bims-mosdis 2020-04-26 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2020‒04‒26
thirty papers selected by
Richard Halfpenny
Staffordshire University

Impact of Insecticide Resistance on P. falciparum Vectors' Biting, Feeding, and Resting Behaviour in Selected Clusters in Teso North and South Subcounties in Busia County, Western Kenya.
High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas.
Distribution and pyrethroid resistance status of Aedes aegypti and Aedes albopictus populations and possible phylogenetic reasons for the recent invasion of Aedes aegypti in Nepal.
Dispersal of female and male Aedes aegypti from discarded container habitats using a stable isotope mark-capture study design in South Texas.
Opinions of key stakeholders on alternative interventions for malaria control and elimination in Tanzania.
Mosquito Control Activities during Local Transmission of Zika Virus, Miami-Dade County, Florida, USA, 2016.
Biological control of Aedes mosquito larvae with carnivorous aquatic plant, Utricularia macrorhiza.
Optimizing the deployment of ultra-low volume and indoor residual spraying for dengue outbreak response.
Mosquito Larvicidal Activity, Antimicrobial Activity, and Chemical Compositions of Essential Oils from Four Species of Myrtaceae from Central Vietnam.
Distribution and seasonal fluctuations of Ae. aegypti and Ae. albopictus larval and pupae in residential areas in an urban landscape.
Vector bionomics and vectorial capacity as emergent properties of mosquito behaviors and ecology.
Stability of the effect of silencing fibronectin type III domain-protein 1 (FN3D1) gene on Anopheles arabiensis reared under different breeding site conditions.
West Nile Virus Epidemic in Germany Triggered by Epizootic Emergence, 2019.
Orthosteric muscarinic receptor activation by the insect repellent IR3535 opens new prospects in insecticide-based vector control.
West Nile virus lineage 2 in humans and mosquitoes in Bulgaria, 2018-2019.
Climate factors and the East Asian summer monsoon may drive large outbreaks of dengue in China.
Effect of long-lasting insecticidal nets with and without piperonyl butoxide on malaria indicators in Uganda (LLINEUP): a pragmatic, cluster-randomised trial embedded in a national LLIN distribution campaign.
Immune priming with inactive dengue virus during the larval stage of Aedes aegypti protects against the infection in adult mosquitoes.
Exploring the Mechanisms of Multiple Insecticide Resistance in a Highly Plasmodium-Infected Malaria Vector Anopheles funestus Sensu Stricto from Sahel of Northern Nigeria.
Larvicidal and repellant effects of Jussiaea repens (L.) leaf ethanol extract and its major phyto-constituent against important human vector mosquitoes (Diptera: Culicidae).
Anopheles gambiae densovirus (AgDNV) negatively affects Mayaro virus infection in Anopheles gambiae cells and mosquitoes.
Acute Lymphatic Filariasis Infection in United States Armed Forces Personnel Deployed to the Pacific Area of Operations during World War II Provides Important Lessons for Today.
Larvicidal, Ovicidal, Synergistic, and Repellent Activities of Sophora alopecuroides and Its Dominant Constituents Against Aedes albopictus.
Dynamics and Distribution of the Invasive Mosquito Aedes koreicus in a Temperate European City.
Comparative Molecular Description of a Novel GST Gene in Culex pipiens (Diptera: Culicidae).
Human West Nile Virus Lineage 2 Infection: Epidemiological, Clinical, and Virological Findings.
Malaria elimination using the 1-3-7 approach: lessons from Sampov Loun, Cambodia.
Species and sex-specific chemosensory gene expression in Anopheles coluzzii and An. quadriannulatus antennae.
Insecticidal and Genotoxic effects of some indigenous plant extracts in Culex quinquefasciatus Say Mosquitoes.
New Challenge for Zika Virus Infection: Human Reservoirs?

J Parasitol Res. 2020 ;2020 9423682

Impact of Insecticide Resistance on P. falciparum Vectors' Biting, Feeding, and Resting Behaviour in Selected Clusters in Teso North and South Subcounties in Busia County, Western Kenya.

Edward K Githinji, Lucy W Irungu, Paul N Ndegwa, Maxwell G Machani, Richard O Amito, Brigid J Kemei, Paul N Murima, Geoffrey M Ombui, Antony K Wanjoya, Charles M Mbogo, Evan M Mathenge.

Introduction: Behavioural resistance to insecticides restrains the efficacy of vector control tools against mosquito-transmitted diseases. The current study is aimed at determining the impact of insecticide resistance on major malaria vectors' biting, feeding, and resting behaviour in areas with and areas without insecticide resistance in Teso North and Teso South, Busia County, Western Kenya.Methods: Mosquito larvae were sampled using a dipper, reared into 3-5-day-old female mosquitoes [4944] which were exposed to 0.75% permethrin and 0.05% deltamethrin using World Health Organization tube assay method. Blood meal, species identification, and kdr Eastgene PCRs were also performed on adult mosquitoes sampled using mosquito collection methods [3448]. Biting, feeding, resting, and exiting behaviours of field-collected mosquitoes from five selected clusters were analysed.
Results: The lowest Kdr genotypic frequency (SS) proportion was found in female Anophelines collected in Kengatunyi at 58% while Rwatama had the highest genotypic frequency at 93%, thus susceptible and resistant clusters, respectively. The peak hour for mosquito seeking a human bite was between 0300 and 0400 hrs in the resistant cluster and 0400-0500 hrs in the susceptible cluster. The heterozygous mosquitoes maintained the known 2100-2200 hrs peak hour. There was a higher proportion of homozygous susceptible vectors (86.4%) seeking humans indoor than outdoor bitters (78.3%). Mosquito blood meals of human origin were 60% and 87% in susceptible Kengatunyi and resistant Rwatama cluster, respectively. There was significant difference between homozygous-resistant vectors feeding on human blood compared to homozygous susceptible mosquitoes (p ≤ 0.05). The proportion of bovine blood was highest in the susceptible cluster. A higher proportion of homozygous-resistant anophelines were feeding and resting indoors. No heterozygous mosquito was found resting indoor while 4.2% of the mosquitoes were caught while exiting the house through the window. Discussion. A shift in resistant Anopheles gambiae sl highest peak hour of aggressiveness from 2100-2200 hrs to 0300-0400 hrs is a key change in its biting pattern. Due to the development of resistance, mosquitoes no longer have to compete against the time the human host enters into the formerly lethal chemical and or physical barrier in the form of long-lasting insecticide-treated net. No heterozygous LS mosquito rested indoors possibly due to disadvantages of heterozygosity which could have increased their fitness costs as well as energy costs in the presence of the insecticidal agents in the treated nets. Conclusions and recommendations. Out of bed biting by female mosquitoes and partial susceptibility may contribute to residual malaria transmission. Insecticide-resistant vectors have become more endophagic and anthropophillic. Hence, insecticidal nets, zooprophylaxis, and novel repellents are still useful chemical, biological, and physical barriers against human blood questing female mosquitoes. Further studies should be done on genetic changes in mosquitoes and their effects on changing mosquito behaviour.

DOI: https://doi.org/10.1155/2020/9423682
Viruses. 2020 Apr 17. pii: E453. [Epub ahead of print]12(4):

High Rate of Non-Human Feeding by Aedes aegypti Reduces Zika Virus Transmission in South Texas.

Mark F Olson, Martial L Ndeffo-Mbah, Jose G Juarez, Selene Garcia-Luna, Estelle Martin, Monica K Borucki, Matthias Frank, José Guillermo Estrada-Franco, Mario A Rodríguez-Pérez, Nadia A Fernández-Santos, Gloria de Jesús Molina-Gamboa, Santos Daniel Carmona Aguirre, Bernardita de Lourdes Reyes-Berrones, Luis Javier Cortés-De la Cruz, Alejandro García-Barrientos, Raúl E Huidobro-Guevara, Regina M Brussolo-Ceballos, Josue Ramirez, Aaron Salazar, Luis F Chaves, Ismael E Badillo-Vargas, Gabriel L Hamer.

  Mosquito-borne viruses are emerging or re-emerging globally, afflicting millions of people around the world. Aedes aegypti, the yellow fever mosquito, is the principal vector of dengue, Zika, and chikungunya viruses, and has well-established populations across tropical and subtropical urban areas of the Americas, including the southern United States. While intense arboviral epidemics have occurred in Mexico and further south in the Americas, local transmission in the United States has been minimal. Here, we study Ae. aegypti and Culex quinquefasciatus host feeding patterns and vertebrate host communities in residential environments of South Texas to identify host-utilization relative to availability. Only 31% of Ae. aegypti blood meals were derived from humans, while 50% were from dogs and 19% from other wild and domestic animals. In Cx. quinquefasciatus, 67% of blood meals were derived from chicken, 22% came from dogs, 9% from various wild avian species, and 2% from other mammals including one human, one cat, and one pig. We developed a model for the reproductive number, R0, for Zika virus (ZIKV) in South Texas relative to northern Mexico using human disease data from Tamaulipas, Mexico. We show that ZIKV R0 in South Texas communities could be greater than one if the risk of human exposure to Ae. aegypti bites in these communities is at least 60% that of Northern Mexico communities. The high utilization of non-human vertebrates and low risk of human exposure in South Texas diminishes the outbreak potential for human-amplified urban arboviruses transmitted by Ae. aegypti.

Keywords:  Aedes aegypti; Culex quinquefasciatus; Zika virus; host selection; reproductive number

DOI:  https://doi.org/10.3390/v12040453
Parasit Vectors. 2020 Apr 22. 13(1): 213

Distribution and pyrethroid resistance status of Aedes aegypti and Aedes albopictus populations and possible phylogenetic reasons for the recent invasion of Aedes aegypti in Nepal.

Hitoshi Kawada, Kyoko Futami, Yukiko Higa, Ganesh Rai, Takashi Suzuki, Shiba Kumar Rai.

  BACKGROUND: When the first systematic list of mosquitoes in Nepal was reported in 1990, there was no description of Aedes aegypti (L.), while Aedes albopictus (Skuse) has been included in the Stegomyia subgroup since the 1950s. The first record of Ae. aegypti in Nepal was reported in 2009, suggesting some coincidence between the invasion of this species and the first record of dengue fever in Nepal in 2006.RESULTS: We performed a field survey of the distribution and insecticide susceptibility of Ae. aegypti and Ae. albopictus in Nepal in 2017 and 2018. Mosquito larvae were collected from used tires located along the streets of Kathmandu, Bharatpur and Pokhara, and a simplified bioassay was used to assess the susceptibility of the larvae to pyrethroid insecticides using d-allethrin. The presence or absence of point mutations in the voltage-gated sodium channel was also detected by direct sequencing. V1016G was detected at a high frequency and a strong correlation was observed between the frequencies of V1016G and susceptibility indices in Ae. aegypti populations. F1534C was also detected at a relatively low frequency. In Ae. albopictus populations, susceptibilities to d-allethrin were high and no point mutations were detected. Analysis of the cytochrome c oxidase subunit 1 (cox1) gene was performed for assessing genetic diversity and the existence of two strains were identified in Ae. aegypti populations. One consisted of 9 globally-distributed haplotypes while the other was derived from an African haplotype.
CONCLUSIONS: The high pyrethroid resistance, high V1016G frequency, and relatively low quantity of insecticides used to control dengue vectors in Nepal may have resulted in only weak selection pressure favoring insecticide resistance and could support the hypothesis that this species has recently been introduced from neighboring Asian countries where pyrethroid resistance is relatively widespread.

Keywords:  Invasion; Nepal; Pyrethroid; Resistance; cox1; kdr

DOI:  https://doi.org/10.1186/s13071-020-04090-6
Sci Rep. 2020 Apr 22. 10(1): 6803

Dispersal of female and male Aedes aegypti from discarded container habitats using a stable isotope mark-capture study design in South Texas.

Jose G Juarez, Selene Garcia-Luna, Luis Fernando Chaves, Ester Carbajal, Edwin Valdez, Courtney Avila, Wendy Tang, Estelle Martin, Roberto Barrera, Ryan R Hemme, John-Paul Mutebi, Nga Vuong, E Brendan Roark, Christopher R Maupin, Ismael E Badillo-Vargas, Gabriel L Hamer.

Aedes aegypti is the main vector of arboviral diseases such as dengue, chikungunya and Zika. A key feature for disease transmission modeling and vector control planning is adult mosquito dispersal. We studied Ae aegypti adult dispersal by conducting a mark-capture study of naturally occurring Ae. aegypti from discarded containers found along a canal that divided two residential communities in Donna, Texas, USA. Stable isotopes were used to enrich containers with either 13C or 15N. Adult mosquitoes were collected outdoors in the yards of households throughout the communities with BG Sentinel 2 traps during a 12-week period. Marked mosquito pools with stable isotopes were used to estimate the mean distance travelled using three different approaches (Net, Strip or Circular) and the probability of detecting an isotopically marked adult at different distances from the larval habitat of origin. We consistently observed, using the three approaches that male (Net: 220 m, Strip: 255 m, Circular: 250 m) Ae. aegypti dispersed further in comparison to gravid (Net: 135 m, Strip: 176 m, Circular: 189 m) and unfed females (Net: 192 m, Strip: 213 m, Circular: 198 m). We also observed that marked male capture probability slightly increased with distance, while, for both unfed and gravid females, such probability decreased with distance. Using a unique study design documenting adult dispersal from natural larval habitat, our results suggest that Ae. aegypti adults disperse longer distances than previously reported. These results may help guide local vector control authorities in their fight against Ae. aegypti and the diseases it transmits, suggesting coverage of 200 m for the use of insecticides and innovative vector control tools.

DOI: https://doi.org/10.1038/s41598-020-63670-9
Malar J. 2020 Apr 23. 19(1): 164

Opinions of key stakeholders on alternative interventions for malaria control and elimination in Tanzania.

Marceline F Finda, Nicola Christofides, Javier Lezaun, Brian Tarimo, Prosper Chaki, Ann H Kelly, Ntuli Kapologwe, Paul Kazyoba, Basiliana Emidi, Fredros O Okumu.

  BACKGROUND: Malaria control in Tanzania currently relies primarily on long-lasting insecticidal nets and indoor residual spraying, alongside effective case management and behaviour change communication. This study explored opinions of key stakeholders on the national progress towards malaria elimination, the potential of currently available vector control interventions in helping achieve elimination by 2030, and the need for alternative interventions that could be used to supplement malaria elimination efforts in Tanzania.METHODS: In this exploratory qualitative study, Focus group discussions were held with policy-makers, regulators, research scientists and community members. Malaria control interventions discussed were: (a) improved housing, (b) larval source management, (c) mass drug administration (MDA) with ivermectin to reduce vector densities, (d) release of modified mosquitoes, including genetically modified or irradiated mosquitoes, (e) targeted spraying of mosquito swarms, and (f) spatial repellents.
RESULTS: Larval source management and spatial repellents were widely supported across all stakeholder groups, while insecticide-spraying of mosquito swarms was the least preferred. Support for MDA with ivermectin was high among policy makers, regulators and research scientists, but encountered opposition among community members, who instead expressed strong support for programmes to improve housing for poor people in high transmission areas. Policy makers, however, challenged the idea of government-supported housing improvement due to its perceived high costs. Techniques of mosquito modification, specifically those involving gene drives, were viewed positively by community members, policy makers and regulators, but encountered a high degree of scepticism among scientists. Overall, policy-makers, regulators and community members trusted scientists to provide appropriate advice for decision-making.
CONCLUSION: Stakeholder opinions regarding alternative malaria interventions were divergent except for larval source management and spatial repellents, for which there was universal support. MDA with ivermectin, housing improvement and modified mosquitoes were also widely supported, though each faced concerns from at least one stakeholder group. While policy-makers, regulators and community members all noted their reliance on scientists to make informed decisions, their reasoning on the benefits and disadvantages of specific interventions included factors beyond technical efficiency. This study suggests the need to encourage and strengthen dialogue between research scientists, policy makers, regulators and communities regarding new interventions.

Keywords:  Alternative interventions; Malaria control; Malaria elimination; Opinion; Stakeholders; Tanzania

DOI:  https://doi.org/10.1186/s12936-020-03239-z
Emerg Infect Dis. 2020 May;26(5): 881-890

Mosquito Control Activities during Local Transmission of Zika Virus, Miami-Dade County, Florida, USA, 2016.

Janet C McAllister, Mario Porcelli, Johana M Medina, Mark J Delorey, C Roxanne Connelly, Marvin S Godsey, Nicholas A Panella, Nicole Dzuris, Karen A Boegler, Joan L Kenney, Linda Kothera, Lucrecia Vizcaino, Audrey E Lenhart, John-Paul Mutebi, Chalmers Vasquez.

  In 2016, four clusters of local mosquitoborne Zika virus transmission were identified in Miami-Dade County, Florida, USA, generating "red zones" (areas into which pregnant women were advised against traveling). The Miami-Dade County Mosquito Control Division initiated intensive control activities, including property inspections, community education, and handheld sprayer applications of larvicides and adulticides. For the first time, the Mosquito Control Division used a combination of areawide ultralow-volume adulticide and low-volume larvicide spraying to effectively control Aedes aegypti mosquitoes, the primary Zika virus vector within the county. The number of mosquitoes rapidly decreased, and Zika virus transmission was interrupted within the red zones immediately after the combination of adulticide and larvicide spraying.

Keywords:  Florida; Miami-Dade County; United States; Zika virus; birth defects; flaviviruses; mosquito control; mosquitoes; vector-borne infections; viruses; zoonoses

DOI:  https://doi.org/10.3201/eid2605.191606
Parasit Vectors. 2020 Apr 21. 13(1): 208

Biological control of Aedes mosquito larvae with carnivorous aquatic plant, Utricularia macrorhiza.

Jannelle Couret, Marco Notarangelo, Sarashwathy Veera, Noah LeClaire-Conway, Howard S Ginsberg, Roger L LeBrun.

  BACKGROUND: Biological controls with predators of larval mosquito vectors have historically focused almost exclusively on insectivorous animals, with few studies examining predatory plants as potential larvacidal agents. In this study, we experimentally evaluate a generalist plant predator of North America, Utricularia macrorhiza, the common bladderwort, and evaluate its larvacidal efficiency for the mosquito vectors Aedes aegypti and Aedes albopictus in no-choice, laboratory experiments. We sought to determine first, whether U. macrorhiza is a competent predator of container-breeding mosquitoes, and secondly, its predation efficiency for early and late instar larvae of each mosquito species.METHODS: Newly hatched, first-instar Ae. albopictus and Ae. aegypti larvae were separately exposed in cohorts of 10 to field-collected U. macrorhiza cuttings. Data on development time and larval survival were collected on a daily basis to ascertain the effectiveness of U. macrorhiza as a larval predator. Survival models were used to assess differences in larval survival between cohorts that were exposed to U. macrorhiza and those that were not. A permutation analysis was used to investigate whether storing U. macrorhiza in laboratory conditions for extended periods of time (1 month vs 6 months) affected its predation efficiency.
RESULTS: Our results indicated a 100% and 95% reduction of survival of Ae. aegypti and Ae. albopictus larvae, respectively, in the presence of U. macrorhiza relative to controls within five days, with peak larvacidal efficiency in plant cuttings from ponds collected in August. Utricularia macrorhiza cuttings, which were prey-deprived, and maintained in laboratory conditions for 6 months were more effective larval predators than cuttings, which were maintained prey-free for 1 month.
CONCLUSIONS: Due to the combination of high predation efficiency and the unique biological feature of facultative predation, we suggest that U. macrorhiza warrants further development as a method for larval mosquito control.

Keywords:  Aedes; Biological control; Bladderworts; Mosquitoes; Utricularia

DOI:  https://doi.org/10.1186/s13071-020-04084-4
PLoS Comput Biol. 2020 Apr 20. 16(4): e1007743

Optimizing the deployment of ultra-low volume and indoor residual spraying for dengue outbreak response.

Sean M Cavany, Guido España, Alun L Lloyd, Lance A Waller, Uriel Kitron, Helvio Astete, William H Elson, Gonzalo M Vazquez-Prokopec, Thomas W Scott, Amy C Morrison, Robert C Reiner, T Alex Perkins.

Recent years have seen rising incidence of dengue and large outbreaks of Zika and chikungunya, which are all caused by viruses transmitted by Aedes aegypti mosquitoes. In most settings, the primary intervention against Aedes-transmitted viruses is vector control, such as indoor, ultra-low volume (ULV) spraying. Targeted indoor residual spraying (TIRS) has the potential to more effectively impact Aedes-borne diseases, but its implementation requires careful planning and evaluation. The optimal time to deploy these interventions and their relative epidemiological effects are, however, not well understood. We used an agent-based model of dengue virus transmission calibrated to data from Iquitos, Peru to assess the epidemiological effects of these interventions under differing strategies for deploying them. Specifically, we compared strategies where spray application was initiated when incidence rose above a threshold based on incidence in recent years to strategies where spraying occurred at the same time(s) each year. In the absence of spraying, the model predicted 361,000 infections [inter-quartile range (IQR): 347,000-383,000] in the period 2000-2010. The ULV strategy with the fewest median infections was spraying twice yearly, in March and October, which led to a median of 172,000 infections [IQR: 158,000-183,000], a 52% reduction from baseline. Compared to spraying once yearly in September, the best threshold-based strategy utilizing ULV had fewer median infections (254,000 vs. 261,000), but required more spraying (351 vs. 274 days). For TIRS, the best strategy was threshold-based, which led to the fewest infections of all strategies tested (9,900; [IQR: 8,720-11,400], a 94% reduction), and required fewer days spraying than the equivalent ULV strategy (280). Although spraying twice each year is likely to avert the most infections, our results indicate that a threshold-based strategy can become an alternative to better balance the translation of spraying effort into impact, particularly if used with a residual insecticide.

DOI: https://doi.org/10.1371/journal.pcbi.1007743
Plants (Basel). 2020 Apr 22. pii: E544. [Epub ahead of print]9(4):

Mosquito Larvicidal Activity, Antimicrobial Activity, and Chemical Compositions of Essential Oils from Four Species of Myrtaceae from Central Vietnam.

Nguyen Thi Giang An, Le Thi Huong, Prabodh Satyal, Thieu Anh Tai, Do Ngoc Dai, Nguyen Huy Hung, Nguyen Thi Bich Ngoc, William N Setzer.

  Mosquitoes are important vectors of several diseases, and control of these insects is imperative for human health. Insecticides have proven useful in controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Additionally, emerging and re-emerging microbial infections are problematic. Essential oils have been shown to be promising mosquito larvicidal agents as well as antimicrobial agents. In this work, the essential oils from four species of Myrtaceae (Baeckea frutescens, Callistemon citrinus, Melaleuca leucadendra, and Syzygium nervosum) growing wild in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The essential oils have been screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. Callistemon citrinus fruit essential oil, rich in α-pinene (35.1%), 1,8-cineole (32.4%), limonene (8.2%), and α-terpineol (5.8%) showed good larvicidal activity with 24-h LC50 = 17.3 μg/mL against both Ae. aegypti and Cx. quinquefasciatus, and good antibacterial activity against E. faecalis (minimum inhibitory concentration (MIC) = 16 μg/mL) The 48-h larvicidal activities of M. leucadendra leaf essential oil, rich in α-eudesmol (17.6%), guaiol (10.9%), linalool (5.1%), (E)-caryophyllene (7.0%), and bulnesol (3.6%) were particularly notable, with LC50 of 1.4 and 1.8 μg/mL on Ae. aegypti and Cx. quinquefasciatus. Similarly, M. leucadendra bark essential oil, with α-eudesmol (24.1%) and guaiol (11.3%), showed good antibacterial activity against. E. faecalis. Both B. frutescens and C. citrinus leaf essential oils demonstrated anti-Candida activities with MIC values of 16 μg/mL. The results of this investigation suggest that essential oils derived from the Myrtaceae may serve as "green" alternatives for the control of mosquitoes and/or complementary antimicrobial agents.

Keywords:  Baeckea frutescens; Callistemon citrinus; Melaleuca leucadendra; Syzygium nervosum

DOI:  https://doi.org/10.3390/plants9040544
PLoS Negl Trop Dis. 2020 Apr 20. 14(4): e0008209

Distribution and seasonal fluctuations of Ae. aegypti and Ae. albopictus larval and pupae in residential areas in an urban landscape.

Jayanthi Rajarethinam, Janet Ong, Zhi-Wei Neo, Lee-Ching Ng, Joel Aik.

Dengue, a vector-borne disease spread by Aedes mosquitoes, is a global threat. In the absence of an efficacious dengue vaccine, vector control is the key intervention tool in Singapore. A good understanding of vector habitats is essential to formulate operational strategies. We examined the distribution, long-term trend and seasonality of Aedes data collected during regulatory inspections in residences and public areas from 2008 to 2017. We also studied the seasonality of climate factors to understand their influence on the detection of Aedes-positive containers. The most frequently reported Aedes-positive containers were domestic containers, drains, discarded receptacles, ornamental containers, flower pot plates/trays, plants, gully traps, canvas/plastic sheet, bins, ground puddle, inspection chambers and roof tops/gutters. We found more Ae. aegypti and Ae. albopictus-positive containers per inspection in residences and public areas, respectively. The seasonality of Ae. aegypti-positive containers in residences and public areas coincided with that of mean temperature. However, the seasonality of Ae. albopictus-positive containers lagged by one month compared to that of mean temperature. Our study demonstrates the seasonal fluctuations of Aedes-positive containers in an urban environment. Understanding the distribution and seasonality of Aedes breeding helps to facilitate resource planning and community awareness to moderate dengue transmission.

DOI: https://doi.org/10.1371/journal.pntd.0008209
PLoS Comput Biol. 2020 Apr 22. 16(4): e1007446

Vector bionomics and vectorial capacity as emergent properties of mosquito behaviors and ecology.

Sean L Wu, Héctor M Sánchez C, John M Henry, Daniel T Citron, Qian Zhang, Kelly Compton, Biyonka Liang, Amit Verma, Derek A T Cummings, Arnaud Le Menach, Thomas W Scott, Anne L Wilson, Steven W Lindsay, Catherine L Moyes, Penny A Hancock, Tanya L Russell, Thomas R Burkot, John M Marshall, Samson Kiware, Robert C Reiner, David L Smith.

Mosquitoes are important vectors for pathogens that infect humans and other vertebrate animals. Some aspects of adult mosquito behavior and mosquito ecology play an important role in determining the capacity of vector populations to transmit pathogens. Here, we re-examine factors affecting the transmission of pathogens by mosquitoes using a new approach. Unlike most previous models, this framework considers the behavioral states and state transitions of adult mosquitoes through a sequence of activity bouts. We developed a new framework for individual-based simulation models called MBITES (Mosquito Bout-based and Individual-based Transmission Ecology Simulator). In MBITES, it is possible to build models that simulate the behavior and ecology of adult mosquitoes in exquisite detail on complex resource landscapes generated by spatial point processes. We also developed an ordinary differential equation model which is the Kolmogorov forward equations for models developed in MBITES under a specific set of simplifying assumptions. While mosquito infection and pathogen development are one possible part of a mosquito's state, that is not our main focus. Using extensive simulation using some models developed in MBITES, we show that vectorial capacity can be understood as an emergent property of simple behavioral algorithms interacting with complex resource landscapes, and that relative density or sparsity of resources and the need to search can have profound consequences for mosquito populations' capacity to transmit pathogens.

DOI: https://doi.org/10.1371/journal.pcbi.1007446
Parasit Vectors. 2020 Apr 19. 13(1): 202

Stability of the effect of silencing fibronectin type III domain-protein 1 (FN3D1) gene on Anopheles arabiensis reared under different breeding site conditions.

Serkadis Debalke, Tibebu Habtewold, George K Christophides, Luc Duchateau.

  BACKGROUND: Malaria vector mosquitoes acquire midgut microbiota primarily from their habitat. The homeostasis of these microbial communities plays an essential role in the mosquito longevity, the most essential factor in the mosquito vectorial capacity. Our recent study revealed that silencing genes involved in regulation of the midgut homeostasis including FN3D1, FN3D3 and GPRGr9 reduced the survival of female adult Anopheles arabiensis mosquitoes. In the present study, we investigate the stability of the gene silencing efficiency of mosquitoes reared in three different breeding conditions representing distinct larval habitat types: town brick pits in Jimma, flood pools in the rural land of Asendabo and roadside pools in Wolkite.METHODS: First-instar larvae of An. arabiensis mosquitoes were reared separately using water collected from the three breeding sites. The resulting adult females were micro-injected with dsRNA targeting the FN3D1 gene (AARA003032) and their survival was monitored. Control mosquitoes were injected with dsRNA Lacz. In addition, the load of midgut microbiota of these mosquitoes was determined using flow cytometry.
RESULTS: Survival of naïve adult female mosquitoes differed between the three sites. Mosquitoes reared using water collected from brick pits and flood pools survived longer than mosquitoes reared using water collected from roadside. However, the FN3D1 gene silencing effect on survival did not differ between the three sites.
CONCLUSIONS: The present study revealed that the efficacy of FN3D1 gene silencing is not affected by variation in the larval habitat. Thus, silencing this gene has potential for application throughout sub-Saharan Africa.

Keywords:  Anopheles arabiensis; FN3D1 gene; Gene silencing stability; Larval breeding sites; Survival

DOI:  https://doi.org/10.1186/s13071-020-04078-2
Viruses. 2020 Apr 15. pii: E448. [Epub ahead of print]12(4):

West Nile Virus Epidemic in Germany Triggered by Epizootic Emergence, 2019.

Ute Ziegler, Pauline Dianne Santos, Martin H Groschup, Carolin Hattendorf, Martin Eiden, Dirk Höper, Philip Eisermann, Markus Keller, Friederike Michel, Robert Klopfleisch, Kerstin Müller, Doreen Werner, Helge Kampen, Martin Beer, Christina Frank, Raskit Lachmann, Birke Andrea Tews, Claudia Wylezich, Monika Rinder, Lars Lachmann, Thomas Grünewald, Claudia A Szentiks, Michael Sieg, Jonas Schmidt-Chanasit, Daniel Cadar, Renke Lühken.

  One year after the first autochthonous transmission of West Nile virus (WNV) to birds and horses in Germany, an epizootic emergence of WNV was again observed in 2019. The number of infected birds and horses was considerably higher compared to 2018 (12 birds, two horses), resulting in the observation of the first WNV epidemy in Germany: 76 cases in birds, 36 in horses and five confirmed mosquito-borne, autochthonous human cases. We demonstrated that Germany experienced several WNV introduction events and that strains of a distinct group (Eastern German WNV clade), which was introduced to Germany as a single introduction event, dominated mosquito, birds, horse and human-related virus variants in 2018 and 2019. Virus strains in this clade are characterized by a specific-Lys2114Arg mutation, which might lead to an increase in viral fitness. Extraordinary high temperatures in 2018/2019 allowed a low extrinsic incubation period (EIP), which drove the epizootic emergence and, in the end, most likely triggered the 2019 epidemic. Spatiotemporal EIP values correlated with the geographical WNV incidence. This study highlights the risk of a further spread in Germany in the next years with additional human WNV infections. Thus, surveillance of birds is essential to provide an early epidemic warning and thus, initiate targeted control measures.

Keywords:  Germany; West Nile virus; bird; epidemic; epizooty; horses; human; mosquitoes; transmission risk; zoonoses

DOI:  https://doi.org/10.3390/v12040448
Sci Rep. 2020 Apr 22. 10(1): 6842

Orthosteric muscarinic receptor activation by the insect repellent IR3535 opens new prospects in insecticide-based vector control.

Eléonore Moreau, Karolina Mikulska-Ruminska, Mathilde Goulu, Stéphane Perrier, Caroline Deshayes, Maria Stankiewicz, Véronique Apaire-Marchais, Wieslaw Nowak, Bruno Lapied.

The insect repellent IR3535 is one of the important alternative in the fight against mosquito-borne disease such as malaria, dengue, chikungunya, yellow fever and Zika. Using a multidisciplinary approach, we propose the development of an innovative insecticide-based vector control strategy using an unexplored property of IR3535. We have demonstrated that in insect neurosecretory cells, very low concentration of IR3535 induces intracellular calcium rise through cellular mechanisms involving orthosteric/allosteric sites of the M1-muscarinic receptor subtype, G protein βγ subunits, background potassium channel inhibition generating depolarization, which induces voltage-gated calcium channel activation. The resulting internal calcium concentration elevation increases nicotinic receptor sensitivity to the neonicotinoid insecticide thiacloprid. The synergistic interaction between IR3535 and thiacloprid contributes to significantly increase the efficacy of the treatment while reducing concentrations. In this context, IR3535, used as a synergistic agent, seems to promise a new approach in the optimization of the integrated vector management for vector control.

DOI: https://doi.org/10.1038/s41598-020-63957-x
J Clin Virol. 2020 Apr 11. pii: S1386-6532(20)30107-4. [Epub ahead of print]127 104365

West Nile virus lineage 2 in humans and mosquitoes in Bulgaria, 2018-2019.

Iva Christova, Anna Papa, Iva Trifonova, E Panayotova, Styliani Pappa, Ognyan Mikov.

  BACKGROUND: West Nile virus (WNV) lineage 2, and especially the Hungarian clade, predominates in Europe. Most of the Hungarian clade strains cluster into 2 groups: Central/South-West European and Balkan.OBJECTIVES: Since there was not any study on WNV in mosquitoes in Bulgaria, the present study was designed to test Culex spp. mosquitoes in areas near the Danube river. The aim of the study was to gain an insight into the recent molecular epidemiology of WNV in Bulgaria.
STUDY DESIGN: A total of 1871 Culex pipiens mosquitoes collected in 2018 and clinical samples from 23 patients with West Nile neuroinavsive disease observed in 2018 and 2019 were tested by TaqMan RT-PCR and RT-nested PCR and PCR products were sequenced.
RESULTS: WNV RNA was detected in clinical samples from 10 patients and in five (12.2 %) of 41 pools of Cx. pipiens mosquitos by realtime RT-PCR, resulting in a minimum infection rate of mosquitoes of 0.27 %. Phylogenetic analysis based on partial NS3 gene sequences from one clinical sample and four mosquito pools showed that all sequences clustered into the Hungarian clade of WNV lineage 2 and all but one were identical to respective sequences from Romania. Whole genome sequences of one mosquito pool belong to the Hungarian group of WNV lineage 2 and cluster in a separate subclade from the Bulgarian strain from 2015, suggesting that at least two different introductions occurred in Bulgaria.
CONCLUSIONS: The current study provides insights into the geographic distribution of WNV in Bulgaria.

Keywords:  Culex pipiens; Mosquitoes; Sequencing; West Nile virus

DOI:  https://doi.org/10.1016/j.jcv.2020.104365
Environ Res. 2020 Apr;pii: S0013-9351(20)30082-7. [Epub ahead of print]183 109190

Climate factors and the East Asian summer monsoon may drive large outbreaks of dengue in China.

Keke Liu, Xiang Hou, Zhoupeng Ren, Rachel Lowe, Yiguan Wang, Ruiyun Li, Xiaobo Liu, Jimin Sun, Liang Lu, Xiupin Song, Haixia Wu, Jun Wang, Wenwu Yao, Chutian Zhang, Shaowei Sang, Yuan Gao, Jing Li, Jianping Li, Lei Xu, Qiyong Liu.

  OBJECTIVE: To investigate the relationship between climate variables, East Asian summer monsoon (EASM) and large outbreaks of dengue in China.METHODS: We constructed ecological niche models (ENMs) to analyse the influence of climate factors on dengue occurrence and predict dengue outbreak areas in China. Furthermore, we formulated a generalised additive model (GAM) to quantify the impact of the EASM on dengue occurrence in mainland China from 1980 to 2016.
RESULTS: Mean Temperature of Coldest Quarter had a 62.6% contribution to dengue outbreaks. Southern China including Guangdong, Guangxi, Fujian and Yunnan provinces are more vulnerable to dengue emergence and resurgence. In addition, we found population density had a 68.7% contribution to dengue widely distribution in China using ENMs. Statistical analysis indicated a dome-shaped association between EASM and dengue outbreak using GAM, with the greatest impact in the South-East of China. Besides, there was a positive nonlinear association between monthly average temperature and dengue occurrence.
CONCLUSION: We demonstrated the influence of climate factors and East Asian summer monsoon on dengue outbreaks, providing a framework for future studies on the association between climate change and vector-borne diseases.

Keywords:  Climate variables; Dengue; EASM; Ecological niche model; Generalised additive model

DOI:  https://doi.org/10.1016/j.envres.2020.109190
Lancet. 2020 Apr 18. pii: S0140-6736(20)30214-2. [Epub ahead of print]395(10232): 1292-1303

Effect of long-lasting insecticidal nets with and without piperonyl butoxide on malaria indicators in Uganda (LLINEUP): a pragmatic, cluster-randomised trial embedded in a national LLIN distribution campaign.

Sarah G Staedke, Samuel Gonahasa, Grant Dorsey, Moses R Kamya, Catherine Maiteki-Sebuguzi, Amy Lynd, Agaba Katureebe, Mary Kyohere, Peter Mutungi, Simon P Kigozi, Jimmy Opigo, Janet Hemingway, Martin J Donnelly.

BACKGROUND: Long-lasting insecticidal nets (LLINs) are the primary malaria prevention tool, but their effectiveness is threatened by pyrethroid resistance. We embedded a pragmatic cluster-randomised trial into Uganda's national LLIN campaign to compare conventional LLINs with those containing piperonyl butoxide (PBO), a synergist that can partially restore pyrethroid susceptibility in mosquito vectors.METHODS: 104 health sub-districts, from 48 districts in Uganda, were randomly assigned to LLINs with PBO (PermaNet 3.0 and Olyset Plus) and conventional LLINs (PermaNet 2.0 and Olyset Net) by proportionate randomisation using an iterative process. At baseline 6, 12, and 18 months after LLIN distribution, cross-sectional surveys were done in 50 randomly selected households per cluster (5200 per survey); a subset of ten households per cluster (1040 per survey) were randomly selected for entomological surveys. The primary outcome was parasite prevalence by microscopy in children aged 2-10 years, assessed in the as-treated population at 6, 12, and 18 months. This trial is registered with ISRCTN, ISRCTN17516395.
FINDINGS: LLINs were delivered to households from March 25, 2017, to March 18, 2018, 32 clusters were randomly assigned to PermaNet 3.0, 20 to Olyset Plus, 37 to PermaNet 2.0, and 15 to Olyset Net. In the as-treated analysis, three clusters were excluded because no dominant LLIN was received, and four clusters were reassigned, resulting in 49 PBO LLIN clusters (31 received PermaNet 3.0 and 18 received Olyset Plus) and 52 non-PBO LLIN clusters (39 received PermaNet 2.0 and 13 received Olyset Net). At 6 months, parasite prevalence was 11% (386/3614) in the PBO group compared with 15% (556/3844) in the non-PBO group (prevalence ratio [PR] adjusted for baseline values 0·74, 95% CI 0·62-0·87; p=0·0003). Parasite prevalence was similar at month 12 (11% vs 13%; PR 0·73, 95% CI 0·63-0·85; p=0·0001) and month 18 (12% vs 14%; PR 0·84, 95% CI 0·72-0·98; p=0·029).
INTERPRETATION: In Uganda, where pyrethroid resistance is high, PBO LLINs reduced parasite prevalence more effectively than did conventional LLINs for up to 18 months. This study provides evidence needed to support WHO's final recommendation on use of PBO LLINs.
FUNDING: The Against Malaria Foundation, UK Department for International Development, Innovative Vector Control Consortium, and Bill and Melinda Gates Foundation.

DOI: https://doi.org/10.1016/S0140-6736(20)30214-2
Sci Rep. 2020 Apr 21. 10(1): 6723

Immune priming with inactive dengue virus during the larval stage of Aedes aegypti protects against the infection in adult mosquitoes.

Valeria Vargas, Jorge Cime-Castillo, Humberto Lanz-Mendoza.

Several studies have observed that the immune response in insects can be conserved, a phenomenon known as immune priming, which has been mostly tested in adult stages. However, it is unknown if induction of immune priming in larval stages protects against dengue virus (DENV) infections in adult mosquitoes. In this work, we primed larval instar 3rd of Aedes aegypti with inactive dengue virus, producing adult mosquitoes with i) an enhanced antiviral-immune response; ii) a reduction in the load and replication of RNA of dengue virus (DENV); iii) a decline in viral infective particles production. Adult mosquitoes previously primed during larval stages over-expressed RNA interference (RNAi) markers Argonaute-2 (AGO-2) and Dicer-2 (DCR-2). We also observed inter-individual variations of DENV infection in adult mosquitoes, indicating a heterogeneous response to DENV infection in the same mosquito strain. However, mosquitoes primed during larval stages appear to control the infection, reducing the viral load. The over-expression of interferon-like factors (VAGO) and AGO-2 in the pupa stage suggests a fast activation of antiviral mechanisms after immune priming in larvae, creating a condition in which adult mosquitoes are resistant to the pathogen in the posterior exposure.

DOI: https://doi.org/10.1038/s41598-020-63402-z
Genes (Basel). 2020 Apr 22. pii: E454. [Epub ahead of print]11(4):

Exploring the Mechanisms of Multiple Insecticide Resistance in a Highly Plasmodium-Infected Malaria Vector Anopheles funestus Sensu Stricto from Sahel of Northern Nigeria.

Sulaiman S Ibrahim, Muhammad M Mukhtar, Helen Irving, Jacob M Riveron, Amen N Fadel, Williams Tchapga, Jack Hearn, Abdullahi Muhammad, Faruk Sarkinfada, Charles S Wondji.

  The Nigerian Government is scaling up the distribution of insecticide-treated bed nets for malaria control, but the lack of surveillance data, especially in the Sudan/Sahel region of the country, may hinder targeting priority populations. Here, the vectorial role and insecticide resistance profile of a population of a major malaria vector Anopheles funestus sensu stricto from Sahel of Nigeria was characterised. An. funestus s.s. was the only vector found, with a high human blood index (100%) and a biting rate of 5.3/person/night. High Plasmodium falciparum infection was discovered (sporozoite rate = 54.55%). The population is resistant to permethrin (mortality = 48.30%, LT50 = 65.76 min), deltamethrin, DDT (dichlorodiphenyltrichloroethane) and bendiocarb, with mortalities of 29.44%, 56.34% and 54.05%, respectively. Cone-bioassays established loss of efficacy of the pyrethroid-only long-lasting insecticidal nets (LLINs); but 100% recovery of susceptibility was obtained for piperonylbutoxide (PBO)-containing PermaNet®3.0. Synergist bioassays with PBO and diethyl maleate recovered susceptibility, implicating CYP450s (permethrin mortality = 78.73%, χ2 = 22.33, P < 0.0001) and GSTs (DDT mortality = 81.44%, χ2 = 19.12, P < 0.0001). A high frequency of 119F GSTe2 mutation (0.84) was observed (OR = 16, χ2 = 3.40, P = 0.05), suggesting the preeminent role of metabolic resistance. These findings highlight challenges associated with deployment of LLINs and indoor residual spraying (IRS) in Nigeria.

Keywords:  119F mutation; Anopheles funestus; GSTe2; Plasmodium falciparum; malaria; metabolic; resistance

DOI:  https://doi.org/10.3390/genes11040454
Environ Sci Pollut Res Int. 2020 Apr 24.

Larvicidal and repellant effects of Jussiaea repens (L.) leaf ethanol extract and its major phyto-constituent against important human vector mosquitoes (Diptera: Culicidae).

Kaliyamoorthy Krishnappa, Mathalaimuthu Baranitharan, Kuppusamy Elumalai, Jeganathan Pandiyan.

  Jussiaea repens (L.) leaf ethanol extract (LEE) and its major phyto-compound (MPC) have effects against larvae and adults of dengue, malarial, and filarial vectors. Total larval death rates were recorded from LEE and MPC has significant larval killing activity with LC50/LC90 values of Ae. albopictus, An. stephensi, and Cx. quinquefasciatus that were 118.3/229.9, 116.1/216.8, 114.4/213.5 and 17.7/27.5, 15.6/25.4 and 12.3/21.1 μg/ml, respectively. A best repellent activity was ascertained at 3.057 mg/cm2 concentration of LEE and MPC provided 100% protection upto 240 min against selected human vector mosquitoes (HVMs). The functional groups were confirmed by FT-IR analysis and their presence in ethanol extract and mass spectral analysis: 4-piperidineacetic acid, 1-acetyl-5-ethyl-2-[3-(2-hydroxyethyl]-1H-indol-2-yl]-á-methyl-, methyl ester compound was identified in the LEE. The results obtained suggest that J. repens LEE and its MPC were important and responsible for health protection and control of HVMs.

Keywords:  Aedes albopictus; Anopheles stephensi; Culex quinquefasciatus; FT-IR; Jussiaea repens; Mass spectra; Phyto-compound

DOI:  https://doi.org/10.1007/s11356-020-08917-8
Parasit Vectors. 2020 Apr 22. 13(1): 210

Anopheles gambiae densovirus (AgDNV) negatively affects Mayaro virus infection in Anopheles gambiae cells and mosquitoes.

Nadya Urakova, Marco Brustolin, Renuka E Joseph, Rebecca M Johnson, Sujit Pujhari, Jason L Rasgon.

  BACKGROUND: Recent studies demonstrate that insect-specific viruses can influence the ability of their mosquito hosts to become infected with and transmit arboviruses of medical and veterinary importance. The aim of this study was to evaluate the interactions between Anopheles gambiae densovirus (AgDNV) (Parvoviridae) (a benign insect-specific virus that infects An. gambiae mosquitoes) and Mayaro virus (MAYV) (Togaviridae) (an emerging human pathogen that can be transmitted by An. gambiae) in both insect cell culture and mosquitoes.METHODS: For in vitro studies, An. gambiae Mos55 cells infected or uninfected with AgDNV were infected with MAYV. For in vivo studies, An. gambiae mosquitoes were injected intrathoracically with AgDNV and 4 days later orally infected with MAYV. Mosquitoes were dissected 10 days after MAYV infection, and MAYV titers in the body, legs and saliva samples quantified using focus-forming assay.
RESULTS: MAYV virus replication was reduced 10-100-fold in An. gambiae Mos55 cells infected with AgDNV. In mosquitoes, there was a significant negative correlation between AgDNV and MAYV body titers 10 days post-blood meal.
CONCLUSIONS: AgDNV infection was associated with reduced production of MAYV in cell culture, and reduced body titers of MAYV in An. gambiae mosquitoes. As densovirus infections are common in natural mosquito populations, these data suggest that they may affect the epidemiology of viruses of medical importance.

Keywords:  Anopheles gambiae; Cell culture; Densovirus; Mayaro virus; Vector competence

DOI:  https://doi.org/10.1186/s13071-020-04072-8
Trop Med Infect Dis. 2020 Apr 17. pii: E63. [Epub ahead of print]5(2):

Acute Lymphatic Filariasis Infection in United States Armed Forces Personnel Deployed to the Pacific Area of Operations during World War II Provides Important Lessons for Today.

Wayne D Melrose, Peter A Leggat.

  The deployment of United States (US) Armed Forces personnel into the central Pacific islands of Samoa and Tonga, which is highly-endemic for lymphatic filariasis (LF), resulted in thousands of cases of the acute form of this disease and greatly reduced their ability to carry out their mission. The major driving factor for the intensity of transmission was the aggressiveness and efficiency of the Aedes species mosquito vectors, especially the day-biting Ae. Polynesiensis. The paper reminds us of the danger that tropical diseases can pose for troops sent into endemic areas and constant and careful surveillance that is required to prevent rapid resurgence of Aedes-transmitted LF in populations, where the LF elimination program has been successful.

Keywords:  Pacific; WW2; helminth; lymphatic filariasis; medical history; military

DOI:  https://doi.org/10.3390/tropicalmed5020063
Insects. 2020 Apr 15. pii: E246. [Epub ahead of print]11(4):

Larvicidal, Ovicidal, Synergistic, and Repellent Activities of Sophora alopecuroides and Its Dominant Constituents Against Aedes albopictus.

Rana Fartab Shoukat, Muhammad Shakeel, Syed Arif Hussain Rizvi, Junaid Zafar, Yuxin Zhang, Shoaib Freed, Xiaoxia Xu, Fengliang Jin.

  In the current study, to combat insecticide resistance, we explored larvicidal, ovicidal, synergistic, and repellent activities of Sophora alopecuroides extract and its dominant constituents against Aedes albopictus. The results of the toxicity bioassays demonstrated that the extract of S. alopecuroides exerted significant larvicidal activity (16.66-86.66%) against the third-instar larvae of Ae. albopictus at different concentrations (5-50 ug/mL) and low hatchability of eggs (2.32-75%) at 5-50 ug/mL. The constituents of S. alopecuroides showed a synergistic effect when applied as a mixture (LC30 + LC30) against larvae, while no synergistic effect was observed against the eggs of Ae. albopictus. S. alopecuroides extract provided 93.11% repellency in the first 90 min and gradually decreased to 53.14% after 240 min, while the positive control DEET (N,N-diethyl-3-methylbenzamide) showed 94.18% in the first 90 min and 55.33% after 240 min. All of the results exhibited a concentration-dependent effect. To the best of our knowledge, this is the first time that a study has identified a highly effective extract of S. alopecuroides, which could be used as an alternative agent to control larvae and eggs and to repel adults of Ae. albopictus.

Keywords:  Asian tiger; Sophocarpin; Sophordine; botanicals; dengue; plant extract; repellency

DOI:  https://doi.org/10.3390/insects11040246
Int J Environ Res Public Health. 2020 Apr 15. pii: E2728. [Epub ahead of print]17(8):

Dynamics and Distribution of the Invasive Mosquito Aedes koreicus in a Temperate European City.

Kornélia Kurucz, Mattia Manica, Luca Delucchi, Gábor Kemenesi, Giovanni Marini.

  Aedes koreicus is a mosquito species native to Asia that has recently successfully invaded new areas in several European countries. Here, we provide important data on Ae. koreicus establishment in Pécs (Southern Hungary). Mosquito surveillance was carried out weekly between 2016 and 2019 at 10 different sites located throughout the city from May to September. We conducted a statistical analysis to evaluate the most important abiotic factors driving Ae. koreicus abundance. We then calibrated a previously developed temperature-dependent mathematical model to the recorded captures to evaluate mosquito abundance in the study area. We found that too high summer temperatures negatively affect mosquito abundance. The model accurately replicated the observed capture patterns, providing an estimate of Ae. koreicus density for each breeding season, which we interpolated to map Ae. koreicus abundance throughout Pécs. We found a negative correlation between mosquito captures and human density, suggesting that Ae. koreicus does not necessarily require humans for its blood meals. Our study provides a successful application of a previously published mathematical model to investigate Ae. koreicus population dynamics, proving its suitability for future studies, also within an epidemiological framework.

Keywords:  Culicidae; invasive species; mathematical model; mosquito surveillance; urban area

DOI:  https://doi.org/10.3390/ijerph17082728
J Med Entomol. 2020 Apr 23. pii: tjaa075. [Epub ahead of print]

Comparative Molecular Description of a Novel GST Gene in Culex pipiens (Diptera: Culicidae).

Hagar Samy Ali, Amany Soliman Khaled, Laila Sayed Hamouda, Enas Hamdy Ghallab.

  Repeated exposure to insecticides, particularly pyrethroids and organophosphates, has resulted in the development of insecticide resistance in the mosquito Culex pipiens, a primary disease vector. Glutathione S-transferase (GST) is involved in the phase II detoxification of numerous xenobiotics, including insecticides. In this study, a GST gene (CPIJ002678) was amplified, sequenced, and used in comprehensive molecular analyses ending up in development of a rapid assay to distinguish more tolerant individuals from susceptible Culex pipiens using the Restriction Fragment Length Polymorphism (RFLP) technique. Field collected Culex pipiens strains from untreated areas, organophosphates-treated areas and a lab strain reared for many generations, all were used in CDC bottle bioassays to evaluate the susceptibility status of the studied individuals to malathion insecticide. Interestingly, both field sites collected groups showed high levels of resistance at the malathion diagnostic time. Gene amplification, and bidirectional direct sequencing results were analyzed. Compared with the reference genome sequence, the pairwise alignment of the amplified sequences showed 96.6% similarity to the reference sequence in the GenBank database. The confirmed gene sequences were assembled and aligned using various bioinformatic softwares. The assembled contigs were used in NEBcutter V2.0 for constructing restriction maps and checked for the availability of differences (if present) between susceptible and more tolerant strains. Specific molecular RFLP markers were successfully recognized to differentiate the more tolerant from the susceptible Culex pipiens phenotypes.

Keywords:  culicidae vectors; glutathione S-transferase; insecticide resistance

DOI:  https://doi.org/10.1093/jme/tjaa075
Viruses. 2020 Apr 18. pii: E458. [Epub ahead of print]12(4):

Human West Nile Virus Lineage 2 Infection: Epidemiological, Clinical, and Virological Findings.

Monia Pacenti, Alessandro Sinigaglia, Elisa Franchin, Silvana Pagni, Enrico Lavezzo, Fabrizio Montarsi, Gioia Capelli, Luisa Barzon.

  West Nile virus (WNV) lineage 2 is expanding and causing large outbreaks in Europe. In this study, we analyzed the epidemiological, clinical, and virological features of WNV lineage 2 infection during the large outbreak that occurred in northern Italy in 2018. The study population included 86 patients with neuroinvasive disease (WNND), 307 with fever (WNF), and 34 blood donors. Phylogenetic analysis of WNV full genome sequences from patients' samples showed that the virus belonged to the widespread central/southern European clade of WNV lineage 2 and was circulating in the area at least since 2014. The incidence of WNND and WNF progressively increased with age and was higher in males than in females. Among WNND patients, the case fatality rate was 22%. About 70% of blood donors reported symptoms during follow-up. Within the first week after symptom onset, WNV RNA was detectable in the blood or urine of 80% of patients, while 20% and 40% of WNND and WNF patients, respectively, were WNV IgM-seronegative. In CSF samples of WNND patients, WNV RNA was typically detectable when WNV IgM antibodies were absent. Blunted or no WNV IgM response and high WNV IgG levels were observed in seven patients with previous flavivirus immunity.

Keywords:  West Nile virus; diagnosis; encephalitis; epidemiology; fever; mosquitoes; neuroinvasive disease; outbreak; surveillance; symptoms

DOI:  https://doi.org/10.3390/v12040458
BMC Public Health. 2020 Apr 22. 20(1): 544

Malaria elimination using the 1-3-7 approach: lessons from Sampov Loun, Cambodia.

Soy Ty Kheang, Siv Sovannaroth, Lawrence M Barat, Lek Dysoley, Bryan K Kapella, Ly Po, Sokomar Nguon, John Gimnig, Rida Slot, Top Samphornarann, Seak Kong Meng, Gunawardena Dissanayake, Hala Jassim AlMossawi, Colleen Longacre, Neeraj Kak.

  BACKGROUND: Cambodia has targeted malaria elimination within its territory by 2025 and is developing a model elimination package of strategies and interventions designed to achieve this goal.METHODS: Cambodia adopted a simplified 1-3-7 surveillance model in the Sampov Loun operational health district in western Cambodia beginning in July 2015. The 1-3-7 approach targets reporting of confirmed cases within one day, investigation of specific cases within three days, and targeted control measures to prevent further transmission within seven days. In Sampov Loun, response measures included reactive case detection (testing of co-travelers, household contacts and family members, and surrounding households with suspected malaria cases), and provision of health education, and insecticide-treated nets. Day 28 follow up microscopy was conducted for all confirmed P. falciparum and P. falciparum-mixed-species malaria cases to assess treatment efficacy.
RESULTS: The number of confirmed malaria cases in the district fell from 519 in 2015 to 181 in 2017, and the annual parasite incidence (API) in the district fell from 3.21 per 1000 population to 1.06 per 1000 population. The last locally transmitted case of malaria in Sampov Loun was identified in March 2016. In response to the 408 index cases identified, 1377 contacts were screened, resulting in the identification of 14 positive cases. All positive cases occurred among index case co-travelers.
CONCLUSION: The experience of the 1-3-7 approach in Sampov Loun indicates that the basic essential malaria elimination package can be feasibly implemented at the operational district level to achieve the goal of malaria elimination in Cambodia and has provided essential information that has led to the refinement of this package.

Keywords:  1-3-7 approach; Malaria; Malaria elimination; Surveillance

DOI:  https://doi.org/10.1186/s12889-020-08634-4
Parasit Vectors. 2020 Apr 22. 13(1): 212

Species and sex-specific chemosensory gene expression in Anopheles coluzzii and An. quadriannulatus antennae.

Giridhar Athrey, Zachary Popkin-Hall, Luciano Veiga Cosme, Willem Takken, Michel Andre Slotman.

  BACKGROUND: Olfactory cues drive mosquito behaviors such as host-seeking, locating sugar sources and oviposition. These behaviors can vary between sexes and closely related species. For example, the malaria vector Anopheles coluzzii is highly anthropophilic, whereas An. quadriannulatus is not. These behavioral differences may be reflected in chemosensory gene expression.METHODS: The expression of chemosensory genes in the antennae of both sexes of An. coluzzii and An. quadriannulatus was compared using RNA-seq. The sex-biased expression of several genes in An. coluzzii was also compared using qPCR.
RESULTS: The chemosensory expression is mostly similar in the male antennae of An. coluzzii and An. quadriannulatus, with only a few modest differences in expression. A handful of chemosensory genes are male-biased in both species; the highly expressed gustatory receptor AgGr33, odorant binding proteins AgObp25, AgObp26 and possibly AgObp10. Although the chemosensory gene repertoire is mostly shared between the sexes, several highly female-biased AgOrs, AgIrs, and one AgObp were identified, including several whose expression is biased towards the anthropophilic An. coluzzii. Additionally, the expression of several chemosensory genes is biased towards An. coluzzii in both sexes.
CONCLUSIONS: Chemosensory gene expression is broadly similar between species and sexes, but several sex- biased/specific genes were identified. These may modulate sex- and species-specific behaviors. Although the male behavior of these species remains poorly studied, the identification of sex- and species-specific chemosensory genes may provide fertile ground for future work.

Keywords:  Anopheles; Chemosensation; Host seeking; Mating; Olfaction

DOI:  https://doi.org/10.1186/s13071-020-04085-3
Sci Rep. 2020 Apr 22. 10(1): 6826

Insecticidal and Genotoxic effects of some indigenous plant extracts in Culex quinquefasciatus Say Mosquitoes.

Muhammad Zulhussnain, Muhammad Kashif Zahoor, Hina Rizvi, Muhammad Asif Zahoor, Azhar Rasul, Aftab Ahmad, Humara Naz Majeed, Amer Rasul, Kanwal Ranian, Farhat Jabeen.

Five different weed plants viz. Convulvulus arvensis, Chenopodium murale, Tribulus terrestris, Trianthema portulacastrum, and Achyranthes aspera were investigated for their entomocidal and genotoxic effects against Culex quinquefasciatus mosquitoes. High mortality was observed at 72 hours in a dose dependent manner. Among all the tested plants, A. aspera was found highly significant which showed 100% mortality at 250 ppm after 72 hours with LC50 of 87.46, 39.08 and 9.22 ppm at 24, 48, respectively. In combination with Bacillus thuringiensis israelensis (Bti); A. aspera also caused 100% mortality at 250 ppm concentration after 72 hours (LC50 8.29 ppm). Phytochemical analysis of all the tested weed plants showed the presence of flavonoids, saponins, tannins, steroids, cardiac glycosides, alkaloids, anthrequinones and terpenoids. Random Amplification of Polymorphic DNA-Polymerase chain reaction (RAPD-PCR) and comet assay were performed to assess the genotoxic effect of A. aspera but no change in DNA profile was observed. Furthermore, FTIR showed the presence of phenolic compounds in A. aspera extract. It is suggested that certain phenolic compounds such as flavonoids modulate the enzymatic activity and, hence, cause the death of larvae of Cx. quinquefasciatus. Altogether, current study would serve as an initial step towards replacement of synthetic insecticides to plant-microbe based biopesticide against Culex mosquitoes in future.

DOI: https://doi.org/10.1038/s41598-020-63815-w
Viral Immunol. 2020 Apr 20.

New Challenge for Zika Virus Infection: Human Reservoirs?

Gubio Soares Campos, Rejane Hughes Carvalho, Antonio Carlos Bandeira, Luciana Reboredo-Oliveira, Ryan Dos Santos Costa, Camila Alexandrina Figueiredo, Silvia Ines Sardi.

  Zika virus (ZIKV) is considered to cause an acute self-limited infection in adults, and microcephaly in fetus. Presence of the virus for long periods has been detected in body fluids; however, persistent viremia in serum for more than 1 year has not yet been reported. We have investigated persistence of ZIKV in serum samples of 77 subjects who were infected by the virus between 18 months and 3 years before the start of this study. The subjects included children with microcephaly and their parents. Serum samples were subjected to routine RT-qPCR assay for ZIKV, Chikungunya virus, and Dengue virus. From the 77 subjects, five showed positive for the presence of ZIKV particles by RT-qPCR, including four members of the same family. Viral isolation in Vero cells and C6/36 cells confirmed the result and showed the viral particles were active. We have detected viremia in healthy carriers up to 3 years after symptom onset. Humans acting as potential viral reservoirs have major implication for the current understanding of ZIKV infection.

Keywords:  Zika virus; immune complacency; persistence; viremia

DOI:  https://doi.org/10.1089/vim.2019.0187