title: Natural variation in virulence of the entomopathogenic fungus Beauveria bassiana against malaria mosquitoes.
abstract: BACKGROUND
  Insecticide resistance is greatly hampering current efforts to control malaria and therefore alternative methods are needed. Entomopathogenic fungi have been proposed as an alternative with a special focus on the cosmopolitan species Beauveria bassiana. However, few studies have analysed the effects of natural variation within fungal isolates on mosquito survival, and the implications and possible exploitation for malaria control.
  
  
  METHODS
  Laboratory bioassays were performed on adult female mosquitoes (Anopheles coluzzii) with spores from 29 isolates of B. bassiana, originating from different parts of the world. In addition, phenotypic characteristics of the fungal isolates such as sporulation, spore size and growth rate were studied to explore their relationship with virulence.
  
  
  RESULTS
  All tested isolates of B. bassiana killed An. coluzzii mosquitoes, and the rate at which this happened differed significantly among the isolates. The risk of mosquitoes dying was around ten times higher when they were exposed to the most virulent as compared to the least virulent isolate. There was significant variation among isolates in spore size, growth rate and sporulation, but none of these morphological characteristics were correlated, and thus predictive, for the ability of the fungal isolate to kill malaria mosquitoes.
  
  
  CONCLUSIONS
  This study shows that there is a wide natural variation in virulence of isolates of B. bassiana, and that selecting an appropriate fungal isolate is highly relevant in killing and thus controlling malaria mosquitoes, particularly if used as part of an integrated vector management strategy. Also, the wide variation observed in virulence offers the opportunity to better understand the molecular and genetic mechanisms that drive this variation and thus to address the potential development of resistance against entomopathogenic fungi.
authors.affiliation: Laboratory of Genetics, Wageningen University, P,O Box 309, 6700, AH Wageningen, The Netherlands. claudio.valero@wur.nl.
authors.forename: Claudio A
authors.initials: CA
authors.lastname: Valero-Jiménez
authors.forename: Alfons J M
authors.initials: AJ
authors.lastname: Debets
authors.forename: Jan A L
authors.initials: JA
authors.lastname: van Kan
authors.forename: Sijmen E
authors.initials: SE
authors.lastname: Schoustra
authors.forename: Willem
authors.initials: W
authors.lastname: Takken
authors.forename: Bas J
authors.initials: BJ
authors.lastname: Zwaan
authors.forename: Constantianus J M
authors.initials: CJ
authors.lastname: Koenraadt
mesh_terms: D000818:Animals; D000852:Anopheles / Q000382:microbiology* / Q000502:physiology*; D052982:Beauveria / Q000254:growth & development / Q000472:pathogenicity / Q000502:physiology*; D001681:Biological Assay; D005260:Female; D016019:Survival Analysis; D014774:Virulence