Identification of the sibling species of the Anopheles maculipennis complex by heteroduplex analysis

Molecular characterization of anopheline species diversity in the Andaman and Nicobar archipelago, with a particular emphasis on Anopheles barbirostris

This study investigates anopheline species diversity in the Andaman and Nicobar Islands, employing morphological and molecular methods, focusing on the D3 domain of 28S rRNA (D3) and second internal spacer (ITS2). Ten Anopheline species were identified morphologically and confirmed with molecular markers. While the D3 region demonstrated low level of inter- and intra-specific genetic distance in all the species, ITS2 revealed clear barcoding gap. Among the ten species, A. barbirostris exhibited significant diversity when compared with the sequences from other countries available in GenBank. Further analyses of additional samples of A. barbirostris were carried out using ITS2 and cytochrome oxidase I (COI) markers. Limited variations among the sequences from the islands were observed, suggesting a prevalent single molecular form. However, when compared with the GenBank sequences, our samples formed a separate cluster closely related to the A3 species. The genetic distance between our samples and the A3 cluster was 0.02 for COI but very high (0.104) for ITS2, suggesting a potentially new molecular form or species in the island region. This warrants a more comprehensive and detailed analysis of A. barbirostris in these islands at both genetic and morphometric levels. Overall, these observations added-up the new knowledge in the understanding of anopheline diversity in the Andaman and Nicobar archipelago and highlight the necessity for continuous molecular investigations to unravel complexities within mosquito population dynamics.

Updated occurrence and bionomics of potential malaria vectors in Europe: a systematic review (2000-2021)

Despite the eradication of malaria across most European countries in the 1960s and 1970s, the anopheline vectors are still present. Most of the malaria cases that have been reported in Europe up to the present time have been infections acquired in endemic areas by travelers. However, the possibility of acquiring malaria by locally infected mosquitoes has been poorly investigated in Europe, despite autochthonous malaria cases having been occasionally reported in several European countries. Here we present an update on the occurrence of potential malaria vector species in Europe. Adopting a systematic review approach, we selected 288 papers published between 2000 and 2021 for inclusion in the review based on retrieval of accurate information on the following Anopheles species: An. atroparvus, An. hyrcanus sensu lato (s.l.), An. labranchiae, An. maculipennis sensu stricto (s.s.), An. messeae/daciae, An. sacharovi, An. superpictus and An. plumbeus. The distribution of these potential vector species across Europe is critically reviewed in relation to areas of major presence and principal bionomic features, including vector competence to Plasmodium. Additional information, such as geographical details, sampling approaches and species identification methods, are also reported. We compare the information on each species extracted from the most recent studies to comparable information reported from studies published in the early 2000s, with particular reference to the role of each species in malaria transmission before eradication. The picture that emerges from this review is that potential vector species are still widespread in Europe, with the largest diversity in the Mediterranean area, Italy in particular. Despite information on their vectorial capacity being fragmentary, the information retrieved suggests a re-definition of the relative importance of potential vector species, indicating An. hyrcanus s.l., An. labranchiae, An. plumbeus and An. sacharovi as potential vectors of higher importance, while An. messeae/daciae and An. maculipennis s.s. can be considered to be moderately important species. In contrast, An. atroparvus and An. superpictus should be considered as vectors of lower importance, particularly in relation to their low anthropophily. The presence of gaps in current knowledge of vectorial systems in Europe becomes evident in this review, not only in terms of vector competence but also in the definition of sampling approaches, highlighting the need for further research to adopt the appropriate surveillance system for each species.

Speculation on the possibility for introducing Anopheles stephensi as a species complex: preliminary evidence based on odorant binding protein 1 intron I sequence

BACKGROUND

Anopheles stephensi is considered an important malaria vector in Iran, Asia, and recently in the Horn of Africa. Recently, Ansteobp1 intron I sequence has been introduced a new molecular marker for identification of its biological forms including, mysorensis, intermediate and type, using insectary colony specimens.

METHODS

In the current study, new marker ability in molecular identification of biological forms has been evaluated with An. stephensi specimens collected from Iran and Afghanistan malarious provinces. Following DNA extraction and PCR amplification, sequence analysis and constructed phylogenetic tree revealed that type and intermediate forms are distributed in Iran.

RESULTS

The specimens collected from Afghanistan identified as intermediate and mysorensis forms. Therefore, intermediate form is sympatric species in both countries. Based on the results of Ansteobp1 intron I sequences, An. stephensi could be suggested as new Anopheles complex species including An. stephensi sibling A (type form), An. stephensi sibling B (intermediate form) and An. stephensi sibling C (mysorensis form). This is the first report on the presence of An. stephensi biological forms in Afghanistan.

CONCLUSIONS

Iran is going to eliminate malaria transmission from the country, precise species identification, especially in complex species will be helpful in the prevention of malaria resurgence in the country, mainly because of common fauna of Anopheles species and through border malaria and population movement within Afghanistan, Pakistan, and Iran.

Larval habitats characterization and species composition of Anopheles mosquitoes in Tunisia, with particular attention to Anopheles maculipennis complex

In Tunisia, malaria transmission has been interrupted since 1980. However, the growing number of imported cases and the persistence of putative vectors stress the need for additional studies to assess the risk of malaria resurgence in the country. In this context, our aim was to update entomological data concerning Anopheles mosquitoes in Tunisia. From May to October of 2012, mosquito larval specimens were captured in 60 breeding sites throughout the country and identified at the species level using morphological keys. Environmental parameters of the larval habitats were recorded. Specimens belonging to the An. maculipennis complex were further identified to sibling species by the ribosomal deoxyribonucleic acid (rDNA)-internal transcribed spacer 2 (ITS2) polymerase chain reaction (PCR) technique. In total, 647 Anopheles larvae were collected from 25 habitats. Four species, including An. labranchiae, An. multicolor, An. sergentii, and An. algeriensis, were morphologically identified. rDNA-ITS2 PCR confirmed that An. labranchiae is the sole member of the An. maculipennis complex in Tunisia. An. labranchiae was collected throughout northern and central Tunisia, and it was highly associated with rural habitat, clear water, and sunlight areas. Larvae of An. multicolor and An. sergentii existed separately or together and were collected in southern Tunisia in similar types of breeding places.

Molecular phylogenetic analysis of Anopheles and Cellia subgenus anophelines (Diptera: Culicidae) in temperate and tropical regions of Iran

Molecular studies on population genetics of speciation across Iran have recently started. Morphological and molecular studies have showed that 25 species of genus Anopheles are present in the country; however, relationships between vector and non-vector species as well as compatibility of morphological characters with molecular data have not been verified. Molecular phylogenetic analysis was undertaken on the Anopheles and Cellia subgenus members internal transcribed spacer 2 (ITS2) sequences submitted to GenBank among the Oriental and Palearctic members in north and southern Iran. rDNA-ITS2 sequences were extracted from the GenBank and analyzed using bioinformatics softwares: BLAST, ITS2 annotation tool (version 3.0.13), ClustalW, and MEGA5 in neighbor-joining and maximum likelihood algorithms. There are not any submitted sequences in GenBank from Iran for the following seven species: Anopheles algeriensis, Anopheles marteri, Anopheles plumbeus, Anopheles peditaeniatus, Anopheles melanoon, Anopheles subpictus, and Anopheles mongolensis; therefore, they have not been included in the study. Although these molecular-based phylogenetic trees match well enough with classical morphological taxonomy, the arrangement of species did not match with morphological classification in some cases. Correct species identification is essential for control of vector born disease such as malaria; therefore, phylogenetic methods will help to understand the relationship among the members of the target species within the genus Anopheles. It could also help us to design molecular markers for species differentiation particularly in cryptic species, which is difficult to classify them based on morphological features.

Identification of Anopheles daciae in Germany through ITS2 sequencing

Until the middle of the twentieth century, malaria was frequently endemic in parts of Germany; Anopheles maculipennis complex species were considered the primary vectors. Three species of this complex have been identified in Germany: A. maculipennis s.s., Anopheles messeae and Anopheles atroparvus; the last predominantly from the coastal regions of Northern Germany. Anopheles daciae is a recently described member of the A . maculipennis complex and resembles the well-characterised species A. messeae, although the two species can be distinguished through their egg morphology and sequencing of the internal transcribed spacer 2 (ITS2) region of their nuclear rDNA. In this study, we harvested larval and adult mosquito samples from five breeding sites and ten CO(2) trap collection sites in the Upper Rhine Valley of Southwestern Germany to analyse the complement of anopheline species present. Mosquito ITS2 DNA was extracted and polymerase chain reaction (PCR)-amplified using established protocols. Genomic analysis was performed by a species-diagnostic restriction fragment length polymorphism assay as well as by sequencing of PCR products; the data obtained were aligned against nucleic acid sequences from English mosquitoes retrieved from GenBank. Additionally, the larval breeding sites of A. messeae were characterised through water quality measurement. Forty-seven samples were successfully processed, of which 6 were identified as A. daciae and 41 as A. messeae. All samples of A. daciae, which has not previously been found in Central Europe, originated from one CO(2) trap collection site in Dettenheim, close to Karlsruhe, Southwestern Germany. The identification of this malarial vector in a novel area may have implications for the re-emergence of disease subsequent to climatic changes.

DNA barcodes confirm the presence of a single member of the Anopheles maculipennis group in Morocco and Algeria: An. sicaulti is conspecific with An. labranchiae

Anopheles labranchiae Falleroni is the only member of the Maculipennis Group known to occur in northern Africa; however, confusion exists as to the taxonomic status of its junior synonym, An. sicaulti Roubaud (type locality: near Rabat, Morocco). Based on morphological and behavioural distinctions, it has been suggested that Moroccan populations have been isolated from other North African populations by the Atlas Mountains, and that Moroccan populations may represent An. sicaulti, originally described as a variety of An. maculipennis Meigen. DNA barcodes (658bp of the mitochondrial COI gene) obtained from 89 An. maculipennis s.l. collected in Morocco (n=79) and Algeria (n=10) in 2007 and 2008 were used to determine if Moroccan populations are genetically isolated from those east of the Atlas Mountains (Algeria), and whether there is molecular evidence to support the presence of more than one member of the Maculipennis Group in the region. No evidence for speciation was found between Moroccan and Algerian populations, or within populations in northern Morocco. Moreover shared COI haplotypes between Algeria and Morocco indicate ongoing gene flow between populations in these countries, suggesting that the Atlas Mountains are not a boundary to gene flow in An. labranchiae. The synonymy of An. sicaulti with An. labranchiae is confirmed. That An. labranchiae comprises the same species in these North African countries is important for malaria control.

The second internal transcribed spacer of nuclear ribosomal DNA as a tool for Latin American anopheline taxonomy - a critical review

Among the molecular markers commonly used for mosquito taxonomy, the internal transcribed spacer 2 (ITS2) of the ribosomal DNA is useful for distinguishing among closely-related species. Here we review 178 GenBank accession numbers matching ITS2 sequences of Latin American anophelines. Among those, we found 105 unique sequences corresponding to 35 species. Overall the ITS2 sequences distinguish anopheline species, however, information on intraspecific and geographic variations is scarce. Intraspecific variations ranged from 0.2% to 19% and our analysis indicates that misidentification and/or sequencing errors could be responsible for some of the high values of divergence. Research in Latin American malaria vector taxonomy profited from molecular data provided by single or few field capture mosquitoes. However we propose that caution should be taken and minimum requirements considered in the design of additional studies. Future studies in this field should consider that: (1) voucher specimens, assigned to the DNA sequences, need to be deposited in collections, (2) intraspecific variations should be thoroughly evaluated, (3) ITS2 and other molecular markers, considered as a group, will provide more reliable information, (4) biological data about vector populations are missing and should be prioritized, (5) the molecular markers are most powerful when coupled with traditional taxonomic tools.

Molecular identification of Palearctic members of Anopheles maculipennis in northern Iran

BACKGROUND

Members of Anopheles maculipennis complex are effective malaria vectors in Europe and the Caspian Sea region in northern Iran, where malaria has been re-introduced since 1994. The current study has been designed in order to provide further evidence on the status of species composition and to identify more accurately the members of the maculipennis complex in northern Iran.

METHODS

The second internal transcribed spacer of ribosomal DNA (rDNA-ITS2) was sequenced in 28 out of 235 specimens that were collected in the five provinces of East Azerbayjan, Ardebil, Guilan, Mazandaran and Khorassan in Iran.

RESULTS

The length of the ITS2 ranged from 283 to 302 bp with a GC content of 49.33-54.76%. No intra-specific variations were observed. Construction of phylogenetic tree based on the ITS2 sequence revealed that the six Iranian members of the maculipennis complex could be easily clustered into three groups: the An. atroparvus-Anopheles labranchiae group; the paraphyletic group of An. maculipennis, An. messeae, An. persiensis; and An. sacharovi as the third group.

CONCLUSION

Detection of three species of the An. maculipennis complex including An. atroparvus, An. messae and An. labranchiae, as shown as new records in northern Iran, is somehow alarming. A better understanding of the epidemiology of malaria on both sides of the Caspian Sea may be provided by applying the molecular techniques to the correct identification of species complexes, to the detection of Plasmodium composition in Anopheles vectors and to the status of insecticide resistance by looking to related genes.

Potential vectors of West Nile virus following an equine disease outbreak in Italy

In the late summer of 1998, an outbreak of equine encephalomyelitis due to West Nile virus (WNV) occurred in the Tuscany region of central Italy. The disease was detected in 14 race horses from nine localities in four Provinces: Firenze, Lucca, Pisa and Pistoia. The outbreak area included Fucecchio wetlands (1800 ha), the largest inland marsh in Italy, and the adjacent hilly Cerbaie woodlands with farms breeding horses. To detect potential vectors of WNV, entomological surveys of Fucecchio and Cerbaie were undertaken during 1999-2002 by collecting mosquito larvae from breeding sites and adult mosquitoes by several methods of sampling. Among 6023 mosquitoes (Diptera: Culicidae) collected, 11 species were identified: Aedes albopictus (Skuse), Ae. vexans (Meigen), Anopheles atroparvus Van Thiel, An. maculipennis Meigen s.s., An. plumbeus Stephens, Culex impudicus Ficalbi, Cx. pipiens L., Culiseta longiareolata Macquart), Ochlerotatus caspius (Pallas), Oc. detritus (Haliday) and Oc. geniculatus (Olivier). In Fucecchio marshes, Cx. impudicus predominated with seasonal peak densities in spring and autumn: its greatest abundance during early spring coincides with arrival of migratory birds from Africa. In Cerbaie hills, Cx. pipiens predominated with peak population density in late summer. No viruses were isolated from 665 mosquitoes processed. These findings, plus other data on Italian mosquito bionomics, suggest a possible mode of WNV transmission involving the most abundant Culex in the Fucecchio-Cerbaie areas. Culex impudicus, being partly ornithophilic, might transmit WNV from migratory to non-migratory birds during springtime; Cx. pipiens, having a broader host range, would be more likely to transmit WNV from birds to horses and, perhaps, to humans by late summer.

Molecular systematics of Anopheles: from subgenera to subpopulations

The century-old discovery of the role of Anopheles in human malaria transmission precipitated intense study of this genus at the alpha taxonomy level, but until recently little attention was focused on the systematics of this group. The application of molecular approaches to systematic problems ranging from subgeneric relationships to relationships at and below the species level is helping to address questions such as anopheline phylogenetics and biogeography, the nature of species boundaries, and the forces that have structured genetic variation within species. Current knowledge in these areas is reviewed, with an emphasis on the Anopheles gambiae model. The recent publication of the genome of this anopheline mosquito will have a profound impact on inquiries at all taxonomic levels, supplying better tools for estimating phylogeny and population structure in the short term, and ultimately allowing the identification of genes and/or regulatory networks underlying ecological differentiation, speciation, and vectorial capacity.

Anopheles sacharovi (Diptera: Culicidae): a reemerging malaria vector in the Ararat Valley of Armenia

In 1994, the first indigenous case of malaria since the 1960s was reported in Armenia, and the number of cases quickly increased in the ensuing years. In 1998, a roll-back malaria program was developed to eliminate the recently established foci of malaria infection and to prevent the reestablishment of malaria in Armenia. As part of this program, we carried out entomological surveys to identify the potential malaria vectors in the Ararat Valley, the area where most of the indigenous malaria cases had been reported. In particular, we attempted to ascertain the presence of Anopheles sacharovi Favre, which is historically the most important malaria vector in Armenia yet which had not been reported since 1965. In 1998-2000, we collected adult mosquitoes and larvae in the city of Masis and in three rural villages of the Ararat Valley. Species identification of the members of the Anopheles maculipennis complex was performed through egg and larval morphology, heteroduplex analysis, and sequencing of the second internal transcribed spacer of ribosomal DNA. Two species of the complex were identified: An. sacharovi, found in all of the study sites, andAn. maculipennis s.s. Meigen, the most common species in the area. The reemergence of An. sacharovi in the study sites shows that the receptivity for malaria is still high in the Ararat Valley and, likely, in other regions of Armenia.