Big questions in disease ecology??

Lately, I’ve been on a quest for big, open questions in disease ecology. I have lots of specific questions on my system, and some general developmental questions about the particular techniques I use, but fewer clear ideas about the big avenues that disease research will (or should) follow in the next ten years. In light of this apparent failing in creativity, I got the CIDD grad student group at Penn State to do some brainstorming with me a few weeks ago. Here are some of the questions we hit on, and in the last paragraph, some notable shortcomings.

Parasites as elements of ecosystems
1. What happens to vacated niches?
2. When does the dilution effect apply?

Questions about pathogen/host evolution
3. How do we measure “tolerance”, and can we rigorously describe selective drivers that control magnitude of host inflammatory responses?
4. What makes an evolution-proof vaccine?
5. What conditions lead to the virulence/tranmission trade-off, and what conditions produce evolution toward avirulence?
6. How do parasites transition to mutualists?

Questions about transmission within host populations
7. In general, what makes a super-spreader (and what counts more, super-spreaders or super-shedders)?
8. What selective pressures to pathogens impose on group size, and what’s our evidential basis for claims about that relationships?

Questions about within-host processes
9. To what extent is immune function an emergent property of the host’s microbiome?
10. Are there general features that describe how coinfection alters host immune response?
11. How does stress interact with immune response?
12. To what extent can we assume that within-host pathogen dynamics follow density-dependent growth processes? What are the costs of that assumption?

Questions about spillover
13. How does density of each host species shape spillover? Do general rules about density- and frequency-dependent transmission apply to spillover, and if not, what revisions are required?
14. How do we simultaneously manage for spillover and endemic disease in each host species (especially social hosts)?

Nina Wale pointed out that many of these questions are ecological in focus (she’s right: ecology is where I come from), and probably need to be reframed in an evolutionary light. I originally claimed that I was in seach of hypotheses, and Megan Greischar pointed out that modelers tend to spend lots of time aimed specifically at generating hypotheses. She has a point… but it seems to me like most models are built with some idea as to what hypotheses might eventually be relevant. In general, we found that asking big, general questions is uncomfortable. We much prefer asking specific questions about our systems. This is probably good: we should focus on the task at hand. On the other hand, I tend to get very focussed on the details of my work. As such, it’s important for me to occassionally try to nest my work in a broader scientific context. On the whole, it was an interesting discussion, albeit one that probably deserves quite a lot more of my time.

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