The Effects of Host and Pathogen Variation on Infection Dynamics in the Amphibian-Chytrid System Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/j098zg44c

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  • This dissertation uses manipulative experiments to explore amphibian-Bd infection dynamics. Although there has been almost two decades research since the discovery of Bd, many questions still remain regarding what conditions mediate chytridiomycosis virulence. My research shows how certain host and pathogen factors can influence disease virulence. Identifying how host and pathogen factors mediate disease virulence is important in order to understand, predict, and mitigate this infectious amphibian disease. Worldwide biodiversity loss is occurring at unprecedented rates. Numerous factors are contributing to this loss, including infectious disease. Among vertebrate groups, amphibians are experiencing the highest rate of population declines and extinctions and are vulnerable to numerous infectious pathogens that appear to be contributing to amphibian biodiversity loss. A widespread infectious chytrid fungus, Batrachochytrium dendrobatidis (Bd), causing the disease, chytridiomycosis, is implicated in numerous amphibian population declines and extinctions and can induce sublethal effects within individuals. My dissertation research examines host-pathogen factors that mediate infection outcomes in the amphibian-Bd system. The severity of an infectious disease is the result of specific host-pathogen interactions. Thus, there may be large variation in disease outcome depending on host and pathogen related factors. In Chapter 2, I conducted a comparative experimental study in larval amphibians using multiple host species and Bd strains. I showed that host species varied in Bd susceptibility but that susceptibility was also contingent on Bd strain type. Thus, I showed chytridiomycosis virulence depended upon host and pathogen traits and that a sensitive host species could be robust to certain pathogen strains. In Chapter 3, I experimentally investigated multiple pathogen interactions with amphibian three amphibian host species to examine how Bd infection dynamics might change under simultaneous coinfection with a common water mold, Saprolegnia ferax (Sf). Coinfecting pathogens might interact within a host in a synergistic and antagonistic manner. In two host species, Bd infection intensity was slightly higher in hosts that were exposed to both Bd and Sf compared to just Bd alone indicating a small synergistic interaction with Sf. However, the differences were not significant in either host species. Survival differences were only detected in one host species; hosts exposed to Bd only experienced lower survival than those in the coinfected group. Additionally, I found host weight and days survived were predictive of Bd infection level for some hosts species showing species variation in infection response. Lastly, in Chapter 4, I experimentally examined age-dependent differences in Bd infection heterogeneity in two host species. I followed this with another experiment to test whether age-dependent differences in infection intensity of these hosts (‘donors’) influenced subsequent Bd transmission to a naïve conspecific host (‘recipients’). I found Bd infection intensity differences among juvenile and adult donors of both species. However, trend directions were not consistent; in one host species, adults had significantly higher infection levels than juveniles while the opposite was true in the second host species. Regardless of donor infection intensity, recipients had comparable infection levels within each host species. Survival also differed among host species and age groups suggesting Bd susceptibility may change with age and is species specific.
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  • description.provenance : Rejected by Julie Kurtz(julie.kurtz@oregonstate.edu), reason: Hi Trang,Everything looks good except to change the commencement date on the bottom of the title page to read - Commencement June 2018.Once revised, log back into ScholarsArchive and go to the upload page. Replace the attached file with the revised PDF and resubmit.Thanks,Julie on 2017-06-20T18:08:13Z (GMT)
  • description.provenance : Submitted by Trang Dang (dangtra) on 2017-06-20T16:30:09ZNo. of bitstreams: 2license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5)DangTrangD2017.pdf: 2854137 bytes, checksum: b1a2eac8e0759f323e5876bf5949c8d6 (MD5)
  • description.provenance : Approved for entry into archive by Steven Van Tuyl(steve.vantuyl@oregonstate.edu) on 2017-06-26T22:52:55Z (GMT) No. of bitstreams: 2DangTrangD2017.pdf: 1506313 bytes, checksum: 9863f65654fb12dc5612191f3197c63b (MD5)license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5)
  • description.provenance : Submitted by Trang Dang (dangtra) on 2017-06-20T20:57:04ZNo. of bitstreams: 2DangTrangD2017.pdf: 1506313 bytes, checksum: 9863f65654fb12dc5612191f3197c63b (MD5)license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5)
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2017-06-26T21:08:23Z (GMT) No. of bitstreams: 2DangTrangD2017.pdf: 1506313 bytes, checksum: 9863f65654fb12dc5612191f3197c63b (MD5)license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5)
  • description.provenance : Made available in DSpace on 2017-06-26T22:52:55Z (GMT). No. of bitstreams: 2DangTrangD2017.pdf: 1506313 bytes, checksum: 9863f65654fb12dc5612191f3197c63b (MD5)license_rdf: 1232 bytes, checksum: bb87e2fb4674c76d0d2e9ed07fbb9c86 (MD5) Previous issue date: 2017-06-09

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