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Archived Comments for: Progress towards malaria elimination in Sabang Municipality, Aceh, Indonesia

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  1. Vector species incrimination crucial for malaria elimination

    Michael Bangs, International SOS

    13 November 2013

    As regular readers of the Malaria Journal, we would like to point out an obvious weakness of the paper by Herdiana et al. (2013, 12:42) regarding the entomological analysis. Several aspects of the authors¿ conclusions are unacceptable, especially the conclusion that Anopheles dirus and An. minimus are present on Sabang Island (northern Sumatra). Even if true, such a pronouncement is inappropriate without performing definitive confirmation of species identity. Given they failed to do so, the findings should have been properly presented in the context of this shortcoming and what implications it might have for eliminating malaria from the island. Neither the subject paper nor cited reference (Hudson et al. 1985) indicates the primary malaria vector(s) on Sabang Island, other than to state the location has a ¿diverse mosquito fauna¿. It appears the primary malaria vector remains unknown. Therefore, technically the authors did not perform a vector ¿assessment¿, rather a mosquito faunal and behavioral survey. Moreover, it is nearly impossible to draw any conclusions based on only 23 adult Anopheles captured during six evening collections. Although malaria elimination is clearly a laudable goal, any attempts at targeted vector control would be met with uncertainty, especially if only applying IRS and LLINs as interventions against indoor frequenting vectors. It seems unusual to promote the idea of malaria elimination and use of vector control without having a better knowledge of the actual vectors or clearly stating more information is needed to better reduce transmission.
    With the advancement of molecular technology, it is insufficient to identify certain malaria vectors present in Southeast Asia based on morphology alone. Therefore, two possibilities must be considered: (1) authors must use established PCR assays to accurately identify Anopheles specimens belonging to recognized species complexes; or (2) clearly state that the specimens were not definitively identified to species level, and use ¿s.l.¿ (sensu lato) to indicate that the taxon/taxa is/are referred to in the broad sense, i.e. the group of sibling species that were recognized as a single species prior to the advent of molecular methods of unambiguous identification. In this case, it is surprising that Herdiana et al. did not use a molecular assay to confirm the identification of certain anopheline mosquitoes since they used sophisticated molecular detection methods for malaria parasites from mass blood screening.
    Advanced molecular methods must be used if possible when encountering sibling species. The entomological data provided in this article are unreliable because the authors did not apply the most appropriate and definitive methods of species identification. Therefore, they cannot confidently or legitimately state ¿This represents the first report of An. dirus from Indonesia¿. The occurrence of An. dirus, An. minimus, and An. sundaicus (all species in the strict sense, i.e. the nominotypical members of sibling species complexes) in Indonesia is highly questionable. The most recent literature on these three species complexes has shown the presence of An. cracens of the Dirus Complex (but not An. dirus) in northern Sumatra. For the Minimus Complex, An. minimus might possibly occur on Sabang Island; however, in the adult stage this species is easily misidentified as An. flavirostris, a species of the Minimus Subgroup that is found on Sabang Island and is widely distributed in Indonesia. Within the Sundaicus Complex, An. sundaicus has only been collected on Borneo Island, whereas An. sundaicus species `E¿ occurs in Sumatra, Java and outer eastern islands of Indonesia. The focus of this paper on malaria elimination using vector control is on shaky grounds as An. cracens and An. flavirostris are considered secondary (even incidental) malaria vectors, nothing compared to the major role that highly efficient vectors, An. dirus and An. minimus, play in malaria transmission on mainland Southeast Asia. Additionally, each species of a complex may have specific behavioral traits, ecological requirements, host preferences, vectorial capacity, etc. based on location and circumstances that must be better understood. Consequently, not unambiguously identifying the anopheline species signifies that the results are wholly insufficient for vector incrimination and operational control purposes, objectives clearly stated in the paper.

    Prof. Sylvie Manguin, PhD.
    Research Professor
    Medical Entomologist Laboratoire d'Immuno-Physiopathologie Moléculaire Comparée
    (LIPMC), UMR-MD3
    Institut de Recherche pour le Développement
    Faculté de Pharmacie, Bât D, Université Montpellier I (UMI)
    15, Ave Charles Flahault, 34093 Montpellier cedex 5, France

    Ralph E. Harbach, PhD.
    Merit Researcher
    Department of Life Sciences
    Natural History Museum
    Cromwell Road
    London SW7 5BD, UK

    Michael J. Bangs, MSPH, PhD.
    Senior Malaria and Vector Control Technical Advisor
    International SOS
    Kuala Kencana 99930
    Papua, Indonesia

    Competing interests

    The contributors have no financial or non-financial competing interests regard subject matter comments.