Prelim question: what would be different in a world without parasites?

Thought experiment time! Let’s say you could somehow (1) find/identify/locate and (2) eliminate every parasite on the planet. In this case we’ll lump pathogens and viruses and parasitoids and maybe even micropredators/vectors into the category of “parasites.” If you waved your magic wand and eliminated parasites from the planet, what effects would that elimination have on individuals, populations, communities, and ecosystems? I think that’s a great disease ecology prelim question, and you should all start using it immediately.

If you’re interested in the answers that other people have proposed to answer that question, I have some links for you! You can check out Wood and Johnson’s recent Frontiers in Ecology and Evolution paper (“A world without parasites: exploring the hidden ecology of infection“), and the similar and wonderful “soapbox” paper written by Bob Holt (“A World free of parasites and vectors: Would it be heaven, or would it be hell?“). Then there are these thought-provoking papers parasite conservation by Gomez et al. (“Parasite conservation, conservation medicine, and ecosystem health” and “Neglected wild life: Parasitic biodiversity as a conservation target“). Doughtery and colleagues also have a parasite conservation paper out in press that you might be interested in (“Paradigms for parasite conservation”).

Preparing for Disease Ecology Prelims

Here’s a little post for all you PhD students nearing your qualifying/comprehensive/preliminary exams.  If I were asked to study disease ecology for such an exam, this is what I would know:

Who are the most influential modern day disease ecologists (or parasite ecologists)?  You might start with my list of the most prolific parasite ecologists in the 21st century.

What is the disease triangle?

What were Koch’s Postulates?

What proportion of Earth’s species are parasites/pathogens?  What proportion of the total biomass in an ecosystem is parasite biomass?  I have some related posts: here and here.

Do parasites/pathogens regulate host populations?  Somehow, I think I I’ve only blogged about this once

How do parasites affect food webs?  You might start here and here.

What are the differences between microparasites and macroparasites?  Here.

What are the differences between predators, parasites, and parasitoids?  Here.

Why are macroparasites aggregately distributed among hosts, and why does it matter?  Here and here and here.

What are the hypotheses regarding the evolution of virulence?  I haven’t blogged about that much, but there’s a bit here.

What are SIR models?  SI models?  SIS models?  SEIR models? Vector transmission models?  

What is R0?  What happens when R0 > 1 and when R0 < 1?  How can you reduce R0?  What is the critical proportion of susceptible individuals that needs to be vaccinated so that R0 < 1?  Somehow, I haven’t covered this in any detail.  But I have a cute cow cartoon about herd immunity.

What are density dependent and frequency dependent parasite transmission?  Here and here.

Are there invasion thresholds is disease systems? Link to PDF.

Is culling a viable strategy for disease management?  See previous two questions.

What role does contact heterogeneity play in disease transmission?  What are superspreaders?  What is a superreceiver? Here, here, and here.

Is disease risk related to biodiversity?  What is the dilution effect?  Amplification effect? Neutral effect?  Here and here, for starters.

What are the main types of pathogen transmission? E.g., direct vs. indirect, sexually transmitted, vectored, trophically transmitted, etc.

Explain the concept of parasite manipulation of host behavior.  Is it adaptive?  What are the consequences for communities/ecosystems?  Here and here, but there is waaay more material out there.

Do hosts and parasites coevolve?  Is there evidence of parasite-mediated selection?

What is parasite-mediated competition?  Does it happen in real systems?

Are there general laws in parasite ecology?  PDF link.

How are resistance and tolerance different? Here.

Did I miss anything?  Add in the comments or shoot me an email!