Predicting the consequences of diverse life history in malaria parasites : synchrony and transmission investment
- Greischar, Megan
- [University Park, Pennsylvania] : Pennsylvania State University, 2014.
- Physical Description:
- 1 electronic document
- Additional Creators:
- Read, Ottar N. Bjornstad and Andrew F. and Read, A. F.
- Graduate Program:
- Restrictions on Access:
- Open Access.
- Malaria parasites have evolved astonishingly varied means of solving the same basic problem of converting host resources---red blood cells---into parasite biomass that can be transmitted to vectors and ultimately, new hosts. This diversity is challenging to explain, because if a life history trait improved transmission, parasites with that trait would be expected to displace others. How can such divergent strategies all lead to sustained transmission success? I focus on two aspects of the malaria life cycle, synchronization of blood stage infection and allocation to transmission, to examine how within-host ecology can maintain diverse parasite strategies. The models I develop to address that question are also used to identify robust methods for inferring parasite traits from time series data.The models show that the advantages of synchrony depend on the interplay between competition for host resources, immune clearance, and the odds of transmitting to a vector, all of which vary with parasite densities. Using data from lab-cultured parasites, I examine the intra-strain competitive interactions in more detail, finding preliminary support for a form of density-dependent competition that, counterintuitively, may benefit synchronous parasites. The model demonstrates that traditional inference methods can give misleading estimates of parasites' life cycle length. Within the host, the model suggests that competition between coinfecting strains should reduce allocation to transmission stage production. Allowing transmission investment to vary through time, the model indicates that transmission investment is especially costly early in infection. Inspired by the controversy in the literature concerning how best to infer transmission investment, I use the model to show that current methods are likely incapable of ruling out the null hypothesis that transmission investment is fixed through time rather than plastic, and develop improved methods for inferring transmission investment. The theory developed here can inform efforts to describe the rich diversity in parasite life history as well as the adaptive significance of that diversity.
- Other Subject(s):
- Dissertation Note:
- Ph.D. Pennsylvania State University 2014.
- Reproduction Note:
- Microfilm (positive). 1 reel ; 35 mm. (University Microfilms 36-47449)
- Technical Details:
- The full text of the dissertation is available as an Adobe Acrobat .pdf file ; Adobe Acrobat Reader required to view the file.
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