bims-mosdis 2020-06-14 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2020‒06‒14
twenty-six papers selected by
Richard Halfpenny
Staffordshire University

Insecticide resistance, fitness and susceptibility to Zika infection of an interbred Aedes aegypti population from Rio de Janeiro, Brazil.
The mosquitoes of Armenia: review of knowledge and results of a field survey with first report of Aedes albopictus.
Susceptibility of mosquito vectors of the city of Praia, Cabo Verde, to Temephos and Bacillus thuringiensis var israelensis.
Malaria Vectors and Vector Surveillance in Limpopo Province (South Africa): 1927 to 2018.
Entomological Surveillance for Zika and Dengue Virus in Aedes Mosquitoes: Implications for Vector Control in Thailand.
Diversity and Molecular Characterization of Mosquitoes (Diptera: Culicidae) in Selected Ecological Regions in Kenya.
The need for new vector control approaches targeting outdoor biting Anopheline malaria vector communities.
Environmental influences on Aedes aegypti catches in Biogents Sentinel traps during a Californian "rear and release" program: Implications for designing surveillance programs.
Emergence of Arboviruses in the United States: The Boom and Bust of Funding, Innovation, and Capacity.
Use of pyriproxyfen in control of Aedes mosquitoes: A systematic review.
Larval habitat diversity and mosquito species distribution along the coast of Kenya.
Surveillance of Culicine Mosquitoes in Six Villages of Taita-Taveta County, Kenya, With Host Determinations From Blood-Fed Females.
Bacterial Microbiome in Wild-Caught Anopheles Mosquitoes in Western Thailand.
Design, development and assessment of an essential oil based slow release vaporizer against mosquitoes.
Relationships between traditional larval indices and meteorological factors with the adult density of Aedes albopictus captured by BG-mosquito trap.
Embryo Microinjection Techniques for Efficient Site-Specific Mutagenesis in Culex quinquefasciatus.
Vertical Transmission of Zika Virus in Aedes aegypti Produces Potentially Infectious Progeny.
Effect of life stage and pesticide exposure on the gut microbiota of Aedes albopictus and Culex pipiens L.
A comparative analysis of the 2007 and 2017 Italian chikungunya outbreaks and implication for public health response.
Assessment of selected larvicides for the control of Culex pipiens biotype pipiens and Culex pipiens biotype molestus under laboratory and semi-field conditions.
Infection of Aedes mosquitoes by native Wolbachia in urban cemeteries of Southern Mexico.
Malaria Risk Factors in Banjarnegara, Indonesia: A Matched Case-Control Study.
[Response of Aedes aegypti L. (Diptera: Culicidae) to transfluthrin and linalool impregnated in different of fabric types].
Microbial communities of container aquatic habitats shift in response to Culex restuans larvae.
Mosquitoes are attracted by the odour of Plasmodium-infected birds.
Buzzkill: targeting the mosquito auditory system.

Parasit Vectors. 2020 Jun 08. 13(1): 293

Insecticide resistance, fitness and susceptibility to Zika infection of an interbred Aedes aegypti population from Rio de Janeiro, Brazil.

Carlucio Rocha Dos Santos, Cynara de Melo Rodovalho, Willy Jablonka, Ademir Jesus Martins, José Bento Pereira Lima, Luciana Dos Santos Dias, Mário Alberto Cardoso da Silva Neto, Georgia Correa Atella.

  BACKGROUND: Aedes aegypti is a vector of high relevance, since it transmits several arboviruses, including dengue, chikungunya and Zika. Studies on vector biology are usually conducted with laboratory strains presenting a divergent genetic composition from field populations. This may impair vector control policies that were based on laboratory observations employing only long maintained laboratory strains. In the present study we characterized a laboratory strain interbreed with Ae. aegypti collected from five different localities in Rio de Janeiro (Aedes Rio), for insecticide resistance (IR), IR mechanisms, fitness and Zika virus infection.METHODS: We compared the recently established Aedes Rio with the laboratory reference strain Rockefeller. Insecticide resistance (deltamethrin, malathion and temephos), activity of metabolic resistance enzymes and kdr mutation frequency were determined. Some life table parameters (longevity, blood-feeding, number and egg viability) and Zika virus susceptibility was also determined.
RESULTS: Aedes Rio showed resistance to deltamethrin (resistance ratio, RR50 = 32.6) and temephos (RR50 = 7.0) and elevated activity of glutathione S-transferase (GST) and esterases (α-EST and pNPA-EST), but not acetylcholinesterase (AChE). In total, 92.1% of males genotyped for kdr presented a "resistant" genotype. Weekly blood-fed females from both strains, presented reduced mortality compared to sucrose-fed mosquitoes; however, Aedes Rio blood-fed females did not live as long (mean lifespan: Rockefeller = 70 ± 3.07; Aedes Rio = 53.5 ± 2.16 days). There were no differences between strains in relation to blood-feeding and number of eggs, but Aedes Rio eggs presented reduced viability (mean hatch: Rockefeller = 77.79 ± 1.4%; Aedes Rio = 58.57 ± 1.77%). Zika virus infection (plaque-forming unit, PFU) was similar in both strains (mean PFU ± SE: Aedes Rio: 4.53 × 104 ± 1.14 × 104 PFU; Rockefeller: 2.02 × 104 ± 0.71 × 104 PFU).
CONCLUSION: Selected conditions in the field, such as IR mechanisms, may result in pleiotropic effects that interfere in general physiology of the insect. Therefore, it is important to well characterize field populations to be tested in parallel with laboratory reference strains. This practice would improve the significance of laboratory tests for vector control methods.

Keywords:  Aedes aegypti; Fitness; Insecticide resistance; Mosquito

DOI:  https://doi.org/10.1186/s13071-020-04166-3
Parasite. 2020 ;27 42

The mosquitoes of Armenia: review of knowledge and results of a field survey with first report of Aedes albopictus.

Lusine Paronyan, Lilit Babayan, Arsen Manucharyan, Dezdemonia Manukyan, Haykuhi Vardanyan, Gayane Melik-Andrasyan, Francis Schaffner, Vincent Robert.

  BACKGROUND: In 2016, a field study was implemented in all Armenian provinces in order to update knowledge on the presence and distribution of both native and invasive mosquito species. Larvae and adult mosquitoes were sampled and identified on the basis of their morphology. Supplementary field surveys were performed in 2017-2018.RESULTS: Between June 20 and July 12, 2016, 117 localities were visited. A total number of 197 sampling units were checked, of which 143 (73%) were positive for mosquitoes (with 1-6 species per sampling unit). A total number of 4157 mosquito specimens were identified to species or species complex level. Ten species represent first records for Armenia: Aedes albopictus, Ae. annulipes, Ae. cataphylla, Ae. cinereus/geminus (probably Ae. cinereus), Ae. flavescens, Anopheles plumbeus, Coquillettidia richiardii, Culex martinii, Cx. torrentium and Culiseta subochrea. The invasive species Ae. albopictus was recorded in a single locality (Bagratashen) at the border point with Georgia, along the main road Tbilisi-Yerevan. This species was further recorded in 2017 and 2018, demonstrating its establishment and spread in north Armenia. These surveys confirm the presence of vectors of malaria parasites (in particular An. sacharovi) and West Nile virus (Cx. pipiens).
CONCLUSION: The knowledge of the Armenian mosquito fauna is extended to a list of 28 species. The record of Aedes albopictus, an important potential vector of many arboviruses, has important implications for public health.

Keywords:  Arbovirus; Biodiversity; Culicidae; Invasive species; Malaria; Vector

DOI:  https://doi.org/10.1051/parasite/2020039
PLoS One. 2020 ;15(6): e0234242

Susceptibility of mosquito vectors of the city of Praia, Cabo Verde, to Temephos and Bacillus thuringiensis var israelensis.

Sílvia Pires, Joana Alves, Ibrahima Dia, Lara F Gómez.

Many vector-borne diseases circulate in the Republic of Cabo Verde. These include malaria during the colonization of the archipelago by the Portuguese explorers and several arboviruses such as yellow fever (now eradicated), dengue and zika. To control these vector-borne diseases, an integrated vector control program was implemented. The main targeted mosquito vectors are Aedes aegypti and Anopheles arabiensis, and in a lesser extent the potential arbovirus vector Culex pipiens s.l. The main control strategy is focused on mosquito aquatic stages using diesel oil and Temephos. This latter has been applied in Cabo Verde since 1979. Its continuous use was followed by the emergence of resistance in mosquito populations. We investigated the current susceptibility to Temephos of the three potential mosquito vectors of Cabo Verde through bioassays tests. Our results showed various degrees of susceptibility with 24h post-exposure mortality rates ranging from 43.1% to 90.9% using WHO diagnostic doses. A full susceptibility was however observed with Bacillus thurigiensis var israelensis with mortality rates from 99.6% to 100%.

DOI: https://doi.org/10.1371/journal.pone.0234242
Int J Environ Res Public Health. 2020 Jun 09. pii: E4125. [Epub ahead of print]17(11):

Malaria Vectors and Vector Surveillance in Limpopo Province (South Africa): 1927 to 2018.

Leo Braack, Riana Bornman, Taneshka Kruger, Yael Dahan-Moss, Allison Gilbert, Maria Kaiser, Shüné V Oliver, Anthony J Cornel, Yoosook Lee, Douglas E Norris, Maureen Coetzee, Basil Brooke, Christiaan de Jager.

  Despite the annual implementation of a robust and extensive indoor residual spraying programme against malaria vectors in Limpopo Province (South Africa), significant transmission continues and is a serious impediment to South Africa's malaria elimination objectives. In order to gain a better understanding regarding possible causes of this residual malaria, we conducted a literature review of the historical species composition and abundance of malaria vector mosquitoes in the Limpopo River Valley region of the Vhembe District, northern Limpopo Province, the region with the highest remaining annual malaria cases in South Africa. In addition, mosquito surveys were carried out in the same region between October 2017 and October 2018. A total of 2225 adult mosquitoes were collected using CO2-baited tent and light traps, human landing catches and cow-baited traps. Of the 1443 Anopheles collected, 516 were members of the An. gambiae complex and 511 An. funestus group. In the malaria endemic rural areas outside the Kruger National Park, one specimen each of An. gambiae s.s. and An. funestus and only three of An. arabiensis were collected. The latter species was abundant at a remote hot spring in the neighboring Kruger National Park. Eighteen other species of Anopheles were collected. Our survey results support the historical findings that An. arabiensis, the species widely held to be the prime malaria vector in South Africa, is a rare species in the malaria endemic Limpopo River Valley. The implications of the mosquito surveys for malaria transmission, elimination and vector control in northern Limpopo Province and neighboring regions are discussed.

Keywords:  Anopheles; Limpopo Province; South Africa; malaria; vector surveillance

DOI:  https://doi.org/10.3390/ijerph17114125
Pathogens. 2020 Jun 04. pii: E442. [Epub ahead of print]9(6):

Entomological Surveillance for Zika and Dengue Virus in Aedes Mosquitoes: Implications for Vector Control in Thailand.

Nathamon Kosoltanapiwat, Jarinee Tongshoob, Preeraya Singkhaimuk, Chanyapat Nitatsukprasert, Silas A Davidson, Alongkot Ponlawat.

  Entomological surveillance for arthropod-borne viruses is vital for monitoring vector-borne diseases and informing vector control programs. In this study, we conducted entomological surveillance in Zika virus endemic areas. In Thailand, it is standard protocol to perform mosquito control within 24 h of a reported dengue case. Aedes females were collected within 72 h of case reports from villages with recent Zika-human cases in Kamphaeng Phet Province, Thailand in 2017 and 2018. Mosquitoes were bisected into head-thorax and abdomen and then screened for Zika (ZIKV) and dengue (DENV) viruses using real-time RT-PCR. ZIKV RNA was detected in three samples from two female Ae. aegypti (1.4%). A partial envelope sequence analysis revealed that the ZIKV sequences were the Asian lineage identical to sequences from ZIKV-infected cases reported in Thailand during 2016 and 2017. Dengue virus-1 (DENV-1) and dengue virus-4 (DENV-4) were found in four Ae. aegypti females (2.8%), and partial capsid sequences were nearly identical with DENV-1 and DENV-4 from Thai human cases reported in 2017. Findings in the current study demonstrate the importance of entomological surveillance programs to public health mosquito-borne disease prevention measures and control.

Keywords:  Aedes aegypti; Thailand; dengue virus; mosquito surveillance; zika virus

DOI:  https://doi.org/10.3390/pathogens9060442
F1000Res. 2019 ;8 262

Diversity and Molecular Characterization of Mosquitoes (Diptera: Culicidae) in Selected Ecological Regions in Kenya.

Moni Makanda, Gladys Kemunto, Lucy Wamuyu, Joel Bargul, Jackson Muema, James Mutunga.

  Mosquitoes play a predominant role as leading agents in the spread of vector-borne diseases and the consequent mortality in humans. Despite reports on increase of new and recurrent mosquito borne-disease outbreaks such as chikungunya, dengue fever and Rift Valley fever in Kenya, little is known about the genetic characteristics and diversity of the vector species that have been incriminated in transmission of disease pathogens. In this study, mosquito species were collected from Kisumu city, Kilifi town and Nairobi city and we determined their genetic diversity and phylogenetic relationships. PCR was used to amplify the partial cytochrome oxidase subunit 1 (CO1) gene of mosquito samples. Molecular-genetic and phylogenetic analysis of the partial cytochrome oxidase subunit 1 (CO1) gene were employed to identify their relationship with known mosquito species. Fourteen (14) haplotypes belonging to genus Aedes, nine (9) haplotypes belonging to genus Anopheles and twelve (12) haplotypes belonging to genus Culex were identified in this study. Findings from this study revealed a potentially new haplotype belonging to Anopheles genus and reported the first molecular characterization of Aedes cumminsii in Kenya. Sequence results revealed variation in mosquito species from Kilifi, Kisumu and Nairobi. Since vector competence varies greatly across species as well as species-complexes and is strongly associated with specific behavioural adaptations, proper species identification is important for vector control programs.

Keywords:  Aedes; Anopheles; Culex; Rift Valley fever; chikungunya; dengue fever

DOI:  https://doi.org/10.12688/f1000research.18262.2
Parasit Vectors. 2020 Jun 10. 13(1): 295

The need for new vector control approaches targeting outdoor biting Anopheline malaria vector communities.

Seynabou Sougoufara, Emmanuel Chinweuba Ottih, Frederic Tripet.

  Since the implementation of Roll Back Malaria, the widespread use of insecticide-treated nets (ITNs) and indoor residual spraying (IRS) is thought to have played a major part in the decrease in mortality and morbidity achieved in malaria-endemic regions. In the past decade, resistance to major classes of insecticides recommended for public health has spread across many malaria vector populations. Increasingly, malaria vectors are also showing changes in vector behaviour in response to current indoor chemical vector control interventions. Changes in the time of biting and proportion of indoor biting of major vectors, as well as changes in the species composition of mosquito communities threaten the progress made to control malaria transmission. Outdoor biting mosquito populations contribute to malaria transmission in many parts of sub-Saharan Africa and pose new challenges as they cannot be reliably monitored or controlled using conventional tools. Here, we review existing and novel approaches that may be used to target outdoor communities of malaria vectors. We conclude that scalable tools designed specifically for the control and monitoring of outdoor biting and resting malaria vectors with increasingly complex and dynamic responses to intensifying malaria control interventions are urgently needed. These are crucial for integrated vector management programmes designed to challenge current and future vector populations.

Keywords:  Anopheles; Exophagy; Exophily; Mosquitoes; Outdoor biting; Pesticide resistance; Traps

DOI:  https://doi.org/10.1186/s13071-020-04170-7
PLoS Negl Trop Dis. 2020 Jun 12. 14(6): e0008367

Environmental influences on Aedes aegypti catches in Biogents Sentinel traps during a Californian "rear and release" program: Implications for designing surveillance programs.

Kyran M Staunton, Jacob E Crawford, Devon Cornel, Peter Yeeles, Mark Desnoyer, Josh Livni, Jodi Holeman, F Stephen Mulligan, Nigel Snoad, Scott A Ritchie.

As Aedes aegypti continues to expand its global distribution, the diseases it vectors (dengue, Zika, chikungunya and yellow fever) are of increasing concern. Modern efforts to control this species include "rear and release" strategies where lab-reared mosquitoes are distributed throughout the landscape to replace or suppress invasive populations. These programs require intensive surveillance efforts to monitor their success, and the Biogents Sentinel (BGS) trap is one of the most effective tools for sampling adult Ae. aegypti. BGS trap catches can be highly variable throughout landscapes, so we investigated the potential impacts of environmental factors on adult Ae. aegypti capture rates during a "rear and release" program in California to better understand the relative contributions of true variability in population density across a landscape and trap context. We recorded male and female Ae. aegypti catches from BGS traps, with and without CO2, throughout control sites where no mosquitoes were released and in treatment sites where males infected with Wolbachia were released. BGS trap catches were positively influenced by higher proportions of shade or bushes in the front yard of the premises as well as the presence of potential larval habitats such as subterranean vaults. In contrast, an increase in residential habitat within a 100 m radius of trap locations negatively influenced BGS trap catches. For male Ae. aegypti, increased visual complexity of the trap location positively influenced capture rates, and the presence of yard drains negatively affected catch rates in control sites. Lastly, for BGS traps using CO2, higher catch rates were noted from traps placed greater than one meter from walls or fences for both male and female mosquitoes. These results have important implications for surveillance programs of Ae. aegypti throughout the Californian urban environment including adult monitoring during "rear and release" programs.

DOI: https://doi.org/10.1371/journal.pntd.0008367
Trop Med Infect Dis. 2020 Jun 06. pii: E96. [Epub ahead of print]5(2):

Emergence of Arboviruses in the United States: The Boom and Bust of Funding, Innovation, and Capacity.

Rebekah C Kading, Lee W Cohnstaedt, Ken Fall, Gabriel L Hamer.

  Mosquito-borne viruses will continue to emerge and generate a significant public health burden around the globe. Here, we provide a longitudinal perspective on how the emergence of mosquito-borne viruses in the Americas has triggered reactionary funding by sponsored agencies, stimulating a number of publications, innovative development of traps, and augmented capacity. We discuss the return on investment (ROI) from the oscillation in federal funding that influences demand for surveillance and control traps and leads to innovation and research productivity.

Keywords:  Aedes; Culex; West Nile virus; Zika virus; emerging virus; mosquito; outbreak; surveillance; trap

DOI:  https://doi.org/10.3390/tropicalmed5020096
PLoS Negl Trop Dis. 2020 Jun 12. 14(6): e0008205

Use of pyriproxyfen in control of Aedes mosquitoes: A systematic review.

John Christian Hustedt, Ross Boyce, John Bradley, Jeffrey Hii, Neal Alexander.

Dengue is the most rapidly spreading arboviral disease in the world. The current lack of fully protective vaccines and clinical therapeutics creates an urgent need to identify more effective means of controlling Aedes mosquitos, principally Aedes aegypti, as the main vector of dengue. Pyriproxyfen (PPF) is an increasingly used hormone analogue that prevents juvenile Aedes mosquitoes from becoming adults and being incapable of transmitting dengue. The objectives of the review were to (1) Determine the effect of PPF on endpoints including percentage inhibition of emergence to adulthood, larval mortality, and resistance ratios; and (2) Determine the different uses, strengths, and limitations of PPF in control of Aedes. A systematic search was applied to Pubmed, EMBASE, Web of Science, LILACS, Global Health, and the Cochrane database of Systematic Reviews. Out of 1,369 records, 90 studies met the inclusion criteria. Nearly all fit in one of the following four categories 1) Efficacy of granules, 2) Auto-dissemination/horizontal transfer, 3) use of ultra-low volume thermal fogging (ULV), thermal fogging (TF), or fumigant technologies, and 4) assessing mosquito resistance. PPF granules had consistently efficacious results of 90-100% inhibition of emergence for up to 90 days. The evidence is less robust but promising regarding PPF dust for auto-dissemination and the use of PPF in ULV, TF and fumigants. Several studies also found that while mosquito populations were still susceptible to PPF, the lethal concentrations increased among temephos-resistant mosquitoes compared to reference strains. The evidence is strong that PPF does increase immature mortality and adult inhibition in settings represented in the included studies, however future research should focus on areas where there is less evidence (e.g. auto-dissemination, sprays) and new use cases for PPF. A better understanding of the biological mechanisms of cross-resistance between PPF, temephos, and other insecticides will allow control programs to make better informed decisions.

DOI: https://doi.org/10.1371/journal.pntd.0008205
Wellcome Open Res. 2019 ;4 175

Larval habitat diversity and mosquito species distribution along the coast of Kenya.

Miriam Karuitha, Joel Bargul, Joel Lutomiah, Simon Muriu, Joseph Nzovu, Rosemary Sang, Joseph Mwangangi, Charles Mbogo.

  Background: Management of arboviruses relies heavily on vector control. Implementation and sustenance of effective control measures requires regular surveillance of mosquito occurrences, species abundance and distribution. The current study evaluated larval habitat diversity and productivity, mosquito species diversity and distribution in selected sites along the coast of Kenya. Methods: A cross-sectional survey of mosquito breeding habitats, species diversity and distribution was conducted in urban, peri-urban and forested ecological zones in Mombasa and Kilifi counties. Results: A total of 13,009 immature mosquitoes were collected from 17 diverse aquatic habitats along the coast of Kenya. Larval productivity differed significantly (F (16, 243) = 3.21, P < 0.0001) among the aquatic habitats, with tyre habitats recording the highest larval population. Culex pipiens (50.17%) and Aedes aegypti (38.73%) were the dominant mosquito species in urban areas, while Ae. vittatus (89%) was the dominant species in forested areas. In total, 4,735 adult mosquitoes belonging to 19 species were collected in Haller Park, Bamburi, Gede and Arabuko Sokoke forest. Urban areas supported higher densities of Ae. aegypti compared to peri-urban and forest areas, which, on the other hand, supported greater mosquito species diversity. Conclusions: High Ae. aegypti production in urban and peri-urban areas present a greater risk of arbovirus outbreaks. Targeting productive habitats of Aedes aegypti, such as discarded tyres, containers and poorly maintained drainage systems in urban areas and preventing human-vector contact in peri-urban and forested areas could have a significant impact on the prevalence of arboviruses along the coast of Kenya, forestalling the periodic outbreaks experienced in the region.

Keywords:  Aedes; Arbovirus; Culex; Larval habitats; culicine diversity; habitat productivity

DOI:  https://doi.org/10.12688/wellcomeopenres.15550.1
J Med Entomol. 2020 Jun 13. pii: tjaa109. [Epub ahead of print]

Surveillance of Culicine Mosquitoes in Six Villages of Taita-Taveta County, Kenya, With Host Determinations From Blood-Fed Females.

Vanessa Munyao, Jonathan Karisa, Carol Munini Munyao, Moses Ngari, Nelson Menza, Norbert Peshu, Martin Rono, Charles Mbogo, Joseph Mwangangi.

  Culicine mosquitoes are vectors of human disease-causing pathogens like filarial worms and several arthropod-borne viruses (arboviruses). Currently, there has been an increase in emerging and re-emerging vector-borne diseases along coastal Kenya, which has been of major concern in public health. This study aimed at determining culicine mosquito species abundance, diversity and their host feeding preferences in Taita-Taveta County, Coastal Kenya. Entomological sampling was done during the long-wet season (March and May) and long dry season (June to October) 2016-2018. Mosquito sampling was done using CDC light traps and Backpack aspiration for indoor and outdoor environments. All culicine mosquitoes collected were identified morphologically and categorized according to their physiological status. Blood fed culicine mosquitoes were tested for bloodmeal sources using ELISA. In total, 3,278 culicine mosquitoes were collected, of which 738 (22.5 %) were found indoors and 2,540, (77.5 %) outdoors. The mosquitoes consisted of 18 species belonging to four genera: Aedes (7), Culex (8), Mansonia (2), and Coquillettidia (1). Overall, there was high mosquito species diversity (H) in outdoors (H = 2.4339) than in indoors (H = 2.2523), whereas even distribution (EH) was higher in indoors (EH = 0.9064) than outdoors (EH = 0.8266). Majorly the bloodmeals identified were from multiple host sources with (51.6%), single hosts (41.3%), and unidentified (7.2%). This study has demonstrated a high diversity of culicine mosquitoes with relaxed feeding tendencies. These mosquitoes are contributing to mosquito biting nuisance and the likelihood of exposure of populations to diseases of public health.

Keywords:  Culicine; abundance; bloodmeal; diversity

DOI:  https://doi.org/10.1093/jme/tjaa109
Front Microbiol. 2020 ;11 965

Bacterial Microbiome in Wild-Caught Anopheles Mosquitoes in Western Thailand.

Krajana Tainchum, Chloé Dupont, Theeraphap Chareonviriyaphap, Estelle Jumas-Bilak, Michael J Bangs, Sylvie Manguin.

  Among the complex microbial community living in the mosquito midgut, some bacteria (e.g., Enterobacter spp.) can deliver effector molecules with anti-Plasmodium effects suppressing the development of malaria parasites (Plasmodium falciparum) before the öokinete can penetrate the mosquito midgut epithelium. Despite knowledge of this phenomenon, only a few studies have defined the diversity of microbiota in wild-caught adult Anopheles species. The objective of this study was to analyze and compare the bacterial microbiota in different Anopheles species, including representatives of the primary malaria vectors in western Thailand. Wild female Anopheles species were sampled from malaria-endemic areas in Tak and Mae Hong Son provinces near the Thai-Myanmar border. Midgut/abdominal bacterial diversity was assessed by examining the 16S rRNA gene, V3 hypervariable region, using PCR-Temporal Temperature Gel Electrophoresis (PCR-TTGE) profiling and sequence analysis. A total of 24 bacterial genera were identified from eight Anopheles species. Five bacterial genera were newly reported in Anopheles mosquitoes (Ferrimonas, Megasphaera, Pectobacterium, Shimwellia, and Trabulsiella). Five genera, including Megasphaera, were detected exclusively in a single-malaria (Plasmodium vivax) infected Anopheles minimus and not observed in other non-infected mosquitoes. The use of PCR-TTGE provides the first characterization of the midgut bacterial microbiome present in wild adult Anopheles in Thailand. Evidence that microbiota might impact pathogen development (suppression) in Anopheles and thereby reduce the risk of pathogen transmission deserves more studies to describe the presence and better understand the biological role of bacteria in natural mosquito populations.

Keywords:  Anopheles mosquitoes; Thailand; bacterial microbiota; biodiversity; malaria

DOI:  https://doi.org/10.3389/fmicb.2020.00965
Acta Trop. 2020 Jun 04. pii: S0001-706X(19)31509-8. [Epub ahead of print] 105573

Design, development and assessment of an essential oil based slow release vaporizer against mosquitoes.

Hemanga Hazarika, Varun Tyagi, Harshita Krishnatreyya, Probin K Roy, Johirul Islam, Sourav Chakraborty, Neelutpal Gogoi, Sumit Kishor, Yangchen D Bhutia, Danswrang Goyary, Sanjeev Karmakar, Sanjai K Dwivedi, Kamaruz Zaman, Pronobesh Chattopadhyay.

  Mosquitoes (Diptera; Culicidae) are a biting nuisance and are of economic and health importance, especially for people living in tropical countries like India. Given the environmental concerns and health hazards of synthetic insecticides, development of natural products for the control of mosquito and mosquito-borne diseases are needed. In view of this, an essential oil based novel liquid vaporizer formulation with citronella and eucalyptus oils has been developed using a computer aided Artificial Neural Network and Particle Swarm Optimization (ANN-PSO) algorithm approach aiming to predict the best optimized formulation (OF). Following the development, OF was characterized by Fourier Transform-Infra Red (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). The efficacy of the OF was assessed against two major mosquito vectors viz. Anopheles stephensi and Aedes albopictus using a Peet-Grady chamber. Finally, toxicological impacts of the OF following its inhalation were investigated as per the Organization for Economic Co-operation and Development (OECD) guidelines. The results revealed all the ideal characteristics of the OF which were found to provide a slow release of up to 450 hours at room temperature. Most importantly, the OF, exhibited 50% mosquito knock down (KT50) within 11.49±1.34 and 14.15±2.15 min against An. stephensi and Ae. albopictus respectively. Toxicity assessment showed a non toxic nature of the OF following inhalation. Thus the present development would be beneficial for controlling both An. stephensi and Ae. albopictus without any associated health hazards.

Keywords:  Eucalyptus oil; Mosquito repellent; Safety assessment; Vaporizer formulation; citronella oil

DOI:  https://doi.org/10.1016/j.actatropica.2020.105573
PLoS One. 2020 ;15(6): e0234555

Relationships between traditional larval indices and meteorological factors with the adult density of Aedes albopictus captured by BG-mosquito trap.

Jin-Na Wang, Juan Hou, Jian-Yue Zhong, Guo-Ping Cao, Zhang-You Yu, Yu-Yan Wu, Tian-Qi Li, Qin-Mei Liu, Zhen-Yu Gong.

OBJECTIVES: Larval indices have been used for Ae. albopictus surveillance for many years, while there is limited use in assessing dengue transmission risk and adult mosquito emergence. This study is aimed to explore the relationships between larval indices and the Ae. albopictus density captured by BG-mosquito trap (BG-trap) method, with considering the meteorological factors.METHODS: Data on larval density, adult mosquito density and meteorology factors were collected in an entomological survey carried out in Quzhou City, Zhejiang Province of China in 2018. The Spearman's rank correlation and Pearson correlation were used for the analysis on the correlation of density indices. Generalized additive models were established to analyze the influencing factors of mosquito density.
RESULTS: Breteau index (BI), House index (HI) and Container index (CI) were highly correlated with each other (r>0.7, p<0.05). The Ae. albopictus density was significantly correlated with CI (rs = 0.260, p<0.05), CI pre one week (rs = 0.259, p<0.05), and CI pre three weeks (rs = 0.329, p<0.05). BI was correlated with female Ae. albopictus density pre 4 weeks (r = -0.299, p<0.05). Female Ae. albopictus density was correlated with CI pre 3 weeks (rs = 0.303, p<0.05). The influencing factors of BI were average wind speed pre 1 week, average temperature and female Ae. albopictus density pre 4 weeks. The influencing factors of CI were average humidity pre 3 weeks and average temperature. The influencing factors of HI were average temperature and precipitation pre 4 weeks. The influencing factor of Ae. albopictus density and female Ae. albopictus density was temperature.
CONCLUSIONS: The adult Ae. albopictus density had low correlation with certain larval indices. Some of the meteorology factors played significant roles in the density of adult Ae. albopictus and larva with or without a time lag.

DOI: https://doi.org/10.1371/journal.pone.0234555
J Vis Exp. 2020 May 24.

Embryo Microinjection Techniques for Efficient Site-Specific Mutagenesis in Culex quinquefasciatus.

Michelle Bui, Ming Li, Robyn R Raban, Nannan Liu, Omar S Akbari.

Culex quinquefasciatus is a vector of a diverse range of vector-borne diseases such as avian malaria, West Nile virus (WNV), Japanese encephalitis, Eastern equine encephalitis, lymphatic filariasis, and Saint Louis encephalitis. Notably, avian malaria has played a major role in the extinction of numerous endemic island bird species, while WNV has become an important vector-borne disease in the United States. To gain further insight into C. quinquefasciatus biology and expand their genetic control toolbox, we need to develop more efficient and affordable methods for genome engineering in this species. However, some biological traits unique to Culex mosquitoes, particularly their egg rafts, have made it difficult to perform microinjection procedures required for genome engineering. To address these challenges, we have developed an optimized embryo microinjection protocol that focuses on mitigating the technical obstacles associated with the unique characteristics of Culex mosquitoes. These procedures demonstrate optimized methods for egg collection, egg raft separation and other handling procedures essential for successful microinjection in C. quinquefasciatus. When coupled with the CRISPR/Cas9 genome editing technology, these procedures allow us to achieve site-specific, efficient and heritable germline mutations, which are required to perform advanced genome engineering and develop genetic control technologies in this important, but currently understudied, disease vector.

DOI: https://doi.org/10.3791/61375
Am J Trop Med Hyg. 2020 Jun 08.

Vertical Transmission of Zika Virus in Aedes aegypti Produces Potentially Infectious Progeny.

Genevieve Comeau, Robert A Zinna, Taylor Scott, Kacey Ernst, Kathleen Walker, Yves Carrière, Michael A Riehle.

Vertical transmission, or pathogen transfer from female to offspring, can facilitate the persistence of emerging arboviruses, such as Zika virus (ZIKV), through periods of low horizontal transmission or adverse environmental conditions. We aimed at determining the rate of vertical transmission for ZIKV in its principal vector, Aedes aegypti, and the vector competence of vertically infected progeny. Aedes aegypti females that consumed a blood meal provisioned with ZIKV were maintained under three temperature conditions (27°C, 30°C, and 33°C) following the infectious blood meal and allowed to complete three reproductive cycles. The overall vertical transmission rate was 6.5% (95% CI = 3.9-9.9). Vertical transmission of ZIKV was observed across all temperature conditions and virus detected in adult progeny up to 2 weeks postemergence. In total, 3.4% (95% CI = 1.6-6.2) of adult progeny produced saliva with ZIKV, indicating their vector competence. These results suggest the virus may be maintained in Ae. aegypti populations without a vertebrate host for short periods.

DOI: https://doi.org/10.4269/ajtmh.19-0698
Sci Rep. 2020 Jun 11. 10(1): 9489

Effect of life stage and pesticide exposure on the gut microbiota of Aedes albopictus and Culex pipiens L.

Elijah O Juma, Brian F Allan, Chang-Hyun Kim, Christopher Stone, Christopher Dunlap, Ephantus J Muturi.

Pesticides commonly contaminate the aquatic environments inhabited by mosquito juveniles. However, their role in shaping the mosquito microbiota is not well understood. We hypothesized that environmentally relevant concentrations of atrazine, permethrin and malathion will mediate a shift in the mosquito gut bacterial community structure due to their toxic effect on the aquatic bacterial communities, and reduce mosquito gut bacterial diversity by enriching pesticide-degrading bacterial communities over susceptible taxa. Illumina MiSeq sequencing of the V3-V4 hypervariable regions of the 16 S rRNA gene was used to characterize the microbial communities of larval and adult stages of the two mosquito species and the water samples from microcosms treated with each of the pesticides, separately. Bacterial community composition differed by sample type (larval stage vs. adult stage) and water sampling date (day 3 vs. day 7), but not by pesticide treatment. In larval stages, bacterial OTU richness was highest in samples exposed to malathion, intermediate in permethrin, and lowest in controls. Bacterial richness was significantly higher in larval stages compared to adult stages for all treatments. This study provides a primer for future studies evaluating mosquito microbial responses to exposures to chemical pesticides and the possible implications for mosquito ecology.

DOI: https://doi.org/10.1038/s41598-020-66452-5
PLoS Negl Trop Dis. 2020 Jun;14(6): e0008159

A comparative analysis of the 2007 and 2017 Italian chikungunya outbreaks and implication for public health response.

Beniamino Caputo, Gianluca Russo, Mattia Manica, Francesco Vairo, Piero Poletti, Giorgio Guzzetta, Stefano Merler, Carolina Scagnolari, Angelo Solimini.

KEY RESULTS: Both outbreaks started in small towns, but cases were also detected in nearby larger cities where transmission was limited to small clusters. The time spans between the first and the last symptom onsets were similar between the 2 outbreaks, and the delay from the symptom onset of the index case and the first case notified was considerable. Comparable infection and transmission rates were observed in laboratory. The basic reproductive number (R0) was estimated in the range of 1.8-6 (2007) and 1.5-2.6 (2017). Clinical characteristics were similar between outbreaks, and no acute complications were reported, though a higher frequency of ocular symptoms, myalgia, and rash was observed in 2017. Very little is known about the immune mediator profile of CHIKV-infected patients during the 2 outbreaks. Regarding public health responses, after the 2007 outbreak, the Italian Ministry of Health developed national guidelines to implement surveillance and good practices to prevent and control autochthonous transmission. However, only a few regional authorities implemented it, and the perception of outbreak risk and knowledge of clinical symptoms and transmission dynamics by general practitioners remained low.MAJOR CONCLUSIONS: Efforts should be devoted to developing suitable procedures for early detection of virus circulation in the population, possibly through the analysis of medical records in near real time. Increasing the awareness of CHIKV of general practitioners and public health officials through tailored education may be effective, especially in small coastal towns where the outbreak risk may be higher. A key element is also the shift of citizen awareness from considering Aedes mosquitoes not only as a nuisance problem but also as a public health one. We advocate the need of strengthening the surveillance and of promoting the active participation of the communities to prevent and contain future outbreaks.

DOI: https://doi.org/10.1371/journal.pntd.0008159
Pest Manag Sci. 2020 Jun 13.

Assessment of selected larvicides for the control of Culex pipiens biotype pipiens and Culex pipiens biotype molestus under laboratory and semi-field conditions.

Christos I Rumbos, Christos G Athanassiou.

  BACKGROUND: The insecticidal efficacy of selected mosquito larvicides [teflubenzuron, s-methoprene, diflubenzuron, temephos, Bacillus thuringiensis var. israelensis (Bti), polydimethylsiloxane], applied alone or in combination, was comparatively investigated against two Culex pipiens biotypes, i.e., Cx. p. biotype pipiens and Cx. p. biotype molestus, under laboratory and semi-field conditions. Registered larvicides were evaluated at their label dose, while those not registered for mosquito control were tested at their label dose per area, i.e., as plant protection products. Teflubenzuron and temephos were evaluated also at half of their label dose, alone or in combination with a non-ionic surfactant. Larval mortalityand adult emergence were assessed after 1, 3, 5, 7, 9, 11, 16 and 20 d of exposure.RESULTS: In all cases, polydimethylsiloxane provided complete (100%) larval control after 3 d of exposure against both biotypes. With temephos, all larvae were dead after 1 d of exposure, even at half of its label dose. For teflubenzuron, mortality reached 100% at the end of the bioassays and adult emergence was totally avoided, while for diflubenzuron, mortality was close to 100% at the end of the trials. In contrast, in s-methoprene treated-water control was under the 90% mortality threshold for both biotypes. In the semi-field trails, in all treatments with Bti, all larvae of both biotypes were dead already after 1 d of exposure.
CONCLUSIONS: Based on our data, larvicides tested, with the exception of s-methoprene, remained under threshold for effective treatment against larvae of Cx. p. pipiens and Cx. P. molestus for the entire duration of the study. This article is protected by copyright. All rights reserved.

Keywords:  Culex pipiens; larvicides; mosquito emergence; semi-field trials

DOI:  https://doi.org/10.1002/ps.5847
Salud Publica Mex. 2020 Jan 09.

Infection of Aedes mosquitoes by native Wolbachia in urban cemeteries of Southern Mexico.

Jorge Aurelio Torres-Monzón, Mauricio Casas-Martínez, Teresa López-Ordóñez.

  OBJECTIVE: To evaluate the prevalence of Wolbachia infections in Aedes spp. field populations from cemeteries of Southern Mexico.MATERIALS AND METHODS: Six cemeteries were selected to be sampled in the central part of the Soconusco region, Chiapas. Aedes albopictus and Ae. aegypti mosquitoes were collected during the rainy season of 2015. Females were analyzed individually by PCR to determine the presence of Wolbachia.
RESULTS: A field overall prevalence of 38% was found; only Ae. albopictus mosquitoes were positive.
CONCLUSIONS: Local strains of Wolbachia were detected and have the potential to be applied as a biological method for vector control.

Keywords:  Aedes albopictus; Mexico; Soconusco; Wolbachia

DOI:  https://doi.org/10.21149/10163
J UOEH. 2020 ;42(2): 161-166

Malaria Risk Factors in Banjarnegara, Indonesia: A Matched Case-Control Study.

Sulistyawati Sulistyawati, Rokhmayanti Rokhmayanti, Fajar Fatmawati.

  Malaria is a matter of concern in public health worldwide. Identifying its risk factors is essential to determine control efforts. We studied the potential environmental and human behaviour risk factors in malaria by a matched case-control study conducted in the Banjarmangu I Public Health Centre area, Banjarnegara, from June to August 2018. A structured questionnaire and checklist were employed to collect data from 50 participants. Data were analysed by Chi-Square, Fisher exact and logistic regression. A positive association was found between malaria and not sleeping under bed mosquito netting (OR=2.087 [95% CI: 1.148 - 3.795]), not using wire netting in the house ventilation (OR = 3.907 [95% CI: 0.647 - 24.452]), and inadequate prevention practices during outdoor activities (OR = 2.020 [95% CI: 1.033 - 3.953]). These three factors were identified as independent risk factors for malaria.

Keywords:  Indonesia; behaviour; environmental; malaria; risk factors

DOI:  https://doi.org/10.7888/juoeh.42.161
Salud Publica Mex. 2020 Jun 02.

[Response of Aedes aegypti L. (Diptera: Culicidae) to transfluthrin and linalool impregnated in different of fabric types].

Keila Elizabeth Paiz-Moscoso, Ildefonso Fernández-Salas, John Paul Grieco, Nicole L Achee, José Luis Torres-Estrada.

  OBJECTIVE: Evaluate the effect of spatial repellency against Ae. aegypti of two chemical compounds impregnated in different types of fabrics.MATERIALS AND METHODS: The study was carried out in the year 2015-2016 in the Centro Regional de Investigación en Salud Pública, del Instituto Nacional de Salud Pública. The high-throughput screening system was used to evaluate the response of Ae. aegypti to transfluthrin and linalool, impregnated individually at different concentrations in poplin, cotton and polyester. The effect of their mixtures was also determined, washing on residuality and percentage of protection.
RESULTS: The highest spatial repellency response was for 0.1% linalool-cotton treatment (RE = 70 ± 5.77%). The mixture of 0.1% linalool and 0.001% transfluthrin presented a similar spatial repellence percentage for the three types of fabric. The transfluthrin-poplin treatment 0.001% maintained a residual of five days. 0.1% linalool produced a 62.50% protection in the presence of an attraction stimulus.
CONCLUSIONS: It is suggested the impregnation of 0.1% linalool in clothing as a protection measure for Ae. aegypti.

Keywords:  Aedes aegypti; Zika; chikungunya; dengue; spatial repellents

DOI:  https://doi.org/10.21149/10158
FEMS Microbiol Ecol. 2020 Jun 12. pii: fiaa112. [Epub ahead of print]

Microbial communities of container aquatic habitats shift in response to Culex restuans larvae.

Ephantus J Muturi, Christopher Dunlap, Carla E Cáceres.

  We examined how larvae of Culex restuans mosquito influences the bacterial abundance, composition, and diversity in simulated container aquatic habitats. The microbiota of Cx. restuans larvae were also characterized and compared to those of their larval habitats. The presence of Cx. restuans larvae altered the bacterial community composition and reduced the bacterial abundance, diversity and richness. Azohydromonas sp., Delftia sp., Pseudomonas sp., Zooglea sp., unclassified Enterobacteriaceae, and unclassified Bacteroidales were suppressed while Prosthecobacter sp., Hydrogenaphaga sp., Clostridium sp., unclassified Clostridiaceae, and Chryseobacterium sp. were enhanced in the presence of Cx. restuans larvae. Cx. restuans larvae harbored distinct and less diverse bacterial community compared to their larval habitats. These findings demonstrate that Cx. restuans larvae play a key role in structuring the microbial communities in container aquatic habitats and may lower the nutritional quality and alter the decomposition process and food web dynamics in these aquatic systems. The findings also demonstrate that mosquito larvae are highly selective of the bacterial taxa from the larval environment that colonize their bodies. These findings provide new opportunities for more focused studies to identify the specific bacterial taxa that serve as food for mosquito larvae and those that could be harnessed for disease control.

Keywords:   Culex restuans ; Bacterial communities; Container aquatic habitats; Detritus

DOI:  https://doi.org/10.1093/femsec/fiaa112
Int J Parasitol. 2020 Jun 04. pii: S0020-7519(20)30119-3. [Epub ahead of print]

Mosquitoes are attracted by the odour of Plasmodium-infected birds.

Alazne Díez-Fernández, Josué Martínez-de la Puente, Laura Gangoso, Pilar López, Ramón Soriguer, José Martín, Jordi Figuerola.

  Parasites can manipulate their hosts to increase their transmission success. Avian malaria parasites (Plasmodium) are thought to alter the cues such as host odour, used by host-seeking mosquitoes. Bird odour is affected by secretions from the uropygial gland and may play a role in modulating vector-host interactions. We tested the hypothesis that mosquitoes are more attracted to the uropygial secretions and/or whole-body odour (headspace) of Plasmodium-infected house sparrows (Passer domesticus) than to those of uninfected birds. We tested the attraction of nulliparous (e.g. uninfected mosquitoes without previous access to blood) Culex pipiens females towards these stimuli in a dual-choice olfactometer. We used Gas Chromatography-Mass Spectrometry (GC-MS) analyses to assess whether Plasmodium infection is associated with differences in the chemical composition of uropygial secretions. Mosquitoes were more attracted to the odours of infected than uninfected birds, regardless of sex. However, the significant interaction between infection status and the stimuli (uropygial secretion or headspace) showed that mosquitoes were more attracted to the headspace of infected birds; no differences were found in the case of uropygial secretions. The compounds in the volatile lipophilic fraction of the uropygial secretion did not differ between infected and uninfected birds. These results support the host manipulation hypothesis since avian Plasmodium parasites may be capable of altering their host's body odour, thereby making infected individuals more attractive to mosquitoes.

Keywords:  Chemical communication; Host preference; Infectious diseases; Olfaction; Olfactometer; Wild birds

DOI:  https://doi.org/10.1016/j.ijpara.2020.03.013
Curr Opin Insect Sci. 2020 May 06. pii: S2214-5745(20)30049-3. [Epub ahead of print]40 11-17

Buzzkill: targeting the mosquito auditory system.

Marta Andrés, Matthew P Su, Joerg Albert, Lauren J Cator.

Sound plays an important role in mosquito sensory ecology. Acoustic perception and acoustically driven behaviours therefore represent potentially effective control targets. Previous scientific efforts around acoustic-based control and surveillance have not been systematic and ambiguity around the exact role of acoustic communication in conspecific interactions remains. Here, we briefly review recent advances in mosquito auditory physiology and behavioural ecology as well as ongoing activities to incorporate sound into control and surveillance tools. We highlight areas where increased collaboration between physiologists, molecular biologists, behavioural ecologists and control experts is needed to capitalize on this progress and realize the potential of sound-based technologies and strategies.

DOI: https://doi.org/10.1016/j.cois.2020.04.003