Mosquito Survey Research Articles

Survey of malaria vectors on the Cambodia, Thailand and China-Laos Borders

BackgroundAnopheles maculatus, Anopheles minimus and Anopheles dirus are the major vectors of malaria transmission in the Greater Mekong Subregion (GMS). The malaria burden in this region has decreased significantly in recent years as all GMS countries progress towards malaria elimination. It is necessary to investigate the Anopheles diversity and abundance status and assess the Plasmodium infection rates to understand the malaria transmission potential of these vector species in GMS countries to guide the development of up-to-date vector control strategies and interventions.MethodsA survey of mosquitoes was conducted in Stung Treng, Sainyabuli and Phongsaly Provinces on the Cambodia-Laos, Thailand-Laos and China-Laos borders, respectively. Mosquito collection was done by overnight trapping at sentinel sites in each province. After morphological identification, the 18S rRNA-based nested-PCR was performed to detect malaria parasites in the captured Anopheles mosquitoes.ResultsA total of 18 965 mosquitoes comprising of 35 species of 2 subgenera (Subgenus Anopheles and Subgenus Cellia) and 4 tribes (Tribes Culicini, Aedini, Armigerini and Mansoniini) were captured. Tribe Culicini accounted for 85.66% of captures, followed by Subgenus Anopheles (8.15%). Anopheles sinensis dominated the Subgenus Anopheles by 99.81%. Plasmodium-infection was found in 25 out of the 1 683 individual or pooled samples of Anopheles. Among the 25 positive samples, 19, 5 and 1 were collected from Loum, Pangkhom and Siem Pang village, respectively. Eight Anopheles species were found infected with Plasmodium, i.e., An. sinensis, Anopheles kochi, Anopheles vagus, An. minimus, Anopheles annularis, Anopheles philippinensis, Anopheles tessellatus and An. dirus. The infection rates of Plasmodium falciparum, Plasmodium vivax and mixture of Plasmodium parasite species were 0.12% (2/1 683), 1.31% (22/1 683) and 0.06% (1/1 683), respectively.ConclusionsOverall, this survey re-confirmed that multiple Anopheles species carry malaria parasites in the international border areas of the GMS countries. Anopheles sinensis dominated the Anopheles collections and as carriers of malaria parasites, therefore may play a significant role in malaria transmission. More extensive investigations of malaria vectors are required to reveal the detailed vector biology, ecology, behaviour, and genetics in GMS regions in order to assist with the planning and implementation of improved malaria control strategies.Graphical

Population Dynamics of Six Species of <i>Culex pipiens</i> L. Group (Diptera: Culicidae) from Chandigarh

During the present study, detailed mosquito surveys were carried out from various habitats of developed areas, gardens, slums and surrounding villages of Chandigarh from June 2017 to November 2019 to explore the mosquito fauna. Six species of Culex pipiens L group were recorded with maximum distribution of Culex quinquefasciatus Say (89.61%) followed by Culex univittatus Theobald (6.39%) while, rest of the species viz; Culex vagans Wiedemann, Cx. hutchinsoni Barraud, Cx. theileri Theobald and Cx. fuscocephala Theobald collectively formed only 3.99% in almost in all habitats. The population dynamics was analyzed from regular surveys to assess the relationship between abundance of six vector species of Cx. pipiens group with meteorological variables. The data revealed varied abundance of species of Cx. pipiens group in different seasons. Survey of literature revealed that no data is available on the species of Cx. pipiens group in the region with particular reference to weather parameters. Hence, the present study on the seasonal abundance and population dynamics of Culex pipiens group in Chandigarh and its surroundings has been carried out.

Strategies for conducting Anopheles stephensi surveys in non-endemic areas

Anopheles stephensi, a malaria vector species previously only known from Asia, was first detected in Africa in Djibouti in 2012, has been subsequently collected in Ethiopia, Sudan, and Somalia, and may be spreading further. Countries may wish to implement mosquito surveys to determine if An. stephensi is present, or to determine the extent of its distribution, if present. Furthermore, mosquito surveys can provide data on the bionomics of An. stephensi and its adaptation to the local environment that can help plan and implement control activities. The present strategies provide suggestions on surveillance approaches for monitoring An. stephensi. The first step is to determine the aim of the study, as this will determine the specific activities conducted in each location. Challenges related to identification and detection of resistance and sporozoites are also discussed. Results should be communicated to relevant stakeholders in a timely manner, both in country and internationally, to help understand the introduction, distribution, and bionomics of An. stephensi in a given country and work towards cross-border and coordinated international response.

The Distribution of Uranotaenia sapphirina and Ur. socialis in Tabasco, Southern Mexico.

In Mexico, the genus Uranotaenia includes 11 species distributed mainly in the tropical and subtropical regions in the southeast of the country. Uranotaenia sapphirina has been reported in 18 states in Mexico: Campeche, Coahuila, Colima, Chiapas, Guerrero, Hidalgo, Jalisco, Mexico City, Mexico State, Michoacán, Morelos, Oaxaca, Quintana Roo, Sinaloa, Tabasco, Tamaulipas, Veracruz, and Yucatán; whereas Ur. socialis has been reported in Chiapas and Quintana Roo. In recent surveillance studies of mosquito species in Tabasco, Ur. sapphirina and Ur. socialis were omitted due to the lack of recent collection records, but in historical records, the presence of Ur. sapphirina and one species consistent with the description of Ur. socialis were mentioned. During a mosquito survey collection, immature stages from ground-level natural habitats in conservation areas of Tabasco, Ur. sapphirina and Ur. socialis were collected in association with Anopheles albimanus, Culex erraticus, Mansonia titillans, and Ur. lowii. Additionally, 2 Mexican entomological collections were reviewed, searching additional records of those species. An identification key to separate larvae and adult females of Ur. sapphirina and Ur. socialis is provided. With the addition of Ur. sapphirina and Ur. socialis to the mosquito fauna of Tabasco, there are currently 107 species in the state, being the 3rd state in Mexico with the highest richness of mosquito species. Specimens collected during this study were deposited in the Collection of the Entomological and Bioassay Research Unit of Tabasco.

Mosquito and Arbovirus Surveillance at Bradshaw Field Training Area, Northern Territory, Australia.

Mosquito surveillance and mosquito-borne arbovirus detections in the area of Bradshaw Field Training Area (BFTA) in Northern Territory, Australia, have not been previously documented. A survey to record the mosquito species within BFTA and determine if arboviruses are present in them was conducted in April 2013. A total of 8,530 mosquitoes were collected, using carbon dioxide-baited encephalitis virus surveillance traps, and the predominant species were Aedes normanensis, which was 74.2% of the mosquitoes collected, and Anopheles annulipes (11.1%), An. amictus (2.9%), and An. meraukensis (2.4%). The mean number of mosquitoes collected was 120.1 ± 13.7 per trap in the 71 traps placed. This study has shown mosquito abundance in the eastern area of BFTA during 2 wk of April 2013 was of high density, and therefore a heightened risk of arbovirus transmission. Reverse transcriptase-polymerase chain reaction and virus isolation identified a single Barmah Forest virus strain from a pool of Ae. normanensis, a positive rate of 1/174 (0.57%). This study has provided the 1st survey of mosquitoes and potential mosquito-borne virus transmission in BFTA.

Three Days Extensive Survey of Malaria, Dengue and Chikungunya Mosquitoes in The Capital of Rajasthan, India

The mosquito-borne diseases are transmitted among people by the bite of an infected mosquito. In India, the major mosquito vectors belong to three genera Aedes, Anopheles and Culex. The mosquito-borne disease transmission dynamics is ruled by a series of various type of factors like changes in climatic conditions, and other man-made factors like different types of land use, community hygiene and their behaviors etc. The presence of mosquitoes is a major concern for public health due to possibility of transmitting arboviral diseases like malaria, dengue and chikungunya; which repeatedly occurs in India and cause substantial morbidity and mortality annually. Current study was carried out in Jaipur district to determine the larval density, breeding preference and relative abundance of Anopheline and Aedes mosquitoes during October month of 2021 because there is less information available regarding vector breeding preference and other associated factors in surveyed areas. Survey was carried out in various place of Jaipur district [Chand Pole, Chhoti Chopad, Mahal Road, Jagatpura and Chaksu (Kothun)]. Total 185 houses were surveyed, among them 140 houses were found positive for Aedes and Anopheline mosquitoes. The larval indices like House Index (HI), Container Index (CI), Breteau Index (BI) and Pupae Index (PI) were calculated as 75.67%, 46.89%, 142.70 and 25.94 respectively. Total 46.89% of inspected containers were found positive for mosquitoes’ immature stages. The cattle drinking tanks were found as the most suitable breeding container with 82.75% positivity. This study concludes that Aedes aegypti, Aedes albopictus and Anopheles stephensi was found as the most abundant mosquito in this region so this area at high risk for mosquito-borne disease. The study recommends that the surveillance program regarding vector ecology and biology should be carried out in this area and an awareness program should be also conducted regarding vector and their breeding preferences

MOSQUITOS (DIPTERA: CULICIDAE) DEL ÁREA DE LA REPRESA HIDROELÉCTRICA DE PALMAR, URUGUAY

A survey of adult mosquitoes in the area of the Palmar dam, Uruguay, was conducted from October 1980 to March 1981, prior to filling the reservoir. The Culicidae fauna consisted of 22 species in 7 genera: Aedeomyia Theobald, Aedes Meigen, Anopheles Meigen, Culex Linnaeus, Mansonia Blanchard, Psorophora Robineau-Desvoidy and Uranotaenia Lynch-Arribálzaga; the most diverse genera being Aedes (subgenus Ochlerotatus Lynch-Arribálzaga), Anopheles, Culex and Psorophora. Most abundant species was Aedes (Ochlerotatus) crinifer (Theobald), and was collected in all the sampling points. Mansonia pseudotitillans (Theobald) and Culex (Melanoconion) vaxus Dyar are recorded for the first time in Uruguay.

The Centres for Disease Control light trap (CDC-LT) and the human decoy trap (HDT) compared to the human landing catch (HLC) for measuring Anopheles biting in rural Tanzania

BackgroundVector mosquito biting intensity is an important measure to understand malaria transmission. Human landing catch (HLC) is an effective but labour-intensive, expensive, and potentially hazardous entomological surveillance tool. The Centres for Disease Control light trap (CDC-LT) and the human decoy trap (HDT) are exposure-free alternatives. This study compared the CDC-LT and HDT against HLC for measuring Anopheles biting in rural Tanzania and assessed their suitability as HLC proxies.MethodsIndoor mosquito surveys using HLC and CDC-LT and outdoor surveys using HLC and HDT were conducted in 2017 and in 2019 in Ulanga, Tanzania in 19 villages, with one trap/house/night. Species composition, sporozoite rates and density/trap/night were compared. Aggregating the data by village and month, the Bland–Altman approach was used to assess agreement between trap types.ResultsOverall, 66,807 Anopheles funestus and 14,606 Anopheles arabiensis adult females were caught with 6,013 CDC-LT, 339 indoor-HLC, 136 HDT and 195 outdoor-HLC collections. Indoors, CDC-LT caught fewer An. arabiensis (Adjusted rate ratio [Adj.RR] = 0.35, 95% confidence interval [CI]: 0.27–0.46, p < 0.001) and An. funestus (Adj.RR = 0.63, 95%CI: 0.51–0.79, p < 0.001) than HLC per trap/night. Outdoors, HDT caught fewer An. arabiensis (Adj.RR = 0.04, 95%CI: 0.01–0.14, p < 0.001) and An. funestus (Adj.RR = 0.10, 95%CI: 0.07–0.15, p < 0.001) than HLC. The bias and variability in number of mosquitoes caught by the different traps were dependent on mosquito densities. The relative efficacies of both CDC-LT and HDT in comparison to HLC declined with increased mosquito abundance. The variability in the ratios was substantial for low HLC counts and decreased as mosquito abundance increased. The numbers of sporozoite positive mosquitoes were low for all traps.ConclusionsCDC-LT can be suitable for comparing mosquito populations between study arms or over time if accuracy in the absolute biting rate, compared to HLC, is not required. CDC-LT is useful for estimating sporozoite rates because large numbers of traps can be deployed to collect adequate mosquito samples. The present design of the HDT is not amenable for use in large-scale entomological surveys. Use of HLC remains important for estimating human exposure to mosquitoes as part of estimating the entomological inoculation rate (EIR).

Island biogeography and human practices drive ecological connectivity in mosquito species richness in the Lakshadweep Archipelago

Mosquitoes are globally distributed and adapted to a broad range of environmental conditions. As obligatory hosts of many infectious pathogens, mosquito abundance and distribution are primarily determined by the presence and quality of larval habitats. To understand the dynamics and productivity of larval habitats in changing island environments, we conducted a four-month mosquito survey across ten inhabited islands in the Lakshadweep archipelago. Using fine-resolution larval habitat mapping, we recorded 7890 mosquitoes representing 13 species and 7 genera. Of these, four species comprised 95% of the total collections—Aedes albopictus (Stegomyia) was the dominant species followed by Armigeres subalbatus, Culex quinquefasciatus and Malaya genurostris. We found larval species richness was positively associated with the island area and mosquito larval richness (Chao1 estimator) was higher in artificial habitats than in natural habitats. Furthermore, mosquito species composition did not deteriorate with distance between islands. Mosquito abundance by species was associated with microclimatic variables—pH and temperature. We detected co-existence of multiple species at a micro-habitat level with no evidence of interactions like competition or predation. Our study analyzed and identified the most productive larval habitats –discarded plastic container and plastic drums contributing to high larval indices predicting dengue epidemic across the Lakshadweep islands. Our data highlight the need to devise vector control strategies by removal of human-induced plastic pollution (household waste) which is a critical driver of disease risk.

Landscape Composition Affects Elements of Metacommunity Structure for Culicidae Across South-Eastern Illinois.

The interplay among invasive alien vectors and the species assemblage of native potential vectors in areas of range expansion may affect the dynamics of pathogen transmission. In this study we investigate how Aedes albopictus, an invasive mosquito of considerable public health concern fits within mosquito communities at the edge of its range of distribution. This was addressed using a 2-year field survey of mosquitoes in south-eastern Illinois. We found that Ae. albopictus was more broadly distributed in this region than previously realized, with new occurrence records for nine counties. Abundance of this species varied strongly and peaked in locations of low-intermediate overall mosquito species richness. This differed from overall mosquito abundance, as well as abundance of another important vector, Cx. pipiens, for which the abundance-richness relationships were best described with power functions. Metacommunity analyses revealed that mosquito communities showed a non-random distribution with a Clementsian gradient, which suggests a pattern whereby distinct species assemblages are associated with specific habitats or environmental conditions. Land use was a significant underlying factor shaping mosquito community structure and species assemblages. Multivariate analyses showed that while Ae. canadensis and Cx. pipiens complex mosquitoes were associated with high and low proportions of wetlands in the environment, respectively, Ae. albopictus was most strongly associated with urban settlements. This work sheds light on landscape-level processes, such as niche differentiation driven by urban and agricultural development, structuring mosquito communities. We suggest that mosquito community assessments across habitats be incorporated as part of a One Health vector surveillance approach to aid in the goal of prediction and prevention of new and (re-)emerging vector-borne diseases.

Confirmed presence of aedes (rusticoidus) refiki Medschid, 1928 in a continental dry Mediterranean peri-urban environment in south-central Spain

BackgroundThe ‘snow-melt mosquito’ aedes (rusticoidus) refiki is a rare species with a wide distribution in Europe that is usually defined as an aggressive mosquito for mammals, including humans. During a mosquito survey in a peri-urban area in south-central mainland Spain, adult Ae. refiki females were captured and identified by morphological traits. The presence of this species of mosquito has never been molecularly confirmed under continental dry Mediterranean climatic influence with scarce number of days with snow on soil. The aim of this study was to confirm by amplification and sequencing of mitochondrial cytochrome c oxidase subunit I (COI) and internal transcribed spacer 2 (ITS2) region.ResultsWe also successfully amplified and typed the species molecularly by COI and ITS2 regions. The peri-urban area where Ae. refiki was found contrasts with the reported cold, humid and snowy environments required by the species to breed.ConclusionsThis finding suggests that the species is already adapted to continental dry Mediterranean environments, questioning whether it is a truly stenotopic species of cold snowy environments.

Bionomic aspects of dengue vectors Aedes aegypti and Aedes albopictus at domestic settings in urban, suburban and rural areas in Gampaha District, Western Province of Sri Lanka

BackgroundThe lack of information on behavioural patterns of Aedes aegypti and Aedes albopictus has become a significant limitation in vector control and disease management programmes. Therefore, the current study was focused on determining some bionomics aspects: breeding, resting, host-seeking and feeding preferences of Ae. aegypti and Ae. albopictus in Sri Lanka.MethodsLarval and adult surveys were conducted from April 2017 to April 2019 monthly in six selected Medical Officer of Health (MOH) areas in Gampaha Distinct, Western province, Sri Lanka, representing urban, suburban and rural settings. Resting preferences of adult mosquitoes were observed from indoor and outdoor places using a Prockopack aspirator. The information on resting height, surface, material and locality was recorded. Human-baited double-net traps were used to determine the host-seeking time of Aedes mosquitoes. Statistical differences in the spatial distribution of mosquitoes in selected MOH areas and prevalence of vectors were analysed using general linear model (GLM). A chi-square test was used to analyse the resting behaviour.ResultsTotal of 19,835 potential breeding sites were examined at 13,563 premises, and 18.5% (n = 1856) were positive for Aedes larvae. Distribution of Ae. aegypti and Ae. albopictus was statistically significant at species level (df = 1; F = 137.134; P < 0.05 GLM) and study setting (df = 2; F = 8.125; P < 0.05). Aedes aegypti breeding was found mainly in temporary removals (18.8%; n = 34), discarded non-degradables (12.15%; n = 22) and tyres (9.95%; n = 18). Natural (14.7%; n = 246) and temporary removals (13.6%; n = 227) and discarded non-reusable items were the key ovipositing sites for Ae. albopictus. In the adult mosquito survey, the majority was comprised of Ae. albopictus (54.5%; n = 999), which denoted exophilic nature (90.8%; n = 758), and 45.5% (n = 835) represented by Ae. aegypti mosquitoes who were mainly endophilic (84.3%; n = 842). Aedes aegypti rested on cloth hangings and curtains, followed by the furniture, while Aedes albopictus was predominant in outdoor vegetation. In both vectors, biting patterns denoted a typical diurnal pattern with two peaks of host-seeking and biting activity in the morning and afternoon.ConclusionsThe majority (80%) of the larval habitats were artificial containers. The use of larvicides for vector control as the prominent measure is questionable since applying these chemicals may target only 20% of the total breeding grounds, which are permanent. The resting places of adult mosquitoes are mainly indoors. Therefore, using thermal space spraying of insecticide may not be appropriate, and indoor residual spraying is recommended as a suitable intervention to target adult mosquitoes. This study warrants a holistic vector control approach for all medically important mosquitoes and insects, ensuring the rational use of finance and resources.Graphical

Temporally consistent predominance and distribution of secondary malaria vectors in the Anopheles community of the upper Zambezi floodplain

Regional optimisation of malaria vector control approaches requires detailed understanding both of the species composition of Anopheles mosquito communities, and how they vary over spatial and temporal scales. Knowledge of vector community dynamics is particularly important in settings where ecohydrological conditions fluctuate seasonally and inter-annually, such as the Barotse floodplain of the upper Zambezi river. DNA barcoding of anopheline larvae sampled in the 2019 wet season revealed the predominance of secondary vector species, with An. coustani comprising > 80% of sampled larvae and distributed ubiquitously across all ecological zones. Extensive larval sampling, plus a smaller survey of adult mosquitoes, identified geographic clusters of primary vectors, but represented only 2% of anopheline larvae. Comparisons with larval surveys in 2017/2018 and a contemporaneous independent 5-year dataset from adult trapping corroborated this paucity of primary vectors across years, and the consistent numerical dominance of An. coustani and other secondary vectors in both dry and wet seasons, despite substantial inter-annual variation in hydrological conditions. This marked temporal consistency of spatial distribution and anopheline community composition presents an opportunity to target predominant secondary vectors outdoors. Larval source management should be considered, alongside prevalent indoor-based approaches, amongst a diversification of vector control approaches to more effectively combat residual malaria transmission.

Introduction of spatial technology for surveillance of vectors of mosquito-borne diseases as an innovative training tool for undergraduate medical students: Qualitative assessment

Introduction: Innovative teaching has been the topic of research with variable learning outcomes. This study was done with an objective to assess the undergraduate medical students' perception about the effect of introducing spatial technology training for surveillance of vectors of dengue and other mosquito borne diseases. Methods: Undergraduate medical students were invited to participate in the training program on Mosquito borne diseases. A total of 80 students participated in the program. After the training, they were divided into two groups to conduct mosquito larval survey using conventional method and GIS technology. Qualitative feedback was collected about their experience in writing from participants using open-ended questions. The feedbacks were analyzed using thematic analysis and participants' observation, NVivo 12 software. Results: Non-response rate was 20-30% in conventional group compared to GIS group. About 44% (n=63) of the participants found the training content to be educational, interesting and informative , 53.4% (n=58) of the participants said the field activity experience was interesting, 72.3%(n=58) found the overall training program to be amazing, engaging in addition to being informative and educational hands on learning experience. Field activity was liked by 50.8% (n=57) participants while 36.8% liked presentation and field activity both. NVivo 12 was used to build a word cloud and the concept diagram. Conclusion: The findings suggest that introduction of new technology acted as an engaging factor and increased the interest in the topic. Participants were more willing to get hands-on experience of GIS. Innovative teaching with hands-on experience of the topics could be an effective way of teaching in medical education.

Distribution and Abundance of Dengue Vector(S) Mosquito and Their Breeding Preferences in Five Selected Administrative Wards of Dhaka North City Corporation, Bangladesh

Dengue fever (DF) and Dengue haemorrhagic fever (DHF) is the most significant arising arboviral disease which is spread from dengue virus infection. Aedes aegypti and Aedes albopictus are the known vectors of dengue virus worldwide. A house based entomological survey was conducted to identify the distribution, abundance of dengue vector(s) mosquitoes and their preferable breeding sites in five selected wards at Dhaka North City Corporation, during July to December 2019. Stegomyia indices were calculated using the exact binomial test. Association between climatic factors and Aedes species abundance were also studied. The highest prevalence of Aedes mosquitoes were found in July. We did not found any Ae.albopictus during the study period. The overall house index (HI), container index, and Breteau index were found 20, 2 and 31 respectively, during the survey period. The present study did not find any significant association (p &gt; 0.05) with meteorological factors (mean temperature, lag rainfall &amp; relative humidity) and the density of Aedes mosquitoes. It is not possible to get an exact idea of the dengue outbreak through a short-term Aedes mosquito survey. So, this study suggests year-long mosquito surveillance program to acquire more conception of dengue transmission and how dengue vector(s) species abundance playing the role.

The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia

BackgroundIrrigation schemes may result in subsequent changes in malaria disease dynamics. Understanding the mechanisms and effects of irrigation on malaria vector bionomics and transmission intensity is essential to develop new or alternative surveillance and control strategies to reduce or control malaria risk. This study was designed to assess the effect of rice irrigation on malaria vector bionomics and transmission intensity in the Gambella Region, Ethiopia.MethodsComparative cross-sectional study was conducted in Abobo District of the Gambella Region, Ethiopia. Accordingly, clusters (kebeles) were classified into nearby and faraway clusters depending on their proximity to the irrigation scheme. Adult mosquito survey was conducted in February, August and November 2018 from three nearby and three faraway clusters using Centers for Disease Control and Prevention (CDC) light traps (LTs). During the November survey, human landing catch (HLC) and pyrethrum spray catch (PSC) were also conducted. The collected mosquitoes were morphologically identified to species and tested for Plasmodium infection using circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA). Furthermore, species-specific polymerase chain reaction (PCR) was performed to identify member species of the Anopheles gambiae complex. Chi-square and t-tests were used to analyze the data using the SPSS version 20 software package.ResultsA total of 4319 female anopheline mosquitoes comprising An. gambiae sensu lato, An. funestus group, An. pharoensis, An. coustani complex and An. squamosus were collected. Overall, 84.5% and 15.5% of the anopheline mosquitoes were collected from the nearby and faraway clusters, respectively. Anopheles gambiae s.l. was the predominant (56.2%) anopheline species in the area followed by An. pharoensis (15.7%). The density of anopheline mosquitoes was significantly higher in the nearby clusters in both HLCs [t(3) = 5.14, P = 0.0143] and CDC LT catches [t(271.97) = 7.446, P < 0.0001). The overall sporozoite rate of anopheline species from the nearby clusters was 10-fold higher compared to the faraway clusters.ConclusionsSignificantly higher mosquito population density was observed in areas close to the irrigation sites. Sporozoite infection rate in the mosquito population was also markedly higher from the nearby clusters. Therefore, the irrigation scheme could increase the risk of malaria in the area.Graphical abstract

Updated distribution of anopheline mosquitoes in Hokkaido, Japan, and the first evidence of Anopheles belenrae in Japan

BackgroundIn Hokkaido, northern island of Japan, at least seven cases of falciparum malaria were reported by 1951. A survey conducted at that time was unsuccessful in implicating any mosquito species as the possible vector. Although active anopheline mosquito surveillance continued until the middle of the 1980s, there is very limited information on their current status and distribution in Japan. Therefore, this study is an update on the current status and distribution of anopheline mosquitoes in Hokkaido based on a 15-year entomological surveillance between 2001 and 2015.MethodsA survey of mosquitoes was conducted at 22 sites in Hokkaido, Japan, from 2001 to 2015. Adult mosquitoes were collected from cowsheds, lakesides, shrubs, and habitats ranging from open grassland to coniferous forest using a Centers for Disease Control and Prevention (CDC) miniature light trap enhanced with dry ice, aspirators, and sweeping nets. Larvae were collected from lakes, ponds, swamps, stagnant and flowing rivers, and paddy fields. All specimens were morphologically identified and subjected to polymerase chain reaction (PCR)-based sequence analysis of the internal transcribed spacer 2 ( ITS2) region of rDNA. Phylogenetic trees were reconstructed using the neighbor-joining method with the Kimura 2-parameter model on MEGA X version 10.2.2.ResultsA total of 46 anopheline specimens were used for the phylogenetic analysis. During the survey, a new member of the Anopheles hyrcanus group, An. belenrae, was discovered in eastern Hokkaido in 2004. Anopheles belenrae has since then been consistently found and confirmed to inhabit only this area of Japan. Four members of the An. hyrcanus group, namely An. belenrae, An. engarensis, An. lesteri, and An. sineroides, have been found in Hokkaido. The results also suggest that An. sinensis, formerly a dominant species throughout Japan, has become a rarely found species, at least currently in Hokkaido.ConclusionThe updated distribution of anopheline mosquitoes in Hokkaido, Japan, showed considerable differences from that observed in previous surveys conducted from 1969 to 1984. In particular, areas where An. sinensis was previously distributed may have been greatly reduced in Hokkaido. The phylogenetic analysis revealed a novel An. hyrcanus group member identified as An. belenrae, described in South Korea in 2005. It is interesting that An. belenrae was confirmed to inhabit only eastern Hokkaido, Japan.Graphical abstract

Prevalence of Larval Breeding Sites and Seasonal Variations of Aedesaegypti Mosquitoes (Diptera: Culicidae) in Makkah Al-Mokarramah, Saudi Arabia.

Since 1994, dengue fever (DF) transmission rates have increased significantly in Saudi Arabia (KSA). Climatic, geographic, and demographic conditions make KSA especially suitable for DF’s spread. Still, there are insufficient strategies for controlling the Aedes species that transmit DF virus (DENV). To develop effective management strategies, it is necessary to identify Aedes species and the ecological habitat of larvae in Makkah Al-Mokarramah, KSA. We conducted a longitudinal survey of Aedes mosquitoes in 14 localities from January 2015 to December 2015. World Health Organization (WHO) inspection kits for larvae were used to detect and sample larvae, along with pictorial keys. A total of 42,981 potential Aedes larval breeding sites were surveyed. A total of 5403 (12.6%) sites had at least one water source positive for Aedes aegypti (Linnaeus) mosquitoes. Among the total of 15,133 water sources surveyed within the sampled sites, 1815 (12.0%) were positive for Aedes aegypti. Aedes aegypti was the only Aedes species identified in the course of the survey. The presence of such a large immature population may indicate an imminent outbreak of DF in the near future unless proper implementation of control and elimination of Aedes aegypti are undertaken. Additionally, the adaptation of Aedes aegypti to the arid climate of Makkah needs further investigation.

Assessment of Mosquito Collection Methods for Dengue Surveillance.

Several methods exist to collect and assess the abundance of dengue vector mosquitoes, i.e., morning adult collection, pupal collection, ovitraps, human landing, and larval collection. Several of these methods are officially implemented to monitor mosquito density and make decisions on treatments for dengue control. This monitoring is also constrained by the need to conduct this assessment on a “one point/one day” process, meaning that once the threshold of 100 households is reached, the assessment is made, and the collectors teams move to another place, thus preventing the use of long-term sampling methods. This diversity of methods might be a source of variability and lack of statistical significance. There is also a lack of published data regarding the efficacy of these methods. Furthermore, the Stegomyia indices are shown to be not reliable for assessing the risk of dengue outbreaks. A mosquito survey was, thus, conducted in 39 locations corresponding to 15 dengue endemic provinces in Indonesia by using the different adult and larval collection methods recommended nationwide. A total of 44,675 mosquitoes were collected. The single larva method was the most efficient. Out of a total of 89 dengue-positive pools, the most frequently encountered virus was DENV2, which made up half of the positive samples, followed by DENV3 and DENV1, respectively. Factor analysis of mixed data showed that no correlation could be found between any methods and the presence of dengue virus in mosquitoes. Moreover, no correlation could be found between any methods and the incidence of dengue. There was no consistency in the efficacy of a given method from one site to another. There was no correlation between any of the parameters considered, i.e., method, incidence of dengue, location, and the presence of dengue virus in mosquitoes.

Key breeding sites of Aedes mosquitoes in Huaylau village, Pakse city, Champasack province, Lao People Democratic Republic 2019

Objectives: The elimination of key breeding sites of dengue vector is applied worldwide to control the vector density under the critical epidemic threshold. This study aimed to identify key breeding sites of Aedes mosquitos and associated factors in Huaylau village, Pakse city, Champasack province in Laos in 2019. Methods: This was a cross-sectional study, combining of immature stage survey of Aedes mosquitoes in all water and discarded containers and the community’s knowledge and practices on the prevention of dengue fever in all 240 households in Huaylau village. Multivariate logistic regression was applied to identify factors associated with the absence of Aedes larvae and pupae in the village. Statistical significance was set at a p-value less than 0.05. Results: Among the 720 water and discarded containers surveyed, the study found 654 Aedes larvae and pupae; of which 94.6% were immature Aedes aegypti. Key breeding sites of Aedes aegypti included water jars (34.2%), plastic drums (30.7%), tanks &lt; 500 litter (14.7%), and discarded containers (12.6%), while that of all Aedes albopictus was discarded containers. The community’s better practices on the prevention of dengue fever contributed to the increased odds of the absence of Aedes larvae ad pupae by 1.612 (95%CI: 1.218-2.134, p&lt;0.01), and the cleanliness of the house were associated with the increased odds of 4.072 of the absent Aedes larvae and pupae in the participated households (95%CI: 1.589-10.434, p&lt;0.01). Conclusions: Aedes aegypti mosquitoes in the Huaylau village laid their eggs in various breeding sites, including water containers and discarded containers while discarded containers were the only key breeding site of Aedes albopictus. Better practices on dengue prevention and better hygiene conditions of the houses contributed to the absence of Aedes larvae and pupae. Special attention should be paid to the clearance of all discarded containers and education of the community people to cover water containers in the village. Keywords: key breeding sites, Aedes, mosquito, pupae, larvae, Champasack province, Lao PDR