1
|
Morand S, Blasdell K, Bordes F, Buchy P, Carcy B, Chaisiri K, Chaval Y, Claude J, Cosson JF, Desquesnes M, Jittapalapong S, Jiyipong T, Karnchanabanthoen A, Pornpan P, Rolain JM, Tran A. Changing landscapes of Southeast Asia and rodent-borne diseases: decreased diversity but increased transmission risks. ECOLOGICAL APPLICATIONS : A PUBLICATION OF THE ECOLOGICAL SOCIETY OF AMERICA 2019; 29:e01886. [PMID: 30986339 DOI: 10.1002/eap.1886] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 10/26/2018] [Accepted: 12/04/2018] [Indexed: 05/15/2023]
Abstract
The reduction in biodiversity from land use change due to urbanization and agricultural intensification appears to be linked to major epidemiological changes in many human diseases. Increasing disease risks and the emergence of novel pathogens result from increased contact among wildlife, domesticated animals, and humans. We investigated the relationship between human alteration of the environment and the occurrence of generalist and synanthropic rodent species in relation to the diversity and prevalence of rodent-borne pathogens in Southeast Asia, a hotspot of threatened and endangered species, and a foci of emerging infectious diseases. We used data from an extensive pathogen survey of rodents from seven sites in mainland Southeast Asia in conjunction with past and present land cover analyses. At low spatial resolutions, we found that rodent-borne pathogen richness is negatively associated with increasing urbanization, characterized by increased habitat fragmentation, agriculture cover and deforestation. However, at a finer spatial resolution, we found that some major pathogens are favored by environmental characteristics associated with human alteration including irrigation, habitat fragmentation, and increased agricultural land cover. In addition, synanthropic rodents, many of which are important pathogen reservoirs, were associated with fragmented and human-dominated landscapes, which may ultimately enhance the opportunities for zoonotic transmission and human infection by some pathogens.
Collapse
Affiliation(s)
- Serge Morand
- CNRS - CIRAD, Faculty of Veterinary Technology, Kasetsart University, Bangkok, Thailand
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchavithi Road, Ratchathevi, Bangkok, 10400, Thailand
| | - Kim Blasdell
- CSIRO Health and Biosecurity Business Unit, Australian Animal Health Laboratory, 5 Portarlington Road, Geelong, Victoria, 3220, Australia
| | - Frédéric Bordes
- Institut des Sciences de l'Evolution, UMR CNRS-IRD-UM2, Université de Montpellier, 35095, Montpellier Cedex, France
| | - Philippe Buchy
- Virology Unit, Institut Pasteur in Cambodia, 5 Monivong Boulevard, Phnom Penh, Cambodia
- GlaxoSmithKline Vaccines, Gateway West, 150 Beach Road, Singapore City, 189720, Singapore
| | - Bernard Carcy
- LBCM/EA4558 VAP, UFR Sciences Pharmaceutiques et Biologiques, Université de Montpellier, Montpellier, France
| | - Kittipong Chaisiri
- Department of Helminthology, Faculty of Tropical Medicine, Mahidol University, 420/6 Ratchavithi Road, Ratchathevi, Bangkok, 10400, Thailand
| | - Yannick Chaval
- Comportement et Ecologie de la Faune Sauvage, INRA, Chemin de Borde Rouge, Auzeville, 31326, Castanet-Tolosan Cedex, France
| | - Julien Claude
- Institut des Sciences de l'Evolution, UMR CNRS-IRD-UM2, Université de Montpellier, 35095, Montpellier Cedex, France
| | - Jean-François Cosson
- BIPAR-INRA Biologie Moléculaire et Immunologie Parasitaires et Fongiques, ENVA Maisons Alfort, 7 Avenue du Général de Gaulle, 94704, Maisons-Alfort Cedex, France
| | - Marc Desquesnes
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
- CIRAD-Bios, UMR17 InterTryp, Montpellier, F-34000, France
| | | | - Tawisa Jiyipong
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
- URMITE CNRS INSERM IRD, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, 27 Bd Jean Moulin, 13385, Marseille Cedex 5, France
| | - Anamika Karnchanabanthoen
- LBCM/EA4558 VAP, UFR Sciences Pharmaceutiques et Biologiques, Université de Montpellier, Montpellier, France
- Faculty of Veterinary Technology, Kasetsart University, Bangkok, Thailand
| | - Pumhom Pornpan
- Department of Parasitology, Faculty of Veterinary Medicine, Kasetsart University, Bangkok, Thailand
- Center for Agricultural Biotechnology, Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom, Thailand
| | - Jean-Marc Rolain
- URMITE CNRS INSERM IRD, IHU Méditerranée Infection, Faculté de Médecine et de Pharmacie, Aix-Marseille Université, 27 Bd Jean Moulin, 13385, Marseille Cedex 5, France
| | - Annelise Tran
- CIRAD, UMR TETIS, F-34093, Montpellier, France
- CIRAD, UMR ASTRE, Montpellier, France
| |
Collapse
|
2
|
The impact of resource quality on the evolution of virulence in spatially heterogeneous environments. J Theor Biol 2017; 416:1-7. [DOI: 10.1016/j.jtbi.2016.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 12/03/2016] [Accepted: 12/21/2016] [Indexed: 02/02/2023]
|
3
|
Su M, Hui C, Lin Z. Effects of the transmissibility and virulence of pathogens on intraguild predation in fragmented landscapes. Biosystems 2015; 129:44-9. [PMID: 25659991 DOI: 10.1016/j.biosystems.2015.02.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 12/02/2014] [Accepted: 02/03/2015] [Indexed: 10/24/2022]
Abstract
It is well known that pathogenic infection can have a profound effect on the outcome of competition and predation, however the role of pathogenic infection in systems where predators and prey also compete for other resources is yet to be explored (i.e. in systems of intraguild predation). Using a cellular automaton model, we here explore the effect of pathogenic infection on the spatial dynamics of species that also engage in intraguild predation (IGP) in a fragmented landscape. First, the shared pathogen by the predator and prey can enhance species coexistence in the IGP system, consistent with results for non-spatial IGP systems. Second, equilibrium population sizes of the predator and prey depend crucially on the pathogen virulence to the predator but are insensitive to the change in the virulence to the prey. This asymmetric response to virulence change is due to the fact that the predator species has to juggle between predation, resource competition and pathogenic infection. Finally, the response of the pathogen to habitat fragmentation is largely determined by its life-history strategy (transmissibility and virulence) and the trophic level of its host. These results enrich our understanding on the role of pathogens in the ecosystem functioning of eco-epidemiological systems.
Collapse
Affiliation(s)
- Min Su
- School of Geography Science, Nanjing Normal University, Nanjing 210046, China; School of Mathematics, Hefei University of Technology, Hefei 230009, China.
| | - Cang Hui
- Centre for Invasion Biology, Department of Mathematical Sciences, Stellenbosch University, Matieland 7602, South Africa; Mathematical and Physical Biosciences, African Institute for Mathematical Sciences, Muizenberg 7945, South Africa
| | - Zhenshan Lin
- School of Geography Science, Nanjing Normal University, Nanjing 210046, China
| |
Collapse
|
4
|
Sevila J, Richomme C, Hoste H, Candela MG, Gilot-Fromont E, Rodolakis A, Cebe N, Picot D, Merlet J, Verheyden H. Does land use within the home range drive the exposure of roe deer (Capreolus capreolus) to two abortive pathogens in a rural agro-ecosystem? ACTA ACUST UNITED AC 2014. [DOI: 10.1007/s13364-014-0197-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
5
|
Vander Wal E, Garant D, Calmé S, Chapman CA, Festa-Bianchet M, Millien V, Rioux-Paquette S, Pelletier F. Applying evolutionary concepts to wildlife disease ecology and management. Evol Appl 2014; 7:856-68. [PMID: 25469163 PMCID: PMC4227862 DOI: 10.1111/eva.12168] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 04/08/2014] [Indexed: 12/17/2022] Open
Abstract
Existing and emerging infectious diseases are among the most pressing global threats to biodiversity, food safety and human health. The complex interplay between host, pathogen and environment creates a challenge for conserving species, communities and ecosystem functions, while mediating the many known ecological and socio-economic negative effects of disease. Despite the clear ecological and evolutionary contexts of host-pathogen dynamics, approaches to managing wildlife disease remain predominantly reactionary, focusing on surveillance and some attempts at eradication. A few exceptional studies have heeded recent calls for better integration of ecological concepts in the study and management of wildlife disease; however, evolutionary concepts remain underused. Applied evolution consists of four principles: evolutionary history, genetic and phenotypic variation, selection and eco-evolutionary dynamics. In this article, we first update a classical framework for understanding wildlife disease to integrate better these principles. Within this framework, we explore the evolutionary implications of environment-disease interactions. Subsequently, we synthesize areas where applied evolution can be employed in wildlife disease management. Finally, we discuss some future directions and challenges. Here, we underscore that despite some evolutionary principles currently playing an important role in our understanding of disease in wild animals, considerable opportunities remain for fostering the practice of evolutionarily enlightened wildlife disease management.
Collapse
Affiliation(s)
- Eric Vander Wal
- Département de biologie, Université de SherbrookeSherbrooke, QC, Canada
| | - Dany Garant
- Département de biologie, Université de SherbrookeSherbrooke, QC, Canada
| | - Sophie Calmé
- Département de biologie, Université de SherbrookeSherbrooke, QC, Canada
- El Colegio de la Frontera SurChetumal, Quintana Roo, Mexico
| | - Colin A Chapman
- Department of Anthropology and McGill School of Environment, McGill UniversityMontreal, QC, Canada
- Wildlife Conservation SocietyBronx, New York, NY, USA
| | | | | | | | - Fanie Pelletier
- Département de biologie, Université de SherbrookeSherbrooke, QC, Canada
| |
Collapse
|
6
|
Lutambi AM, Chitnis N, Briët OJT, Smith TA, Penny MA. Clustering of vector control interventions has important consequences for their effectiveness: a modelling study. PLoS One 2014; 9:e97065. [PMID: 24823656 PMCID: PMC4019655 DOI: 10.1371/journal.pone.0097065] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 04/14/2014] [Indexed: 11/23/2022] Open
Abstract
Vector control interventions have resulted in considerable reductions in malaria morbidity and mortality. When universal coverage cannot be achieved for financial or logistical reasons, the spatial arrangement of vector control is potentially important for optimizing benefits. This study investigated the effect of spatial clustering of vector control interventions on reducing the population of biting mosquitoes. A discrete-space continuous-time mathematical model of mosquito population dynamics and dispersal was extended to incorporate vector control interventions of insecticide treated bednets (ITNs), Indoor residual Spraying (IRS), and larviciding. Simulations were run at varying levels of coverage and degree of spatial clustering. At medium to high coverage levels of each of the interventions or in combination was more effective to spatially spread these interventions than to cluster them. Suggesting that when financial resources are limited, unclustered distribution of these interventions is more effective. Although it is often stated that locally high coverage is needed to achieve a community effect of ITNs or IRS, our results suggest that if the coverage of ITNs or IRS are insufficient to achieve universal coverage, and there is no targeting of high risk areas, the overall effects on mosquito densities are much greater if they are distributed in an unclustered way, rather than clustered in specific localities. Also, given that interventions are often delivered preferentially to accessible areas, and are therefore clustered, our model results show this may be inefficient. This study provides evidence that the effectiveness of an intervention can be highly dependent on its spatial distribution. Vector control plans should consider the spatial arrangement of any intervention package to ensure effectiveness is maximized.
Collapse
Affiliation(s)
- Angelina Mageni Lutambi
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Ifakara Health Institute, Dar es Salaam, Tanzania
| | - Nakul Chitnis
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Fogarty International Center, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Olivier J. T. Briët
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Thomas A. Smith
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | - Melissa A. Penny
- Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| |
Collapse
|
7
|
|
8
|
Beasley JC, Eagan TS, Page LK, Hennessy CA, Rhodes OE. Baylisascaris procyonis infection in white-footed mice: predicting patterns of infection from landscape habitat attributes. J Parasitol 2013; 99:743-7. [PMID: 23656487 DOI: 10.1645/ge-2887.1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
There is a growing body of evidence that habitat fragmentation resulting from anthropogenic land use can alter the transmission dynamics of infectious disease. Baylisascaris procyonis , a parasitic roundworm with the ability to cause fatal central nervous system disease in many mammals, including humans, is a zoonotic threat, and research suggests that parasite recruitment rates by intermediate hosts are highly variable among forest patches in fragmented landscapes. During 2008, we sampled 353 white-footed mice ( Peromyscus leucopus ) from 22 forest patches distributed throughout a fragmented agricultural ecosystem to determine the influence of landscape-level habitat attributes on infection rates of B. procyonis in mice. We characterized each mouse in terms of infection status and intensity of infection, and calculated (on a patch-wide basis) prevalence, mean abundance of B. procyonis , and mean intensity of infection. We used an information-theoretic approach to develop a suite of candidate models characterizing the influence of landscape attributes on each of our measured characteristics of B. procyonis infection in white-footed mice, based on previous knowledge of raccoon ( Procyon lotor ) ecology and B. procyonis distribution in agricultural ecosystems. We observed evidence of B. procyonis infection in mice across all 22 habitat patches sampled. However, parasite recruitment rates and intensity were highly variable among patches, and the results of our analyses suggest that spatial variability in B. procyonis infections was primarily driven by emergent properties of fragmented ecosystems. In particular, prevalence, abundance, and intensity of B. procyonis infections in mice were negatively associated with the size and connectivity of forest patches. These results support previous studies indicating that habitat fragmentation can alter the transmission dynamics of infectious disease, and suggest that factors below the scale of landscape, i.e., fine-scale habitat structure or demographic and behavioral attributes of intermediate and/or definitive hosts, also may be important for predicting patterns of B. procyonis infection in intermediate hosts.
Collapse
Affiliation(s)
- J C Beasley
- Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, South Carolina 29802
| | | | | | | | | |
Collapse
|
9
|
Brearley G, Rhodes J, Bradley A, Baxter G, Seabrook L, Lunney D, Liu Y, McAlpine C. Wildlife disease prevalence in human-modified landscapes. Biol Rev Camb Philos Soc 2012; 88:427-42. [PMID: 23279314 DOI: 10.1111/brv.12009] [Citation(s) in RCA: 159] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 11/11/2012] [Accepted: 11/20/2012] [Indexed: 11/28/2022]
Abstract
Human-induced landscape change associated with habitat loss and fragmentation places wildlife populations at risk. One issue in these landscapes is a change in the prevalence of disease which may result in increased mortality and reduced fecundity. Our understanding of the influence of habitat loss and fragmentation on the prevalence of wildlife diseases is still in its infancy. What is evident is that changes in disease prevalence as a result of human-induced landscape modification are highly variable. The importance of infectious diseases for the conservation of wildlife will increase as the amount and quality of suitable habitat decreases due to human land-use pressures. We review the experimental and observational literature of the influence of human-induced landscape change on wildlife disease prevalence, and discuss disease transmission types and host responses as mechanisms that are likely to determine the extent of change in disease prevalence. It is likely that transmission dynamics will be the key process in determining a pathogen's impact on a host population, while the host response may ultimately determine the extent of disease prevalence. Finally, we conceptualize mechanisms and identify future research directions to increase our understanding of the relationship between human-modified landscapes and wildlife disease prevalence. This review highlights that there are rarely consistent relationships between wildlife diseases and human-modified landscapes. In addition, variation is evident between transmission types and landscape types, with the greatest positive influence on disease prevalence being in urban landscapes and directly transmitted disease systems. While we have a limited understanding of the potential influence of habitat loss and fragmentation on wildlife disease, there are a number of important areas to address in future research, particularly to account for the variability in increased and decreased disease prevalence. Previous studies have been based on a one-dimensional comparison between unmodified and modified sites. What is lacking are spatially and temporally explicit quantitative approaches which are required to enable an understanding of the range of key causal mechanisms and the reasons for variability. This is particularly important for replicated studies across different host-pathogen systems. Furthermore, there are few studies that have attempted to separate the independent effects of habitat loss and fragmentation on wildlife disease, which are the major determinants of wildlife population dynamics in human-modified landscapes. There is an urgent need to understand better the potential causal links between the processes of human-induced landscape change and the associated influences of habitat fragmentation, matrix hostility and loss of connectivity on an animal's physiological stress, immune response and disease susceptibility. This review identified no study that had assessed the influence of human-induced landscape change on the prevalence of a wildlife sexually transmitted disease. A better understanding of the various mechanisms linking human-induced landscape change and the prevalence of wildlife disease will lead to more successful conservation management outcomes.
Collapse
Affiliation(s)
- Grant Brearley
- Landscape Ecology and Conservation Group, Centre for Spatial Environmental Research, School of Geography, Planning & Environmental Management, The University of Queensland, Brisbane, 4072, Australia.
| | | | | | | | | | | | | | | |
Collapse
|
10
|
The effect of predation on the prevalence and aggregation of pathogens in prey. Biosystems 2011; 105:300-6. [DOI: 10.1016/j.biosystems.2011.05.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Revised: 05/09/2011] [Accepted: 05/26/2011] [Indexed: 11/21/2022]
|
11
|
Torres-Pérez F, Palma RE, Hjelle B, Holmes EC, Cook JA. Spatial but not temporal co-divergence of a virus and its mammalian host. Mol Ecol 2011; 20:4109-22. [PMID: 21880089 DOI: 10.1111/j.1365-294x.2011.05241.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Co-divergence between host and parasites suggests that evolutionary processes act across similar spatial and temporal scales. Although there has been considerable work on the extent and correlates of co-divergence of RNA viruses and their mammalian hosts, relatively little is known about the extent to which virus evolution is determined by the phylogeographic history of host species. To test hypotheses related to co-divergence across a variety of spatial and temporal scales, we explored phylogenetic signatures in Andes virus (ANDV) sampled from Chile and its host rodent, Oligoryzomys longicaudatus. ANDV showed strong spatial subdivision, a phylogeographic pattern also recovered in the host using both spatial and genealogical approaches, and despite incomplete lineage sorting. Lineage structure in the virus seemed to be a response to current population dynamics in the host at the spatial scale of ecoregions. However, finer scale analyses revealed contrasting patterns of genetic structure across a latitudinal gradient. As predicted by their higher substitution rates, ANDV showed greater genealogical resolution than the rodent, with topological congruence influenced by the degree of lineage sorting within the host. However, despite these major differences in evolutionary dynamics, the geographic structure of host and virus converged across large spatial scales.
Collapse
Affiliation(s)
- Fernando Torres-Pérez
- Instituto de Biología, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile.
| | | | | | | | | |
Collapse
|
12
|
Farrington HL, Petren K. A century of genetic change and metapopulation dynamics in the Galápagos warbler finches (Certhidea). Evolution 2011; 65:3148-61. [PMID: 22023582 DOI: 10.1111/j.1558-5646.2011.01385.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Populations that are connected by immigrants play an important role in evolutionary and conservation biology, yet we have little direct evidence of how such metapopulations change genetically over evolutionary time. We compared historic (1894-1906) to modern (1988-2006) genetic variation in 11 populations of warbler finches at 14 microsatellite loci. Although several lines of evidence suggest that Darwin's finches may be in decline, we found that the genetic diversity of warbler finches has not generally declined, and broad-scale patterns of variation remained similar over time. Contrary to expectations, inferred population sizes have generally increased over time (6-8%) as have immigration rates (8-16%), which may reflect a recent increase in the frequency and intensity of El Niño events. Individual island populations showed significant declines (18-19%) and also substantial gains (18-20%) in allelic richness over time. Changes in genetic diversity were correlated with changes in immigration rates, but did not correspond to population size or human disturbance. These results reflect the expected stabilizing properties of whole metapopulations over time. However, the dramatic and unpredictable changes observed in individual populations during this short time interval suggests that care should be taken when monitoring individual population fragments with snapshots of genetic variation.
Collapse
Affiliation(s)
- Heather L Farrington
- Department of Biological Sciences, University of Cincinnati, OH 45221-0006, USA.
| | | |
Collapse
|
13
|
Echaubard P, Little K, Pauli B, Lesbarrères D. Context-dependent effects of ranaviral infection on northern leopard frog life history traits. PLoS One 2010; 5:e13723. [PMID: 21060894 PMCID: PMC2965661 DOI: 10.1371/journal.pone.0013723] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 10/01/2010] [Indexed: 12/22/2022] Open
Abstract
Pathogens have important effects on host life-history traits, but the magnitude of these effects is often strongly context-dependent. The outcome of an interaction between a host and an infectious agent is often associated with the level of stress experienced by the host. Ranavirus causes disease and mortality in amphibian populations in various locations around the world, but most known cases of ranaviral infection have occurred in North America and the United Kingdom. While Ranavirus virulence has been investigated, the outcome of Ranavirus infection has seldom been related to the host environment. In a factorial experiment, we exposed Northern leopard frog (Lithobates pipiens, formerly Rana pipiens) tadpoles to different concentrations of Ranavirus and investigated the effect of host density on certain life-history traits, namely survival, growth rate, developmental stage and number of days from virus exposure to death. Our results suggest a prominent role of density in driving the direction of the interaction between L. pipiens tadpoles and Ranavirus. We showed that increasing animal holding density is detrimental for host fitness as mortality rate is higher, day of death earlier, development longer and growth rate significantly lower in high-density tanks. We observed a linear increase of detrimental effects when Ranavirus doses increased in low-density conditions, with control tadpoles having a significantly higher overall relative fitness. However, this pattern was no longer observed in high-density conditions, where the effects of increasing Ranavirus dose were limited. Infected and control animals fitness were consequently similar. We speculate that the host may eventually diverts the energy required for a metabolic/immune response triggered by the infection (i.e., direct costs of the infection) to better cope with the increase in environmental "stress" associated with high density (i.e., indirect benefits of the infection). Our results illustrate how the net fitness of organisms may be shaped by ecological context and emphasize the necessity of examining the direct/indirect costs and benefits balance to fully understand host-pathogen interactions.
Collapse
Affiliation(s)
- Pierre Echaubard
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
| | - Kevin Little
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
| | - Bruce Pauli
- Environment Canada, Science and Technology Branch, National Wildlife Research Centre, Carleton University, Ottawa, Canada
| | - David Lesbarrères
- Genetics and Ecology of Amphibians Research Group (GEARG), Department of Biology, Laurentian University, Sudbury, Canada
| |
Collapse
|