title: Wolbachia Reduces the Transmission Potential of Dengue-Infected Aedes aegypti.
abstract: BACKGROUND
  Dengue viruses (DENV) are the causative agents of dengue, the world's most prevalent arthropod-borne disease with around 40% of the world's population at risk of infection annually. Wolbachia pipientis, an obligate intracellular bacterium, is being developed as a biocontrol strategy against dengue because it limits replication of the virus in the mosquito. The Wolbachia strain wMel, which has been introduced into the mosquito vector, Aedes aegypti, has been shown to invade and spread to near fixation in field releases. Standard measures of Wolbachia's efficacy for blocking virus replication focus on the detection and quantification of virus in mosquito tissues. Examining the saliva provides a more accurate measure of transmission potential and can reveal the extrinsic incubation period (EIP), that is, the time it takes virus to arrive in the saliva following the consumption of DENV viremic blood. EIP is a key determinant of a mosquito's ability to transmit DENVs, as the earlier the virus appears in the saliva the more opportunities the mosquito will have to infect humans on subsequent bites.
  
  
  RESULTS
  We used a non-destructive assay to repeatedly quantify DENV in saliva from wMel-infected and Wolbachia-free wild-type control mosquitoes following the consumption of a DENV-infected blood meal. We show that wMel lengthens the EIP, reduces the frequency at which the virus is expectorated and decreases the dengue copy number in mosquito saliva as compared to wild-type mosquitoes. These observations can at least be partially explained by an overall reduction in saliva produced by wMel mosquitoes. More generally, we found that the concentration of DENV in a blood meal is a determinant of the length of EIP, saliva virus titer and mosquito survival.
  
  
  CONCLUSIONS
  The saliva-based traits reported here offer more disease-relevant measures of Wolbachia's effects on the vector and the virus. The lengthening of EIP highlights another means, in addition to the reduction of infection frequencies and DENV titers in mosquitoes, by which Wolbachia should operate to reduce DENV transmission in the field.
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Yixin H
authors.initials: YH
authors.lastname: Ye
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Alison M
authors.initials: AM
authors.lastname: Carrasco
authors.affiliation: Institute for Health and Biomedical Innovation and School of Biomedical Sciences, Queensland University of Technology, Kelvin Grove, Queensland, Australia.
authors.forename: Francesca D
authors.initials: FD
authors.lastname: Frentiu
authors.affiliation: School of Biological Sciences, The University of Queensland, St. Lucia, Queensland, Australia.
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Chenoweth
authors.affiliation: School of Biological Sciences, The University of Queensland, St. Lucia, Queensland, Australia; CSIRO Biosecurity Flagship, Ecosciences Precinct, Dutton Park, Queensland, Australia.
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Beebe
authors.affiliation: Virology, Public and Environmental Health, Forensic and Scientific Services, Department of Health, Queensland Government, Coopers Plains, Queensland, Australia.
authors.forename: Andrew F
authors.initials: AF
authors.lastname: van den Hurk
authors.affiliation: Nossal Institute of Global Health, University of Melbourne, Parkville, Victoria, Australia; Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam; Centre for Tropical Medicine, University of Oxford, Churchill Hospital, Oxford, United Kingdom.
authors.forename: Cameron P
authors.initials: CP
authors.lastname: Simmons
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Scott L
authors.initials: SL
authors.lastname: O'Neill
authors.affiliation: School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: McGraw
mesh_terms: D000330:Aedes / Q000382:microbiology / Q000821:virology*; D000818:Animals; D003715:Dengue / Q000517:prevention & control* / Q000635:transmission; D003716:Dengue Virus / Q000502:physiology*; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000382:microbiology / Q000821:virology*; D008297:Male; D010572:Pest Control, Biological / Q000379:methods*; D010641:Phenotype; D012463:Saliva / Q000821:virology; D013559:Symbiosis; D019562:Viral Load; D014779:Virus Replication; D020577:Wolbachia / Q000502:physiology*