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Parasitism and Disease

Parasitism and Disease. Lyme Disease Cycle in the UK. Evolution of Host-Parasite Interactions . European rabbits as pests in Australia - 1938 . Introduced pests in Australia – red fox, rabbit, cat, pig, & goat. Parasite effect on host population.

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Parasitism and Disease

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  1. Parasitism and Disease Lyme Disease Cycle in the UK

  2. Evolution of Host-Parasite Interactions

  3. European rabbits as pests in Australia - 1938

  4. Introduced pests in Australia – red fox, rabbit, cat, pig, & goat

  5. Parasite effect on host population Parasite can cause direct mortality but then can only persist in a large host population Usually parasite lowers host reproduction, growth or survival - often this effect is indirect by way of 1) lowers host stamina - more subject to predation, competition 2) increases conspicuousness - predation risk increases 3) disorient host via neurological damage 4) alters host response to environmental stimuli

  6. Fungal parasites alter insect behavior Giant ant w/o and with fungus

  7. Moose and White-tailed Deer

  8. Deer – Moose brain worm interaction

  9. Avian malaria occurs in areas below white line on Island of Hawaii – highest incidence between yellow and white lines

  10. Hawaiian Crow – Extinct in Wild

  11. I’iwi Honeycreeper – highly susceptible to avian malaria

  12. Akiapolaau Honeycreeper – restricted to high elevation today

  13. Amakihi Honeycreeper – shows evidence of evolving resistance

  14. Sir Robert May Roy Anderson

  15. Spread of HIV in Russia

  16. Dynamics of parasite populations Most important parameter is basic reproductive rate of the parasite, symbolized Rp Rp will: 1) increase with increasing density of susceptible hosts - N 2) increase with increasing transmission rate beta β 3) increase with increasing fraction of infected hosts that survive long enough to be infectious to other hosts - symbolized by f 4) increase with increasing average time that host remains infectious - symbolized by L

  17. Dynamics of parasite populations • We can also examine the reproductive rate of infection (Ri) = average number of secondary cases of infection generated by one primary case in a population where almost everyone is susceptible to infection • Ri > 1 each infection has more than one "offspring" - chain reaction of epidemic • Ri < 1 infection cannot sustain itself

  18. Incidence of HIV in Africa

  19. You’re never too old to need protection

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