Predicting optimal transmission investment in malaria parasites.
In vertebrate hosts, malaria parasites face a tradeoff between replicating and the production of transmission stages that can be passed onto mosquitoes. This tradeoff is analogous to growth-reproduction tradeoffs in multicellular organisms. We use a mathematical model tailored to the life cycle and dynamics of malaria parasites to identify allocation strategies that maximize cumulative transmission potential to mosquitoes. We show that plastic strategies can substantially outperform fixed allocation because parasites can achieve greater fitness by investing in proliferation early and delaying the production of transmission stages. Parasites should further benefit from restraining transmission investment later in infection, because such a strategy can help maintain parasite numbers in the face of resource depletion. Early allocation decisions are predicted to have the greatest impact on parasite fitness. If the immune response saturates as parasite numbers increase, parasites should benefit from even longer delays prior to transmission investment. The presence of a competing strain selects for consistently lower levels of transmission investment and dramatically increased exploitation of the red blood cell resource. While we provide a detailed analysis of tradeoffs pertaining to malaria life history, our approach for identifying optimal plastic allocation strategies may be broadly applicable.
Center For Infectious Disease Dynamics, Departments of Entomology and Biology, The Pennsylvania State University, University Park, Pennsylvania 16802. megan.greischar@utoronto.ca.|Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada. megan.greischar@utoronto.ca.
Megan A
MA
Greischar
Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada.
Nicole
N
Mideo
Center For Infectious Disease Dynamics, Departments of Entomology and Biology, The Pennsylvania State University, University Park, Pennsylvania 16802.|Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892.
Andrew F
AF
Read
Center For Infectious Disease Dynamics, Departments of Entomology and Biology, The Pennsylvania State University, University Park, Pennsylvania 16802.|Fogarty International Center, National Institutes of Health, Bethesda, Maryland 20892.
Ottar N
ON
Bjørnstad
D000818:Animals; D009033:Culicidae / Q000469:parasitology*; D056084:Genetic Fitness; D006790:Host-Parasite Interactions; D008288:Malaria / Q000635:transmission*; D008954:Models, Biological; D010961:Plasmodium / Q000235:genetics / Q000502:physiology*; D011157:Population Dynamics; D012098:Reproduction
Coinfection; malaria; reproductive restraint; transmission investment; virulence