title: Bottom-up regulation of malaria population dynamics in mice co-infected with lung-migratory nematodes.
abstract: When and how populations are regulated by bottom up vs. top down processes, and how those processes are affected by co-occurring species, are poorly characterised across much of ecology. We are especially interested in the community ecology of parasites that must share a host. Here, we quantify how resources and immunity affect parasite propagation in experiments in near-replicate 'mesocosms'' - i.e. mice infected with malaria (Plasmodium chabaudi) and nematodes (Nippostrongylus brasiliensis). Nematodes suppressed immune responses against malaria, and yet malaria populations were smaller in co-infected hosts. Further analyses of within-host epidemiology revealed that nematode co-infection altered malaria propagation by suppressing target cell availability. This is the first demonstration that bottom-up resource regulation may have earlier and stronger effects than top-down immune mechanisms on within-host community dynamics. Our findings demonstrate the potential power of experimental ecology to disentangle mechanisms of population regulation in complex communities.
authors.affiliation: Department of Entomology, Gardner Hall, Derieux Place, Raleigh NC 27695-7613, USA.
authors.forename: Emily C
authors.initials: EC
authors.lastname: Griffiths
authors.affiliation: Institute of Biodiversity, Animal Health & Comparative Medicine, College of Medical and Veterinary Life Sciences, University of Glasgow, Glasgow, G61 1QH, UK.
authors.forename: Karen
authors.initials: K
authors.lastname: Fairlie-Clarke
authors.affiliation: Institute of Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, EH8 9YL, UK.
authors.forename: Judith E
authors.initials: JE
authors.lastname: Allen
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA.|Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892, USA.
authors.forename: C Jessica E
authors.initials: CJ
authors.lastname: Metcalf
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08544, USA.|Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892, USA.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Graham
mesh_terms: D000818:Animals; D060085:Coinfection / Q000276:immunology / Q000469:parasitology*; D005260:Female; D007113:Immunity, Innate; D008288:Malaria / Q000276:immunology / Q000469:parasitology*; D051379:Mice; D008807:Mice, Inbred BALB C; D009559:Nippostrongylus / Q000502:physiology; D016788:Plasmodium chabaudi / Q000502:physiology; D011157:Population Dynamics; D012376:Rodent Diseases / Q000276:immunology / Q000469:parasitology*; D017206:Strongylida Infections / Q000276:immunology / Q000469:parasitology*
keywords: Co-infection; community ecology; effective propagation; immune profile; parasite ecology; predator community; resource regulation; target cell limitation