title: Fitness consequences of altered feeding behavior in immune-challenged mosquitoes.
abstract: BACKGROUND
  Malaria-infected mosquitoes have been reported to be more likely to take a blood meal when parasites are infectious than when non-infectious. This change in feeding behavior increases the likelihood of malaria transmission, and has been considered an example of parasite manipulation of host behavior. However, immune challenge with heat-killed Escherichia coli induces the same behavior, suggesting that altered feeding behavior may be driven by adaptive responses of hosts to cope with an immune response, rather than by parasite-specific factors. Here we tested the alternative hypothesis that down-regulated feeding behavior prior to infectiousness is a mosquito adaptation that increases fitness during infection.
  
  
  METHODS
  We measured the impact of immune challenge and blood feeding on the fitness of individual mosquitoes. After an initial blood meal, Anopheles stephensi Liston mosquitoes were experimentally challenged with heat-killed E. coli at a dose known to mimic the same temporal changes in mosquito feeding behavior as active malaria infection. We then tracked daily egg production and survivorship of females maintained on blood-feeding regimes that either mimicked down-regulated feeding behaviors observed during early malaria infection, or were fed on a four-day feeding cycle typically associated with uninfected mosquitoes.
  
  
  RESULTS
  Restricting access to blood meals enhanced mosquito survival but lowered lifetime reproduction. Immune-challenge did not impact either fitness component. Combining fecundity and survival to estimate the population-scale intrinsic rate of increase (r), we found that, contrary to the mosquito adaptation hypothesis, mosquito fitness decreased if blood feeding was delayed following an immune challenge.
  
  
  CONCLUSIONS
  Our data provide no support for the idea that malaria-induced suppression of blood feeding is an adaptation by mosquitoes to reduce the impact of immune challenge. Alternatively, the behavioral alterations may be neither host nor parasite adaptations, but rather a consequence of constraints imposed on feeding by activation of the mosquito immune response, i.e. non-adaptive illness-induced anorexia. Future work incorporating field conditions and different immune challenges could further clarify the effect of altered feeding on mosquito and parasite fitness.
authors.affiliation: Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, PA, USA. jo.ohm@psu.edu.
authors.forename: Johanna R
authors.initials: JR
authors.lastname: Ohm
authors.affiliation: Center for Infectious Disease Dynamics, Department of Entomology, Pennsylvania State University, University Park, PA, USA. jlt5194@psu.edu.
authors.forename: Janet
authors.initials: J
authors.lastname: Teeple
authors.affiliation: Department of Biology, Queens University, Kingston, Ontario, Canada. nelsonw@queensu.ca.
authors.forename: William A
authors.initials: WA
authors.lastname: Nelson
authors.affiliation: Center for Infectious Disease Dynamics, Department of Entomology, Pennsylvania State University, University Park, PA, USA. mbt13@psu.edu.
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Thomas
authors.affiliation: Center for Infectious Disease Dynamics, Departments of Biology and Entomology, Pennsylvania State University, University Park, PA, USA. a.read@psu.edu.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Read
authors.affiliation: Grand Challenges in Ecosystems and Environment, Department of Life Sciences, Imperial College, Silwood Park Campus, London, UK. l.cator@imperial.ac.uk.
authors.forename: Lauren J
authors.initials: LJ
authors.lastname: Cator
mesh_terms: D000818:Animals; D000852:Anopheles / Q000276:immunology / Q000502:physiology*; D004926:Escherichia coli / Q000276:immunology*; D005247:Feeding Behavior; D012098:Reproduction; D016019:Survival Analysis