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Whither Disease Ecology Multi -host, Multi Parasite in Wildlife

Whither Disease Ecology Multi -host, Multi Parasite in Wildlife 3 Points to think about Ecology & Disease. R 0 o R N o t ?. HUD. DOB. Grouse. Wolf. Maasai. Rats Tenrec. Sheep. Mouse.

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Whither Disease Ecology Multi -host, Multi Parasite in Wildlife

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  1. Whither Disease Ecology Multi-host, Multi Parasite in Wildlife 3Points to think about Ecology & Disease R0oRNot ? HUD DOB Grouse Wolf Maasai Rats Tenrec Sheep Mouse PeterHudson, KeziaManlove, Emily Almberg, Paul Cross, Francis Cassirer, …..and of course: Andy Dobson Discussion: Isabella Cattadori& Jamie Lloyd Smith Deep Thanks to: RAPIDD, NIH, NSF, MAF,

  2. Key Point 1: Vaccinating with Lemons: Save America Eat More Citrus Fruit ……… 3

  3. 1: Spurious Correlations : The Need for a Killer Experiment “If we Import 4,500 Tons of Lemons per annum we could eradicate all Highway Fatalities!” Only 24.8 million Lemons = 0.1 lemons per person! Spurious correlations do not prove cause & effect why should models? 4

  4. 1. Killer Experiments : Needs an Experimental test Do parasites reduce fecundity? • Step 1 E Births  Deaths E E Host E  C E E E Parasite C C C C E  C C  2 C Free Living Stages • Step 3 5 Hudson et al. 1992 J.Anim Ecol

  5. 1. Parasites embedded in the Community System Community Impact Grazing Stable Dynamics Rainfall Underlying Rock Food Quality Sunshine Peat Depth Survival Raptors Fecundity Predation Cover Corvids Foxes Parasite Host Density Ticks Deer & Sheep Viral Pathogens Hares Dispersal Social Behavior Aggression Relatedness Unstable Dynamics 12 Hudson et al. 2002 Phil Trans Roy Soc

  6. 1. The Dilution Hypothesis: In desperate need of Experimental tests Biodiversity reduces risk of exposure to zoonotic infections ~ Non competent hosts are a sink to infection (wasted bites) Generalized: The Competent Hosts are The Resilient hosts So depauperate communities more likely to transmit NC NC Density of Non Competent Host NC C Ixodes vectors Norman et al 1999 Borrelia Density of Competent Host NC NC 6

  7. 1. The Dilution Hypothesis: In desperate need of Experimental tests Biodiversity reduces risk of exposure to zoonotic infections Generalized: The Competent Hosts are The Resilient hosts So depauperate communities more likely to transmit Experimental manipulation? Predictions: Norman model Experimentally Remove competent Negative Control: Remove non competent – Chipmunk Ixodes vectors Borrelia 7

  8. Key Point 1: Neither correlations or models provide proof …. We need perturbation experiments to reveal mechanisms…… 8

  9. 2. Multiscale Issues:Coinfection, heterogeneity and transmission Pandemic Between Host Models Dynamics Transmission Community Interaction Within Host Models Julius Jauregg1857-1940 Indirect-Comp: Immuno Modulated Hypothesis: Coinfections generate transmission heterogeneities Protein 9

  10. 9 M2 M2 M2 M2 M2 M2 M2 M2 M2 M3 M3 M3 M3 M3 M3 M3 M3 M3 8 M4 M4 M4 M4 M4 M4 M4 M4 M4 M5 M5 M5 M5 M5 M5 M5 M5 M5 7 M6 M6 M6 M6 M6 M6 M6 M6 M6 M7 M7 M7 M7 M7 M7 M7 M7 M7 6 M8 M8 M8 M8 M8 M8 M8 M8 M8 M9 M9 M9 M9 M9 M9 M9 M9 M9 5 M10 M10 M10 M10 M10 M10 M10 M10 M10 intensity 4 3 2 1 0 2 4 6 8 10 12 14 16 18 Month 2013 1977 2. Multiscale Issues:Coinfection, heterogeneity and transmission M3 T. retortaeformis Rabbits Bordetella bronchiseptica Trichostrongylus retortaeformis Graphidiumstrigosum Cittotaeniadenticulata Mosgovoylapectinata Myxoma Virus Passalurus ambiguous RHD Virus 10

  11. 2. Multiscale Issues:Coinfection, heterogeneity and transmission Single Parasite Immune Pathway Models (Note: Chronic Infections) Bordetellabronchiseptica Trichsotrongylusretortaeformis Compartment I = Local Response Compartment II = Systemic Response 11 Thakar et al. 2012 Plos Comp Biol

  12. The Co-infection Hypothesis: Prevalence changes with coinfection Co-infection Immune Pathway Model – No Direct Lung Small Intestine Common Cytokines 12 Thakar et al. 2012 PLOS Comp Biol

  13. [ ] Knock out node experiments ~ Parasite activity from simulations -= Key nodes for persistence Bordetella Bordetella+ Worm [ ] Worm Worm + Bordetella IL12 II stimulates Th1 response is necessary for bacteria clearance IL10 ..stimulated subversely by bacteria as a regulatory cytokine 13

  14. Broad Spectrum Systemic Anthlemintic: Kills Helminths, Mites, Bed bugs, Lice, Ticks Toxic to some genotypes Stimulates immune response Bordetella bronchiseptica Trichostrongylus retortaeformis Graphidiumstrigosum Cittotaeniadenticulata Mosgovoylapectinata Myxoma Virus Passalurus ambiguous RHD Virus 14

  15. Key Point 2: Coinfections introduce important transmission heterogeneities? How & When?

  16. 3: R0: Whence the Alternative Hypotheses: Persistence R0 ~ initial spread, likelihood of epidemic, vaccination proportion BUT Selection does not always maximize R0: e.g. Superinfection NEED to test other hypotheses & Models – Persistence R0 = Transmission* Infectious Period (1/mortality) R0 with High transmission * Low infectious period = Low Transmission * High infectious period But Different dynamics & Persistence likelihood Epidemic Fadeout 16 Grenfell 2002 Grenfell 2002

  17. 3: R0 , Dynamics & Persistence: The Alternative Hypotheses Simple, Direct, Monoxenic Life Cylce R0= βλH. (α+b+μP) (γ+βH) R0= T 1 M1M2 a Births  b Deaths Host  Parasite Threshold Host Density ~ Persistence HT = M1γ β(λ-M1) Critical Community Size Host Replenishment μ M1 T  Epidemic Fadeout  γ Free Living Stages M2 Trichostrongylus life cycle 17 Dobson & Hudson Model

  18. 3. Persistence Mechanisms: Arrested Development = Hypobiosis No Arrested Development Arrested Development a Births  b R0 Deaths Host  Free living larvae life expectancy Parasite μ T  AD  γ Free Living Stages M2 18 Dobson & Hudson Model

  19. 1. MacroparasiteComplex Life Cycles: Heteroxenic ~ Complex Life Cycles ~ Indirect ~ Heteroxenic Geoff Parker : Complex life cycle evolved to increase R0.Reduced larval mortality & increased adult body size leads to high fecundity M3 T3 T1 T2 M1 M2 Opisthorcis life cycle R0= T1 T2 T31 M1M2 M3 HT= lower 19 Dobson, Hudson & Lyles 1992

  20. Key Point 3: Maximizing R0 is but one Hypothesis.. Alternative: Persistence Persistence Mechanisms in Neuro infections Chicken Pox ~ Shingles Rabies ~ Multiple Host Species? 20

  21. Point 1: Need for Experiments Point 2: Coinfections generate heterogeneities Point 3: R0 is but one hypothesis ~ Persistence

  22. 4. What happens After Disease Invasion? … Bighorn Sheep Wild Lamb Experimental Infection Mycoplasma ovipneumoniae[= M.ovi] 21 21

  23. 4. What happens After Disease Invasion? Host or Pathogen? 22 37 Cassirer et al . 2013

  24. 4. What happens After Invasion? … Pathogen or Host Selection ? Keypoint 4: Alternative hypotheses: Pathogen evolution: Host selection ~ those with long infectious periods ~ but not humans Phocine Distemper Virus Rabbit Hemorrhagic Virus Mycoplasma in Bighorns

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