walsman JC, Strauss AT, Hall SR. Parasite‐driven cascades or hydra effects: Susceptibility and foraging depression shape parasite–host–resource interactions. Funct Ecol 2022. [DOI: 10.1111/1365-2435.14030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Penczykowski RM, Shocket MS, Ochs JH, Lemanski BCP, Sundar H, Duffy MA, Hall SR. Virulent Disease Epidemics Can Increase Host Density by Depressing Foraging of Hosts. Am Nat 2022; 199:75-90. [DOI: 10.1086/717175] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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7
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Jaramillo JM, Ma J, van den Driessche P, Yakubu AA. Disease-Induced Hydra Effect with Overcompensatory Recruitment. Bull Math Biol 2021; 84:17. [PMID: 34923617 DOI: 10.1007/s11538-021-00975-4] [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: 04/12/2021] [Accepted: 11/18/2021] [Indexed: 11/27/2022]
Abstract
In ecological systems, the hydra effect is an increase in population size caused by an increase in mortality. This seemingly counterintuitive effect has been observed in several populations, including fish, blowflies, snails and plants, and has been modeled in both continuous and discrete time. A similar effect induced by disease has recently been observed empirically. Here we present theoretical and simulation results for an infectious disease-induced hydra effect, namely conditions under which the total population size, composed of those that are infectious as well as those that are susceptible, at an endemic equilibrium is greater than the population size at the disease-free equilibrium. (For an endemic k-cycle, this can be similarly defined using the average population.) We find this disease-induced hydra effect occurs when the intra-specific competition is strong and disease infection sufficiently inhibits the reproductive output of infected individuals. For our continuous time model, we give a necessary and sufficient condition for a disease-induced hydra effect. This condition requires overcompensatory recruitment. With a discrete time model, we show there is no disease-induced hydra effect without overcompensatory recruitment. We illustrate by simulations that a disease-induced hydra effect may occur with Ricker recruitment when the endemic system converges to either a fixed equilibrium or a 2-cycle.
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Affiliation(s)
- J M Jaramillo
- Department of Mathematics and Statistics, University of Victoria, Victoria, BC, V8W 2Y2, Canada.
| | - Junling Ma
- Department of Mathematics and Statistics, University of Victoria, Victoria, BC, V8W 2Y2, Canada
| | - P van den Driessche
- Department of Mathematics and Statistics, University of Victoria, Victoria, BC, V8W 2Y2, Canada
| | - Abdul-Aziz Yakubu
- Department of Mathematics, Howard University, Washington, DC, 20059, USA
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Preston DL, Layden TJ, Segui LM, Falke LP, Brant SV, Novak M. Trematode parasites exceed aquatic insect biomass in Oregon stream food webs. J Anim Ecol 2020; 90:766-775. [PMID: 33368227 DOI: 10.1111/1365-2656.13409] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 11/16/2020] [Indexed: 11/30/2022]
Abstract
Although parasites are increasingly recognized for their ecosystem roles, it is often assumed that free-living organisms dominate animal biomass in most ecosystems and therefore provide the primary pathways for energy transfer. To examine the contributions of parasites to ecosystem energetics in freshwater streams, we quantified the standing biomass of trematodes and free-living organisms at nine sites in three streams in western Oregon, USA. We then compared the rates of biomass flow from snails Juga plicifera into trematode parasites relative to aquatic vertebrate predators (sculpin, cutthroat trout and Pacific giant salamanders). The trematode parasite community had the fifth highest dry biomass density among stream organisms (0.40 g/m2 ) and exceeded the combined biomass of aquatic insects. Only host snails (3.88 g/m2 ), sculpin (1.11 g/m2 ), trout (0.73 g/m2 ) and crayfish (0.43 g/m2 ) had a greater biomass. The parasite 'extended phenotype', consisting of trematode plus castrated host biomass, exceeded the individual biomass of every taxonomic group other than snails. The substantial parasite biomass stemmed from the high snail density and infection prevalence, and the large proportional mass of infected hosts that consisted of trematode tissue (M = 31% per snail). Estimates of yearly biomass transfer from snails into trematodes were slightly higher than the combined estimate of snail biomass transfer into the three vertebrate predators. Pacific giant salamanders accounted for 90% of the snail biomass consumed by predators. These results demonstrate that trematode parasites play underappreciated roles in the ecosystem energetics of some freshwater streams.
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Affiliation(s)
- Daniel L Preston
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Leah M Segui
- Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
| | - Landon P Falke
- Department of Forest and Wildlife Ecology, University of Wisconsin-Madison, Madison, WI, USA
| | - Sara V Brant
- Museum of Southwestern Biology, Division of Parasites, Department of Biology, University of New Mexico, Albuquerque, NM, USA
| | - Mark Novak
- Department of Integrative Biology, Oregon State University, Corvallis, OR, USA
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