High seasonal malaria transmission rates in the intermediate rainfall zone of Sri Lanka

Ramasamy, Ranjan; Ramasamy, M. S.; Wijesundera, D. A.; Wijesundera, Anula; Dewit, I.; Ranasinghe, Charani; Srikrishnaraj, K. Alagaratnam; Wickremaratne, C.

doi:10.1080/00034983.1992.11812714

Cited by 31 publications

(26 citation statements)

References 7 publications

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“…The present molecular characterization of the Subpictus complex in Sri Lanka shows the existence of two distinct sibling species namely species A and B and reports a DNA based diagnostic technique to distinguish them in Sri Lanka. Studies in coastal areas in the North Central Province [9] and inland areas of North Central and Eastern Provinces [3,4] of Sri Lanka indicate the involvement of An. subpictus in malaria transmission.…”

Section: Resultsmentioning

confidence: 99%

Molecular characterization and identification of members of the Anopheles subpictus complex in Sri Lanka

Surendran

Sarma

Jude

et al. 2013

Malar J

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BackgroundAnopheles subpictus sensu lato is a major malaria vector in South and Southeast Asia. Based initially on polytene chromosome inversion polymorphism, and subsequently on morphological characterization, four sibling species A-D were reported from India. The present study uses molecular methods to further characterize and identify sibling species in Sri Lanka.MethodsMosquitoes from Sri Lanka were morphologically identified to species and sequenced for the ribosomal internal transcribed spacer-2 (ITS2) and the mitochondrial cytochrome c oxidase subunit-I (COI) genes. These sequences, together with others from GenBank, were used to construct phylogenetic trees and parsimony haplotype networks and to test for genetic population structure.ResultsBoth ITS2 and COI sequences revealed two divergent clades indicating that the Subpictus complex in Sri Lanka is composed of two genetically distinct species that correspond to species A and species B from India. Phylogenetic analysis showed that species A and species B do not form a monophyletic clade but instead share genetic similarity with Anopheles vagus and Anopheles sundaicus s.l., respectively. An allele specific identification method based on ITS2 variation was developed for the reliable identification of species A and B in Sri Lanka.ConclusionFurther multidisciplinary studies are needed to establish the species status of all chromosomal forms in the Subpictus complex. This study emphasizes the difficulties in using morphological characters for species identification in An. subpictus s.l. in Sri Lanka and demonstrates the utility of an allele specific identification method that can be used to characterize the differential bio-ecological traits of species A and B in Sri Lanka.

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Section: Resultsmentioning

confidence: 99%

Molecular characterization and identification of members of the Anopheles subpictus complex in Sri Lanka

Surendran

Sarma

Jude

et al. 2013

Malar J

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“…culicifacis complex and An. sinensis , the major malaria vectors reported in Thailand [33,34], India and Sri Lanka [35,36], and central China [37], respectively, are less abundant. That is not to say that these minor Anopheles populations do not have a potential vectorial role in the transmission of malaria in this boundary region.…”

Section: Discussionmentioning

confidence: 99%

The Anopheles community and the role of Anopheles minimus on malaria transmission on the China-Myanmar border

Yan

Zhang

et al. 2013

Parasites Vectors

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BackgroundMalaria around the China-Myanmar border is a serious health problem in the countries of South-East Asia. An. minimus is a principle malaria vector with a wide geographic distribution in this area. Malaria is endemic along the boundary between Yunnan province in China and the Kachin State of Myanmar where the local Anopheles community (species composition) and the malaria transmission vectors have never been clarified.MethodsAdult Anopheles specimens were collected using CDC light traps in four villages along the border of China and Myanmar from May 2012 to April 2013. Morphological and molecular identification of mosquito adults confirmed the species of Anopheles. Blood-meal identification using the female abdomens was conducted using multiplex PCR. For sporozoite detection in An. minimus, sets of 10 female salivary glands were pooled and identified with SSU rDNA using nested PCR. Monthly abundance of An. minimus populations during the year was documented. The diversity of Anopheles and the role of An. minimus on malaria transmission in this border area were analyzed.Results4,833 adult mosquitoes in the genus Anopheles were collected and morphologically identified to species or species complex. The Anopheles community is comprised of 13 species, and 78.83% of our total specimens belonged to An. minimus s.l., followed by An. maculatus (5.55%) and the An. culicifacies complex (4.03%). The quantity of trapped An. minimus in the rainy season of malaria transmission was greater than during the non-malarial dry season, and a peak was found in May 2012. An. minimus fed on the blood of four animals: humans (79.8%), cattle (10.6%), pigs (5.8%) and dogs (3.8%). 1,500 females of An. minimus were pooled into 150 samples and tested for sporozoites: only 1 pooled sample was found to have sporozoites of Plasmodium vivax.ConclusionAnopheles is abundant with An. minimus being the dominant species and having a high human blood index along the China-Myanmar border. The sporozoites in An. minimus were determined to be Plasmodium vivax with a 0.07-0.7% infection rate.

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“…subpictus s.l . is the major vector in the Jaffna district [3], and an important secondary vector elsewhere in Sri Lanka [2-5], India and Southeast Asia [6-9]. The taxon An.…”

Section: Introductionmentioning

confidence: 99%

Variations in susceptibility to common insecticides and resistance mechanisms among morphologically identified sibling species of the malaria vector Anopheles subpictus in Sri Lanka

et al. 2012

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BackgroundAnopheles subpictus s.l., an important malaria vector in Sri Lanka, is a complex of four morphologically identified sibling species A-D. Species A-D reportedly differ in bio-ecological traits that are important for vector control. We investigated possible variations that had not been reported previously, in the susceptibility to common insecticides and resistance mechanisms among the An. subpictus sibling species.MethodsAdult An. subpictus were collected from localities in four administrative districts in the dry zone of Sri Lanka. Single female isoprogeny lines were established and sibling species status determined according to reported egg morphology. World Health Organization's standard protocols were used for insecticide bioassays and biochemical assays to determine insecticide susceptibility and resistance mechanisms. Susceptibility of mosquitoes was tested against DDT (5%), malathion (4%), deltamethrin (0.05%) and λ-cyhalothrin (0.05%). Biochemical basis for resistance was determined through assaying for esterase, glutathione-S-transferase and monooxygenase activities and the insensitivity of acetycholinesterase (AChE) to propoxur inhibition.ResultsAll sibling species were highly resistant to DDT. However there were significant differences among the sibling species in their susceptibility to the other tested insecticides. Few species A could be collected for testing, and where testing was possible, species A tended to behave more similarly to species C and D than to B. Species B was more susceptible to all the tested insecticides than the other sibling species. This difference may be attributed to the predominance of species B in coastal areas where selection pressure due to indoor residual spraying of insecticides (IRS) was lower. However there were significant differences between the more inland species C and D mainly towards pyrethroids. Higher GST activities in species C and D might have contributed to their greater DDT resistance than species B. Malathion resistance in both species C and D may be caused by elevated GST activity and an altered insensitive target site in AChE. In addition, a carboxylesterase based malathion resistance mechanisms was also detected in species C and D. Elevated esterase levels in species C and D might have contributed to the low levels of pyrethroid resistance. However an absence of elevated activity of monooxygenases in species B, C and D indicates that monooxygenases are unlikely to be the cause of this partial resistance to pyrethroids.ConclusionsThe differences in insecticide susceptibility and insecticide resistance mechanism shown by An. subpictus sibling species are important considerations for developing the malaria control and eradication program in Sri Lanka. Similar studies on species complexes of other anopheline vectors of malaria are necessary for effective malaria control worldwide. The differential susceptibility findings are also consistent with most, if not all, morphologically identified An. subpictus species B in Sri Lanka belonging to the An. ...

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High seasonal malaria transmission rates in the intermediate rainfall zone of Sri Lanka

Cited by 31 publications

References 7 publications

Molecular characterization and identification of members of the Anopheles subpictus complex in Sri Lanka

Molecular characterization and identification of members of the Anopheles subpictus complex in Sri Lanka

The Anopheles community and the role of Anopheles minimus on malaria transmission on the China-Myanmar border

Variations in susceptibility to common insecticides and resistance mechanisms among morphologically identified sibling species of the malaria vector Anopheles subpictus in Sri Lanka

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