Anopheles Mosquito Species Research Articles

Determination of Species Identity and Genetic Diversity of Aedes aegypti and Other Medically Important Mosquitoes of India Using DNA Barcoding.

Aedes aegypti-borne viruses (i.e., dengue, chikungunya, and Zika) have become endemic to India, posing a severe threat to public health. Vector control remains the mainstay of disease management due to nonavailability of licensed vaccines/therapeutics. Conventional morpho-taxonomical methods cannot differentiate between closely related sibling species or species complexes, and hence we evaluated two molecular markers, mitochondrial cytochrome c oxidase subunit 1 (Cox1) and nuclear DNA internal transcribed spacer 2 (-2) gene sequences, to characterize seven populations of Ae. aegypti and four medically important mosquito species (Aedes albopictus, Anopheles stephensi, Culex tritaeniorhyncus, and Culex murrelli). DNA extracted from the 11 mosquito populations (two mosquitoes per population) was polymerase chain reaction amplified, sequenced, and analyzed. Molecular characterization was found to be congruent with morphological identification, suggesting no variants or cryptic species exist in Ae. aegypti and the other mosquitoes studied. Phylogenetic analysis with sequences obtained with Cox1 gene of Ae. aegypti and other Aedes and non-Aedes mosquito species showed clustering of sequences from different species representing different clades, distinctly separating one taxon from the other, whereas ITS-2 sequences of Aedes aegypti from across the world clustered tightly. Nucleotide divergence values revealed a low percentage of intraspecies variation and a higher percentage of interspecies variation. The present study authenticates the applicability of Cox1 and ITS-2 in the precise identification of Ae. aegypti mosquitoes against cryptic or sibling species. Cox1 appeared to be a more reliable marker because it showed distinct clustering of mosquito species, and some sequence variations to represent genetic diversity.

Identification of Southeast Asian Anopheles mosquito species using MALDI-TOF mass spectrometry.

Malaria elimination in Southeast Asia remains a challenge, underscoring the importance of accurately identifying malaria mosquitoes to understand transmission dynamics and improve vector control. Traditional methods such as morphological identification require extensive training and cannot distinguish between sibling species, while molecular approaches are costly for extensive screening. Matrix-assisted laser desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) has emerged as a rapid and cost-effective tool for Anopheles species identification, yet its current use is limited to few specialized laboratories. This study aimed to develop and validate an online reference database for MALDI-TOF MS identification of Southeast Asian Anopheles species. The database, constructed using the in-house data analysis pipeline MSI2 (Sorbonne University), comprised 2046 head mass spectra from 209 specimens collected at the Thailand-Myanmar border. Molecular identification via COI and ITS2 DNA barcodes enabled the identification of 20 sensu stricto species and 5 sibling species complexes. The high quality of the mass spectra was demonstrated by a MSI2 median score (min-max) of 61.62 (15.94-77.55) for correct answers, using the best result of four technical replicates of a test panel. Applying an identification threshold of 45, 93.9% (201/214) of the specimens were identified, with 98.5% (198/201) consistency with the molecular taxonomic assignment. In conclusion, MALDI-TOF MS holds promise for malaria mosquito identification and can be scaled up for entomological surveillance in Southeast Asia. The free online sharing of our database on the MSI2 platform (https://msi.happy-dev.fr/) represents an important step towards the broader use of MALDI-TOF MS in malaria vector surveillance.

Spatiotemporal distribution and bionomics of Anopheles stephensi in different eco-epidemiological settings in Ethiopia

BackgroundMalaria is a major public health concern in Ethiopia, and its incidence could worsen with the spread of the invasive mosquito species Anopheles stephensi in the country. This study aimed to provide updates on the distribution of An. stephensi and likely household exposure in Ethiopia.MethodsEntomological surveillance was performed in 26 urban settings in Ethiopia from 2021 to 2023. A kilometer-by-kilometer quadrant was established per town, and approximately 20 structures per quadrant were surveyed every 3 months. Additional extensive sampling was conducted in 50 randomly selected structures in four urban centers in 2022 and 2023 to assess households’ exposure to An. stephensi. Prokopack aspirators and CDC light traps were used to collect adult mosquitoes, and standard dippers were used to collect immature stages. The collected mosquitoes were identified to species level by morphological keys and molecular methods. PCR assays were used to assess Plasmodium infection and mosquito blood meal source.ResultsCatches of adult An. stephensi were generally low (mean: 0.15 per trap), with eight positive sites among the 26 surveyed. This mosquito species was reported for the first time in Assosa, western Ethiopia. Anopheles stephensi was the predominant species in four of the eight positive sites, accounting for 75–100% relative abundance of the adult Anopheles catches. Household-level exposure, defined as the percentage of households with a peridomestic presence of An. stephensi, ranged from 18% in Metehara to 30% in Danan. Anopheles arabiensis was the predominant species in 20 of the 26 sites, accounting for 42.9–100% of the Anopheles catches. Bovine blood index, ovine blood index and human blood index values were 69.2%, 32.3% and 24.6%, respectively, for An. stephensi, and 65.4%, 46.7% and 35.8%, respectively, for An. arabiensis. None of the 197 An. stephensi mosquitoes assayed tested positive for Plasmodium sporozoite, while of the 1434 An. arabiensis mosquitoes assayed, 62 were positive for Plasmodium (10 for P. falciparum and 52 for P. vivax).ConclusionsThis study shows that the geographical range of An. stephensi has expanded to western Ethiopia. Strongly zoophagic behavior coupled with low adult catches might explain the absence of Plasmodium infection. The level of household exposure to An. stephensi in this study varied across positive sites. Further research is needed to better understand the bionomics and contribution of An. stephensi to malaria transmission.Graphical

Chemical composition and mosquitocidal properties of essential oil from Indian indigenous plants Ocimum tenuiflorum L. and Ocimum americanum L. against three vector mosquitoes

Mosquitoes stand out as the most perilous and impactful vectors on a global scale, transmitting a multitude of infectious diseases to both humans and other animals. The primary objective of the current research was to assess the effectiveness of EOs from Ocimum tenuiflorum L. and Ocimum americanum L. in controlling Anopheles stephensi Liston. Culex quinquefasciatus Say and Aedes aegypti L. mosquitoes. The larvae, pupae and eggs of the mosquitoes were exposed to four different concentrations (6.25–50 ppm). The tested EOs resulted in >99–100 % mortality at 120 h for the eggs of all examined mosquito species. It also showed robust larvicidal and pupicidal activity with LC50 and LC90 values of 17–39, 23–60 ppm and 46–220, and 73–412 ppm against Aedes, Culex and Anopheles mosquito species, respectively, at 24 h of treatment. The Suitability Index or Predator Safety Factor demonstrated that the EOs extracted from O. tenuiflorum L. and O. americanum L. did not cause harm to P. reticulata, D. indicus (water bug), G. affinis and nymph (dragonfly). GC-MS analysis identified the major probable constituents of the oil, including Phenol, 2-Methoxy-4-(1-Propenyl)- (28.29 %); 1-Methyl-3-(1′-Methylcyclopropyl) Cyclopentene (46.46 %); (E,E,E)-3,7,11,15-Tetramethylhexadeca-1,3,6,10,14-Pentaene (18.91 %) and 1,3-Isobenzofurandione, 3a,4,7,7a-Tetrahydro-4,7-Dimethyl (33.02 %). These constituents may play a significant role in the mosquitocidal activity of the oil. The same results were identified in the formulation prepared from the EOs. This marks the first report confirming the successful utilization of EOs derived from O. tenuiflorum L. and O. americanum L. in mosquito population control initiatives.

Anopheles arabiensis continues to be the primary vector of Plasmodium falciparum after decades of malaria control in southwestern Ethiopia

BackgroundInvestigating the species distribution and their role in malaria transmission is important as it varies from place to place and is highly needed to design interventions appropriate to the site. The current study aimed to investigate the Anopheles mosquito species distribution and their infection rate in southwestern Ethiopia.MethodsThe study was conducted in 14 malaria-endemic kebeles (the smallest administrative unit), which were situated in eight different malaria-endemic districts and four zones in southwestern Ethiopia. Ten per cent of households in each village were visited to collect adult mosquitoes using Centers for Disease Control and Prevention (CDC) light traps. The larval and pupal collection was done from breeding sites within the villages, and reared to adults. Female mosquitoes were morphologically identified. The head and thorax of adult Anopheles mosquitoes were tested for circumsporozoite proteins (CSPs) using ELISA. At the same time, legs, wings, and abdomen were used to identify sibling species using PCR targeting the rDNA intergenic spacers region for species typing of the Anopheles funestus group and the internal transcribed spacer 2 region genes for Anopheles gambiae complex.ResultsA total of 1445 Anopheles mosquitoes comprising eight species were collected. Of 813 An. gambiae complex tested by PCR, 785 (97%) were Anopheles arabiensis, and the remaining 28 (3%) were not amplified. There were 133 An. funestus group captured and tested to identify the species, of which 117 (88%) were positive for Anopheles parensis, and 15 (11%) were not amplified. A single specimen (1%) showed a band with a different base pair length from the known An. funestus group species. Sequencing revealed this was Anopheles sergentii. Among 1399 Anopheles tested for CSPs by ELISA, 5 (0.4%) An. arabiensis were positive for Plasmodium falciparum and a single (0.07%) was positive for Plasmodium vivax.ConclusionsAnopheles arabiensis continues to play the principal role in malaria transmission despite implementing indoor-based interventions for decades. Sequencing results suggest that An. sergentii was amplified by the An. funestus group primer, producing PCR amplicon size of different length. Therefore, relying solely on amplifying a specific gene of interest in grouping species could be misleading, as different species may share the same gene.

Species composition, infection rate and feeding preference of Anopheles mosquito species (Diptera: Culicidae) in the west Amhara Region, northwest Ethiopia.

Reports showed that Amhara Region is accounting for 31% of Ethiopia`s malaria burden. Reports also depicted that despite the existing malaria vector control tools implemented by the regional government, currently there is an increment in malaria prevalence in the region. This might be due to lack of entomological monitoring and comprehensive information on the prevailing species composition, infection rate and feeding presences of An. mosquito species in the study areas. Therefore, this study aimed to address this information. A community-based cross-sectional study was conducted from 18 February to 30 March 2023 at three districts of the west Amhara Region. For this, six CDC light traps (three indoor and three outdoor) were used to collect adult female An. mosquito species. In this study, 261 An. mosquito species comprising seven species were collected. Their morphological identification and abdominal status determination were carried out using standard morphological identification keys under a dissection microscope. While their infection rates and blood meal sources were determined, using circumsporozoite protein-ELISA and blood meal-ELISA based on the standard protocol. Data were entered to SPSS versions 20 for analysis and p- value < 0.05 was considered as statistically significant. In our study, total of 261 An. mosquito species were identified. An. demeilloni was the most abundant species accounted for 112(42.9%) of all captures. It was also the most predominant species at Ayehu-Guagusa followed by Jabitehnan districts. An. demeilloni and An. cinereus altogether accounting for infection rate of 3(1.1%) for P. vivax parasite. Furthermore, our study showed that more than 50% of An. mosquito species collected fed on cattle blood showing shifting of feeding behaviors. Our study depicted that An. demeilloni and An. cinereus were the most abundant species and infected with P. vivax parasite. Therefore, further comprehensive study should be done in the future.

The Monthly Oviposition Characteristics of the Mosquito Species Anopheles maculipennis sensu stricto, Anopheles claviger, and Culiseta longiareolata Observed at Some Artificial Containers under Natural Circumstances in a Selected Area of Thrace, Türkiye

The Monthly Oviposition Characteristics of the Mosquito Species Anopheles maculipennis sensu stricto, Anopheles claviger, and Culiseta longiareolata Observed at Some Artificial Containers under Natural Circumstances in a Selected Area of Thrace, Türkiye

Patterns of genetic differentiation imply distinct phylogeographic history of the mosquito species Anopheles messeae and Anopheles daciae in Eurasia.

Detailed knowledge of phylogeography is important for control of mosquito species involved in the transmission of human infectious diseases. Anopheles messeae is a geographically widespread and genetically diverse dominant vector of malaria in Eurasia. A closely related species, An. daciae, was originally distinguished from An. messeae based on five nucleotide substitutions in its ribosomal DNA (rDNA). However, the patterns of phylogeographic history of these species in Eurasia remain poorly understood. Here, using internal transcribed spacer 2 (ITS2) of rDNA and karyotyping for the species identification we determined the composition of five Anopheles species in 28 locations in Eurasia. Based on the frequencies of 11 polymorphic chromosomal inversions used as genetic markers, a large-scale population genetics analysis was performed of 1932 mosquitoes identified as An. messeae, An. daciae and their hybrids. The largest genetic differences between the species were detected in the X sex chromosome suggesting a potential involvement of this chromosome in speciation. The frequencies of autosomal inversions in the same locations differed by 13%-45% between the species demonstrating a restricted gene flow between the species. Overall, An. messeae was identified as a diverse species with a more complex population structure than An. daciae. The clinal gradients in frequencies of chromosomal inversions were determined in both species implicating their possible involvement in climate adaptations. The frequencies of hybrids were low ~1% in northern Europe but high up to 50% in south-eastern populations. Thus, our study revealed critical differences in patterns of phylogeographic history between An. messeae and An. daciae in Eurasia. This knowledge will help to predict the potential of the malaria transmission in the northern territories of the continent.

Characterisation of Anopheles species composition and genetic diversity in Meghalaya, northeast India, using molecular identification tools.

Malaria in India is declining, in part due to the use of long-lasting insecticide-treated nets (LLINs) and vector control. Historically, the north-eastern region of India has contributed ~10%-12% of the nation's malaria burden. The important mosquito vectors in northeast India have long been considered to be Anopheles baimaii and An. minimus, both associated with forest habitats. Local deforestation and increased rice cultivation, along with widespread LLIN use, may be changing vector species composition. Understanding if and how vector species composition is changing is critical to successful malaria control. In Meghalaya state, malaria is now at a low level of endemicity with occasional seasonal outbreaks. In a biodiverse setting like Meghalaya, where >24 Anopheles mosquito species have been recorded, accurate morphological identification of all species is logistically challenging. To accurately determine Anopheles species richness in the West Khasi Hills (WKH) and West Jaintia Hills (WJH) districts, adult and larval mosquitoes were collected and identified using molecular methods of allele-specific PCR and cytochrome oxidase I DNA barcoding. In 14 villages across both districts, we identified high species richness, 19 species in total. Molecular findings indicated that An. minimus and An. baimaii were rare, while four other species (An. maculatus, An. pseudowillmori, An. jeyporiensis and An. nitidus) were abundant. Anopheles maculatus was highly prevalent in WKH (39% of light trap collections) and An. pseudowillmori in WJH (45%). Larvae of these four species were found in rice fields, suggesting that land cover change is influencing species composition change. Our results suggest that rice fields might be contributing to the observed abundance of An. maculatus and An. pseudowillmori, which could be playing a role in malaria transmission, either independently due to their high abundance, or in combination with An. baimaii and/or An. minimus.

Anopheles mosquito diversity, entomological indicators of malaria transmission and challenges of morphological identification in southwestern Ethiopia

BackgroundA number of Anopheles species play either a primary or secondary role in malaria transmission. This necessitates understanding the species composition, bionomics, and behaviors of malaria mosquitoes in a particular geographic area, which is relevant to design and implement tailored intervention tools. This study aimed to assess the species composition, sporozoite infection rate, and blood meal origins of malaria mosquitoes in two malaria-endemic villages of Boreda district in Gamo Zone, southwest Ethiopia. MethodsThirty houses, 20 for Center for Disease Control and Prevention (CDC) light traps and 10 for Pyrethrum Spray Catches (PSC) were randomly selected for bimonthly mosquito collection from October 2019 to February 2020. An enzyme-linked immunosorbent assay (ELISA) was carried out to detect the blood meal origins and circumsporozoite proteins (CSPs). The entomological inoculation rate (EIR) was calculated by multiplying the sporozoite and human biting rates from PSCs. Anopheles gambiae complex and An. funestus group samples were further identified to species by the polymerase chain reaction (PCR). Anopheles species with some morphological similarity with An. gambiae complex or An. funestus group were tested using the primers of the two species complexes.ResultsA total of 14 Anopheles species were documented, of which An. demeilloni was found to be the dominant species. An. arabiensis was found to be positive for P. falciparum CSP with the overall CSP rate of 0.53% (1/190: 95% CI 0.01–2.9). The overall estimated P. falciparum EIR of An. arabiensis from PSC was 1.5 infectious bites/person/5 months. Of the 145 freshly fed Anopheles mosquitoes tested for blood meal sources, 57.9% (84/145) had bovine blood meal, 15.2% (22/145) had human blood meal origin alone, and 16.5% (24/145) had a mixed blood meal origin of human and bovine. Anopheles demeilloni were more likely to feed on blood meals of bovine origin (102/126 = 80.9%), while An. arabiensis were more likely to have blood meals of human origin. Eleven samples (2.6%; 11/420) were morphologically categorized as An. demeilloni, but it has been identified as An. leesoni (the only An. funestus group identified in the area) by PCR, though it requires additional verification by sequencing, because different species genes may have amplified for these species specific primers. Similarly, a small number of An. arabiensis were morphologically identified as An. salbaii, An. maculipalpis and An. fuscivenosus.Conclusions and recommendationsIn spite of the wide variety of Anopheles mosquito species, An. arabiensis dominates indoor malaria transmission, necessitating additional interventions targeting this species. In addition, increasing entomological knowledge may make morphological identification less difficult.

Inference of selection pressures that drive insecticide resistance in Anopheles and Culex mosquitoes in Korea

Pyrethroids are primarily used for mosquito control in Korea. However, high frequencies of mutations conferring resistance to not only pyrethroids but also to other insecticides have been found in mosquito populations. This study aimed to examine the hypothesis that insecticides used outside of public health may play a role in selection. Briefly, the resistance mutation frequencies to three insecticide groups (pyrethroids, organophosphates, and cyclodienes) were estimated in two representative groups of mosquito species (Anopheles Hyrcanus Group and Culex pipiens complex). The relationship between these frequencies and the land-use status of the collection sites was investigated through multiple regression analysis. In the Anopheles Hyrcanus Group, the frequencies of both ace1 (organophosphate resistance) and rdl (cyclodiene resistance) mutations were positively correlated with ‘proximity to golf course’, possibly be due to the insecticides used for turf maintenance. They also showed positive correlations with field area and rice paddy area, respectively, suggesting the role of agricultural insecticides in the selection of these resistance traits. For the Cx. pipiens complex, the kdr (pyrethroid resistance), ace1, and rdl mutations were positively correlated with the residential area, field, and rice paddy, respectively. Therefore, pyrethroids used for public health could serve as a direct source of resistance selection pressure against kdr, whereas non-public health insecticides may pose primary selection pressure against the ace1 and rdl traits. The current findings suggest that the insecticides used in agriculture and the golf industry play a significant role in mosquito selection, despite variations in the extent of indirect selection pressure according to the mosquito groups and insecticide classes.

Assessing vector competence of mosquitoes from northeastern France to West Nile virus and Usutu virus.

West Nile virus (WNV) and Usutu virus (USUV) are two arthropod-borne viruses that circulate in mainland France. Assessing vector competence has only been conducted so far with mosquitoes from southern France while an increasingly active circulation of WNV and USUV has been reported in the last years. The main vectors are mosquitoes of the Culex genus and the common mosquito Culex pipiens. Here, we measure the vector competence of five mosquito species (Aedes rusticus, Aedes albopictus, Anopheles plumbeus, Culex pipiens and Culiseta longiareolata) present in northeastern France. Field-collected populations were exposed to artificial infectious blood meal containing WNV or USUV and examined at different days post-infection. We show that (i) Cx. pipiens transmitted WNV and USUV, (ii) Ae. rusticus only WNV, and (iii) unexpectedly, Ae. albopictus transmitted both WNV and USUV. Less surprising, An. plumbeus was not competent for both viruses. Combined with data on distribution and population dynamics, these assessments of vector competence will help in developing a risk map and implementing appropriate prevention and control measures.

Semi-field evaluation of a volatile transfluthrin-based intervention reveals efficacy as a spatial repellent and evidence of other modes of action.

Presently, the most common malaria control tools-i.e., long lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS)-are limited to targeting indoor biting and resting behaviors of Anopheles mosquito species. Few interventions are targeted towards malaria control in areas where transmission is driven or persists due to outdoor biting behaviors. This study investigated a volatile pyrethroid-based spatial repellent (VPSR) designed to bridge this gap and provide protection from mosquito bites in outdoor spaces. Southern Province, Zambia, is one such environment where outdoor biting is suspected to contribute to malaria transmission, where people are active in the evening in open-walled outdoor kitchens. This study assessed the VPSR in replica kitchens within a controlled semi-field environment. Endpoints included effects on mosquito host seeking, immediate and delayed mortality, deterrence, blood feeding inhibition, and fertility. Host-seeking was reduced by approximately 40% over the course of nightly releases in chambers containing VPSR devices. Mosquito behavior was not uniform throughout the night, and the modeled effect of the intervention was considerably higher when hourly catch rates were considered. These two observations highlight a limitation of this overnight semi-field design and consideration of mosquito circadian rhythms is recommended for future semi-field studies. Additionally, deterrence and immediate mortality were both observed in treatment chambers, with evidence of delayed mortality and a dose related response. These results demonstrate a primarily personal protective mode of action with possible positive and negative community effects. Further investigation into this primary mode of action will be conducted through a field trial of the same product in nearby communities.

The first genome sequence of Anopheles squamous from Macha, Zambia.

Despite efforts to minimize the impacts of malaria and reduce the number of primary vectors, malaria has yet to be eliminated in Zambia. Understudied vector species may perpetuate malaria transmission in pre-elimination settings. Anopheles squamosus is one of the most abundantly caught mosquito species in southern Zambia and has previously been found with Plasmodium falciparum sporozoites, a causal agent of human malaria. This species may be a critical vector of malaria transmission, however, there is a lack of genetic information available for An. squamosus. We report the first genome data and the first complete mitogenome (Mt) sequence of An. squamosus. The sequence was extracted from one individual mosquito from the Chidakwa area in Macha, Zambia. The raw reads were obtained using Illumina Novaseq 6000 and assembled through NOVOplasty alignment with related species. The length of the An. squamosus Mt was 15,351 bp, with 77.9 % AT content. The closest match to the whole mitochondrial genome in the phylogenetic tree is the African malaria mosquito, Anopheles gambiae. Its genome data is available through National Center for Biotechnology Information (NCBI) Sequencing Reads Archive (SRA) with accession number SRR22114392. The mitochondrial genome was deposited in NCBI GenBank with the accession number OP776919. The ITS2 containing contig sequence was deposited in GenBank with the accession number OQ241725. Mitogenome annotation and a phylogenetic tree with related Anopheles mosquito species are provided.

Sense the moist and feel the heat: mosquito host and oviposition site detection

Laursen et al. identified coreceptor Ir93a that is required for humidity and thermal sensing in the mosquito species Anopheles gambiae and Aedes aegypti. Behavioural studies with mutant mosquitoes with disrupted Ir93a revealed that they were less attracted to a blood meal source and oviposition site at close distance.

Cattle feeding tendency of Anopheles mosquitoes and their infection rates in Aradum village, North Wollo, Ethiopia: an implication for animal-based malaria control strategies

BackgroundSurveillance of indoor and outdoor resting malaria vector populations is crucial to monitor possible changes in vector resting and feeding behaviours. This study was conducted to assess the resting behaviour, blood meal sources and circumsporozoite (CSP) rates of Anopheles mosquito in Aradum village, Northern Ethiopia.MethodsMosquito collection was conducted from September 2019 to February 2020 using clay pots (indoor and outdoor), pit shelter and pyrethrum spray catches (PSC). The species of Anopheles gambiae complex and Anopheles funestus group were identified using polymerase chain reaction (PCR). Enzyme-linked immunosorbent assay (ELISA) was done to determine CSP and blood meal sources of malaria vectors.ResultsA total of 775 female Anopheles mosquitoes were collected using the clay pot, PSC and pit shelter. Seven Anopheles mosquito species were identified morphologically, of which Anopheles demeilloni (593; 76.5%) was the dominant species followed by An. funestus group (73; 9.4%). Seventy-three An. funestus group screened by PCR, 91.8% (67/73) were identified as Anopheles leesoni and only 2.7% (2/73) were found to be Anopheles parensis. The molecular speciation of 71 An. gambiae complex confirmed 91.5% (65/71) of Anopheles arabiensis. The majority of Anopheles mosquitoes were collected from outdoor pit shelter (42.2%) followed by outdoor clay pots. The majority of the blood meal of An. demeilloni (57.5%; 161/280), An. funestus sensu lato 10 (43.5%) and An. gambiae (33.3%; 14/42) originated from bovine. None of the 364 Anopheles mosquitoes tested for Plasmodium falciparum and Plasmodium vivax sporozoite infections were positive.ConclusionSince the Anopheles mosquitoes in the area prefer to bite cattle, it may be best to target them with an animal-based intervention. Clay pots could be an alternative tool for outdoor monitoring of malaria vectors in areas where pit shelter construction is not possible.

Screening eaves of houses reduces indoor mosquito density in rural, western Kenya

Despite the scale-up of insecticide-treated nets and indoor residual spraying, the bulk of malaria transmission in western Kenya still occurs indoors, late at night. House improvement is a potential long-term solution to further reduce malaria transmission in the region. The impact of eave screening on mosquito densities was evaluated in two rural villages in western Kenya. One-hundred-and-twenty pairs of structurally similar, neighbouring houses were used in the study. In each pair, one house was randomly selected to receive eave screening at the beginning of the study while the other remained unscreened until the end of the sampling period. Mosquito sampling was performed monthly by motorized aspiration method for 4 months. The collected mosquitoes were analysed for species identification. Compared to unscreened houses, significantly fewer female Anopheles funestus (RR = 0.40, 95% CI 0.29-0.55), Anopheles gambiae Complex (RR = 0.46, 95% CI 0.34-0.62) and Culex species (RR = 0.53, 95% CI 0.45-0.61) were collected in screened houses. No significant differences in the densities of the mosquitoes were detected in outdoor collections. Significantly fewer Anopheles funestus were collected indoors from houses with painted walls (RR = 0.05, 95% CI 0.01-0.38) while cooking in the house was associated with significantly lower numbers of Anopheles gambiae Complex indoors (RR = 0.60, 95% CI 0.45-0.79). Nearly all house owners (99.6%) wanted their houses permanently screened, including 97.7% that indicated a willingness to use their own resources. However, 99.2% required training on house screening. The cost of screening a single house was estimated at KES6,162.38 (US$61.62). Simple house modification by eave screening has the potential to reduce the indoor occurrence of both Anopheles and Culex mosquito species. Community acceptance was very high although education and mobilization may be needed for community uptake of house modification for vector control. Intersectoral collaboration and favourable government policies on housing are important links towards the adoption of house improvements for malaria control.

In-silico characterization and evolutionary analysis of conserved GPI-anchored protein SGU (Secretory Glycoconjugate of Unknownfunction) in Anopheles gambiae

To control malaria, researchers are focused on immunogenic protein to develop a vaccine against this life-threatening disease. The target immunogenic proteins against parasite infection and other diseases are mostly focused on GPI-anchor proteins. AgSGU is secretory glycoconjugate, the second most expressed protein in mosquito midgut after blood feeding. Recent studies confirmed that Pfs47 is the key protein for ookinetes invasion in the mosquito midgut and AGAP006398 act as a receptor for Pfs47. Protein interaction pathway analysis using bioinformatics approaches shows that AgSGU makes a complex with AGAP006398 and Pfs47, so here we target AgSGU protein for its functional and molecular characterization. Blastp analysis showing its conservancy in most Anopheles mosquito species. Phylogenetic evolutionary analysis shows that AgSGU is an independently evolved protein and closely related to ACON000570 in Anopheles coluzzii. Domain architecture analysis results that it is composed of a single MBF2 domain which acts as a transcriptional activator factor. The 3-D structure was prepared by I-TASSER and refined with the Galaxy Refine tool. The calculated RMSD value for the predicted structure was 0.558, suggesting the reliability of the 3-D structure. AgSGU was docked with AGAP006398 and Pfs47 and interacted effectively with both the protein. The antigenicity evaluation confirmed its potential to activate the immune response. The C-ImmSim immune response analysis proved that AgSGU protein activates both humoral and acquired immune responses. Finally, these studies conclude that AgSGU protein is a potential target for developing a transmission-blocking vaccine against malaria.

Outdoor and early hour human biting activities of malaria mosquitoes and the suitability of clay pot for outdoor resting mosquito collection in malaria endemic villages of southern Rift Valley, Ethiopia

BackgroundSampling adult Anopheles mosquitoes is important for assessing vector density, estimating the sporozoite infection rate, and quantifying the impact of vector control interventions. The objective of this study was to assess the Anopheles mosquito species composition, and their outdoor and indoor biting activities, and to evaluate the suitability of clay pots for indoor and outdoor resting mosquito collections. MethodsTwo malaria-endemic villages in the Gamo zone were purposely selected. Forty clay pots were deployed for outdoor resting mosquitoes sampling and another forty for indoor resting sampling. Twenty pit shelters were constructed for outdoor resting mosquito collection. The human landing catch (HLC) technique was employed to collect indoor and outdoor host-seeking mosquitoes in two households in each village. Morphological identification of the Anopheles mosquito was done using an identification key. Enzyme-linked immunosorbent assay technique was used for blood meal origin and circumsporozoite proteins (CSP) test. Speciation of An. gambiae complex was done using polymerase chain reaction. A Chi-square test was used to compare the effectiveness of clay pot and pit shelters for outdoor resting sampling. ResultsA total of 904 female Anopheles mosquitoes comprising An. gambiae complex, An. pharoensis, An. tenebrosus, An. dencalicus and An. demelloni were sampled. The majority (64%) of them were sampled by the HLC technique. There was a slight difference between the outdoor clay pot (19%) and pit shelter (17%) collection. No Anopheles mosquitoes were collected indoor using clay pots. All mosquitoes were tested for CSPs, but none of them were found to be positive. Anopheles mosquitoes were tending to bite humans outdoor than indoors, and their peak biting hours was 10–11 pm. The human blood meal index of Anopheles mosquitoes was 0.07 from pit shelters and it was 0.04 from clay pots. The bovine blood meal index was 0.45 for mosquitoes from both pit shelters and clay pot collections. ConclusionAnopheles arabiensis was the predominant species and it was tending to bite cattle more than humans. Clay pot could be suitable for outdoor resting mosquito collection, but not for indoor resting species.

Adapting field-mosquito collection techniques in a perspective of near-infrared spectroscopy implementation.

BackgroundNear-infrared spectroscopy (NIRS) has the potential to be a useful tool for assessing key entomological parameters of malaria-transmitting mosquitoes, including age, infectious status and species identity. However, before NIRS can be reliably used in the field at scale, methods for killing mosquitoes and conserving samples prior to NIRS scanning need to be further optimized. Historically, mosquitoes used in studies have been killed with chloroform, although this approach is not without health hazards and should not be used in human dwellings. For the application of NIRS scanning it is also unclear which mosquito preservation method to use. The aim of the study reported here was to investigate the use of pyrethrum spray, a commercially available insecticide spray in Burkina Faso, for killing mosquitoesMethodsLaboratory-reared Anopheles gambiae and Anopheles coluzzii were killed using either a pyrethrum insecticide spray routinely used in studies involving indoor mosquito collections (Kaltox Paalga®; Saphyto, Bobo-Dioulasso, Burkina Faso) or chloroform (“gold standard”). Preservative methods were also investigated to determine their impact on NIRS accuracy in predicting the species of laboratory-reared Anopheles and wild-caught mosquito species. After analysis of fresh samples, mosquitoes were stored in 80% ethanol or in silica gel for 2 weeks and re-analyzed by NIRS. In addition, experimentally infected An. coluzzii and wild-caught An. gambiae sensu lato (s.l.) were scanned as fresh samples to determine whether they contained sporozoites, then stored in the preservatives mentioned above for 2 weeks before being re-analyzed.ResultsThe difference in the accuracy of NIRS to differentiate between laboratory-reared An. gambiae mosquitoes and An. coluzzii mosquitoes killed with either insecticide (90%) or chloroform (92%) was not substantial. NIRS had an accuracy of 90% in determining mosquito species for mosquitoes killed with chloroform and preserved in ethanol or silica gel. The accuracy was the same when the pyrethrum spray was used to kill mosquitoes followed by preservation in silica gel, but was lower when ethanol was used as a preservative (80%). Regarding infection status, NIRS was able to differentiate between infected and uninfected mosquitoes, with a slightly lower accuracy for both laboratory and wild-caught mosquitoes preserved in silica gel or ethanol.ConclusionsThe results show that NIRS can be used to classify An. gambiae s.l. species killed by pyrethrum spray with no loss of accuracy. This insecticide may have practical advantages over chloroform for the killing of mosquitoes in NIRS analysis.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1186/s13071-022-05458-6.