Captivity-induced Evolution: Role of Humans in Modifying Virulence - - PDF document

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Captivity-induced Evolution: Role of Humans in Modifying Virulence - - PDF document

Sep 12, 2023 342 likes •410 views

Captivity-induced Evolution: Role of Humans in Modifying Virulence R. Mazzoni M. Niemiller Matthew J. Gray University of Tennessee Center for Wildlife Health Department of Forestry, Wildlife and Fisheries Outline I. Virulence Evolution II.

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Captivity-induced Evolution:

Role of Humans in Modifying Virulence

University of Tennessee

Center for Wildlife Health Department of Forestry, Wildlife and Fisheries

Matthew J. Gray

  • M. Niemiller
  • R. Mazzoni

Outline

I. Virulence Evolution II. Captive Isolates

  • III. Conservation Implications

Required Reading: Bull JJ, Lauring AS (2014) Theory and Empiricism in Virulence Evolution. PLoS Pathog 10(10): e1004387. doi:10.1371/ journal.ppat.1004387

Supplemental Reading: Alizon S, Hurford A, Mideo N, Van Baalen M (2009)

Virulence evolution and the trade-off hypothesis: history, current state of affairs and the future. Journal of Evolutionary Biology, 22: 245–259. doi: 10.1111/j. 1420-9101.2008.01658.x

Pathogen Virulence

Virulence:

  • Increase in death rate of the host due to the

pathogen

  • Evade host immune system
  • Replication rate
  • Transmission rate

Two Hypotheses:

  • Trade-off:
  • Evolution toward low to intermediate virulence
  • Short-sighted Evolution:
  • Evolution toward high virulence
  • Rapid replication and transmission

Pathogenicity?

Alizon et al. (2009), Bull and Lauring (2014)

When would you expect evolution to be favored for increased virulence?

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Captive Conditions

https://www.youtube.com/watch?v=f2q5jqdsTeA

The perfect cauldron for virulence evolution!

  • Hosts
  • Strains
  • Immunocompromised

First Evidence

Majji et al. (2006) Storfer et al. (2007)

Bullfrog Die-off: Alapaha, GA

Miller et al. (2007)

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Percent mortality Ranaculture isolate 2X more lethal than FV3

Trends in Susceptibility

Hoverman et al. (2011a): 19 Species Tested

Single-species FV3-like Challenges

Amphibians

0" 10" 20" 30" 40" 50" 60" 70" 80" 90" 100" AMBA" AMGR" AMJE" AMTE" ANBO" ANTE" LIAR" LIBO" LITE" PSFE" PSOR" NOPE" CYPY" SCCO" XELA" HESC"

InfecCon"(%)"

FV3" RI" SM" Brenes (2013): UT Dissertation 16 Additional Species Total: RI > FV3 25/35 = 71%; RI>SM for 7 spp

Single-species FV3-like Challenges

Amphibians

Brenes (2013) 35 Species

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Pallid

Another FV3-like Isolate from Captivity

Waltzek, Gray, and Miller

0% mortality in controls 85% 80% 95% 5%

Gray Bull Wood

80% RI 10% RI 100% RI 35% 45%

Pallid Isolate Caused Mortality; Bullfrog Isolate Resulted in Infection

5%

Pallid vs. GA Bullfrog Isolate

Waltzek, Gray, and Miller

0% mortality in controls

Multiple Captive Isolates

Geng, Gray, Waltzek, Une, and Miller

Captive = GA bullfrog, MO pallid Pseudo-wild = Japan (Am. Bullfrog) Wild = TN, MN, and ME Lithobates clamitans (green frog) Lithobates catesbeianus (American bullfrog) Six Isolates:

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Survival Curves

Green Frogs

2 4 6 8 10 12 14 16 18 20 1 2 3 4 5 6 7 8 9 1 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 2 1 D ays N um b ers

  • f

I nd i vi d ual s

G eorgi a M i ssouri Japan Tennessee M i nnesota M ai ne Significant Necrosis in Liver

GA MO JP

Final Mortality & Infection

Green Frog

0% 20% 40% 60% 80% 100% G eorgi a M i ssouri Japan Tennessee M i nnesota M ai ne Isolates % Indiviuals Infected D i e+I nfected Survi ved+I nfected Survi ved+N

  • t

I nfected D i e+N

  • t

I nfected

Survival & Infection

American Bullfrog

2 4 6 8 10 12 14 16 18 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Days Numbers of Individuals G eorgi a M i ssouri Japan Tennessee M i nnesota M ai ne

0% 20% 40% 60% 80% 100% G eorgi a M i ssouri Japan Tennessee M i nnesota M ai ne Isolates % Indiviuals Infected D i e+I nfected Survi ved+I nfected Survi ved+N

  • t

I nfected D i e+N

  • t

I nfected

Only GA Captive Isolate

GA

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Risk of Pathogen Pollution

Majji et al. (2006), Storfer et al. (2007), Mazzoni et al. (2009), Hoverman et al. (2011a), Brenes (2013)

Mazzoni

Conservation Implications

From 2000-2006, the U.S. imported >1.5 billion individual animals (fish & wildlife; Smith et al. 2009)

— 90% fish, 2% amphibians, 1% reptiles — 25 million live amphibians imported to U.S./year

Ranavirus Positive

  • Hong Kong = 89%
  • Dominican Republic = 70%
  • Madagascar = 57%

Kristine Smith, DVM Smith et al. (unpubl. data)

Questions??

mgray11@utk.edu +1-865-974-2740

Photo:

  • N. Wheelwright