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Davies K, Lenhart S, Day J, Lloyd AL, Lanzas C. Extensions of mean-field approximations for environmentally-transmitted pathogen networks. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2023; 20:1637-1673. [PMID: 36899502 DOI: 10.3934/mbe.2023075] [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] [Indexed: 06/18/2023]
Abstract
Many pathogens spread via environmental transmission, without requiring host-to-host direct contact. While models for environmental transmission exist, many are simply constructed intuitively with structures analogous to standard models for direct transmission. As model insights are generally sensitive to the underlying model assumptions, it is important that we are able understand the details and consequences of these assumptions. We construct a simple network model for an environmentally-transmitted pathogen and rigorously derive systems of ordinary differential equations (ODEs) based on different assumptions. We explore two key assumptions, namely homogeneity and independence, and demonstrate that relaxing these assumptions can lead to more accurate ODE approximations. We compare these ODE models to a stochastic implementation of the network model over a variety of parameters and network structures, demonstrating that with fewer restrictive assumptions we are able to achieve higher accuracy in our approximations and highlighting more precisely the errors produced by each assumption. We show that less restrictive assumptions lead to more complicated systems of ODEs and the potential for unstable solutions. Due to the rigour of our derivation, we are able to identify the reason behind these errors and propose potential resolutions.
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Affiliation(s)
- Kale Davies
- Department of Mathematics, University of Chicago, Chicago, IL, USA
- Department of Population Health and Pathobiology, North Carolina State University, Raleigh, NC, USA
| | - Suzanne Lenhart
- Department of Mathematics, University of Tennessee, Knoxville, TN, USA
| | - Judy Day
- Department of Mathematics, University of Tennessee, Knoxville, TN, USA
- Department of Electrical Engineering and Computer Science, University of Tennessee, Knoxville, TN, USA
| | - Alun L Lloyd
- Biomathematics Graduate Program and Department of Mathematics, North Carolina State University, Raleigh, NC, USA
| | - Cristina Lanzas
- Department of Population Health and Pathobiology, North Carolina State University, Raleigh, NC, USA
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2
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Wagner K, Pierce R, Gordon E, Hay A, Lessard A, Telling GC, Ballard JR, Moreno JA, Zabel MD. Tissue-specific biochemical differences between chronic wasting disease prions isolated from free-ranging white-tailed deer (Odocoileus virginianus). J Biol Chem 2022; 298:101834. [PMID: 35304100 PMCID: PMC9019250 DOI: 10.1016/j.jbc.2022.101834] [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: 12/12/2021] [Revised: 03/08/2022] [Accepted: 03/10/2022] [Indexed: 01/21/2023] Open
Abstract
Chronic wasting disease (CWD) is an invariably fatal prion disease affecting cervid species worldwide. Prions can manifest as distinct strains that can influence disease pathology and transmission. CWD is profoundly lymphotropic, and most infected cervids likely shed peripheral prions replicated in lymphoid organs. However, CWD is a neurodegenerative disease, and most research on prion strains has focused on neurogenic prions. Thus, a knowledge gap exists comparing neurogenic prions to lymphogenic prions. In this study, we compared prions from the obex and lymph nodes of naturally exposed white-tailed deer to identify potential biochemical strain differences. Here, we report biochemical evidence of strain differences between the brain and lymph node from these animals. Conformational stability assays, glycoform ratio analyses, and immunoreactivity scanning across the structured domain of the prion protein that refolds into the amyloid aggregate of the infectious prion reveal significantly more structural and glycoform variation in lymphogenic prions than neurogenic prions. Surprisingly, we observed greater biochemical differences among neurogenic prions than lymphogenic prions across individuals. We propose that the lymphoreticular system propagates a diverse array of prions from which the brain selects a more restricted pool of prions that may be quite different than those from another individual of the same species. Future work should examine the biological and zoonotic impact of these biochemical differences and examine more cervids from multiple locations to determine if these differences are conserved across species and locations.
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Affiliation(s)
- Kaitlyn Wagner
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Robyn Pierce
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Elizabeth Gordon
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Arielle Hay
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Avery Lessard
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Glenn C. Telling
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Jennifer R. Ballard
- Research Division, Arkansas Game and Fish Commission, Little Rock, Arkansas, USA
| | - Julie A. Moreno
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Environmental and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Mark D. Zabel
- Prion Research Center, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,Department of Microbiology, Immunology and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA,For correspondence: Mark D. Zabel
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3
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Pritzkow S, Gorski D, Ramirez F, Soto C. Prion Dissemination through the Environment and Medical Practices: Facts and Risks for Human Health. Clin Microbiol Rev 2021; 34:e0005919. [PMID: 34319151 PMCID: PMC8404694 DOI: 10.1128/cmr.00059-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Prion diseases are a group of fatal, infectious neurodegenerative disorders affecting various species of mammals, including humans. The infectious agent in these diseases, termed prion, is composed exclusively of a misfolded protein that can spread and multiply in the absence of genetic materials. In this article, we provide an overview of the mechanisms of prion replication, interindividual transmission, and dissemination in communities. In particular, we review the potential role of the natural environment in prion transmission, including the mechanisms and pathways for prion entry and accumulation in the environment as well as its roles in prion mutation, adaptation, evolution, and transmission. We also discuss the transmission of prion diseases through medical practices, scientific research, and use of biological products. Detailed knowledge of these aspects is crucial to limit the spreading of existing prion diseases as well as to prevent the emergence of new diseases with possible catastrophic consequences for public health.
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Affiliation(s)
- Sandra Pritzkow
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Damian Gorski
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Frank Ramirez
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, Texas, USA
| | - Claudio Soto
- Mitchell Center for Alzheimer’s Disease and Related Brain Disorders, Department of Neurology, University of Texas Medical School at Houston, Houston, Texas, USA
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Galloway NL, Monello RJ, Brimeyer D, Cole EK, Hobbs NT. Supporting adaptive management with ecological forecasting: chronic wasting disease in the Jackson Elk Herd. Ecosphere 2021. [DOI: 10.1002/ecs2.3776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Nathan L. Galloway
- Biological Resources Division National Park Service Fort Collins Colorado USA
| | - Ryan J. Monello
- Pacific Island Inventory and Monitoring Network National Park Service Hawai'i Volcanoes National Park Hawaii USA
| | - Doug Brimeyer
- Wyoming Game and Fish Department Jackson Wyoming USA
| | - Eric K. Cole
- National Elk Refuge US Fish and Wildlife Service Jackson Wyoming USA
| | - N. Thompson Hobbs
- Department of Ecosystem Science and Sustainability Natural Resource Ecology Laboratory Colorado State University Fort Collins Colorado USA
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5
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Alterations in gut microbiota linked to provenance, sex, and chronic wasting disease in white-tailed deer (Odocoileus virginianus). Sci Rep 2021; 11:13218. [PMID: 34168170 PMCID: PMC8225879 DOI: 10.1038/s41598-021-89896-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 05/04/2021] [Indexed: 01/04/2023] Open
Abstract
Chronic wasting disease (CWD) is a fatal, contagious, neurodegenerative prion disease affecting both free-ranging and captive cervid species. CWD is spread via direct or indirect contact or oral ingestion of prions. In the gastrointestinal tract, prions enter the body through microfold cells (M-cells), and the abundance of these cells can be influenced by the gut microbiota. To explore potential links between the gut microbiota and CWD, we collected fecal samples from farmed and free-ranging white-tailed deer (Odocoileus virginianus) around the Midwest, USA. Farmed deer originated from farms that were depopulated due to CWD. Free-ranging deer were sampled during annual deer harvests. All farmed deer were tested for CWD via ELISA and IHC, and we used 16S rRNA gene sequencing to characterize the gut microbiota. We report significant differences in gut microbiota by provenance (Farm 1, Farm 2, Free-ranging), sex, and CWD status. CWD-positive deer from Farm 1 and 2 had increased abundances of Akkermansia, Lachnospireacea UCG-010, and RF39 taxa. Overall, differences by provenance and sex appear to be driven by diet, while differences by CWD status may be linked to CWD pathogenesis.
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6
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Belsare AV, Millspaugh JJ, Mason JR, Sumners J, Viljugrein H, Mysterud A. Getting in Front of Chronic Wasting Disease: Model-Informed Proactive Approach for Managing an Emerging Wildlife Disease. Front Vet Sci 2021; 7:608235. [PMID: 33585599 PMCID: PMC7874108 DOI: 10.3389/fvets.2020.608235] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 12/07/2020] [Indexed: 11/23/2022] Open
Abstract
Continuing geographic spread of chronic wasting disease (CWD) poses a serious threat to the sustainable future of cervids and hunting in North America. Moreover, CWD has been detected in captive cervids in South Korea and, in recent years, in free-ranging reindeer in Europe (Norway). Management of this disease is limited by logistical, financial, and sociopolitical considerations, and current strategies primarily focus on reducing host densities through hunter harvest and targeted culling. The success of such strategies in mitigating the spread and prevalence of CWD only upon detection is questionable. Here, we propose a proactive approach that emphasizes pre-emptive management through purposeful integration of virtual experiments (simulating alternate interventions as model scenarios) with the aim of evaluating their effectiveness. Here, we have used a published agent-based model that links white-tailed deer demography and behavior with CWD transmission dynamics to first derive a CWD outbreak trajectory and then use the trajectory to highlight issues associated with different phases of the CWD outbreak (pre-establishment/transition/endemic). Specifically, we highlight the practical constraints on surveillance in the pre-establishment phase and recommend that agencies use a realistic detection threshold for their CWD surveillance programs. We further demonstrate that many disease introductions are "dead ends" not leading to a full epidemic due to high stochasticity and harvesting in the pre-establishment phase of CWD. Model evaluated pre-emptive (pre-detection) harvest strategies could increase the resilience of the deer population to CWD spread and establishment. We conclude it is important to adaptively position CWD management ahead of, rather than behind, the CWD front.
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Affiliation(s)
- Aniruddha V. Belsare
- Department of Fisheries and Wildlife, Boone and Crockett Quantitative Wildlife Center, Michigan State University, East Lansing, MI, United States
| | - Joshua J. Millspaugh
- W.A. Franke College of Forestry and Conservation, Wildlife Biology Program, University of Montana, Missoula, MT, United States
| | - J. R. Mason
- Michigan Department of Natural Resources Executive in Residence, College of Agriculture and Natural Resources, Michigan State University, East Lansing, MI, United States
| | - Jason Sumners
- Missouri Department of Conservation, Columbia, MO, United States
| | | | - Atle Mysterud
- Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, Oslo, Norway
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7
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Barbera E. Mathematical models for diseases in wildlife populations with indirect transmission. INT J BIOMATH 2020. [DOI: 10.1142/s1793524520500424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this paper, five different models for five different kinds of diseases occurring in wildlife populations are introduced. In all models, a logistic growth term is taken into account and the disease is transmitted to the susceptible population indirectly through an environment reservoir. The time evolution of these diseases is described together with its spatial propagation. The character of spatial homogeneous equilibria against the uniform and non-uniform perturbations together with the occurrence of Hopf bifurcations are discussed through a linear stability analysis. No Turing instability is observed. The partial differential field equations are also integrated numerically to validate the stability results herein obtained and to extract additional information on the temporal and spatial behavior of the different diseases.
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Affiliation(s)
- Elvira Barbera
- Department of Mathematical, Computer, Physical and Earth Sciences, University of Messina, V.le F. D’Alcontres 31, 98166 Messina, Italy
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8
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Mawdsley JR. Phylogenetic Patterns Suggest Broad Susceptibility to Chronic Wasting Disease Across Cervidae. WILDLIFE SOC B 2020. [DOI: 10.1002/wsb.1059] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Jonathan R. Mawdsley
- Association of Fish and Wildlife Agencies 1100 First Street NE Washington D.C. 20002 USA
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9
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Glatzel M, Sigurdson CJ. Recent advances on the molecular pathogenesis of prion diseases. Brain Pathol 2019; 29:245-247. [PMID: 30588674 DOI: 10.1111/bpa.12693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 12/01/2022] Open
Affiliation(s)
- Markus Glatzel
- Institute of Neuropathology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
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10
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Assessing the role of dens in the spread, establishment and persistence of sarcoptic mange in an endangered canid. Epidemics 2019; 27:28-40. [DOI: 10.1016/j.epidem.2019.01.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Revised: 01/03/2019] [Accepted: 01/07/2019] [Indexed: 11/21/2022] Open
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11
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Mysterud A, Edmunds DR. A review of chronic wasting disease in North America with implications for Europe. EUR J WILDLIFE RES 2019. [DOI: 10.1007/s10344-019-1260-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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12
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Huyvaert KP, Russell RE, Patyk KA, Craft ME, Cross PC, Garner MG, Martin MK, Nol P, Walsh DP. Challenges and Opportunities Developing Mathematical Models of Shared Pathogens of Domestic and Wild Animals. Vet Sci 2018; 5:E92. [PMID: 30380736 PMCID: PMC6313884 DOI: 10.3390/vetsci5040092] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/04/2018] [Accepted: 10/18/2018] [Indexed: 01/19/2023] Open
Abstract
Diseases that affect both wild and domestic animals can be particularly difficult to prevent, predict, mitigate, and control. Such multi-host diseases can have devastating economic impacts on domestic animal producers and can present significant challenges to wildlife populations, particularly for populations of conservation concern. Few mathematical models exist that capture the complexities of these multi-host pathogens, yet the development of such models would allow us to estimate and compare the potential effectiveness of management actions for mitigating or suppressing disease in wildlife and/or livestock host populations. We conducted a workshop in March 2014 to identify the challenges associated with developing models of pathogen transmission across the wildlife-livestock interface. The development of mathematical models of pathogen transmission at this interface is hampered by the difficulties associated with describing the host-pathogen systems, including: (1) the identity of wildlife hosts, their distributions, and movement patterns; (2) the pathogen transmission pathways between wildlife and domestic animals; (3) the effects of the disease and concomitant mitigation efforts on wild and domestic animal populations; and (4) barriers to communication between sectors. To promote the development of mathematical models of transmission at this interface, we recommend further integration of modern quantitative techniques and improvement of communication among wildlife biologists, mathematical modelers, veterinary medicine professionals, producers, and other stakeholders concerned with the consequences of pathogen transmission at this important, yet poorly understood, interface.
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Affiliation(s)
- Kathryn P Huyvaert
- Department of Fish, Wildlife, and Conservation Biology, Colorado State University, Fort Collins, CO 80523, USA.
| | - Robin E Russell
- U.S. Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA.
| | - Kelly A Patyk
- Center for Epidemiology and Animal Health, United States Department of Agriculture, Animal and Plant Health Inspection Service, Fort Collins, CO 80526, USA.
| | - Meggan E Craft
- Department of Veterinary Population Medicine, University of Minnesota, St. Paul, MN 55108, USA.
| | - Paul C Cross
- U.S. Geological Survey, Northern Rocky Mountain Science Center, Bozeman, MT 59715, USA.
| | - M Graeme Garner
- European Commission for the Control of Foot-and-Mouth Disease-Food and Agriculture Organization of the United Nations, 00153 Roma RM, Italy.
| | - Michael K Martin
- Livestock Poultry Health Division, Clemson University, Columbia, SC 29224, USA.
| | - Pauline Nol
- Center for Epidemiology and Animal Health, United States Department of Agriculture, Animal and Plant Health Inspection Service, Fort Collins, CO 80526, USA.
| | - Daniel P Walsh
- U.S. Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA.
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13
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A penalized simulated maximum likelihood method to estimate parameters for SDEs with measurement error. Comput Stat 2018. [DOI: 10.1007/s00180-018-0846-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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14
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Schuler KL, Jenks JA, Klaver RW, Jennelle CS, Bowyer RT. Chronic wasting disease detection and mortality sources in semi-protected deer population. WILDLIFE BIOLOGY 2018. [DOI: 10.2981/wlb.00437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- Krysten L. Schuler
- K. L. Schuler , J. A. Jenks, Dept of Wildlife and Fisheries Sciences, South Dakot
| | - Jonathan A. Jenks
- K. L. Schuler , J. A. Jenks, Dept of Wildlife and Fisheries Sciences, South Dakot
| | - Robert W. Klaver
- R. W. Klaver, US Geological Survey, Iowa Cooperative Fish and Wildlife Unit, Iowa State Univ., Ames,
| | | | - R. Terry Bowyer
- R. T. Bowyer, Dept of Biological Sciences, Idaho State Univ., Pocatello, ID, USA
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15
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CATTLE ( BOS TAURUS) RESIST CHRONIC WASTING DISEASE FOLLOWING ORAL INOCULATION CHALLENGE OR TEN YEARS' NATURAL EXPOSURE IN CONTAMINATED ENVIRONMENTS. J Wildl Dis 2018; 54:460-470. [PMID: 29715064 DOI: 10.7589/2017-12-299] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We conducted a 10-yr study to establish whether chronic wasting disease (CWD) was readily transmissible to domestic cattle ( Bos taurus) following oral inoculation or by cohousing cattle with captive cervids in outdoor research facilities where CWD was enzootic. Calves ( n=12) were challenged orally on one occasion using brain homogenate derived from CWD-infected mule deer ( Odocoileus hemionus). Five uninoculated cattle served as unchallenged controls. Two other groups of cattle ( n=10-11/group) were housed outdoors for 10 yr in captive cervid research facilities. The environmentally challenged cattle were exposed to CWD-associated prions through common paddocks, feed, and water and via direct daily contact with known and potentially infected mule deer or wapiti ( Cervus canadensis) throughout the decade-long study period. None of the exposed cattle developed neurologic disease during the study. We euthanized cattle surviving to 10 yr postchallenge and examined all for lesions or disease-associated prion protein (PrPd) by histopathology, immunohistochemistry, and western immunoblot analysis of central nervous system and lymphoid tissue. None had evidence of PrPd accumulation. We conclude that the risks of CWD transmission to cattle following oral inoculation or after prolonged exposure to contaminated environments are low.
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16
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Maji C, Mukherjee D, Kesh D. Deterministic and stochastic analysis of an eco-epidemiological model. J Biol Phys 2018; 44:17-36. [PMID: 28988403 PMCID: PMC5834997 DOI: 10.1007/s10867-017-9472-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 09/20/2017] [Indexed: 10/18/2022] Open
Abstract
Chronic wasting disease (CWD) is a contagious prion disease among the deer family that has the potential to disrupt the ecosystems where deer occur in abundance. To understand the dynamics of this emerging infectious disease, we consider a simple eco-epidemic model where the host population is infected by CWD. Boundedness of the system is established. The structure of equilibria and their linearized stability are investigated. The persistence condition is discussed. By constructing a suitable Lyapunov function, we discuss the global stability of the endemic equilibrium. Local bifurcation (transcritical) around the boundary equilibria is developed. Sufficient conditions for the existence of Hopf-bifurcation are derived. Further, we have also introduced white type of noise into the system to investigate stochastic stability. This suggests that the deterministic model is robust with respect to stochastic perturbation. Some numerical simulations are performed to validate our results.
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Affiliation(s)
- Chandan Maji
- Department of Mathematics, Vivekananda College, Thakurpukur, 269 D.H. Road, Kolkata, 700063 India
| | - Debasis Mukherjee
- Department of Mathematics, Vivekananda College, Thakurpukur, 269 D.H. Road, Kolkata, 700063 India
| | - Dipak Kesh
- Centre for Mathematical Biology and Ecology, Department of Mathematics, Jadavpur University, Kolkata, 700032 India
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17
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Affiliation(s)
- Mevin B. Hooten
- U.S. Geological Survey, Colorado Cooperative Fish and Wildlife Research Unit, Department of Fish, Wildlife, and Conservation Biology, Department of Statistics, Colorado State University, Fort Collins, CO
| | - Devin S. Johnson
- Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, Seattle, WA
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18
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Abstract
Chronic wasting disease (CWD) affects cervids and is the only known prion disease readily transmitted among free-ranging wild animal populations in nature. The increasing spread and prevalence of CWD among cervid populations threaten the survival of deer and elk herds in North America, and potentially beyond. This review focuses on prion ecology, specifically that of CWD, and the current understanding of the role that the environment may play in disease propagation. We recount the discovery of CWD, discuss the role of the environment in indirect CWD transmission, and consider potentially relevant environmental reservoirs and vectors. We conclude by discussing how understanding the environmental persistence of CWD lends insight into transmission dynamics and potential management and mitigation strategies.
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19
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Mejía-Salazar MF, Goldizen AW, Menz CS, Dwyer RG, Blomberg SP, Waldner CL, Cullingham CI, Bollinger TK. Mule deer spatial association patterns and potential implications for transmission of an epizootic disease. PLoS One 2017; 12:e0175385. [PMID: 28388681 PMCID: PMC5384682 DOI: 10.1371/journal.pone.0175385] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 03/24/2017] [Indexed: 12/04/2022] Open
Abstract
Animal social behaviour can have important effects on the long-term dynamics of diseases. In particular, preferential spatial relationships between individuals can lead to differences in the rates of disease spread within a population. We examined the concurrent influence of genetic relatedness, sex, age, home range overlap, time of year, and prion disease status on proximal associations of adult Rocky Mountain mule deer (Odocoileus hemionus hemionus) in a chronic wasting disease endemic area. We also quantified the temporal stability of these associations across different sex, age, and disease status classes. We used three years of high frequency telemetry data from 74 individuals to record encounters within 25 m of each other, and to calculate seasonal home range overlap measured by volume of intersection (VI). The strength of pairwise spatial association between adult mule deer was independent of genetic relatedness, age and disease status. Seasonal variation in association strength was not consistent across years, perhaps due to annual changes in weather conditions. The influence of home range overlap on association strength varied seasonally, whereby associations were stronger in pre-rut and fawning than in the rest of the seasons. The sexes of individuals also interacted with both VI and season. At increasing levels of VI, associations were stronger between females than between males and between females and males. The strongest associations in pre-rut were between males, while the strongest in rut were between females and males. The temporal stability of associations was markedly dependant on the sex and the diagnosis of the associating pair. Our findings highlight the importance of considering concurrent effects of biological and environmental factors when seeking to understand the role of social preference in behavioural ecology and disease spread. Applying this knowledge in epidemiological modelling will shed light on the dynamics of disease transmission among mule deer.
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Affiliation(s)
| | - Anne W. Goldizen
- School of Biological Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Clementine S. Menz
- School of Biological Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Ross G. Dwyer
- School of Biological Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Simon P. Blomberg
- School of Biological Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Cheryl L. Waldner
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | | | - Trent K. Bollinger
- Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Canadian Wildlife Health Cooperative (CWHC), Saskatoon, Saskatchewan, Canada
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20
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Samuel MD, Storm DJ. Chronic wasting disease in white-tailed deer: infection, mortality, and implications for heterogeneous transmission. Ecology 2016; 97:3195-3205. [PMID: 27870037 DOI: 10.1002/ecy.1538] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 06/29/2016] [Accepted: 07/05/2016] [Indexed: 11/08/2022]
Abstract
Chronic wasting disease (CWD) is a fatal neurodegenerative disease affecting free-ranging and captive cervids that now occurs in 24 U.S. states and two Canadian provinces. Despite the potential threat of CWD to deer populations, little is known about the rates of infection and mortality caused by this disease. We used epidemiological models to estimate the force of infection and disease-associated mortality for white-tailed deer in the Wisconsin and Illinois CWD outbreaks. Models were based on age-prevalence data corrected for bias in aging deer using the tooth wear and replacement method. Both male and female deer in the Illinois outbreak had higher corrected age-specific prevalence with slightly higher female infection than deer in the Wisconsin outbreak. Corrected ages produced more complex models with different infection and mortality parameters than those based on apparent prevalence. We found that adult male deer have a more than threefold higher risk of CWD infection than female deer. Males also had higher disease mortality than female deer. As a result, CWD prevalence was twofold higher in adult males than females. We also evaluated the potential impacts of alternative contact structures on transmission dynamics in Wisconsin deer. Results suggested that transmission of CWD among male deer during the nonbreeding season may be a potential mechanism for producing higher rates of infection and prevalence characteristically found in males. However, alternatives based on high environmental transmission and transmission from females to males during the breeding season may also play a role.
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Affiliation(s)
- Michael D Samuel
- U.S. Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin , Madison, Wisconsin, 53706, USA
| | - Daniel J Storm
- Department of Forest and Wildlife Ecology, University of Wisconsin , Madison, Wisconsin, 53706, USA.,Wisconsin Department of Natural Resources, Rhinelander, Wisconsin, 54501, USA
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Uehlinger FD, Johnston AC, Bollinger TK, Waldner CL. Systematic review of management strategies to control chronic wasting disease in wild deer populations in North America. BMC Vet Res 2016; 12:173. [PMID: 27549119 PMCID: PMC4994292 DOI: 10.1186/s12917-016-0804-7] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 08/18/2016] [Indexed: 01/01/2023] Open
Abstract
Background Chronic wasting disease (CWD) is a contagious, fatal prion disease affecting cervids in a growing number of regions across North America. Projected deer population declines and concern about potential spread of CWD to other species warrant strategies to manage this disease. Control efforts to date have been largely unsuccessful, resulting in continuing spread and increasing prevalence. This systematic review summarizes peer-reviewed published reports describing field-applicable CWD control strategies in wild deer populations in North America using systematic review methods. Ten databases were searched for peer-reviewed literature. Following deduplication, relevance screening, full-text appraisal, subject matter expert review and qualitative data extraction, nine references were included describing four distinct management strategies. Results Six of the nine studies used predictive modeling to evaluate control strategies. All six demonstrated one or more interventions to be effective but results were dependant on parameters and assumptions used in the model. Three found preferential removal of CWD infected deer to be effective in reducing CWD prevalence; one model evaluated a test and slaughter strategy, the other selective removal of infected deer by predators and the third evaluated increased harvest of the sex with highest prevalence (males). Three models evaluated non-selective harvest of deer. There were only three reports that examined primary data collected as part of observational studies. Two of these studies supported the effectiveness of intensive non-selective culling; the third study did not find a difference between areas that were subjected to culling and those that were not. Seven of the nine studies were conducted in the United States. Conclusions This review highlights the paucity of evaluated, field-applicable control strategies for CWD in wild deer populations. Knowledge gaps in the complex epidemiology of CWD and the intricacies inherent to prion diseases currently pose significant challenges to effective control of this disease in wild deer in North America. Electronic supplementary material The online version of this article (doi:10.1186/s12917-016-0804-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- F D Uehlinger
- Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, S7N 5B4, Canada.
| | - A C Johnston
- Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, S7N 5B4, Canada
| | - T K Bollinger
- Canadian Wildlife Health Cooperative, Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, S7N 5B4, Canada
| | - C L Waldner
- Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, S7N 5B4, Canada
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Abstract
Infectious disease dynamics are determined, to a great extent, by the social structure of the host. We evaluated sociality, or the tendency to form groups, in Rocky Mountain mule deer (Odocoileus hemionus hemionus) from a chronic wasting disease (CWD) endemic area in Saskatchewan, Canada, to better understand factors that may affect disease transmission. Using group size data collected on 365 radio-collared mule deer (2008–2013), we built a generalized linear mixed model (GLMM) to evaluate whether factors such as CWD status, season, habitat and time of day, predicted group occurrence. Then, we built another GLMM to determine factors associated with group size. Finally, we used 3 measures of group size (typical, mean and median group sizes) to quantify levels of sociality. We found that mule deer showing clinical signs of CWD were less likely to be reported in groups than clinically healthy deer after accounting for time of day, habitat, and month of observation. Mule deer groups were much more likely to occur in February and March than in July. Mixed-sex groups in early gestation were larger than any other group type in any season. Groups were largest and most likely to occur at dawn and dusk, and in open habitats, such as cropland. We discuss the implication of these results with respect to sociobiology and CWD transmission dynamics.
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23
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Potapov A, Merrill E, Pybus M, Lewis MA. Chronic Wasting Disease: Transmission Mechanisms and the Possibility of Harvest Management. PLoS One 2016; 11:e0151039. [PMID: 26963921 PMCID: PMC4786122 DOI: 10.1371/journal.pone.0151039] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Accepted: 02/23/2016] [Indexed: 01/30/2023] Open
Abstract
We develop a model of CWD management by nonselective deer harvest, currently the most feasible approach available for managing CWD in wild populations. We use the model to explore the effects of 6 common harvest strategies on disease prevalence and to identify potential optimal harvest policies for reducing disease prevalence without population collapse. The model includes 4 deer categories (juveniles, adult females, younger adult males, older adult males) that may be harvested at different rates, a food-based carrying capacity, which influences juvenile survival but not adult reproduction or survival, and seasonal force of infection terms for each deer category under differing frequency-dependent transmission dynamics resulting from environmental and direct contact mechanisms. Numerical experiments show that the interval of transmission coefficients β where the disease can be controlled is generally narrow and efficiency of a harvest policy to reduce disease prevalence depends crucially on the details of the disease transmission mechanism, in particular on the intensity of disease transmission to juveniles and the potential differences in the behavior of older and younger males that influence contact rates. Optimal harvest policy to minimize disease prevalence for each of the assumed transmission mechanisms is shown to depend on harvest intensity. Across mechanisms, a harvest that focuses on antlered deer, without distinguishing between age classes reduces disease prevalence most consistently, whereas distinguishing between young and older antlered deer produces higher uncertainty in the harvest effects on disease prevalence. Our results show that, despite uncertainties, a modelling approach can determine classes of harvest strategy that are most likely to be effective in combatting CWD.
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Affiliation(s)
- Alex Potapov
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Centre for Mathematical Biology, University of Alberta, Edmonton, Alberta, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
- * E-mail:
| | - Evelyn Merrill
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Margo Pybus
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Alberta Sustainable Resource Development, Edmonton, Alberta, Canada
| | - Mark A. Lewis
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
- Centre for Mathematical Biology, University of Alberta, Edmonton, Alberta, Canada
- Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
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Leach CB, Webb CT, Cross PC. When environmentally persistent pathogens transform good habitat into ecological traps. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160051. [PMID: 27069672 PMCID: PMC4821283 DOI: 10.1098/rsos.160051] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Accepted: 02/19/2016] [Indexed: 06/05/2023]
Abstract
Habitat quality plays an important role in the dynamics and stability of wildlife metapopulations. However, the benefits of high-quality habitat may be modulated by the presence of an environmentally persistent pathogen. In some cases, the presence of environmental pathogen reservoirs on high-quality habitat may lead to the creation of ecological traps, wherein host individuals preferentially colonize high-quality habitat, but are then exposed to increased infection risk and disease-induced mortality. We explored this possibility through the development of a stochastic patch occupancy model, where we varied the pathogen's virulence, transmission rate and environmental persistence as well as the distribution of habitat quality in the host metapopulation. This model suggests that for pathogens with intermediate levels of spread, high-quality habitat can serve as an ecological trap, and can be detrimental to host persistence relative to low-quality habitat. This inversion of the relative roles of high- and low-quality habitat highlights the importance of considering the interaction between spatial structure and pathogen transmission when managing wildlife populations exposed to an environmentally persistent pathogen.
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Affiliation(s)
- Clinton B. Leach
- Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | - Colleen T. Webb
- Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA
| | - Paul C. Cross
- US Geological Survey, Northern Rocky Mountain Science Center, Bozeman, MT, USA
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25
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Environmentally transmitted parasites: Host-jumping in a heterogeneous environment. J Theor Biol 2016; 397:33-42. [PMID: 26921466 DOI: 10.1016/j.jtbi.2016.02.025] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Revised: 01/14/2016] [Accepted: 02/17/2016] [Indexed: 01/17/2023]
Abstract
Groups of chronically infected reservoir-hosts contaminate resource patches by shedding a parasite׳s free-living stage. Novel-host groups visit the same patches, where they are exposed to infection. We treat arrival at patches, levels of parasite deposition, and infection of the novel host as stochastic processes, and derive the expected time elapsing until a host-jump (initial infection of a novel host) occurs. At stationarity, mean parasite densities are independent of reservoir-host group size. But within-patch parasite-density variances increase with reservoir group size. The probability of infecting a novel host declines with parasite-density variance; consequently larger reservoir groups extend the mean waiting time for host-jumping. Larger novel-host groups increase the probability of a host-jump during any single patch visit, but also reduce the total number of visits per unit time. Interaction of these effects implies that the waiting time for the first infection increases with the novel-host group size. If the reservoir-host uses resource patches in any non-uniform manner, reduced spatial overlap between host species increases the waiting time for host-jumping.
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26
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Al-Arydah M, Croteau MC, Oraby T, Smith RJ, Krewski D. Applications of mathematical modeling in managing the spread of chronic wasting disease (CWD) in wild deer under alternative harvesting scenarios. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2016; 79:690-699. [PMID: 27556563 DOI: 10.1080/15287394.2016.1174001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The application of a recently developed mathematical model for predicting the spread of chronic wasting disease (CWD) in wild deer was assessed under different scenarios where harvesting is employed in disease management. A process-based mathematical model for CWD transmission in wild deer populations was recently developed and parameterized by Al-arydah et al. (2011) to provide a scientific basis for understanding the factors that affect spread of CWD and evaluate concomitant disease-control strategies. The impact of gender on CWD transmission was shown to have a significant influence on the spread of the disease in the wild. Our model demonstrates a range of harvesting rates in which CWD is controlled and deer populations survive. However, if harvesting rates are too low, the disease remains endemic for decades. Conversely, the Canadian deer population is eradicated if harvesting rates are excessive. Future investigation includes building the model to assess the spread of CWD under different disease-management scenarios.
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Affiliation(s)
- M Al-Arydah
- a Masdar Institute of Science and Technology , Abu Dhabi , UAE
| | - M C Croteau
- b McLaughlin Centre for Population Health Risk Assessment , University of Ottawa , Ottawa , Ontario , Canada
| | - T Oraby
- c School of Mathematical and Statistical Sciences , University of Texas Rio Grande Valley , Edinburg , Texas , USA
| | - R J Smith
- d Department of Mathematics and Faculty of Medicine , University of Ottawa , Ottawa , Ontario , Canada
| | - D Krewski
- b McLaughlin Centre for Population Health Risk Assessment , University of Ottawa , Ottawa , Ontario , Canada
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27
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Drovandi CC, McCutchan RA. Alive SMC2: Bayesian model selection for low-count time series models with intractable likelihoods. Biometrics 2015; 72:344-53. [DOI: 10.1111/biom.12449] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Revised: 10/01/2015] [Accepted: 10/01/2015] [Indexed: 11/27/2022]
Affiliation(s)
- Christopher C. Drovandi
- Mathematical Sciences School; Queensland University of Technology; Brisbane, Queensland Australia
| | - Roy A. McCutchan
- Mathematical Sciences School; Queensland University of Technology; Brisbane, Queensland Australia
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28
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Hobbs NT, Geremia C, Treanor J, Wallen R, White PJ, Hooten MB, Rhyan JC. State-space modeling to support management of brucellosis in the Yellowstone bison population. ECOL MONOGR 2015. [DOI: 10.1890/14-1413.1] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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29
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Geremia C, Miller MW, Hoeting JA, Antolin MF, Hobbs NT. Bayesian Modeling of Prion Disease Dynamics in Mule Deer Using Population Monitoring and Capture-Recapture Data. PLoS One 2015; 10:e0140687. [PMID: 26509806 PMCID: PMC4624844 DOI: 10.1371/journal.pone.0140687] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 09/28/2015] [Indexed: 12/30/2022] Open
Abstract
Epidemics of chronic wasting disease (CWD) of North American Cervidae have potential to harm ecosystems and economies. We studied a migratory population of mule deer (Odocoileus hemionus) affected by CWD for at least three decades using a Bayesian framework to integrate matrix population and disease models with long-term monitoring data and detailed process-level studies. We hypothesized CWD prevalence would be stable or increase between two observation periods during the late 1990s and after 2010, with higher CWD prevalence making deer population decline more likely. The weight of evidence suggested a reduction in the CWD outbreak over time, perhaps in response to intervening harvest-mediated population reductions. Disease effects on deer population growth under current conditions were subtle with a 72% chance that CWD depressed population growth. With CWD, we forecasted a growth rate near one and largely stable deer population. Disease effects appear to be moderated by timing of infection, prolonged disease course, and locally variable infection. Long-term outcomes will depend heavily on whether current conditions hold and high prevalence remains a localized phenomenon.
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Affiliation(s)
- Chris Geremia
- Natural Resource Ecology Laboratory, Department of Ecosystem Science and Sustainability and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, United States of America
| | - Michael W. Miller
- Wildlife Health Program, Colorado Division of Parks and Wildlife, Fort Collins, Colorado, Colorado, United States of America
| | - Jennifer A. Hoeting
- Department of Statistics, Colorado State University, Fort Collins, Colorado, United States of America
| | - Michael F. Antolin
- Department of Biology, Colorado State University, Fort Collins, Colorado, United States of America
| | - N. Thompson Hobbs
- Natural Resource Ecology Laboratory, Department of Ecosystem Science and Sustainability and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, Colorado, United States of America
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30
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Devenish-Nelson ES, Richards SA, Harris S, Soulsbury C, Stephens PA. Demonstrating frequency-dependent transmission of sarcoptic mange in red foxes. Biol Lett 2015; 10:20140524. [PMID: 25296930 DOI: 10.1098/rsbl.2014.0524] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Understanding the relationship between disease transmission and host density is essential for predicting disease spread and control. Using long-term data on sarcoptic mange in a red fox Vulpes vulpes population, we tested long-held assumptions of density- and frequency-dependent direct disease transmission. We also assessed the role of indirect transmission. Contrary to assumptions typical of epidemiological models, mange dynamics are better explained by frequency-dependent disease transmission than by density-dependent transmission in this canid. We found no support for indirect transmission. We present the first estimates of R0 and age-specific transmission coefficients for mange in foxes. These parameters are important for managing this poorly understood but highly contagious and economically damaging disease.
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Affiliation(s)
| | - Shane A Richards
- School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK
| | - Stephen Harris
- School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
| | - Carl Soulsbury
- School of Life Sciences, University of Lincoln, Lincoln, LN6 7TS, UK
| | - Philip A Stephens
- School of Biological and Biomedical Sciences, Durham University, Durham, DH1 3LE, UK
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31
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Sun L, Lee C, Hoeting JA. A penalized simulated maximum likelihood approach in parameter estimation for stochastic differential equations. Comput Stat Data Anal 2015. [DOI: 10.1016/j.csda.2014.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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32
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Schauber EM, Nielsen CK, Kjær LJ, Anderson CW, Storm DJ. Social affiliation and contact patterns among white-tailed deer in disparate landscapes: implications for disease transmission. J Mammal 2015; 96:16-28. [PMID: 26937044 PMCID: PMC4668922 DOI: 10.1093/jmammal/gyu027] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In social species, individuals contact members of the same group much more often than those of other groups, particularly for contacts that could directly transmit disease agents. This disparity in contact rates violates the assumptions of simple disease models, hinders disease spread between groups, and could decouple disease transmission from population density. Social behavior of white-tailed deer has important implications for the long-term dynamics and impact of diseases such as bovine tuberculosis and chronic wasting disease (CWD), so expanding our understanding of their social system is important. White-tailed deer form matrilineal groups, which inhabit stable home ranges that overlap somewhat with others-a pattern intermediate between mass-action and strict territoriality. To quantify how group membership affects their contact rates and document the spectrum of social affiliation, we analyzed location data from global positioning system (GPS) collars on female and juvenile white-tailed deer in 2 study areas: near Carbondale in forest-dominated southern Illinois (2002-2006) and near Lake Shelbyville in agriculture-dominated central Illinois (2006-2009). For each deer dyad (i.e., 2 individual deer with sufficient overlapping GPS data), we measured space-use overlap, correlation of movements, direct contact rate (simultaneous GPS locations < 10 m apart), and indirect contact rate (GPS locations < 10 m apart when offset by 1 or 3 days). Direct contact rates were substantially higher for within-group dyads than between-group dyads, but group membership had little apparent effect on indirect contact rates. The group membership effect on direct contact rates was strongest in winter and weakest in summer, with no apparent difference between study areas. Social affiliations were not dichotomous, with some deer dyads showing loose but positive affiliation. Even for obvious within-group dyads, their strength of affiliation fluctuated between years, seasons, and even days. Our findings highlight the poor fit between deer behavior and simple models of disease transmission and, combined with previous infection data, suggest that direct contact is the primary driver of CWD transmission among free-living female and juvenile white-tailed deer.
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Affiliation(s)
| | - Clayton K. Nielsen
- Cooperative Wildlife Research Laboratory, Southern Illinois University(Mail Code 6504), Carbondale, IL 62901, USA(EMS, CKN, LJK, CWA, DJS)
- Department of Zoology, Southern Illinois University(Mail Code 6501), Carbondale, IL 62901, USA(EMS, LJK, CWA, DJS)
- Department of Forestry, Southern Illinois University(Mail Code 4411), Carbondale, IL 62901, USA(CKN)
- Center for Ecology, Southern Illinois University(Mail Code 317), Carbondale, IL62901, USA(EMS, CKN)
| | - Lene J. Kjær
- Cooperative Wildlife Research Laboratory, Southern Illinois University(Mail Code 6504), Carbondale, IL 62901, USA(EMS, CKN, LJK, CWA, DJS)
- Department of Zoology, Southern Illinois University(Mail Code 6501), Carbondale, IL 62901, USA(EMS, LJK, CWA, DJS)
- Department of Forestry, Southern Illinois University(Mail Code 4411), Carbondale, IL 62901, USA(CKN)
- Center for Ecology, Southern Illinois University(Mail Code 317), Carbondale, IL62901, USA(EMS, CKN)
| | - Charles W. Anderson
- Cooperative Wildlife Research Laboratory, Southern Illinois University(Mail Code 6504), Carbondale, IL 62901, USA(EMS, CKN, LJK, CWA, DJS)
- Department of Zoology, Southern Illinois University(Mail Code 6501), Carbondale, IL 62901, USA(EMS, LJK, CWA, DJS)
- Department of Forestry, Southern Illinois University(Mail Code 4411), Carbondale, IL 62901, USA(CKN)
- Center for Ecology, Southern Illinois University(Mail Code 317), Carbondale, IL62901, USA(EMS, CKN)
| | - Daniel J. Storm
- Cooperative Wildlife Research Laboratory, Southern Illinois University(Mail Code 6504), Carbondale, IL 62901, USA(EMS, CKN, LJK, CWA, DJS)
- Department of Zoology, Southern Illinois University(Mail Code 6501), Carbondale, IL 62901, USA(EMS, LJK, CWA, DJS)
- Department of Forestry, Southern Illinois University(Mail Code 4411), Carbondale, IL 62901, USA(CKN)
- Center for Ecology, Southern Illinois University(Mail Code 317), Carbondale, IL62901, USA(EMS, CKN)
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Milner JM, Van Beest FM, Schmidt KT, Brook RK, Storaas T. To feed or not to feed? Evidence of the intended and unintended effects of feeding wild ungulates. J Wildl Manage 2014. [DOI: 10.1002/jwmg.798] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jos M. Milner
- Department of Forestry and Wildlife Management; Hedmark University College; Campus Evenstad NO-2480 Koppang Norway
- School of Biological Sciences; University of Aberdeen; Tillydrone Avenue Aberdeen AB24 2TZ UK
| | - Floris M. Van Beest
- Department of Bioscience; Aarhus University; Frederiksborgvej 399 Roskilde 4000 Denmark
| | | | - Ryan K. Brook
- Department of Animal and Poultry Science & Indigenous Land Management Institute; College of Agriculture and Bioresources; University of Saskatchewan; 51 Campus Drive Saskatoon SK S7N 5E2 Canada
| | - Torstein Storaas
- Department of Forestry and Wildlife Management; Hedmark University College; Campus Evenstad NO-2480 Koppang Norway
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34
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Williams AL, Kreeger TJ, Schumaker BA. Chronic wasting disease model of genetic selection favoring prolonged survival in Rocky Mountain elk (Cervus elaphus). Ecosphere 2014. [DOI: 10.1890/es14-00013.1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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35
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Jennelle CS, Henaux V, Wasserberg G, Thiagarajan B, Rolley RE, Samuel MD. Transmission of chronic wasting disease in Wisconsin white-tailed deer: implications for disease spread and management. PLoS One 2014; 9:e91043. [PMID: 24658535 PMCID: PMC3962341 DOI: 10.1371/journal.pone.0091043] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Accepted: 02/07/2014] [Indexed: 11/27/2022] Open
Abstract
Few studies have evaluated the rate of infection or mode of transmission for wildlife diseases, and the implications of alternative management strategies. We used hunter harvest data from 2002 to 2013 to investigate chronic wasting disease (CWD) infection rate and transmission modes, and address how alternative management approaches affect disease dynamics in a Wisconsin white-tailed deer population. Uncertainty regarding demographic impacts of CWD on cervid populations, human and domestic animal health concerns, and potential economic consequences underscore the need for strategies to control CWD distribution and prevalence. Using maximum-likelihood methods to evaluate alternative multi-state deterministic models of CWD transmission, harvest data strongly supports a frequency-dependent transmission structure with sex-specific infection rates that are two times higher in males than females. As transmissible spongiform encephalopathies are an important and difficult-to-study class of diseases with major economic and ecological implications, our work supports the hypothesis of frequency-dependent transmission in wild deer at a broad spatial scale and indicates that effective harvest management can be implemented to control CWD prevalence. Specifically, we show that harvest focused on the greater-affected sex (males) can result in stable population dynamics and control of CWD within the next 50 years, given the constraints of the model. We also provide a quantitative estimate of geographic disease spread in southern Wisconsin, validating qualitative assessments that CWD spreads relatively slowly. Given increased discovery and distribution of CWD throughout North America, insights from our study are valuable to management agencies and to the general public concerned about the impacts of CWD on white-tailed deer populations.
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Affiliation(s)
- Christopher S. Jennelle
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Viviane Henaux
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Gideon Wasserberg
- Biology Department, University of North Carolina, Greensboro, North Carolina, United States of America
| | - Bala Thiagarajan
- Department of Forest and Wildlife Ecology, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Robert E. Rolley
- Wisconsin Department of Natural Resources, Madison, Wisconsin, United States of America
| | - Michael D. Samuel
- U.S. Geological Survey, Wisconsin Cooperative Wildlife Research Unit, University of Wisconsin, Madison, Wisconsin, United States of America
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36
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Monello RJ, Powers JG, Hobbs NT, Spraker TR, Watry MK, Wild MA. Survival and population growth of a free-ranging elk population with a long history of exposure to chronic wasting disease. J Wildl Manage 2014. [DOI: 10.1002/jwmg.665] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Ryan J. Monello
- Biological Resource Management Division; National Park Service; 1201 Oakridge STE 200 Fort Collins CO 80525
| | - Jenny G. Powers
- Biological Resource Management Division; National Park Service; 1201 Oakridge STE 200 Fort Collins CO 80525
| | - N. Thompson Hobbs
- Natural Resource Ecology Laboratory and Graduate Degree Program in Ecology; Colorado State University; Fort Collins CO 80523
| | - Terry R. Spraker
- Colorado State Diagnostic Laboratory; College of Veterinary Medicine; Colorado State University; Fort Collins CO 80523
| | - Mary Kay Watry
- Rocky Mountain National Park; National Park Service; Estes Park CO 80517
| | - Margaret A. Wild
- Biological Resource Management Division; National Park Service; 1201 Oakridge STE 200 Fort Collins CO 80525
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Sorensen A, van Beest FM, Brook RK. Impacts of wildlife baiting and supplemental feeding on infectious disease transmission risk: a synthesis of knowledge. Prev Vet Med 2013; 113:356-63. [PMID: 24365654 DOI: 10.1016/j.prevetmed.2013.11.010] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 11/07/2013] [Accepted: 11/11/2013] [Indexed: 10/26/2022]
Abstract
Baiting and supplemental feeding of wildlife are widespread, yet highly controversial management practices, with important implications for ecosystems, livestock production, and potentially human health. An often underappreciated threat of such feeding practices is the potential to facilitate intra- and inter-specific disease transmission. We provide a comprehensive review of the scientific evidence of baiting and supplemental feeding on disease transmission risk in wildlife, with an emphasis on large herbivores in North America. While the objectives of supplemental feeding and baiting typically differ, the effects on disease transmission of these practices are largely the same. Both feeding and baiting provide wildlife with natural or non-natural food at specific locations in the environment, which can result in large congregations of individuals and species in a small area and increased local densities. Feeding can lead to increased potential for disease transmission either directly (via direct animal contact) or indirectly (via feed functioning as a fomite, spreading disease into the adjacent environment and to other animals). We identified numerous diseases that currently pose a significant concern to the health of individuals and species of large wild mammals across North America, the spread of which are either clearly facilitated or most likely facilitated by the application of supplemental feeding or baiting. Wildlife diseases also have important threats to human and livestock health. Although the risk of intra- and inter-species disease transmission likely increases when animals concentrate at feeding stations, only in a few cases was disease prevalence and transmission measured and compared between populations. Mostly these were experimental situations under controlled conditions, limiting direct scientific evidence that feeding practices exacerbates disease occurrence, exposure, transmission, and spread in the environment. Vaccination programs utilizing baits have received variable levels of success. Although important gaps in the scientific literature exist, current information is sufficient to conclude that providing food to wildlife through supplemental feeding or baiting has great potential to negatively impact species health and represents a non-natural arena for disease transmission and preservation. Ultimately, this undermines the initial purpose of feeding practices and represents a serious risk to the maintenance of biodiversity, ecosystem functioning, human health, and livestock production. Managers should consider disease transmission as a real and serious concern in their decision to implement or eliminate feeding programs. Disease surveillance should be a crucial element within the long-term monitoring of any feeding program in combination with other available preventive measures to limit disease transmission and spread.
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Affiliation(s)
- Anja Sorensen
- Department of Animal and Poultry Science & Indigenous Land Management Institute, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada
| | - Floris M van Beest
- Department of Animal and Poultry Science & Indigenous Land Management Institute, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada; Department of Bioscience, Arctic Environment, Aarhus University, Frederiksborgvej 399, 4000 Roskilde, Denmark
| | - Ryan K Brook
- Department of Animal and Poultry Science & Indigenous Land Management Institute, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada.
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Oraby T, Vasilyeva O, Krewski D, Lutscher F. Modeling seasonal behavior changes and disease transmission with application to chronic wasting disease. J Theor Biol 2013; 340:50-9. [PMID: 24035840 DOI: 10.1016/j.jtbi.2013.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 07/11/2013] [Accepted: 09/03/2013] [Indexed: 01/17/2023]
Abstract
Behavior and habitat of wildlife animals change seasonally according to environmental conditions. Mathematical models need to represent this seasonality to be able to make realistic predictions about the future of a population and the effectiveness of human interventions. Managing and modeling disease in wild animal populations requires particular care in that disease transmission dynamics is a critical consideration in the etiology of both human and animal diseases, with different transmission paradigms requiring different disease risk management strategies. Since transmission of infectious diseases among wildlife depends strongly on social behavior, mechanisms of disease transmission could also change seasonally. A specific consideration in this regard confronted by modellers is whether the contact rate between individuals is density-dependent or frequency-dependent. We argue that seasonal behavior changes could lead to a seasonal shift between density and frequency dependence. This hypothesis is explored in the case of chronic wasting disease (CWD), a fatal disease that affects deer, elk and moose in many areas of North America. Specifically, we introduce a strategic CWD risk model based on direct disease transmission that accounts for the seasonal change in the transmission dynamics and habitats occupied, guided by information derived from cervid ecology. The model is composed of summer and winter susceptible-infected (SI) equations, with frequency-dependent and density-dependent transmission dynamics, respectively. The model includes impulsive birth events with density-dependent birth rate. We determine the basic reproduction number as a weighted average of two seasonal reproduction numbers. We parameterize the model from data derived from the scientific literature on CWD and deer ecology, and conduct global and local sensitivity analyses of the basic reproduction number. We explore the effectiveness of different culling strategies for the management of CWD: although summer culling seems to be an effective disease eradication strategy, the total culling rate is limited by the requirement to preserve the herd.
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Affiliation(s)
- Tamer Oraby
- McLaughlin Centre for Population Health Risk Assessment, University of Ottawa, Ottawa, Ontario, Canada.
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Homogenization, sex, and differential motility predict spread of chronic wasting disease in mule deer in southern Utah. J Math Biol 2013; 69:369-99. [DOI: 10.1007/s00285-013-0709-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 06/28/2013] [Indexed: 10/26/2022]
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Powell JH, Kalinowski ST, Higgs MD, Ebinger MR, Vu NV, Cross PC. Microsatellites indicate minimal barriers to mule deerOdocoileus hemionusdispersal across Montana, USA. WILDLIFE BIOLOGY 2013. [DOI: 10.2981/11-081] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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Robinson M, Drossinos Y, Stilianakis NI. Indirect transmission and the effect of seasonal pathogen inactivation on infectious disease periodicity. Epidemics 2013; 5:111-21. [PMID: 23746804 DOI: 10.1016/j.epidem.2013.01.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 11/19/2012] [Accepted: 01/02/2013] [Indexed: 11/18/2022] Open
Abstract
The annual occurrence of many infectious diseases remains a constant burden to public health systems. The seasonal patterns in respiratory disease incidence observed in temperate regions have been attributed to the impact of environmental conditions on pathogen survival. A model describing the transmission of an infectious disease by means of a pathogenic state capable of surviving in an environmental reservoir outside of its host organism is presented in this paper. The ratio of pathogen lifespan to the duration of the infectious disease state is found to be a critical parameter in determining disease dynamics. The introduction of a seasonally forced pathogen inactivation rate identifies a time delay between peak pathogen survival and peak disease incidence. The delay is dependent on specific disease parameters and, for influenza, decreases with increasing reproduction number. The observed seasonal oscillations are found to have a period identical to that of the seasonally forced inactivation rate and which is independent of the duration of infection acquired immunity.
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43
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Cortez MH, Weitz JS. Distinguishing between indirect and direct modes of transmission using epidemiological time series. Am Nat 2013; 181:E43-54. [PMID: 23348785 DOI: 10.1086/668826] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Pathogen transmission can involve direct and/or indirect pathways. Using theoretical models, in this study we ask, "do directly and indirectly transmitted pathogens yield different population-level epidemiological dynamics?" and "can the transmission pathway be inferred from population-level epidemiological data?" Our approach involves comparing the continuous-time dynamics of a class of compartmental epidemiological models with direct versus environmentally mediated indirect transmission pathways. Combing analytical theory and numerical simulations we show that models with direct and indirect transmission can produce quantitatively similar time series when the pathogen cannot reproduce in the environment, particularly when the environmental pathogen dynamics are fast. We apply these results to a previous study on chronic wasting disease and show that identifying the transmission pathway is more difficult than previously acknowledged. Our analysis and simulations also yield conditions under which numerical differences can potentially identify the transmission route in oscillating endemic systems and systems where the environmental pathogen dynamics are not fast. This work begins to identify how differences in the transmission pathway can result in quantitatively different epidemiological dynamics and how those differences can be used to identify the transmission pathway from population level time series.
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Affiliation(s)
- Michael H Cortez
- School of Biology and School of Mathematics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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Storm DJ, Samuel MD, Rolley RE, Shelton P, Keuler NS, Richards BJ, Van Deelen TR. Deer density and disease prevalence influence transmission of chronic wasting disease in white-tailed deer. Ecosphere 2013. [DOI: 10.1890/es12-00141.1] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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VerCauteren KC, Pilon JL, Nash PB, Phillips GE, Fischer JW. Prion remains infectious after passage through digestive system of American crows (Corvus brachyrhynchos). PLoS One 2012; 7:e45774. [PMID: 23082115 PMCID: PMC3474818 DOI: 10.1371/journal.pone.0045774] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 08/24/2012] [Indexed: 11/19/2022] Open
Abstract
Avian scavengers, such as American crows (Corvus brachyrhynchos), have potential to translocate infectious agents (prions) of transmissible spongiform encephalopathy (TSE) diseases including chronic wasting disease, scrapie, and bovine spongiform encephalopathy. We inoculated mice with fecal extracts obtained from 20 American crows that were force-fed material infected with RML-strain scrapie prions. These mice all evinced severe neurological dysfunction 196–231 d postinoculation ( = 198; 95% CI: 210–216) and tested positive for prion disease. Our results suggest a large proportion of crows that consume prion-positive tissue are capable of passing infectious prions in their feces ( = 1.0; 95% CI: 0.8–1.0). Therefore, this common, migratory North American scavenger could play a role in the geographic spread of TSE diseases.
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Affiliation(s)
- Kurt C VerCauteren
- United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center, Fort Collins, Colorado, USA.
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Al-Arydah M, Smith RJ, Lutscher F. Modeling Gender-Structured Wildlife Diseases with Harvesting: Chronic Wasting Disease as an Example. ACTA ACUST UNITED AC 2012. [DOI: 10.5402/2012/802450] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Chronic wasting disease (CWD) is a prion infectious disease that affects members of the deer family in North America. Concerns about the economic consequences of the presence of CWD have led management agencies to seek effective strategies to control CWD distribution and prevalence. Current mathematical models are either based on complex simulations or overly simplified compartmental models. We develop a mathematical model that includes gender structure to describe CWD in a logistically growing population. The model includes harvesting as a management strategy for the disease. We determine the stability conditions of the disease-free equilibrium for the model and calculate the basic reproduction number. We find an optimum interval of harvesting: with too little harvesting, the disease persists, whereas too much harvesting results in extinction of the population. A sensitivity analysis shows that the disease threshold is more sensitive to female than male harvesting and that harvesting has the greatest effect on the basic reproduction number. However, while harvesting may be a way to control CWD, the range of admissible harvesting rates may be very narrow, depending on other parameters.
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Affiliation(s)
- Mo'tassem Al-Arydah
- Department of Mathematics, The University of Ottawa, Ottawa, ON, Canada K1N 6N5
| | - Robert J. Smith
- Department of Mathematics and Faculty of Medicine, The University of Ottawa, Ottawa, ON, Canada K1N 6N5
| | - Frithjof Lutscher
- Department of Mathematics, The University of Ottawa, Ottawa, ON, Canada K1N 6N5
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Potapov A, Merrill E, Lewis MA. Wildlife disease elimination and density dependence. Proc Biol Sci 2012; 279:3139-45. [PMID: 22593103 DOI: 10.1098/rspb.2012.0520] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Disease control by managers is a crucial response to emerging wildlife epidemics, yet the means of control may be limited by the method of disease transmission. In particular, it is widely held that population reduction, while effective for controlling diseases that are subject to density-dependent (DD) transmission, is ineffective for controlling diseases that are subject to frequency-dependent (FD) transmission. We investigate control for horizontally transmitted diseases with FD transmission where the control is via culling or harvest that is non-selective with respect to infection and the population can compensate through DD recruitment or survival. Using a mathematical model, we show that culling or harvesting can eradicate the disease, even when transmission dynamics are FD. Eradication can be achieved under FD transmission when DD birth or recruitment induces compensatory growth of new, healthy individuals, which has the net effect of reducing disease prevalence by dilution. We also show that if harvest is used simultaneously with vaccination, and there is high enough transmission coefficient, application of both controls may be less efficient than vaccination alone. We illustrate the effects of these control approaches on disease prevalence for chronic wasting disease in deer where the disease is transmitted directly among deer and through the environment.
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Affiliation(s)
- Alex Potapov
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.
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48
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Saunders SE, Bartz JC, Bartelt-Hunt SL. Soil-mediated prion transmission: is local soil-type a key determinant of prion disease incidence? CHEMOSPHERE 2012; 87:661-667. [PMID: 22265680 DOI: 10.1016/j.chemosphere.2011.12.076] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2011] [Revised: 12/23/2011] [Accepted: 12/28/2011] [Indexed: 05/31/2023]
Abstract
Prion diseases, including chronic wasting disease (CWD) and scrapie, can be transmitted via indirect environmental routes. Animals habitually ingest soil, and results from laboratory experiments demonstrate prions can bind to a wide range of soils and soil minerals, retain the ability to replicate, and remain infectious, indicating soil could serve as a reservoir for natural prion transmission and a potential prion exposure route for humans. Preliminary epidemiological modeling suggests soil texture may influence the incidence of prion disease. These results are supported by experimental work demonstrating variance in prion interactions with soil, including variance in prion soil adsorption and soil-bound prion replication with respect to soil type. Thus, local soil type may be a key determinant of prion incidence. Further experimental and epidemiological work is required to fully elucidate the dynamics of soil-mediated prion transmission, an effort that should lead to effective disease management and mitigation strategies.
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Affiliation(s)
- Samuel E Saunders
- Department of Civil Engineering, University of Nebraska-Lincoln, Peter Kiewit Institute, Omaha, NE 68182, USA
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49
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Breban R. Role of environmental persistence in pathogen transmission: a mathematical modeling approach. J Math Biol 2012; 66:535-46. [PMID: 22382994 PMCID: PMC7079992 DOI: 10.1007/s00285-012-0520-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 02/17/2012] [Indexed: 11/25/2022]
Abstract
Although diseases such as influenza, tuberculosis and SARS are transmitted through an environmentally mediated mechanism, most modeling work on these topics is based on the concepts of infectious contact and direct transmission. In this paper we use a paradigm model to show that environmental transmission appears like direct transmission in the case where the pathogen persists little time in the environment. Furthermore, we formulate conditions for the validity of this modeling approximation and we illustrate them numerically for the cases of cholera and influenza. According to our results based on recently published parameter estimates, the direct transmission approximation fails for both cholera and influenza. While environmental transmission is typically chosen over direct transmission in modeling cholera, this is not the case for influenza.
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Affiliation(s)
- Romulus Breban
- Unité d'Epidémiologie des Maladies Emergentes, Institut Pasteur, 75724 Paris, France.
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50
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Haley NJ, Mathiason CK, Carver S, Telling GC, Zabel MD, Hoover EA. Sensitivity of protein misfolding cyclic amplification versus immunohistochemistry in ante-mortem detection of chronic wasting disease. J Gen Virol 2012; 93:1141-1150. [PMID: 22278825 DOI: 10.1099/vir.0.039073-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
As the only prion disease affecting free-ranging animals, ante-mortem identification of affected cervids has become paramount in understanding chronic wasting disease (CWD) pathogenesis, prevalence and control of horizontal or vertical transmission. To seek maximal sensitivity in ante-mortem detection of CWD infection, this study used paired tonsil biopsy samples collected at various time points from 48 CWD-exposed cervids to compare blinded serial protein misfolding cyclic amplification (sPMCA) with the assay long considered the 'gold standard' for CWD detection, immunohistochemistry (IHC). sPMCA-negative controls (34 % of the samples evaluated) included tissues from mock-inoculated animals and unspiked negative controls, all of which tested negative throughout the course of the study. It was found that sPMCA on tonsil biopsies detected CWD infection significantly earlier (2.78 months, 95 % confidence interval 2.40-3.15) than conventional IHC. Interestingly, a correlation was observed between early detection by sPMCA and host PRNP genotype. These findings demonstrate that in vitro-amplification assays provide enhanced sensitivity and advanced detection of CWD infection in the peripheral tissues of cervids, with a potential role for spike or substrate genotype in sPMCA amplification efficiency.
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Affiliation(s)
- Nicholas J Haley
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Candace K Mathiason
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Scott Carver
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Glenn C Telling
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Mark D Zabel
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
| | - Edward A Hoover
- Department of Microbiology, Immunology, and Pathology, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA
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