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Megan A. Greischar

Megan A. Greischar

Graduate Student, Entomology
Read Lab and Bjornstad Lab

Emailmag450@psu.edu

Office: W-248 Millennium Science Complex

Research interests

I want to know what parasites are doing inside their hosts and why. It's not easy to measure what's happening within the host, but data from malaria infections suggest that parasites are doing some very strange things, including sometimes synchronizing their life cycles so that waves of parasites invade red blood cells, develop, and burst out in unison. That behavior should maximize competition for host resources for no obvious gain.

Some free-living organisms also synchronize their development because it can help them find mates and overwhelm natural enemies. My favorite example is periodical cicadas, because I witnessed the emergence of the Great Eastern Brood in 2004 on the Indiana University campus. The cicada song was deafening, and it was clear that these insects were not struggling to find each other, nor were they being eaten by predators (in fact, the stench from the carcasses got pretty bad as the brood died off). My within-host model suggests that malaria parasites may synchronize for the same reasons: so that parasites can find each other and mate inside a mosquito's blood meal, and so as to overwhelm host defenses through sheer numbers.

My current projects include modeling malaria dynamics in the petri dish--where synchrony falls apart--to assess how much of infection dynamics are under parasite control (in collaboration with the Ferdig group at Notre Dame) and modeling how malaria parasites balance growth within a host with transmission to new hosts (in collaboration with Nicole Mideo). Finally, since it's so difficult to directly measure what's going on inside a host, we have to make inferences based on some simplifying assumptions, and I'm using my model to try to understand when we can be confident in our estimates of within-host processes, including the degree to which a parasite population is synchronized, and how much parasites are investing into transmission.

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