Defining the larval habitat: abiotic and biotic parameters associated with Anopheles farauti productivity

Kimberley Mclaughlin,Thomas R Burkot,Nigel W Beebe,Jance Oscar,Tanya L Russell

doi:10.1186/s12936-019-3049-7

Abstract

BackgroundIn the Solomon Island, the dominant malaria vector, Anopheles farauti, is highly anthropophagic and increasingly exophilic and early biting. While long-lasting insecticide-treated nets remain effective against An. farauti, supplemental vector control strategies will be needed to achieve malaria elimination. Presently, the only World Health Organization recommended supplemental vector control strategy is larval source management (LSM). Effective targeted larval source management requires understanding the associations between abiotic, chemical and biological parameters of larval habitats with the presence or density of vector larvae.MethodsPotential and actual An. farauti larval habitats were characterized for presence and density of larvae and associated abiotic, chemical and biological parameters.ResultsA third of all sampled potential habitats harboured An. farauti larvae with 80% of An. farauti positive habitats being in three habitat classifications (swamps/lagoons, transient pools and man-made holes). Large swamps were the most abundant positive habitats surveyed (43% of all An. farauti positive habitats). Habitats with An. farauti larvae were significantly associated with abiotic (pH, nitrate, ammonia and phosphate concentrations and elevated temperature) and biotic (predators) parameters.ConclusionLarge swamps and lagoons are the largest and most abundant An. farauti habitats in the Solomon Islands. Positive habitats were more frequently associated with the presence of predators (vertebrates and invertebrates) and higher water temperatures. Cohabitation with predators is indicative of a complex habitat ecosystem and raises questions about the potential of biological control as an effective control strategy. Increased presence of An. farauti with higher water temperature suggests a potential explanation for the coastal distribution of this species which is not found inland at elevated altitudes where temperatures would be cooler.

Highlights

In the Solomon Island, the dominant malaria vector, Anopheles farauti, is highly anthropophagic and increasingly exophilic and early biting
While Anopheles hinesorum is a malaria vector in Papua New Guinea [10], only a single sporozoite positive individual was found in Western Province, Solomon Islands and this species is unlikely to maintain malaria transmission due to its predominantly zoophagic biting habit in the Solomon Islands [6]
Anopheles hinesorum larvae were only collected in Kinamara village, where this species made up 79% of identified specimens

Summary

Introduction

In the Solomon Island, the dominant malaria vector, Anopheles farauti, is highly anthropophagic and increasingly exophilic and early biting. While long-lasting insecticide-treated nets remain effective against An. farauti, supplemental vector control strategies will be needed to achieve malaria elimination. The only World Health Organization recommended supplemental vector control strategy is larval source management (LSM). The only WHO recommended strategy to control vectors outdoors is larval source management (LSM) in areas with seasonal transmission or where the McLaughlin et al Malar J (2019) 18:416 larval habitats are few in number, fixed in location and accessible (including urban areas) [2, 4]. While Anopheles hinesorum is a malaria vector in Papua New Guinea [10], only a single sporozoite positive individual was found in Western Province, Solomon Islands and this species is unlikely to maintain malaria transmission due to its predominantly zoophagic biting habit in the Solomon Islands [6]. Malaria vector control in the Solomon Islands focuses on An. farauti

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