Colloquium Presentation 2010 Bongsoo

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  • Why I have to introduce the disease transmission model is that it will help you to better understand the basic epidemiological background we wiill cover in the next sessions.
  • Here is one example of infected frog by chytrid fungus. Basically, the fungus infects the skin of frogs destroying its structure and function. In the next section, David will cover more detail in this interaction. In the introduction, we will be prepared the basic definition of the those.
  • Name?
  • Persistence of the emerging pathogenBatrachochytrium dendrobatidis outsidethe amphibian host greatly increases theprobability of host extinctionKate M. Mitchell. Proc. R. Soc. B (2008) 275, 329–334“The model predicted that the longer thatB. dendrobatidis was able to persist in water, either due to an increased zoospore lifespan or saprobicreproduction, the more likely it was that it could cause local B. bufo extinction (defined as decrease below athreshold level).”
  • http://animaldiversity.ummz.umich.edu/site/resources/usfws/monteverdetoad.JPG/view.htmlhttp://rana.biologia.ucr.ac.cr/ingles/gallery.html
  • Emerging infectious diseases (EIDs) of free-living wild animals can be classiÞed into three major groupson the basis of key epizootiological criteriaWith agents from reservoir animal populations (often domesticated species) to sympatric wildlife.The translocation of wildlife for conservation, agriculture, and hunting occurs on a global scale, with an inherent risk of exposure of wildlife species to exotic infectious agentsCorrelations between emergence of human diseases (such as cryptosporidiosis, hemorrhagic fevers, cholera, and malaria) and weather patterns [flooding, the El Nin˜o Southern Oscillation (ENSO)] are common (36, 37).
  • Spill-over is a particular threat to endangered species, because the presence of infected reservoir hosts can lower the pathogen’s threshold density and lead to local (population) extinction (8, 9, 11). Populations of the African wild dog (Lycaon pictus) have been declining since the 1960s. This species is now endangered and, with a fragmented population of less than 5000, is susceptible to stochastic events such as disease outbreaks. Wild dogs became extinct in the in 1991, concurrent with epizootic canine distemper in sympatric domestic dogs (18, 24).
  • The introduction of potential hosts into new geographic areas without co-introduction of pathogens can alsoresult in disease emergence. For example, varroasis, a disease of honeybees caused by the mite Varroa jacobsoni, spread globally (except Australia) after the European honeybee (Apis mellifera) was introduced into Asia (28).
  • IUCN: International Union for Conservation of Nature
  • nutrient and water cycling, soil formation and retention, resistance against invasive species, plant pollination, climate regulation, and pest and pollution controlThe monetary value of goods and services provided by ecosystems is estimated to amount to some 33 trillion dollars per year – nearly twice the global production resulting from human activities.
  • Taxol (Medicinal purposes)Mandragora

Transcript

  • 1. Is the end near for amphibians?
    The effect of humans and pathogens
    Bongsoo Park
    David Place
    Oscar Bedoya
    Laura Goodfield
    2/16/2010
    2010 Spring Integrative Biosciences Colloquium
    [http://untitledname.com/2006/07/kermit-2]00
    1
    1
  • 2. Introduction & Disease transmission models
    Bongsoo Park
    2
  • 3. Dr. Collin’s research focus is host-pathogen biology and its relationship to the global decline of amphibians
    James P. Collins
    B.S. from Manhattan College in 1969
    Ph.D. from The University of Michigan in 1975
    Professor in Ecology, Evolution, & Environmental Science
    3
    [http://www.collinslab.asu.edu/]
    3
  • 4. Host-Pathogen Interaction
    Host
    Pathogen
    Amphibians
    (Ex. Frogs, Salamanders)
    Fungus, Bacteria, Virus
    (Ex. Batrachochytrium dendrobatidis)
    [http:// static.howstuffworks.com/gif/frog-1.jpg]
    [http://en.wikipedia.org/wiki/File:Batrachochytrium_dendrobatidis.jpg]
    4
  • 5. Infected Frog by Chytrid fungus
    The fungus infects the skin of frogs
    destroying its structure and function.
    [http://www.dpiw.tas.gov.au/inter.nsf/WebPages/LJEM-673V89?open]
    5
  • 6. Emerging infectious diseases may reduce biodiversity and may account for at least some species extinctions
    The question of whether pathogens can cause host extinction is a key issue in epidemiological theory
    6
  • 7. The question of whether pathogens can cause host extinction is a key issue in epidemiological theory
    Extinction is impossible via an infectious pathogen if two assumptions are met
    (Kermack and McKendrick 1927; Anderson and May 1979)
    7
  • 8. Extinction is impossible via an infectious pathogen if two assumptions are met
    Disease transmission is density dependent (McCallum et al. 2001; Begon et al. 2002)
    Host contact is homogeneous (O’Keefe 2005)
    8
  • 9. Disease transmission models
    [McCallum, H. 2001]
    9
  • 10. Disease transmission is density dependent
    Population (N)
    Susceptible : Unresistant to some stimulus, influence
    Infected : Contaminated with a disease-producing agents
    (Merriam-webster.com)
    [McCallum, H. 2001]
    10
  • 11. Disease transmission is density dependent
    Population (N)
    Transmission rate = βSI
    (β: Transmission coefficient)
    [McCallum, H. 2001]
    11
  • 12. Disease transmission is density dependent
    Assumption : Infected and susceptible hosts mix
    completely with each other and move randomly
    within an arena of fixed size
    [McCallum, H. 2001]
    12
  • 13. Density dependent disease transmission is ‘Mass Action’
    High School Chemistry : Water(H20)
    [McCallum, H. 2001]
    13
  • 14. Disease transmission is frequency dependent
    Population (N)
    Transmission rate = βSI / N
    (β: Transmission coefficient)
    [de Jong et al, 1995]
    14
  • 15. The summary of basic Disease transmission models
    βIS (‘mass action’)
    Transmission in which the number of new infections per unit time is proportional to the product of the density of infected hosts I and the density of susceptible hosts S.
    β IS/N (‘Pseudo mass action’)
    Frequency-dependent transmission is proportional to the product of the density of infected hosts(I) and the proportion(or frequency) of hosts that are susceptible.
    [McCallum, H. 2001]
    15
  • 16. Extinction is impossible via an infectious pathogen if two assumptions are met
    Disease transmission is density dependent (McCallum, Barlow&Home2001; Begon et al. 2002)
    Host contact is homogeneous (O’Keefe 2005)
    16
  • 17. Host contact is homogenous?
    Pathogen
    Host
    Host
    Host
    17
  • 18. Actually, host contact is not homogenous
    Host
    Pathogen
    Host
    Host
    18
  • 19. Actually, host contact is not homogenous
    Host 2
    Host 1
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    Host
    19
  • 20. Actually, host contact is not homogenous
    “For example, we may expect that a cold will spread faster through a dense neighborhood than a rural one because more handshakes and other casual contact occur in the dense neighborhood.”
    State college 40,000
    Philadelphia 5,000,000
    [ O’Keefe, K.J. 2005 ]
    20
  • 21. Extinction is impossible via an infectious pathogen if two assumptions are met
    When two assumptions are not met,
    extinction would be possible via an infectious pathogens
    21
  • 22. When two assumptions are not met, extinction would be possible via an infectious pathogens
    Host extinction can be accommodated within the framework of the basic theory by relaxing the two assumptions
    (de Castro and Bolker 2005)
    22
  • 23. Pathogen-Associated Extinction by Chytridiomycosis
    David Place
    (Wake and Vredenburg 2008)
    23
  • 24. Mass Die-Offs Resulting from
    Batrachochytrium dendrobatidis Infection
    (Lips et al. 2005)
    24
  • 25. Rapid mortality begins in October 2004 at El Copé
    (Lips et al. 2005)
    25
  • 26. Rapid Die-Offs Coincide With Detection of B. dendrobatidis
    (Lips et al. 2005)
    26
  • 27. Batrachochytrium dendrobatidis is the Causative Agent of Chytridiomycosis
    Free-Living Stage
    (Rosenblum et al. 2008)
    27
  • 28. Bd Grows Strictly in the Keratinized Tissues of Tadpoles (Mouth) and Skin of Adults
    Figure 1
    “Thickness of normal stratum corneum is 2–5 μm, but here it is about 60 μm. “
    D= Discharge Tubes
    S= Sporangia
    Figure 2
    Death hypothesized to be due to impaired respiration, osmoregulation, or uptake of fungal toxins.
    (Berger et al. 1998)
    28
  • 29. Under the Proper Conditions, Bd Can Lead to Host Extinction
    (Kate M. Mitchell. 2008)
    29
  • 30. Five Year Study at Monteverde Cloud Forest Preserve in Costa Rica
    20 Species Driven to Extinction
    Bufo periglenes – Golden Toad
    Atelopus varius - Harlequin Frog
    (http://rana.biologia.ucr.ac.cr/ingles/gallery.html)
    (http://rana.biologia.ucr.ac.cr/ingles/gallery.html)
    (Wake and Vredenburg. 2008)
    30
  • 31. Bd is successful in many climates but does not necessarily drive all populations to extinction
    Bd Infects over 400 species of amphibians and is currently widespread
    (Fisher et al. 2009)
    31
  • 32. Bd Is More Lethal at Lower Temperatures
    16 frogs exposed to B. dendrobatidis
    At 17°C and 23°C, all died
    4 of 8 exposed frogs at 27°C died
    (Berger et al. 2004)
    32
  • 33. Human associated pathogen transmission
    Oscar Bedoya Reina
    33
  • 34. Emerging infection diseases (EIDs) of free living animals can be classified into three major groups
    [http:// cache.gawker.com]
    Spilled over from domestic animals to wildlife population
    [http:// www.africanwilddoglearningzone.com]
    Related to host or parasite translocation
    Adapted from [http://www.canids.org]
    Emerged without overt human involvement
    [Daszak et al. 2000]
    34
  • 35. Emerging infection diseases (EIDs) of free living animals can be classified into three major groups
    Spilled over from domestic animals to wildlife population
    [http://www.hillmanwonders.com]
    [Ginsberg et al. 1995]
    [http:// www.africanwilddoglearningzone.com]
    35
    35
  • 36. Emerging infection diseases (EIDs) of free living animals can be classified into three major groups
    Related to host or parasite translocation
    [http://www.dpi.qld.gov.au]
    [http://www.ecoalimenta.com]
    Adapted from [http://www.canids.org]
    36
  • 37. Disease induced host extinction is impossible via infectious diseases
    Disease transmission is density dependant and host contact is homogenous
    Host extinction is unexpected because pathogen transmission is inefficient
    37
  • 38. Fragmentation of habitat could change density across landscapes affecting host contact
    Habitat fragmentation as a result of biotic or abiotic factors controls pathogen transmission
    38
  • 39. In amphibian fragmentation could increase the effective disease transmission
    If biotic and abiotic factors result in differences in host density between ponds, contact rates and pathogen transmission could be different
    39
  • 40. In amphibian fragmentation could increase the effective disease transmission
    If biotic and abiotic factors result in differences in host density between ponds, contact rates and pathogen transmission could be different
    40
  • 41. What can be said about fragmentation in amphibian habitats?
    Fragmentation increase the contact between individuals
    Abiotic and biotic factors fragment the ponds
    41
  • 42. Could fragmentation drive to extinction?
    Arizona tiger salamander:
    1) Populations live in ponds.
    2) The species has an obligate pathogen.
    3) Populations are endangered.
    42
  • 43. Could fragmentation drive to extinction?
    Arizona tiger salamander:
    1) Populations live in ponds.
    2) The species has an obligate pathogen.
    3) Populations are endangered.
    [http://media.photobucket.com]
    sparse
    [http://blog.thepondguy.com]
    Pounds can be fragmented
    dense
    43
  • 44. Could fragmentation drive to extinction?
    Arizona tiger salamander:
    1) Populations live in ponds.
    2) The species has an obligate pathogen.
    3) Populations are endangered.
    Reintroduced to the ponds
    by infected adults
    ATV
    ATV infection is stochastic
    44
  • 45. Could fragmentation drive to extinction?
    Arizona tiger salamander:
    1) Populations live in ponds.
    2) The species has an obligate pathogen.
    3) Populations are endangered.
    Modify natural ponds
    Human action
    Create artificial ponds
    45
    45
  • 46. Could fragmentation drive to extinction?
    Arizona tiger salamander:
    1) Populations live in ponds.
    2) The species has an obligate pathogen.
    3) Populations are endangered.
    Abiotic factors
    [http://www.uwyo.edu/]
    Species habits
    46
  • 47. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    47
  • 48. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    [http://www. wildanimalsonline.com/]
    Adapted from [http://www. wildanimalsonline.com/]
    NEGATIVE
    POSITIVE
    48
    48
  • 49. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    -4
    +4
    49
  • 50. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    50
    0%
    100%
  • 51. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    0
    1
    51
    51
  • 52. Fragmented habitats are more likely to have higher incidence of ATV infections
    Studied 4 ponds in Arizona, taking the following variables:
    ATV presence
    Palmer drought severity index
    Amount of emerging vegetation
    Alteration for management
    Presence of cannibals
    [Adapted from Michimae, H. and Wakahara 2001]
    1
    HWL/LHW>0.9
    0
    HWL/LHW<0.86
    [http://www.uwyo.edu/]
    [http://www. wildanimalsonline.com/]
    52
  • 53. What can be said about fragmentation in amphibian habitats?
    [Adapted from Greers and Collins 2008]
    Drought and management are positively correlated with an increase of ATV, and the amount of emergent vegetation is negatively correlated
    53
  • 54. What can be said about fragmentation in amphibian habitats?
    [Adapted from Greers and Collins 2008]
    Drought years presented a significant higher incidence of ATV
    54
  • 55. What can be said about fragmentation in amphibian habitats?
    [Adapted from Greers and Collins 2008]
    Modified sinkholes presented a significant higher incidence of ATV
    55
  • 56. What can be said about fragmentation in amphibian habitats?
    [Adapted from Greers and Collins 2008]
    The percentage of ATV decreased as vegetation score increase
    56
  • 57. ATV occurrence is modeled by the main effect of two variables
    [Adapted from Greers and Collins 2008]
    The amount of emergent vegetation and management alteration fit the data well
    57
  • 58. Tiger salamander showed different distribution patterns
    Significantly more animals were captured <2m from the pond’s edge, and is more frequent in ponds with sparse vegetation
    58
  • 59. Ponds with sparse vegetation and altered management for livestock have higher incidence of ATV
    Lower emergent vegetation causes an halo effect, and high densities
    Ponds with modified management are deeper and steeper
    59
  • 60. Ponds with sparse vegetation and altered management for livestock have higher incidence of ATV
    Stock tanks and other modified habitat could increase connectivity of populations
    Vegetation can act as paths by which adult move around the pond
    60
  • 61. Conclusions
    Contrarily to the original hypothesis: “Complex habitats would create microhabitats that separated larvae into patches”, they found that ponds with sparse vegetation is fragmented
    61
  • 62. Conclusions
    The intensity of ponds alteration for livestock and the amount of vegetation are positively related to the ATV incidence
    62
  • 63. The Big Picture: Implications of Extinction
    {Clip Art from Microsoft 2007}
    Laura Goodfield
    63
  • 64. The relationships between species in an ecosystem are varied but usually tie species together in a unique and complex manner.
    (Lavigne. 2007)
    64
  • 65. Keystone species can be defined as species that contribute more proportionally to their ecosystem than they take up biomass.
    [Dovel 2008]
    65
  • 66. Endangered Species have been determined by the IUCN and added to the Red List.
    [Table adapted from IUCN, 2009]
    66
  • 67. When it comes to abiotic causes, extinction is normal!
    50% of all species
    83% of all species
    48% of all species
    50% of all species
    57% of all species
    (The Discovery Channel, 2010)
    67
  • 68. “Biodiversity is defined as the totality of different organisms, the genes they contain, and the ecosystems they form.” E.O. Wilson, 1986
    [Myers 2000]
    68
  • 69. High levels of endangered and extinct species inversely correlate to biodiversity levels.
    [IUCN 2008]
    69
  • 70. Implications
    • Food supply
    About 100 million metric tons of aquatic organisms, including fish, mollusks and crustaceans are taken from the wild every year and represent a vital contribution to world food security
    • Medicinal Supply
    An estimated 50,000-70,000 plant species are used in traditional and modern medicine worldwide
    70
  • 71. Consequences of Change in Biodiversity will directly affect us and the world around us.
    (F.S. Chapin III et al, 2000)
    71
  • 72. Summary
    Disease transmission models suggest that extinction could be possible if host contact is not homogenous or disease transmission is not dependant on density.
    The newly emergent pathogen Bd is appears to be able to cause extinction in wild populations of amphibians.
    ATV infection was positively related with anthropic modifications and with habitat fragmentation.
    Although extinction is natural, the loss of biodiversity can result in series of changes, most of which affect us negatively.
  • 73. What will happen if amphibians become extinct?
  • 74. References
    Berger et al. (1998). Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proc NatlAcad Sci. 95(15): 9031–9036.
    Berger L., Speare R., Hines H., Marantelli G., Hyatt A.D., et al. (2004). Effect of season and temperature on mortality in amphibians due to chytridiomycosis. Aust. Vet. J. 82:31–36
    Chapin F.S. III et al (2000) Consequences of changing biodiversity . Nature 405, 234-242.
    de Castro F. and Bolker B. (2005) Mechanisms of disease-induced extinction. Ecology Letters, 8, 117–126.
    de Jong, M.C.M. et al. (1995) How does transmission of infection depend on population size? In Epidemic Models: Their Structure and Relation to Data (Mollison, D., ed.), pp. 84–94, Cambridge University Press.
    Dovel G. (2008) The Truth about Our Wildlife Managers’ Plan to Restore “Native” Ecosystems. The Outdoorsman,  30.
    Fisher M.C., Garner T.W.J., Walker S.F. (2009). Global Emergence of Batrachochytriumdendrobatidis and Amphibian Chytridiomycosis in Space, Time, and Host. Annu. Rev. Microbiol. 63:291-310.
    Ginsberg J.R., Mace G.M. and Albon S. (1995). Local Extinction in a Small and Declining Population: Wild Dogs in the Serengeti. Proceedings: Biological Sciences. 262(1364):221-228.
    Greer A.L., Collins J.P. (2008). Habitat fragmentation as a result of biotic and abiotic factors controls pathogen transmission throughout a host population. Journal of Animal Ecology. 364-369
    74
  • 75. References
    Greer A.R and Collins J.P. (2008) Habitat fragmentation as a result of biotic and abiotic factors controls pathogen transmission throughout a host population. Journal of Animal Ecology, 77, 364-369.
    IUCN (2008) Broadening the coverage of biodiversity assessments. Accessed at http://cmsdata.iucn.org/downloads/broadening_the_coverage_of_biodiversity_assessments_factsheet_en.pdf
    IUCN (2009) Accessed at http://iucn.org/about/work/programmes/species/red_list/?4143/Extinction-crisis-continues-apace
    Lavigne D., Natural Sciences and Engineering Research Council (2007) Cod Food Web Accessed at http://www.visualcomplexity.com/vc/project.cfm?id=47.
    Lips K.R. et al. (2005). Emerging infectious disease and the loss of biodiversity in a Neotropical amphibian community. PNAS. 103:9
    McCallum, H., Barlow, N. & Hone, J. (2001) How should pathogen transmission be modelled? Trends in Ecology and Evolution, 16, 295–300.
    Michimae H. and Wakahara M. (2001). Factors Which Affect the Occurrence of Cannibalism and the Broad-Headed "Cannibal" Morph in Larvae of the Salamander Hynobiusretardatus. Behavioral Ecology and Sociobiology 50(4):339-345.
    Mitchell K.M. (2008). Persistence of the emerging pathogen Batrachochytriumdendrobatidis outside the amphibian host greatly increases the probability of host extinction. Proc. R. Soc. B. 275, 329–334 .
    75
  • 76. References
    Myers N., Mittermeier R.A., Mittermeier G.C., da Fonseca G.A.B. and Kent J. (2000) Biodiversity hotspots for conservation priorities. Nature 403, 853-858
    •O’Keefe, K.J. (2005) The evolution of virulence in pathogens with frequencydependent transmission. Journal of Theoretical Biology, 233, 55–64.
    Prangishvili D., Forterre P. and Garrett R.A. (2006). Viruses of the Archaea: a unifying view. Nature Reviews Microbiology 4, 837-848. •Rosenblum E.B., Stajich J.E., Maddox N., Elsen M.B. (2008). Global gene expression profiles for life stages of the deadly amphibian pathogen Batrachochytriumdendrobatidis. PNAS . 105:44.
    Wake D.B. and Vredenburg V.T. (2008). Are we in the midst of the sixth mass extinction? A view from the world of amphibians . PNAS. vol. 105 suppl. 1 11469.
    76