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

Taxonomy, Bio-Ecology and Insecticide Resistance of Anopheline Vectors of Malaria in Sri Lanka

The objective of this review was to update the current knowledge on major malaria vectors in Sri Lanka and their bio-ecology and insecticide resistance status. Relevant data were collected through a comprehensive literature search performed using databases such as PubMed, NIH, Google Scholar and Web of Science. Sri Lanka had been endemic to malaria for centuries. However, due to a coordinated public health effort last indigenous malaria case was reported in 2012 and the island nation was declared free of malaria in 2016. Although 25 anopheline mosquitoes have been reported so far on the island, only Anopheles culicifacies and An. subpictus have been established as primary and secondary vectors of malaria respectively. Both vector species exist as a species complex, and the sibling species of each complex differ in their bio-ecology and susceptibility to malaria parasites and insecticides. The article provides a comprehensive and updated account of the bio-ecology and insecticide resistance of malaria vectors and highlights the challenges ahead of retaining a malaria-free status.

An overview of the mosquitoes of Saudi Arabia (Diptera: Culicidae), with updated keys to the adult females

Despite the fact that mosquito-borne infections have considerable consequences for public health in Saudi Arabia, there is neither a thorough review of the species that occur in the country nor updated keys for the identification of the adult females. In this study, species accounts are given for 49 Saudi Arabian mosquito species, as well as Aedes albopictus (Skuse), which is not recorded in Saudi Arabia, but is medically important and is found in some countries of the Middle East and North Africa. Taxonomic notes provide additional information for certain taxa and/or aid their identification.

Composition of Anopheles species and bionomic characteristics over the peak malaria transmission season in Bandarban, Bangladesh

BACKGROUND

Joint efforts by government and non-government organizations have helped to reduce malaria in Bangladesh and set the country on a clear path to eventual malaria elimination. However, achieving that goal would be challenging without a comprehensive understanding of vector bionomics.

METHODS

Targeted capturing of Anopheles mosquitoes over a rainy season, utilizing specific sampling methods, including human landing catches (HLCs), CDC-light traps (CDC-LTs), and pyrethrum spray catches (PSCs) were aimed to characterize entomological drivers of transmission in four sites of Bandarban, Bangladesh.

RESULTS

Molecular characterization of a subset of 4637 mosquitoes has demonstrated the presence of at least 17 species whose capture rates were representative of the rainy season. Species compositions and bionomic traits did not vary between sites with Anopheles maculatus having the highest landing rate by HLCs and Anopheles vagus having the highest capture rate with CDC-LTs. Interestingly, Anopheles species compositions and capture rates varied significantly (p < 0.05) for An. vagus, between HLCs and its often-used proxy-CDC-LTs- suggesting impacts on downstream analysis. CDC-LTs capture rates demonstrated differing compositions with indoor and outdoor biting rates. For example, Anopheles nigerrimus and Anopheles nivipes were more endophagic by HLCs and more exophagic by CDC-LTs. The use of a cow-baited CDC-LT also demonstrated significantly different results when compared to a human-baited CDC-LT considering the high degree of anthropophily in these species. The exception to both zoophily and indoor resting was An. vagus, which demonstrated both anthropophily and high resting rates indoors-pointing to this species being a possible primary vector at this site.

CONCLUSION

A diverse Anopheles fauna in Bandarban has been confirmed through molecular methods, highlighting the potential impact of sampling techniques. Given the complexity of the local ecosystem, a better understanding of mosquito behaviour and ecology is required to achieve the goal of malaria elimination in Bangladesh.

Molecular characterization of anopheline mosquitoes from the goat malaria-endemic areas of Thailand

Despite the fact that over a 100 anopheline mosquito species have been identified as human malaria vectors, little is known about ungulate malaria vectors. Consequently, we focused on investigating the bionomics and genetic characterizations of anopheline mosquitoes in goat malaria-endemic regions. We also attempted to screen for ungulate malaria potential vectors. A total of 1019 female anopheline mosquitoes were collected from six goat farms in four provinces of Thailand from 2020 to 2021. Mosquitoes were morphologically identified and subsequently confirmed using the mitochondrial DNA barcoding region-cytochrome oxidase c subunit I (MtDNA-COI), mitochondrial DNA-cytochrome c oxidase subunit II (MtDNA-COII), and ribosomal DNA internal transcribed spacer 2 (rDNA-ITS2) sequences. The current study reveals the genetic characteristics and distribution of nine mosquito species within the Anopheles and Cellia subgenera. Four dominant species, including Anopheles peditaeniatus, Anopheles subpictus, Anopheles vagus, and Anopheles aconitus exhibited significant intraspecific gene flow within their corresponding species. Although malaria parasites were not found in 126 mosquito pools, meaning more investigation is necessary, the current study adds to the existing DNA barcoding data collection and improves the current understanding of the genetic structure and distribution of anopheline mosquito species, which could be useful for effective control of mosquito-borne diseases.

PCR-RFLP assays for the identification of Anopheles (Diptera: Culicidae) species circulating in Honduras

BACKGROUND

Vector populations are a key target for malaria control and elimination. In Honduras, there are at least 12 reported anopheline species, however, the definitive number of species remains uncertain. Due to the inherent limitations of morphological identification of Anopheles species, molecular approaches have been developed to provide accurate identification and robust surveillance of local malaria vectors. The aim of this study was to design and assess three PCR-RFLP assays to identify anopheline species known to presently occur in Honduras.

METHODS

Mosquitoes captured between 2018 and 2022 in seven malaria-endemic and non-endemic departments in Honduras were analysed. The ITS2 ribosomal region and three restriction enzyme-based assays were evaluated in silico and experimentally.

RESULTS

A total of 132 sequences from 12 anopheline species were analysed. The ITS2 marker showed length polymorphisms that generated products between 388 and 592 bp and no relevant intraspecies polymorphisms were found. Furthermore, the three PCR-RFLP assays were able to differentiate 11 species with sufficient precision and resolution.

CONCLUSION

The ITS2 region was shown to be a useful molecular marker for identifying local Anopheles species. In addition, the PCR-RFLP assays evaluated here proved to be capable of discriminating most of the anopheline species present in Honduras. These methods provide alternatives to improve entomological surveillance of Anopheles in Honduras and other Mesoamerican countries.

Molecular forms of the Indian Anopheles subpictus complex differ in their susceptibility to insecticides and the presence of knockdown resistance (kdr) mutations in the voltage-gated sodium channel

OBJECTIVES

To investigate the differential insecticide-susceptibility of two molecular forms of Anopheles subpictus complex (A and B) against DDT and pyrethroids, the occurrence of knockdown resistance (kdr) mutations in these forms, and the association of kdr mutations with insecticide resistance.

METHODS

Insecticide susceptibility tests of An. subpictus s.l., collected from coastal and inland areas of mainland India, were performed against DDT, permethrin and deltamethrin using the WHO standard insecticide susceptibility test kit. The mosquitoes were characterized for molecular forms using a diagnostic PCR developed in this study. Representative samples of An. subpictus molecular forms A and B were sequenced for a genomic region encompassing the IIS4-5 linker to the IIS6 segments of the voltage-gated sodium channel to identify kdr mutations. A common PIRA-PCR was developed for identifying L1014F-kdr mutation and used for genotyping in both molecular forms of An. subpictus.

RESULTS

Molecular form A of An. subpictus was resistant to all three insecticides, i.e., DDT, Permethrin and deltamethrin, whereas Form B was categorized as 'possibly resistant' to these insecticides. Significantly higher mortalities in WHO insecticide susceptibility tests were recorded in Form B compared to Form A in sympatric populations. Molecular characterization of the IIS4-5 linker to IIS-6 segments of the voltage-gated sodium channel revealed the presence of two alternative nucleotide transversions at L1014 residue in Form A, both leading to the same amino acid change, i.e., Leu-to-Phe; however, such mutations could not be observed in Form B. PIRA-PCR-based kdr-genotyping of field populations revealed high frequencies of L1014F-kdr mutations in Form A and the absence of this mutation in Form B. The proportion of L1014F mutation was significantly higher in resistant mosquitoes following insecticide-bioassay with DDT (p<0.0001), permethrin (p<0.001) and deltamethrin (p<0.01) as compared to their susceptible counterparts.

CONCLUSIONS

Significant differences in insecticide susceptibility were found between two molecular forms of An. subpictus complex in sympatric populations. The L1014F-kdr mutation was observed in Form A only, which was found to be associated with DDT, permethrin and deltamethrin resistance.

Morphological and odorant-binding protein 1 gene intron 1 sequence variations in Anopheles stephensi from Jaffna city in northern Sri Lanka

Three Anopheles stephensi biotypes have historically been differentiated through variations in the mode numbers of egg ridges and adult spiracular indices. Anopheles stephensi odorant-binding protein 1 gene (AsteObp1) sequences in Iran and Afghanistan have been recently interpreted to suggest that the three biotypes are sibling species. AsteObp1 intron 1 sequences, mode numbers of egg ridges and spiracular indices of An. stephensi in Jaffna city in Sri Lanka were therefore investigated in field-collected mosquitoes and short-term laboratory colonies established from them. AsteObp1 intron 1 sequences revealed the region to be polymorphic with four unique sequences, ASJF1-4, present in both short-term laboratory colonies and field-collected An. stephensi. The spiracular index did not relate to the mode number of egg ridges in Jaffna An. stephensi. The results suggested that numbers of egg ridges, spiracular indices and AsteObp1 intron 1 sequences were not useful for differentiating An. stephensi biotypes in Jaffna. It is proposed that the observed differences between An. stephensi mosquitoes in Jaffna now result from normal population variance in the context of rapidly changing bionomics in India and northern Sri Lanka.

Mosquito Diversity in an Experimental Township in Tamil Nadu, India

To glean more information on mosquito diversity and distribution in Auroville, a cross-sectional study was carried out by mapping the distribution of water bodies and habitats supporting immature stages on the one hand and the distribution of water bodies/habitats supporting mosquito immature stages on the other. A satellite image covering an area of 8.08 km2 was overlaid with a grid of 500 × 500 m. Fifteen modules were selected and the area of each module served as the sampling site for the entomological survey. Adult and larval stages were sampled. Diversity indices were analyzed to compare mosquito diversity. Rarefaction estimations were used to compare abundance and richness of the mosquito species between different zones. In total, 750 mosquito larvae and 84 resting adults were sampled. Eighteen species of mosquitoes belonging to 11 subgenera and 7 genera were documented. Genera included Aedes (Johann Wilhelm Meigen 1818, Diptera, Culicidae), Anopheles (Johann Wilhelm Meigen 1818, Diptera, Culicidae), Armigeres (Theobald 1901, Diptera, Culicidae), Culex (Carl Linnaeus 1758, Diptera, Culicidae), Lutzia (Theobald 1903, Diptera, Culicidae), and Mimomyia (Theobald 1903, Diptera, Culicidae). Of the 18 mosquito species identified, 8 species are new records for Auroville. The Alpha (α) biodiversity indices show that the mosquito fauna is diverse (S = 18; DMg = 2.732 [95% CI: 2.732-2.732]). The Shannon-Weiner (H' = 2.199 [95% CI: 2.133-2.276]) and Simpson indices (λ = 0.8619 [95% CI: 0.8496-0.8723]) measured species richness, evenness, and dominance. The values of these indices suggest high species richness, evenness, and dominance. Prevailing conditions can provide suitable environment for establishment of different mosquito species in this ecosystem. Given the sociodemographic characteristics of this area, research on mosquito diversity and risk of vector-borne diseases will be of great use.

Redesigning Primer of ITS2 (Internal Transcribed Spacer 2) for Specific Molecular Characterization of Malaria Vectors Anopheles Species

BACKGROUND

Anopheles mosquitoes are vectors of malaria, which is a serious health issue in Indonesia. Thus, vector control is an important approach taken to overcome this disease. The first and most important step in vector control is vector identification. As some Anopheles species share similar morphological features, molecular identification helps make the process more accurate by using specific DNA sequences as molecular markers such as Internal Transcribed Spacer 2 (ITS2). Many of the available ITS2 primers are universally designed for insects and, as such, are typically less specific for identifying certain genera, such as Anopheles sp. Therefore, redesigning a specific ITS2 primer is needed for specific Anopheles identification.

OBJECTIVE

Our objective was to redesign a specific PCR primer for Anopheles species.

METHODS

The redesigned primer, named sma-ITS2, was then tested using mosquito samples from the Anopheles genus and other genera. Each mosquito was identified morphologically and their genomes were extracted. DNA samples were then amplified using the redesigned primer.

RESULTS

The sma-ITS2 primer pair was capable of amplifying ITS2 sequences from all of the Anopheles samples and unable to amplify any of the non-Anopheles samples, suggesting that it is specific to Anopheles only. ll Anopheles samples were also able to be identified, only An. indefinitus were not able to be separated from its complex species, An. vagus.

CONCLUSION

The sma-ITS2 primer pair was able to identify intra-species of Anopheles, but its efficiency in making differentiations within a species complex should be evaluated further.

The genomic signal of local environmental adaptation in Aedes aegypti mosquitoes

Local adaptation is important when predicting arthropod-borne disease risk because of its impacts on vector population fitness and persistence. However, the extent that vector populations are adapted to the environment generally remains unknown. Despite low population structure and high gene flow in Aedes aegypti mosquitoes across Panama, excepting the province of Bocas del Toro, we identified 128 candidate SNPs, clustered within 17 genes, which show a strong genomic signal of local environmental adaptation. This putatively adaptive variation occurred across fine geographical scales with the composition and frequency of candidate adaptive loci differing between populations in wet tropical environments along the Caribbean coast and dry tropical conditions typical of the Pacific coast. Temperature and vegetation were important predictors of adaptive genomic variation in Ae. aegypti with several potential areas of local adaptation identified. Our study lays the foundations of future work to understand whether environmental adaptation in Ae. aegypti impacts the arboviral disease landscape and whether this could either aid or hinder efforts of population control.

New vectors that are early feeders for Plasmodium knowlesi and other simian malaria parasites in Sarawak, Malaysian Borneo

Plasmodium knowlesi is the main cause of malaria in Sarawak, where studies on vectors of P. knowlesi have been conducted in only two districts. Anopheles balabacensis and An. donaldi were incriminated as vectors in Lawas and An. latens in Kapit. We studied a third location in Sarawak, Betong, where of 2169 mosquitoes collected over 36 days using human-landing catches, 169 (7.8%) were Anopheles spp. PCR and phylogenetic analyses identified P. knowlesi and/or P. cynomolgi, P. fieldi, P. inui, P. coatneyi and possibly novel Plasmodium spp. in salivary glands of An. latens and An. introlatus from the Leucosphyrus Group and in An. collessi and An. roperi from the Umbrosus Group. Phylogenetic analyses of cytochrome oxidase subunit I sequences indicated three P. knowlesi-positive An. introlatus had been misidentified morphologically as An. latens, while An. collessi and An. roperi could not be delineated using the region sequenced. Almost all vectors from the Leucosphyrus Group were biting after 1800 h but those belonging to the Umbrosus Group were also biting between 0700 and 1100 h. Our study incriminated new vectors of knowlesi malaria in Sarawak and underscores the importance of including entomological studies during the daytime to obtain a comprehensive understanding of the transmission dynamics of malaria.

Compensatory Base Changes Reveal Sexual Incompatibility among Members of the Anopheles subpictus Sensu Lato (Diptera: Culicidae) Species Complex in Sri Lanka

The mosquito Anopheles (Cellia) subpictus sensu lato (s.l.) is a major secondary vector of malaria in Sri Lanka. The sibling species composition in this species complex in Sri Lanka remains debatable. Compensatory base changes (CBCs) in the secondary structures of internal transcribed spacer 2 (ITS2) are reliable sources to predict sexual incompatibility among closely related species. The objective of the present study was to investigate the An. subpictus s.l. populations in Sri Lanka using the CBC analysis. Mosquito DNA was amplified and sequenced for the ITS2 region. The sequences were annotated using ITS2 Database. ITS2 secondary structures were constructed and analyzed for CBCs using various bioinformatics tools. The ITS2 regions consisted of two different lengths, 575 bp and 480 bp. The two CBCs and three hemi CBCs identified in the present study suggest that there may be at least two sexually incompatible sibling species. In conclusion, it is likely that there may be only two reproductively isolated sibling species in the An. subpictus species complex in Sri Lanka. However, due to high divergence of ITS2 in these species, it is reasonable to assume that they may be undergoing a speciation event to separate as a distinct species.

Molecular forms of Anopheles subpictus and Anopheles sundaicus in the Indian subcontinent

Background

Anopheles subpictus and Anopheles sundaicus are closely related species, each comprising several sibling species. Ambiguities exist in the classification of these two nominal species and the specific status of members of these species complexes. Identifying fixed molecular forms and mapping their spatial distribution will help in resolving the taxonomic ambiguities and understanding their relative epidemiological significance.

Methods

DNA sequencing of Internal Transcribed Spacer-2 (ITS2), 28S-rDNA (D1-to-D3 domains) and cytochrome oxidase-II (COII) of morphologically identified specimens of two nominal species, An. subpictus sensu lato (s.l.) and An. sundaicus s.l., collected from the Indian subcontinent, was performed and subjected to genetic distance and molecular phylogenetic analyses.

Results

Molecular characterization of mosquitoes for rDNA revealed the presence of two molecular forms of An. sundaicus s.l. and three molecular forms of An. subpictus s.l. (provisionally designated as Form A, B and C) in the Indian subcontinent. Phylogenetic analyses revealed two distinct clades: (i) subpictus clade, with a single molecular form of An. subpictus (Form A) prevalent in mainland India and Sri Lanka, and (ii) sundaicus clade, comprising of members of Sundaicus Complex, two molecular forms of An. subpictus s.l. (Form B and C), prevalent in coastal areas or islands in Indian subcontinent, and molecular forms of An. subpictus s.l. reported from Thailand and Indonesia. Based on the number of float-ridges on eggs, all An. subpictus molecular Form B were classified as Species B whereas majority (80%) of the molecular Form A were classified as sibling species C. Fixed intragenomic sequence variation in ITS2 with the presence of two haplotypes was found in molecular Form A throughout its distribution.

Conclusion

A total of three molecular forms of An. subpictus s.l. and two molecular forms of An. sundaicus s.l. were recorded in the Indian subcontinent. Phylogenetically, two forms of An. subpictus s.l. (Form B and C) prevalent in coastal areas or islands in the Indian subcontinent and molecular forms reported from Southeast Asia are members of Sundaicus Complex. Molecular Form A of An. subpictus is distantly related to all other forms and deserve a distinct specific status.

New vectors in northern Sarawak, Malaysian Borneo, for the zoonotic malaria parasite, Plasmodium knowlesi

Background

Plasmodium knowlesi is a significant cause of human malaria in Sarawak, Malaysian Borneo. Only one study has been previously undertaken in Sarawak to identify vectors of P. knowlesi, where Anopheles latens was incriminated as the vector in Kapit, central Sarawak. A study was therefore undertaken to identify malaria vectors in a different location in Sarawak.

Methods

Mosquitoes found landing on humans and resting on leaves over a 5-day period at two sites in the Lawas District of northern Sarawak were collected and identified. DNA samples extracted from salivary glands of Anopheles mosquitoes were subjected to nested PCR malaria-detection assays. The small subunit ribosomal RNA (SSU rRNA) gene of Plasmodium was sequenced, and the internal transcribed spacer 2 (ITS2) and mitochondrial cytochrome c oxidase subunit 1 (cox1) gene of the mosquitoes were sequenced from the Plasmodium-positive samples for phylogenetic analysis.

Results

Totals of 65 anophelines and 127 culicines were collected. By PCR, 6 An. balabacensis and 5 An. donaldi were found to have single P. knowlesi infections while 3 other An. balabacensis had either single, double or triple infections with P. inui, P. fieldi, P. cynomolgi and P. knowlesi. Phylogenetic analysis of the Plasmodium SSU rRNA gene confirmed 3 An. donaldi and 3 An. balabacensis with single P. knowlesi infections, while 3 other An. balabacensis had two or more Plasmodium species of P. inui, P. knowlesi, P. cynomolgi and some species of Plasmodium that could not be conclusively identified. Phylogenies inferred from the ITS2 and/or cox1 sequences of An. balabacensis and An. donaldi indicate that they are genetically indistinguishable from An. balabacensis and An. donaldi, respectively, found in Sabah, Malaysian Borneo.

Conclusions

Previously An. latens was identified as the vector for P. knowlesi in Kapit, central Sarawak, Malaysian Borneo, and now An. balabacensis and An. donaldi have been incriminated as vectors for zoonotic malaria in Lawas, northern Sarawak.

Integrated systematics of Anopheles subpictus (Diptera: Culicidae) in the Oriental Region, with emphasis on forms in Thailand and Sulawesi, Indonesia

The Anopheles subpictus complex consists of four species informally designated, based on fixed inversions of polytene chromosomes and morphology, as species A, B, C and D in India. However, recent studies revealed the presence of only species A and B in Sri Lanka. Little is known about the specific identity of the taxon in other countries in Asia. This paper reports the results of a molecular and morphological study of An. subpictus in Thailand and South Sulawesi, Indonesia. The maxillary palpi of most females from Thailand have the apical pale band longer than the subapical dark band, seta 7-I of pupae branched and short, and eggs with 18-25 float ridges. These characters do not agree with those described for species A, B, C and D in India. The females of An. subpictus from South Sulawesi usually have the subapical dark band of the maxillary palpus equal in length to the apical pale band. Phylogenetic analyses of sequences of the internal transcribed spacer 2 (ITS2) region of rDNA and the cytochrome c oxidase subunit I (COI) gene of mtDNA of specimens from Thailand, and South Sulawesi, and from various localities in GenBank, were conducted. ITS2 sequences of specimens from all localities in Thailand were identical, except for a small divergence in specimen from Phang Nga Province. Three distinct COI clades were detected in specimens from Chiang Mai Province in northern Thailand. However, crossing experiments between the three clades revealed no genetic incompatibility, suggesting that they were conspecific. ITS2 and COI sequences of most specimens from Thailand fell in clades other than those of An. subpictus species A and B and An. subpictus from Indonesia (East Nusa Tenggara, Java, South Sulawesi) and the Philippines. ITS2 sequences from South Sulawesi and East Nusa Tenggara were very similar, and fell in a clade consisting of specimen from Phang Nga in southern Thailand and sequences of some specimens from Cambodia and Vietnam, but their COI sequences were distinct. DNA sequences and morphological differences suggest the presence of two species within An. subpictus in Thailand, and more than one species in Indonesia.

Detection of Exotic Mosquito Species (Diptera: Culicidae) at International Airports in Europe

In Europe, the air-borne accidental introduction of exotic mosquito species (EMS) has been demonstrated using mosquito surveillance schemes at Schiphol International Airport (Amsterdam, The Netherlands). Based upon these findings and given the increasing volume of air transport movements per year, the establishment of EMS after introduction via aircraft is being considered a potential risk. Here we present the airport surveillance results performed by the Centre for Monitoring of Vectors of the Netherlands, by the Monitoring of Exotic Mosquitoes (MEMO) project in Belgium, and by the Public Health England project on invasive mosquito surveillance. The findings of our study demonstrate the aircraft mediated transport of EMS into Europe from a wide range of possible areas in the world. Results show accidental introductions of Aedes aegypti and Ae. albopictus, as well as exotic Anopheles and Mansonia specimens. The findings of Ae. albopictus at Schiphol airport are the first evidence of accidental introduction of the species using this pathway in Europe. Furthermore, our results stress the importance of the use of molecular tools to validate the morphology-based species identifications. We recommend monitoring of EMS at airports with special attention to locations with a high movement of cargo and passengers.

Anopheline bionomics, insecticide resistance and transnational dispersion in the context of controlling a possible recurrence of malaria transmission in Jaffna city in northern Sri Lanka

Background

Malaria was eliminated from Sri Lanka in 2013. However, the influx of infected travelers and the presence of potent anopheline vectors can re-initiate transmission in Jaffna city, which is separated by a narrow strait from the malaria-endemic Indian state of Tamil Nadu.

Methods

Anopheline larvae were collected from different habitats in Jaffna city and the susceptibility of emergent adults to DDT, malathion and deltamethrin investigated.

Results

Anopheline larvae were found in wells, surface-exposed drains, ponds, water puddles and water storage tanks, with many containing polluted, alkaline and brackish water. Anopheles culicifacies, An. subpictus, An. stephensi and An. varuna were identified in the collections. Adults of the four anopheline species were resistant to DDT. Anopheles subpictus and An. stephensi were resistant while An. culicifacies and An. varuna were possibly resistant to deltamethrin. Anopheles stephensi was resistant, An. subpictus possibly resistant while An. varuna and An. culicifacies were susceptible to malathion. DNA sequencing showed a L1014F (TTA to TTC) mutation in the IIS6 transmembrane segment of the voltage-gated sodium channel protein in deltamethrin-resistant An. subpictus—a mutation previously observed in India but not Sri Lanka.

Conclusion

Anopheles subpictus in Jaffna, like An. stephensi, may have recently originated in coastal Tamil Nadu. Besides infected overseas travelers, wind- and boat-borne carriage of Plasmodium-infected anophelines across the Palk Strait can potentially reintroduce malaria transmission to Jaffna city. Adaptation to diverse larval habitats and resistance to common insecticides in anophelines are identified as potential problems for vector control should this happen.

Population structure and genetic diversity of Aedes aegypti and Aedes albopictus in Penang as revealed by mitochondrial DNA cytochrome oxidase I

The population genetics study is crucial as it helps in understanding the epidemiological aspects of dengue and help improving a vector control measures. This research aims to investigate the population genetics structure of two common species of Aedes mosquitoes in Penang; Aedes aegypti and Aedes albopictus using Cytochrome Oxidase I (COI) mitochondrial DNA (mtDNA) marker. Molecular investigations were derived from 440 bp and 418 bp mtDNA COI on 125 and 334 larvae of Aedes aegypti and Aedes albopictus respectively, from 32 locations in Penang. All samples were employed in the BLASTn for species identification. The haplotype diversity, nucleotide diversity, neutrality test and mismatch distribution analysis were conducted in DnaSP version 5.10.1. AMOVA analysis was conducted in ARLEQUIN version 3.5 and the phylogenetic reconstructions based on maximum likelihood (ML) and neighbor-joining (NJ) methods were implemented in MEGA X. The relationships among haplotypes were further tested by creating a minimum spanning tree using Network version 4.6.1. All samples were genetically identified and clustered into six distinct species. Among the species, Ae. albopictus was the most abundant (67.2%), followed by Ae. aegypti (25.2%) and the rest were counted for Culex sp. and Toxorhynchites sp. Both Ae. aegypti and Ae. albopictus show low nucleotide diversity (π) and high haplotype diversity (h), while the neutrality test shows a negative value in most of the population for both species. There are a total of 39 and 64 haplotypes recorded for Ae. aegypti and Ae. albopictus respectively. AMOVA analysis revealed that most of the variation occurred within population for both species. Mismatch distribution analysis showed bimodal characteristic of population differentiation for Ae. aegypti but Ae. albopictus showed unimodal characteristics of population differentiation. Genetic distance based on Tamura-Nei parameter showed low genetic divergent within population and high genetic divergent among population for both species. The maximum likelihood tree showed no obvious pattern of population genetic structure for both Ae. aegypti and Ae. albopictus from Penang and a moderate to high bootstrap values has supported this conclusion. The minimum spanning network for Ae. aegypti and Ae. albopictus showed five and three dominant haplotypes respectively, which indicates a mixture of haplotypes from the regions analysed. This study revealed that there is no population genetic structure exhibited by both Ae. aegypti and Ae. albopictus in Penang. Mutation has occurred rapidly in both species and this will be challenging in controlling the populations. However, further analysis needed to confirm this statement.

Assessment and an updated list of the mosquitoes of Saudi Arabia

BACKGROUND

Mosquito-borne pathogens are important causes of diseases in the Kingdom of Saudi Arabia. Knowledge of the mosquito fauna is needed for the appropriate control of the vectors that transmit the pathogens and prevent the diseases they cause. An important first step is to have an up-to-date list of the species known to be present in the country. Original occurrence records were obtained from published literature and critically scrutinized to compile a list of the mosquito species that occur within the borders of the Kingdom.

RESULTS

Fifty-one species have been recorded in the Kingdom; however, the occurrence of two of these species is unlikely. Thus, the mosquito fauna of the Kingdom comprises 49 species that include 18 anophelines and 31 culicines. Published records are provided for each species. Problematic records based on misidentifications and inappropriate sources are discussed and annotated for clarity.

CONCLUSION

Integrated morphological and molecular methods of identification are needed to refine the list of species and accurately document their distributions in the Kingdom.

Anthropogenic Factors Driving Recent Range Expansion of the Malaria Vector Anopheles stephensi

The malaria vector Anopheles stephensi is found in wide tracts of Asia and the Middle East. The discovery of its presence for the first time in the island of Sri Lanka in 2017, poses a threat of malaria resurgence in a country which had eliminated the disease in 2013. Morphological and genetic characterization showed that the efficient Indian urban vector form An. stephensi sensu stricto or type form, has recently expanded its range to Jaffna and Mannar in northern Sri Lanka that are in proximity to Tamil Nadu state in South India. Comparison of the DNA sequences of the cytochrome oxidase subunit 1 gene in An. stephensi in Jaffna and Mannar in Sri Lanka and Tamil Nadu and Puducherry states in South India showed that a haplotype that is due to a sequence change from valine to methionine in the cytochrome oxidase subunit 1 present in the Jaffna and Mannar populations has not been documented so far in Tamil Nadu/Puducherry populations. The Jaffna An. stephensi were closer to Tamil Nadu/Puducherry populations and differed significantly from the Mannar populations. The genetic findings cannot differentiate between separate arrivals of the Jaffna and Mannar An. stephensi from Tamil Nadu or a single arrival and dispersion to the two locations accompanied by micro-evolutionary changes. Anopheles stephensi was observed to undergo preimaginal development in fresh and brackish water domestic wells and over ground cement water storage tanks in the coastal urban environment of Jaffna and Mannar. Anopheles stephensi in Jaffna was resistant to the common insecticides deltamethrin, dichlorodiphenyltrichloroethane and Malathion. Its preimaginal development in wells and water tanks was susceptible to predation by the larvivorous guppy fish Poecilia reticulata. The arrival, establishment, and spread of An. stephensi in northern Sri Lanka are analyzed in relation to anthropogenic factors that favor its range expansion. The implications of the findings for global public health challenges posed by malaria and other mosquito-borne diseases are discussed.

Susceptibility to common insecticides and detoxifying enzyme activities in Anopheles sundaicus (sensu lato) after cessation of indoor residual spraying of insecticides in the Jaffna Peninsula and its surroundings in northern Sri Lanka

Background

Sri Lanka has been malaria-free since 2013 but re-introduction of malaria transmission by infected overseas travelers is possible due to a prevalence of potent malaria vectors. Knowledge of the insecticide resistance status among Anopheles vectors is important if vector control has to be reintroduced in the island. The present study investigated the insecticide susceptibility levels and resistance mechanisms of Anopheles sundaicus (sensu lato) (previously classified as Anopheles subpictus species B) an important malaria vector in the Jaffna Peninsula and it surroundings in northern Sri Lanka after indoor residual spraying of insecticides was terminated in 2013.

Results

Species-specific PCR assays identified An. sundaicus (s.l.) in four locations in the Jaffna and adjacent Kilinochchi districts. Bioassays confirmed that An. sundaicus (s.l.) collected in Kilinochchi were completely susceptible to 0.05% deltamethrin and 5% malathion and resistant to 4% dichlorodiphenyltrichloroethane (DDT), whereas those from Jaffna were relatively susceptible to all three insecticides. Kilinochchi populations of An. sundaicus (s.l.) showed significantly higher glutathione S-transferase activity than population from Jaffna. However, Jaffna An. sundaicus (s.l.) had significantly higher Propoxur-resistant acetylcholinesterase activity. Activities of non-specific esterases and monooxygenases were not significantly elevated in An. sundaicus (s.l.) collected in both districts.

Conclusions

The susceptibility to malathion and deltamethrin in An. sundaicus (s.l.) suggests that they can be still used for controlling this potential malaria vector in the Jaffna Peninsula and adjacent areas. Continuing country-wide studies on other malaria vectors and their insecticide susceptibilities are important in this regard.

Environmental Factors Associated with Mosquito Vector Larvae in a Malaria-Endemic Area in Ratchaburi Province, Thailand

Malaria is transmitted by female mosquitoes in the genus Anopheles and is a major public health issue. Different species of Anopheles mosquitoes have different epidemiological characteristics, behaviors, and ecological requirements, and so an understanding of their biology and ecology in a particular area is critical for successful disease control. The aim of this study was to determine which environmental factors are associated with Anopheles larvae in a malaria-endemic area in Ratchaburi Province, Thailand, which shares a border with Myanmar. In October 2016, we collected mosquito larvae and measured six environmental factors at 10 study sites located along Lam Pachi River, which flows through Huay Nam Nak village in Ratchaburi Province. We found two species of Anopheles larvae (An. subpictus sensu lato (s.l.) Grassi and An. barbirostris s.l. van der Wulp) at 7 of the 10 study sites, the numbers of which significantly differed between sites (p < 0.05). Pearson correlation analysis showed that the numbers of larvae of both species were significantly positively correlated with the dissolved oxygen level (p < 0.01) and significantly negatively correlated with the width of the river (p < 0.05) and pH (p < 0.01). By contrast, turbidity, water depth, and water temperature were not associated with larval abundance. Mosquito species which belong to genus Anopheles are considered to be of public health and medical importance. Therefore, Anopheles mosquito surveillance and control in the study sites are essential. This information will facilitate vector-borne disease control and improve our understanding of the biology of Anopheles vectors in rivers located along international borders, further reducing the number of patients in this malaria-endemic area.

Alterations and Interchange of Morphometric Characters in Different Life Cycle Stages with Reference to Genomic Variations of Anopheles subpictus (Diptera; Culicidae) Sibling Species Complex in Sri Lanka

The species complex of the mosquito Anopheles subpictus is designated by the sibling species A⁻D, depending on morphological characters of life cycle stages and variations in polytene chromosomes. However, morphological aberrations in the life cycle stages make the identification of sibling species uncertain and imprecise. The objective of the present study is to determine the suitability of morphological variations of sibling species and their genomic variations to identify the sibling species status of an An. subpictus population in Sri Lanka. Life cycle stages of larvae, pupal exuviae, and adults were examined for previously reported distinctive morphological features. Five nuclear and mitochondrial genome regions, including the Internal transcribed spacer 2 (ITS2) region, D3 region, white gene, cytochrome c oxidase I (COI), and Cytochrome b (Cyt-b), were sequenced and analyzed for variations. The eggs changed their distinct sibling morphological characters during metamorphosis (89.33%). The larvae, pupal exuviae, and adult stages showed deviation from their sibling characters by 26.10%, 19.71%, and 15.87%, respectively. However, all the species from the analysis shared two distinct sequence types for all regions, regardless of the morphological variations. In conclusion, the An. subpictus sibling species complex in Sri Lanka is not identifiable using morphological characters due to variations, and the genomic variations are independent from the morphological variations.

Genetic diversity and population structure of malaria vector mosquitoes Anopheles subpictus, Anopheles peditaeniatus, and Anopheles vagus in five districts of Sri Lanka

Background

Although Sri Lanka is considered as a malaria-free nation, the threat of re-emergence of outbreaks still remains due to the high prevalence and abundance of malaria vectors. Analysis of population genetic structure of malaria vectors is considered to be one of the vital components in implementing successful vector control programmes. The present study was conducted to determine the population genetic structure of three abundant malaria vectors; Anopheles subpictus sensu lato (s.l.), Anopheles peditaneatus and Anopheles vagus from five administrative districts in two climatic zones; intermediate zone (Badulla and Kurunegala districts) and dry zone (Ampara, Batticoloa and Jaffna districts) of Sri Lanka using the mitochondrial gene, cytochrome c oxidase subunit I (COI).

Methods

Adult mosquitoes of An. subpictus s.l., An. peditaeniatus, and An. vagus were collected from five study sites located in five districts using cattle baited traps and backpack aspirators. Representative samples of each species that were morphologically confirmed were selected from each locality in generating COI sequences (> 6 good quality sequences per species per locality).

Results

Anopheles subpictus s.l. specimens collected during the study belonged to two sibling species; An. subpictus ‘A’ (from all study sites except from Jaffna) and An. subpictus ‘B’ (only from Jaffna). The results of haplotype and nucleotide diversity indices showed that all the three species are having high genetic diversity. Although a high significant pairwise difference was observed between An. subpictus ‘A’ and ‘B’ (F_st> 0.950, p < 0.05), there were no significant genetic population structures within An. peditaeniatus, An. vagus and An. subpictus species A (p > 0.05), indicating possible gene flow between these populations.

Conclusions

Gene flow among the populations of An. peditaeniatus, An. vagus and An. subpictus species A was evident. Application of vector control measures against all mosquito species must be done with close monitoring since gene flow can assist the spread of insecticide resistance genes over a vast geographical area.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2419-x) contains supplementary material, which is available to authorized users.

Comparative phylogeography of Aedes mosquitoes and the role of past climatic change for evolution within Africa

The study of demographic processes involved in species diversification and evolution ultimately provides explanations for the complex distribution of biodiversity on earth, indicates regions important for the maintenance and generation of biodiversity, and identifies biological units important for conservation or medical consequence. African and forest biota have both received relatively little attention with regard to understanding their diversification, although one possible mechanism is that this has been driven by historical climate change. To investigate this, we implemented a standard population genetics approach along with Approximate Bayesian Computation, using sequence data from two exon-primed intron-crossing (EPIC) nuclear loci and mitochondrial cytochrome oxidase subunit I, to investigate the evolutionary history of five medically important and inherently forest dependent mosquito species of the genus Aedes. By testing different demographic hypotheses, we show that Aedes bromeliae and Aedes lilii fit the same model of lineage diversification, admixture, expansion, and recent population structure previously inferred for Aedes aegypti. In addition, analyses of population structure show that Aedes africanus has undergone lineage diversification and expansion while Aedes hansfordi has been impacted by population expansion within Uganda. This congruence in evolutionary history is likely to relate to historical climate-driven habitat change within Africa during the late Pleistocene and Holocene epoch. We find differences in the population structure of mosquitoes from Tanzania and Uganda compared to Benin and Uganda which could relate to differences in the historical connectivity of forests across the continent. Our findings emphasize the importance of recent climate change in the evolution of African forest biota.

Genotype and biotype of invasive Anopheles stephensi in Mannar Island of Sri Lanka

BACKGROUND

Anopheles stephensi, the major vector of urban malaria in India, was recently detected for the first time in Sri Lanka in Mannar Island on the northwestern coast. Since there are different biotypes of An. stephensi with different vector capacities in India, a study was undertaken to further characterise the genotype and biotype of An. stephensi in Mannar Island.

METHODS

Mosquito larvae were collected in Pesalai village in Mannar and maintained in the insectary until adulthood. Adult An. stephensi were identified morphologically using published keys. Identified adult An. stephensi were molecularly characterized using two mitochondrial (cox1 and cytb) and one nuclear (ITS2) markers. Their PCR-amplified target fragments were sequenced and checked against available sequences in GenBank for phylogenetic analysis. The average spiracular and thoracic lengths and the spiracular index were determined to identify biotypes based on corresponding indices for Indian An. stephensi.

RESULTS

All DNA sequences for the Mannar samples matched reported sequences for An. stephensi from the Middle East and India. However, a single nucleotide variation in the cox1 sequence suggested an amino acid change from valine to methionine in the cox1 protein in Sri Lankan An. stephensi. Morphological data was consistent with the presence of the Indian urban vector An. stephensi type-form in Sri Lanka.

CONCLUSIONS

The present study provides a more detailed molecular characterization of An. stephensi and suggests the presence of the type-form of the vector for the first time in Sri Lanka. The single mutation in the cox1 gene may be indicative of a founder effect causing the initial diversification of An. stephensi in Sri Lanka from the Indian form. The distribution of the potent urban vector An. stephensi type-form needs to be established by studies throughout the island as its spread adds to the challenge of maintaining the country's malaria-free status.

Molecular characterization of Anopheline (Diptera: Culicidae) mosquitoes from eight geographical locations of Sri Lanka

BACKGROUND

Genus Anopheles is a major mosquito group of interest in Sri Lanka as it includes vectors of malaria and its members exist as species complexes. Taxonomy of the group is mainly based on morphological features, which are not conclusive and can be easily erased while handling the specimens. A combined effort, using morphology and DNA barcoding (using the markers cytochrome c oxidase subunit I (COI) gene and internal transcribed spacer 2 (ITS2) region, was made during the present study to recognize anophelines collected from eight districts of Sri Lanka for the first time.

METHODS

Cytochrome c oxidase subunit I and ITS2 regions of morphologically identified anopheline mosquitoes from Sri Lanka were sequenced. These sequences together with GenBank sequences were used in phylogenetic tree construction and molecular characterization of mosquitoes.

RESULTS

According to morphological identification, the field-collected adult mosquitoes belonged to 15 species, i.e., Anopheles aconitus, Anopheles annularis, Anopheles barbirostris, Anopheles culicifacies, Anopheles jamesii, Anopheles karwari, Anopheles maculatus, Anopheles nigerrimus, Anopheles pallidus, Anopheles peditaeniatus, Anopheles pseudojamesi, Anopheles subpictus, Anopheles tessellatus, Anopheles vagus, and Anopheles varuna. However, analysis of 123 COI sequences (445 bp) (16 clades supported by strong bootstrap value in the neighbour joining tree and inter-specific distances of >3%) showed that there are 16 distinct species. Identity of the morphologically identified species, except An. subpictus, was comparable with the DNA barcoding results. COI sequence analysis showed that morphologically identified An. subpictus is composed of two genetic entities: An. subpictus species A and species B (inter-specific K2P distance 0.128). All the four haplotypes of An. culicifacies discovered during the present study belonged to a single species. ITS2 sequences (542 bp) were obtained for all the species except for An. barbirostris, An. subpictus species B, An. tessellatus, and An. varuna. Each of these sequences was represented by a single species-specific haplotype.

CONCLUSIONS

The present study reflects the importance and feasibility of COI and ITS2 genetic markers in identifying anophelines and their sibling species, and the significance of integrated systematic approach in mosquito taxonomy. Wide distribution of malaria vectors in the country perhaps indicates the potential for re-emergence of malaria in the country.

Resting and feeding preferences of Anopheles stephensi in an urban setting, perennial for malaria

Background

The Indian city of Chennai is endemic for malaria and the known local malaria vector is Anopheles stephensi. Plasmodium vivax is the predominant malaria parasite species, though Plasmodium falciparum is present at low levels. The urban ecotype of malaria prevails in Chennai with perennial transmission despite vector surveillance by the Urban Malaria Scheme (UMS) of the National Vector Borne Disease Control Programme (NVBDCP). Understanding the feeding and resting preferences, together with the transmission potential of adult vectors in the area is essential in effective planning and execution of improved vector control measures.

Methods

A yearlong survey was carried out in cattle sheds and human dwellings to check the resting, feeding preferences and transmission potential of An. stephensi. The gonotrophic status, age structure, resting and host seeking preferences were studied. The infection rate in An. stephensi and Anopheles subpictus were analysed by circumsporozoite ELISA (CS-ELISA).

Results

Adult vectors were found more frequently and at higher densities in cattle sheds than human dwellings. The overall Human Blood Index (HBI) was 0.009 indicating the vectors to be strongly zoophilic. Among the vectors collected from human dwellings, 94.2% were from thatched structures and the remaining 5.8% from tiled and asbestos structures. 57.75% of the dissected vectors were nulliparous whereas, 35.83% were monoparous and the rest 6.42% biparous. Sporozoite positivity rate was 0.55% (4/720) and 1.92% (1/52) for An. stephensi collected from cattle sheds and human dwellings, respectively. One adult An. subpictus (1/155) was also found to be infected with P. falciparum.

Conclusions

Control of the adult vector populations can be successful only by understanding the resting and feeding preferences. The present study indicates that adult vectors predominantly feed on cattle and cattle sheds are the preferred resting place, possibly due to easy availability of blood meal source and lack of any insecticide or repellent pressure. Hence targeting these resting sites with cost effective, socially acceptable intervention tools, together with effective larval source management to reduce vector breeding, could provide an improved integrated vector management strategy to help drive down malaria transmission and assist in India’s plan to eliminate malaria by 2030.

Identification of Disease-Transmitting Mosquitoes: Development of Species-Specific Probes for DNA Chip Assay Using Mitochondrial COI and ND2 Genes and Ribosomal Internal Transcribed Spacer 2

Mosquitoes, which transmit infectious diseases, such as malaria and dengue fever, are harmful to human health. Thus, accurate and rapid identification of vectors is a critical step for the control of mosquito-borne diseases. However, phenotypic variations in adults, lack of recognizable features of the immature, and fragility of mosquitoes make identification difficult. Molecular approaches have been widely applied to identify mosquitoes, yet these methods have been focused only on the identification of a few species. This study used sequences of two mitochondrial genes, COI and ND2, and a ribosomal gene, ITS2, to design species-specific probes. Biochips thus developed were able to provide simultaneous identification of nine important medical and veterinary species, including the immature, from genera of Aedes, Anopheles, Armigeres, and Culex. This chip was also applied to samples collected from the field. Despite its inability to resolve the close affinity species of Culex quinquefasciatus and Culex pipiens molestus, pertinent biochips are expected to be applied to a mass screening method.

A review of the mosquito species (Diptera: Culicidae) of Bangladesh

Background

Diseases caused by mosquito-borne pathogens remain an important source of morbidity and mortality in Bangladesh. To better control the vectors that transmit the agents of disease, and hence the diseases they cause, and to appreciate the diversity of the family Culicidae, it is important to have an up-to-date list of the species present in the country. Original records were collected from a literature review to compile a list of the species recorded in Bangladesh.

Results

Records for 123 species were collected, although some species had only a single record. This is an increase of ten species over the most recent complete list, compiled nearly 30 years ago. Collection records of three additional species are included here: Anopheles pseudowillmori, Armigeres malayi and Mimomyia luzonensis.

Conclusions

While this work constitutes the most complete list of mosquito species collected in Bangladesh, further work is needed to refine this list and understand the distributions of those species within the country. Improved morphological and molecular methods of identification will allow the refinement of this list in years to come.

Anopheles subpictus carry human malaria parasites in an urban area of Western India and may facilitate perennial malaria transmission

Background

India contributes 1.5–2 million annual confirmed cases of malaria. Since both parasites and vectors are evolving rapidly, updated information on parasite prevalence in mosquitoes is important for vector management and disease control. Possible new vector-parasite interactions in Goa, India were tested.

Methods

A total of 1036 CDC traps were placed at four malaria endemic foci in Goa, India from May 2013 to April 2015. These captured 23,782 mosquitoes, of which there were 1375 female anopheline specimens with ten species identified using morphological keys. Mosquito DNA was analysed for human and bovine blood as well as for Plasmodium falciparum and Plasmodium vivax infection.

Results

Human host feeding was confirmed in Anopheles stephensi (30 %), Anopheles subpictus (27 %), Anopheles jamesii (22 %), Anopheles annularis (26 %), and Anopheles nigerrimus (16 %). In contrast, Anopheles vagus, Anopheles barbirostris, Anopheles tessellates, Anopheles umbrosus and Anopheles karwari specimens were negative for human blood. Importantly, An. subpictus, which was considered a non-vector in Goa and Western India, was found to be a dominant vector in terms of both total number of mosquitoes collected as well as Plasmodium carriage. Plasmodium infections were detected in 14 An. subpictus (2.8 %), while the traditional vector, An. stephensi, showed seven total infections, two of which were in the salivary glands. Of the 14 An. subpictus infections, nested PCR demonstrated three Plasmodium infections in the salivary glands: one P. vivax and two mixed infections of P. falciparum and P. vivax. In addition, ten gut infections (one P. vivax, six P. falciparum and three mixed infections) were seen in An. subpictus. Longitudinal mosquito collections pointed to a bimodal annual appearance of An. subpictus to maintain a perennial malaria transmission cycle of both P. vivax and P. falciparum in Goa.

Molecular Differentiation of the African Yellow Fever Vector Aedes bromeliae (Diptera: Culicidae) from Its Sympatric Non-vector Sister Species, Aedes lilii

INTRODUCTION

Yellow fever continues to be a problem in sub-Saharan Africa with repeated epidemics occurring. The mosquito Aedes bromeliae is a major vector of yellow fever, but it cannot be readily differentiated from its non-vector zoophilic sister species Ae. lilii using morphological characters. Genetic differences have been reported between anthropophilic Ae. bromeliae and zoophilic Ae. lilii and between forest and domestic populations. However, due to the application of different molecular markers and non-overlapping populations employed in previous studies, interpretation of species delimitation is unclear.

METHODOLOGY/PRINCIPLE FINDINGS

DNA sequences were generated from specimens of Ae. simpsoni s.l. from the Republic of Benin, Tanzania and Uganda for two nuclear genes apolipophorin 2 (apoLp2) and cytochrome p450 (CYPJ92), the ribosomal internal transcribed spacer region (ITS) and the mitochondrial cytochrome c oxidase (COI) barcoding region. Nuclear genes apoLp2 and CYPJ92 were unable to differentiate between species Ae. bromeliae and Ae. lilii due to ancestral lineage sorting, while ITS sequence data provided clear topological separation on a phylogeny. The standard COI barcoding region was shown to be subject to species introgression and unable to clearly distinguish the two taxa. Here we present a reliable direct PCR-based method for differentiation of the vector species Ae. bromeliae from its isomorphic, sympatric and non-biomedically important sister taxon, Ae. lilii, based on the ITS region. Using molecular species verification, we describe novel immature habitats for Ae. lilii and report both sympatric and allopatric populations. Whereas only Ae. lilii is found in the Republic of Benin and only Ae. bromeliae in Tanzania, both species are sympatric in Uganda.

CONCLUSIONS/SIGNIFICANCE

Our accurate identification method will allow informed distribution and detailed ecological studies that will facilitate assessment of arboviral disease risk and development of future targeted vector control.

Karyotypic assignment of Sri Lankan Anopheles culicifacies species B and E does not correlate with cytochrome oxidase subunit I and microsatellite genotypes

BACKGROUND

The identification of species B and E in the Anopheles culicifacies complex in the Indian subcontinent has been based on Y-chromosome karyotype. Since no detectable variations were previously found in DNA markers commonly used for sibling species identification, further molecular characterization using cytochrome oxidase subunit I (COI) and microsatellite markers was carried out on Y-chromosome karyotyped Anopheles culicifacies specie B and E from Unnichchai, Kallady and Ranawarunawa in Sri Lanka.

FINDINGS

COI sequence analysis (n = 22) revealed the presence of nine unique haplotypes with six in each species. Three haplotypes were shared by both species. The two sibling species had a pairwise FST value of 1.338 (p < 0.05) with the number of migrants (Nm) value <1. The genetic structure analysis resulted in two genetic clusters not 100% associated with karyotypes. While none of the species B were incorrectly assigned two were inconclusive. Five out of 26 specimens karyotyped as species E were incorrectly assigned, while further 9 were inconclusive.

CONCLUSIONS

The new molecular data support the existence of two genetically different populations of the Culicifacies Complex in Sri Lanka that are not associated with the Y-chromosome karyotype. Detailed analysis with more microsatellite markers and assortative mating experiments are needed to establish the presence of the two genetically distinct populations and relate them to Y-chromosome morphology.

L1014F-kdr Mutation in Indian Anopheles subpictus (Diptera: Culicidae) Arising From Two Alternative Transversions in the Voltage-Gated Sodium Channel and a Single PIRA-PCR for Their Detection

Leucine-to-phenylalanine substitution at residue L1014 in the voltage-gated sodium channel, target site of action for dichlorodiphenyltrichloroethane (DDT) and pyrethroids, is the most common knockdown resistance (kdr) mutation reported in several insects conferring resistance against DDT and pyrethroids. Here, we report presence of two coexisting alternative transversions, A>T and A>C, on the third codon position of L1014 residue in malaria vector Anopheles subpictus Grassi (species A) from Jamshedpur (India), both leading to the same amino acid substitution of Leu-to-Phe with allelic frequencies of 19 and 67%, respectively. A single primer-introduced restriction analysis-polymerase chain reaction (PIRA-PCR) was devised for the identification of L1014F-kdr mutation in An. subpictus resulting from either type of point mutation. Genotyping of samples with PIRA-PCR revealed high frequency (82%) of L1014F-kdr mutation in the study area.

Bionomic aspects of the Anopheles subpictus species complex in Sri Lanka

Anopheles subpictus Grassi s.l. (Diptera: Culicidae) functions as a secondary malaria vector to Anopheles culicifacies Giles s.l. (Diptera: Culicidae) in Sri Lanka. The taxon A. subpictus is reported to exist as a species complex comprising four sibling species (A-D) that can be differentiated through polytene chromosome banding patterns and stage-specific morphometric traits in India. Based on the morphological characteristics described for the Indian Subpictus Complex, the presence of all four sibling species has been described in Sri Lanka. As sibling species show distinct bio-ecological characteristics that are important for devising appropriate vector control measures, a study was carried out in six districts in the dry zone of Sri Lanka. The results confirm the presence of all four sibling species, with species C predominating in inland areas and species B in coastal areas. Species C and D were indoor-resting and indoor-feeding, while species B was outdoor-resting with no significant preference for indoor- or outdoor-resting. Species B showed distinct morphological variation in the ornamentation of wings and palpi. Blood meal analysis revealed that species B, C, and D can feed on humans as well as cattle. The differential bio-ecological traits shown by the members of the Subpictus Complex are important for developing appropriate vector control measures in Sri Lanka.