title: Larval habitats of the Anopheles farauti and Anopheles lungae complexes in the Solomon Islands.
abstract: BACKGROUND
  There is an urgent need for vector control tools to supplement long-lasting insecticidal nets (LLINs) and indoor residual spraying; particularly in the Solomon Islands where the primary vector, Anopheles farauti, is highly anthropophagic and feeds mainly outdoors and early in the evening. Currently, the only supplementary tool recommended by the World Health Organization is larval source management (LSM). The feasibility and potential effectiveness of LSM requires information on the distribution of anophelines, the productivity of larval habitats and the potential impacts of larval control on adult fitness.
  
  
  METHODS
  The distribution of anophelines in Central and Western Provinces in the Solomon Islands was mapped from cross-sectional larval habitat surveys. The composition and micro-distribution of larval instars within a large permanent river-mouth lagoon was examined with a longitudinal survey. Density-dependent regulation of An. farauti larvae was investigated by longitudinally following the development and survival of different densities of first instars in floating cages in a river-mouth lagoon.
  
  
  RESULTS
  Five anopheline species were molecularly identified from a range of fresh and brackish water habitats: An. farauti s.s., An. hinesorum, An. lungae, An. nataliae and An. solomonis. The most common habitats used by the primary malaria vector, An. farauti, were coastal lagoons and swamps. In the detailed study of lagoon micro-productivity, An. farauti was non-uniformly distributed with highest densities found at collections sites most proximal and distal to the mouth of the lagoon. The survival of An. farauti larvae was more than twofold lower when larvae were held at the highest experimental density (1 larva per 3.8 cm(2)) when compared with the lowest density (1 larva per 38 cm(2)).
  
  
  CONCLUSIONS
  The only documented major malaria vector collected in larval surveys in both Central and Western Provinces was An. farauti. Lagoons and swamps, the most common, largest and (potentially) most productive larval sites of this malaria vector, were "few, fixed and findable" and theoretically, therefore, amenable to successful LSM. However, the immense scale and complexity of these ecosystems in which An. farauti larvae are found raises questions regarding the ability to effectively control the larvae, as incomplete larviciding could trigger density dependent effects resulting in increased larval survivorship. While LSM has the potential to significantly contribute to malaria control of this early and outdoor biting vector, more information on the distribution of larvae within these extensive habitats is required to maximize the effectiveness of LSM.
authors.affiliation: Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, 4870, Australia. tanya.russell@jcu.edu.au.
authors.forename: Tanya L
authors.identifier: http://orcid.org/0000-0002-0920-6844
authors.initials: TL
authors.lastname: Russell
authors.affiliation: Australian Institute of Tropical Health and Medicine, James Cook University, Cairns, QLD, 4870, Australia.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Burkot
authors.affiliation: National Vector Borne Disease Control Programme, Ministry of Health, Honiara, Solomon Islands.
authors.forename: Hugo
authors.initials: H
authors.lastname: Bugoro
authors.affiliation: National Vector Borne Disease Control Programme, Ministry of Health, Honiara, Solomon Islands.
authors.forename: Allan
authors.initials: A
authors.lastname: Apairamo
authors.affiliation: School of Biological Sciences, University of Queensland, St. Lucia, QLD, 4068, Australia.|CSIRO, Dutton Park, Brisbane, QLD, 4102, Australia.
authors.forename: Nigel W
authors.initials: NW
authors.lastname: Beebe
authors.affiliation: Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, 4052, Australia.
authors.forename: Weng K
authors.initials: WK
authors.lastname: Chow
authors.affiliation: Australian Army Malaria Institute, Gallipoli Barracks, Enoggera, 4052, Australia.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Cooper
authors.affiliation: Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.
authors.forename: Frank H
authors.initials: FH
authors.lastname: Collins
authors.affiliation: Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.
authors.forename: Neil F
authors.initials: NF
authors.lastname: Lobo
mesh_terms: D000818:Animals; D000852:Anopheles / Q000254:growth & development*; D003430:Cross-Sectional Studies; D017753:Ecosystem; D005260:Female; D007814:Larva / Q000254:growth & development; D008137:Longitudinal Studies; D008542:Melanesia; D058974:Phylogeography; D011156:Population Density
keywords: Anopheles farauti; Density dependent development; Malaria; Solomon Islands; Species distribution