bims-mosdis 2020-11-01 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2020‒11‒01
nineteen papers selected by
Richard Halfpenny
Staffordshire University

Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania.
Disease Vector Relative Spatio-Temporal Abundances to Water Bodies and Thermal Fitness Across Malaria Endemic Semi-Arid Areas.
No evidence for sylvatic cycles of chikungunya, dengue and Zika viruses in African green monkeys (Chlorocebus aethiops sabaeus) on St. Kitts, West Indies.
Spatiotemporal transmission dynamics of co-circulating dengue, Zika, and chikungunya viruses in Fortaleza, Brazil: 2011-2017.
Development of an Insecticide-Free Trapping Bednet to Control Mosquitoes and Manage Resistance in Malaria Vector Control: A New Way of Thinking.
Assessment of the susceptibility status of Aedes aegypti (Diptera: Culicidae) populations to pyriproxyfen and malathion in a nation-wide monitoring of insecticide resistance performed in Brazil from 2017 to 2018.
Overexposing mosquitoes to insecticides under global warming: A public health concern?
Physicochemical Characteristics of Four Limonene-Based Nanoemulsions and Their Larvicidal Properties against Two Mosquito Species, Aedes albopictus and Culex pipiens molestus.
Estimations of Fine-Scale Species Distributions of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Eastern Florida.
Species diversity and distribution of Anopheles mosquitoes in Bure district, Northwestern Ethiopia.
Impact of sars-cov-2 interventions on dengue transmission.
Wolbachia's Deleterious Impact on Aedes aegypti Egg Development: The Potential Role of Nutritional Parasitism.
Aedes albopictus (Diptera: Culicidae) Monitoring in the Lazio Region (Central Italy).
ZanzaMapp: A Scalable Citizen Science Tool to Monitor Perception of Mosquito Abundance and Nuisance in Italy and Beyond.
The Role of Temperature in Shaping Mosquito-Borne Viruses Transmission.
Rapid spread and population genetics of Aedes japonicus japonicus (Diptera: Culicidae) in southeastern Europe (Croatia, Bosnia and Herzegovina, Serbia).
The diversity of Anopheles blood feeding patterns suggests different malaria protection strategies in different localities.
Entomofaunal survey and larvicidal activity of greener silver nanoparticles: A perspective for novel eco-friendly mosquito control.
Battleground midgut: the cost to the mosquito for hosting the malaria parasite.

Malar J. 2020 Oct 28. 19(1): 383

Malaria vector species composition and entomological indices following indoor residual spraying in regions bordering Lake Victoria, Tanzania.

Charles Kakilla, Alphaxard Manjurano, Karen Nelwin, Jackline Martin, Fabian Mashauri, Safari M Kinung'hi, Eric Lyimo, Doris Mangalu, Lucy Bernard, Nduka Iwuchukwu, Dismasi Mwalimu, Naomi Serbantez, George Greer, Kristen George, Richard M Oxborough, Stephen M Magesa.

  BACKGROUND: Vector control through long-lasting insecticidal nets (LLINs) and focal indoor residual spraying (IRS) is a major component of the Tanzania national malaria control strategy. In mainland Tanzania, IRS has been conducted annually around Lake Victoria basin since 2007. Due to pyrethroid resistance in malaria vectors, use of pyrethroids for IRS was phased out and from 2014 to 2017 pirimiphos-methyl (Actellic® 300CS) was sprayed in regions of Kagera, Geita, Mwanza, and Mara. Entomological surveillance was conducted in 10 sprayed and 4 unsprayed sites to determine the impact of IRS on entomological indices related to malaria transmission risk.METHODS: WHO cone bioassays were conducted monthly on interior house walls to determine residual efficacy of pirimiphos-methyl CS. Indoor CDC light traps with or without bottle rotator were hung next to protected sleepers indoors and also set outdoors (unbaited) as a proxy measure for indoor and outdoor biting rate and time of biting. Prokopack aspirators were used indoors to capture resting malaria vectors. A sub-sample of Anopheles was tested by PCR to determine species identity and ELISA for sporozoite rate.
RESULTS: Annual IRS with Actellic® 300CS from 2015 to 2017 was effective on sprayed walls for a mean of 7 months in cone bioassay. PCR of 2016 and 2017 samples showed vector populations were predominantly Anopheles arabiensis (58.1%, n = 4,403 IRS sites, 58%, n = 2,441 unsprayed sites). There was a greater proportion of Anopheles funestus sensu stricto in unsprayed sites (20.4%, n = 858) than in sprayed sites (7.9%, n = 595) and fewer Anopheles parensis (2%, n = 85 unsprayed, 7.8%, n = 591 sprayed). Biting peaks of Anopheles gambiae sensu lato (s.l.) followed periods of rainfall occurring between October and April, but were generally lower in sprayed sites than unsprayed. In most sprayed sites, An. gambiae s.l. indoor densities increased between January and February, i.e., 10-12 months after IRS. The predominant species An. arabiensis had a sporozoite rate in 2017 of 2.0% (95% CI 1.4-2.9) in unsprayed sites compared to 0.8% (95% CI 0.5-1.3) in sprayed sites (p = 0.003). Sporozoite rates were also lower for An. funestus collected in sprayed sites.
CONCLUSION: This study contributes to the understanding of malaria vector species composition, behaviour and transmission risk following IRS around Lake Victoria and can be used to guide malaria vector control strategies in Tanzania.

Keywords:  Anopheles arabiensis; Anopheles funestus; Anopheles gambiae; Indoor residual spraying; Malaria vectors; Pirimiphos-methyl; Seasonality; Species composition; Tanzania

DOI:  https://doi.org/10.1186/s12936-020-03452-w
J Med Entomol. 2020 Oct 27. pii: tjaa221. [Epub ahead of print]

Disease Vector Relative Spatio-Temporal Abundances to Water Bodies and Thermal Fitness Across Malaria Endemic Semi-Arid Areas.

Mmabaledi Buxton, Ryan J Wasserman, Casper Nyamukondiwa.

  The biophysical environment plays an important role in the spatio-temporal abundance and distribution of mosquitoes. This has implications for the spread of vectors and diseases they cause across diverse landscapes. Here, we assessed vector mosquito abundances in relation to large water bodies, from three malaria districts in a semi-arid environment. Furthermore, we explored thermal limits to activity of the dominant and most medically important malaria vector across malaria-endemic areas. Mosquitoes were trapped near permanent water bodies across different districts. Critical thermal limits (critical thermal-maxima and -minima) to activity of wild adults and 4th instar larvae Anopheles arabiensis (Diptera: Culicidae) were assessed. Our results showed that Anopheles spp. dominate mosquito communities across all three districts, but that their numbers were far greater in Okavango than in other regions. At the Okavango sites, the numbers of Anopheles spp. decreased with distance from main water source. Anopheles spp. sampled in this region comprised Anopheles gambiae (Giles,1902) and Anopheles funestus (Giles, 1900) species complexes, with the former dominating in numbers. Thermal activity assays showed An. arabiensis females had wider thermal tolerance windows than males while larval thermal activity limits differed significantly across space. These results confirm that the Okavango district should be prioritized for vector control measures. Moreover, intervention strategies should consider recommendations for proximity effects to large water bodies, given the differential risk associated with distance from water. The wider thermal window on female vectors has implications for possible future malaria transmission and diverse habitat utilization under changing environments.

Keywords:   An. arabiensis ; Plasmodium ; emerging–reemerging infection; thermal tolerance; vector-borne disease

DOI:  https://doi.org/10.1093/jme/tjaa221
Parasit Vectors. 2020 Oct 30. 13(1): 540

No evidence for sylvatic cycles of chikungunya, dengue and Zika viruses in African green monkeys (Chlorocebus aethiops sabaeus) on St. Kitts, West Indies.

Matthew John Valentine, Brenda Ciraola, Matthew Thomas Aliota, Michel Vandenplas, Silvia Marchi, Bernard Tenebray, Isabelle Leparc-Goffart, Christa Ann Gallagher, Amy Beierschmitt, Tatiana Corey, Kerry McAuliffe Dore, Xavier de Lamballerie, Chengming Wang, Courtney Cuin Murdock, Patrick John Kelly.

  BACKGROUND: Dengue, chikungunya and Zika viruses (DENV, CHIKV and ZIKV) are transmitted in sylvatic transmission cycles between non-human primates and forest (sylvan) mosquitoes in Africa and Asia. It remains unclear if sylvatic cycles exist or could establish themselves elsewhere and contribute to the epidemiology of these diseases. The Caribbean island of St. Kitts has a large African green monkey (AGM) (Chlorocebus aethiops sabaeus) population and is therefore ideally suited to investigate sylvatic cycles.METHODS: We tested 858 AGM sera by ELISA and PRNT for virus-specific antibodies and collected and identified 9704 potential arbovirus vector mosquitoes. Mosquitoes were homogenized in 513 pools for testing by viral isolation in cell culture and by multiplex RT-qPCR after RNA extraction to detect the presence of DENV, CHIKV and ZIKVs. DNA was extracted from 122 visibly blood-fed individual mosquitoes and a polymorphic region of the hydroxymethylbilane synthase gene (HMBS) was amplified by PCR to determine if mosquitoes had fed on AGMs or humans.
RESULTS: All of the AGMs were negative for DENV, CHIKV or ZIKV antibodies. However, one AGM did have evidence of an undifferentiated Flavivirus infection. Similarly, DENV, CHIKV and ZIKV were not detected in any of the mosquito pools by PCR or culture. AGMs were not the source of any of the mosquito blood meals.
CONCLUSION: Sylvatic cycles involving AGMs and DENV, CHIKV and ZIKV do not currently exist on St. Kitts.

Keywords:  Arboviruses; Blood-meal analysis; Chikungunya; Dengue; Mosquitoes; Non-human primates; Sylvatic cycles; Zika

DOI:  https://doi.org/10.1186/s13071-020-04419-1
PLoS Negl Trop Dis. 2020 Oct 26. 14(10): e0008760

Spatiotemporal transmission dynamics of co-circulating dengue, Zika, and chikungunya viruses in Fortaleza, Brazil: 2011-2017.

Lilit Kazazian, Antonio S Lima Neto, Geziel S Sousa, Osmar José do Nascimento, Marcia C Castro.

The mosquito-borne viruses dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV), now co-endemic in the Americas, pose growing threats to health worldwide. However, it remains unclear whether there exist interactions between these viruses that could shape their epidemiology. This study advances knowledge by assessing the transmission dynamics of co-circulating DENV, ZIKV, and CHIKV in the city of Fortaleza, Brazil. Spatiotemporal transmission dynamics of DENV, ZIKV, and CHIKV were analyzed using georeferenced data on over 210,000 reported cases from 2011 to 2017 in Fortaleza, Brazil. Local spatial clustering tests and space-time scan statistics were used to compare transmission dynamics across all years. The transmission of co-circulating viruses in 2016 and 2017 was evaluated at fine spatial and temporal scales using a measure of spatiotemporal dependence, the τ-statistic. Results revealed differences in the diffusion of CHIKV compared to previous DENV epidemics and spatially distinct transmission of DENV/ZIKV and CHIKV during the period of their co-circulation. Significant spatial clustering of viruses of the same type was observed within 14-day time intervals at distances of up to 6.8 km (p<0.05). These results suggest that arbovirus risk is not uniformly distributed within cities during co-circulation. Findings may guide outbreak preparedness and response efforts by highlighting the clustered nature of transmission of co-circulating arboviruses at the neighborhood level. The potential for competitive interactions between the arboviruses should be further investigated.

DOI: https://doi.org/10.1371/journal.pntd.0008760
Insects. 2020 Oct 26. pii: E732. [Epub ahead of print]11(11):

Development of an Insecticide-Free Trapping Bednet to Control Mosquitoes and Manage Resistance in Malaria Vector Control: A New Way of Thinking.

Chouaibou S Mouhamadou, Kun Luan, Behi K Fodjo, Andre J West, Marian G McCord, Charles S Apperson, R Michael Roe.

  Mosquito-borne malaria kills 429,000 people each year with the problem being acute in sub-Saharan Africa. The successes gained with long-lasting pyrethroid-treated bednets are now in jeopardy because of wide-spread, pyrethroid resistance in mosquitoes. Using crowd modeling theory normalized for standard bednet architecture, we were able to design an attract-trap-kill technology for mosquitoes that does not require insecticides. Using three-dimensional polyester knitting and heat fixation, trap funnels were developed with high capture efficacy with no egression under worst-case laboratory conditions. Field testing in Africa in WHO huts with Gen1-3 T (trap)-Nets validated our model, and as predicted, Gen3 had the highest efficacy with a 4.3-fold greater trap-kill rate with no deterrence or repellency compared to Permanet 2.0, the most common bednet in Africa. A T-Net population model was developed based on field data to predict community-level mosquito control compared to a pyrethroid bednet. This model showed the Gen3 non-insecticidal T-Net under field conditions in Africa against pyrethroid resistant mosquitoes was 12.7-fold more efficacious than single chemical, pyrethroid-treated nets.

Keywords:  insecticide resistance; long-lasting bednet; malaria; permanet 2.0; trapping bednet; vector control; vector control failure

DOI:  https://doi.org/10.3390/insects11110732
Parasit Vectors. 2020 Oct 27. 13(1): 531

Assessment of the susceptibility status of Aedes aegypti (Diptera: Culicidae) populations to pyriproxyfen and malathion in a nation-wide monitoring of insecticide resistance performed in Brazil from 2017 to 2018.

Kauara Brito Campos, Ademir Jesus Martins, Cynara de Melo Rodovalho, Diogo Fernandes Bellinato, Luciana Dos Santos Dias, Maria de Lourdes da Graça Macoris, Maria Teresa Macoris Andrighetti, José Bento Pereira Lima, Marcos Takashi Obara.

  BACKGROUND: Chemical mosquito control using malathion has been applied in Brazil since 1985. To obtain chemical control effectiveness, vector susceptibility insecticide monitoring is required. This study aimed to describe bioassay standardizations and determine the susceptibility profile of Ae. aegypti populations to malathion and pyriproxyfen, used on a national scale in Brazil between 2017 and 2018, and discuss the observed impacts in arbovirus control.METHODS: The diagnostic-doses (DD) of pyriproxyfen and malathion were determined as the double of adult emergence inhibition (EI) and lethal doses for 99% of the Rockefeller reference strain, respectively. To monitor natural populations, sampling was performed in 132 Brazilian cities, using egg traps. Colonies were raised in the laboratory for one or two generations (F1 or F2) and submitted to susceptibility tests, where larvae were exposed to the pyriproxyfen DD (0.03 µg/l) and adults, to the malathion DD determined in the present study (20 µg), in addition to the one established by the World Health Organization (WHO) DD (50 µg) in a bottle assay. Dose-response (DR) bioassays with pyriproxyfen were performed on populations that did not achieve 98% EI in the DD assays.
RESULTS: Susceptibility alterations to pyriproxyfen were recorded in six (4.5%) Ae. aegypti populations from the states of Bahia and Ceará, with Resistance Ratios (RR95) ranging from 1.51 to 3.58. Concerning malathion, 73 (55.3%) populations distributed throughout the country were resistant when exposed to the local DD 20 µg/bottle. On the other hand, no population was resistant, and only 10 (7.6%) populations in eight states were considered as exhibiting decreased susceptibility (mortality ratios between 90 and 98%) when exposed to the WHO DD (50 µg/bottle).
CONCLUSIONS: The feasibility of conducting an insecticide resistance monitoring action on a nation-wide scale was confirmed herein, employing standardized and strongly coordinated sampling methods and laboratory bioassays. Brazilian Ae. aegypti populations exhibiting decreased susceptibility to pyriproxyfen were identified. The local DD for malathion was more sensitive than the WHO DD for early decreased susceptibility detection.

Keywords:  Aedes aegypti; Arboviruses; Insecticide resistance; Juvenile hormones; Organophosphate insecticides

DOI:  https://doi.org/10.1186/s13071-020-04406-6
Sci Total Environ. 2020 Oct 17. pii: S0048-9697(20)36599-2. [Epub ahead of print] 143069

Overexposing mosquitoes to insecticides under global warming: A public health concern?

Giovanni Benelli, André B B Wilke, Jeffrey R Bloomquist, Nicolas Desneux, John C Beier.

  The combined effect of global warming and insecticide exposure on the spread of mosquito-borne diseases is poorly studied. In our opinion, more resources should be diverted to this topic to further research efforts and deal with this increasing threat. It is particularly important to determine how Aedes, Anopheles, and Culex vector species cope with insecticide exposure under warming temperatures, as well as how both stressors may impact the activity of mosquito biocontrol agents. Herein, we promote a discussion on the topic, fostering a research agenda with insights for the longer-term implementation of mosquito control strategies under the Integrated Vector Management framework.

Keywords:  Aedes; Anopheles; Climate change; Culex; Insecticide resistance; Urbanization

DOI:  https://doi.org/10.1016/j.scitotenv.2020.143069
Insects. 2020 Oct 28. pii: E740. [Epub ahead of print]11(11):

Physicochemical Characteristics of Four Limonene-Based Nanoemulsions and Their Larvicidal Properties against Two Mosquito Species, Aedes albopictus and Culex pipiens molestus.

Ioanna Theochari, Athanasios Giatropoulos, Vassiliki Papadimitriou, Vasileios Karras, Georgios Balatsos, Dimitrios Papachristos, Antonios Michaelakis.

  Negative impacts on the environment from the continuous use of synthetic insecticides against mosquitoes has driven research towards more ecofriendly products. Phytochemicals, classified as low-risk substances, have been recognized as potential larvicides of mosquitoes; however, problems related to water solubility and stability are limiting factors for their use in mosquito control programs in the field. In this context, many researchers have focused on formulating essential oils in nanoemulsions, exploiting innovative nanotechnology. In the current study, we prepared 4 (R)-(+)-limonene oil-in-water nanoemulsions using low and high energy methods, and we evaluated their physicochemical characteristics (e.g., viscosity, stability, mean droplet diameter, polydispersity index) and their bioactivity against larvae of two mosquito species of great medical importance, namely, Cx. pipiens molestus and Ae. albopictus. According to the dose-response bioassays with the limonene-based nanoemulsions and pure limonene (dissolved in organic solvent), the tested nanoformulations improved the activity of limonene against Ae. albopictus larvae, while the performance of limonene was either the same or better than limonene against Cx. pipiens molestus, depending on the applied system. Overall, we achieved the production of limonene-based delivery nanosystems, with sufficient lethal properties against mosquito larvae to consider them promising larvicidal formulations applicable to mosquito breeding sites.

Keywords:  Aedes albopictus; Culex pipiens molestus; dynamic light scattering (DLS); electron paramagnetic resonance (EPR) spectroscopy; larvicides; limonene; mosquitoes; nanoemulsions

DOI:  https://doi.org/10.3390/insects11110740
J Med Entomol. 2020 Oct 31. pii: tjaa216. [Epub ahead of print]

Estimations of Fine-Scale Species Distributions of Aedes aegypti and Aedes albopictus (Diptera: Culicidae) in Eastern Florida.

Kristen A Hopperstad, Mohamed F Sallam, Michael H Reiskind.

  Many species distribution maps indicate the ranges of Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) overlap in Florida despite the well-documented range reduction of Ae. aegypti. Within the last 30 yr, competitive displacement of Ae. aegypti by Ae. albopictus has resulted in partial spatial segregation of the two species, with Ae. aegypti persisting primarily in urban refugia. We modeled fine-scale distributions of both species, with the goal of capturing the outcome of interspecific competition across space by building habitat suitability maps. We empirically parameterized models by sampling 59 sites in south and central Florida over time and incorporated climatic, landscape, and human population data to identify predictors of habitat suitability for both species. Our results show human density, precipitation, and urban land cover drive Ae. aegypti habitat suitability, compared with exclusively climatic variables driving Ae. albopictus habitat suitability. Remotely sensed variables (macrohabitat) were more predictive than locally collected metrics (microhabitat), although recorded minimum daily temperature showed significant, inverse relationships with both species. We detected minor Aedes habitat segregation; some periurban areas that were highly suitable for Ae. albopictus were unsuitable for Ae. aegypti. Fine-scale empirical models like those presented here have the potential for precise risk assessment and the improvement of operational applications to control container-breeding Aedes mosquitoes.

Keywords:   Aedes aegypti ; Aedes albopictus ; MaxEnt; habitat suitability model; maximum entropy model

DOI:  https://doi.org/10.1093/jme/tjaa216
Heliyon. 2020 Oct;6(10): e05063

Species diversity and distribution of Anopheles mosquitoes in Bure district, Northwestern Ethiopia.

Tilahun Adugna, Emana Getu, Delenasaw Yewhalaw.

  Malaria is one the leading health problem of the Ethiopia. Previously, areas above 2,000 m elevation were considered as malaria free areas. However, the major malaria epidemics were seen in areas at an altitude up to 3,000 m above sea level. These epidemics were due to climate and land-use changes (ecological changes) and still malaria is a growing health problem in highland parts of Ethiopia. This study aimed to investigate the species diversity, abundance and distribution of Anopheles mosquitoes in highland fringe of Bure district, Northwestern Ethiopia. It was done in the three different agroecological villages, Bukta (Irrigated), Workimdr (non-irrigated with few dry season breeding habitats) and Shnebekuma (non-irrigated with many dry season breeding habitats). Anopheles mosquitoes were collected by the Centers for Disease Control and Prevention Light Traps Catches, Pyrethrum Spray Catches, and Artificial Pit Shelters (APSs) from twenty-seven houses, thirty houses, and six APSs, respectively. Anopheles mosquitoes were identified morphologically to species using standard keys. Furthermore, molecular identification of Anopheles gambiae s.l was carried out using species-specific Polymerase Chain Reaction. Independent T-Test and One-way- ANOVA were employed to compare the mean mosquito's density between villages and species, indoor and outdoor host seeking mosquitoes. Descriptive statistic was used to calculate the proportion of each Anopheles species. Nine Anopheles mosquito species were identified in the study area which includes: Anopheles demeilloni, An. arabiensis, An. funestus group, An. coustani, An. squamosus, An. cinereus, An. pharoensis, An. rupicolus, and An. natalensis. Of the 4,703 Anopheles mosquitoes collected, An. demeilloni was the most prominent (50.7%, n = 2383) whereas An. rupicolus (0.03%, n = 3), and An. natalensis (0.02%, n = 1) were the least abundant. Higher mean density of Anopheles mosquitoes was collected from the non-irrigated village (2.395 ± 0.100) than irrigated (1.351 ± 0.109) (p = 0.001). In conclusion, three of the most important malaria vectors (An. arabiensis, An. funestus group and An. pharoensis) of Ethiopia were recorded in the study sites, especially the first two was found thought-out the year. Most of the Anopheles mosquitoes were collected from non-irrigated villages. Thus, breeding habitat management must be practiced throughout the year together with long-lasting insecticide-treated nets and insecticide residual sprays.

Keywords:  Anopheles arabiensis; Anopheles funestus group; Bure district; Ecology; Highland part; Malaria; Molecular biology; Non-irrigated village; Zoology

DOI:  https://doi.org/10.1016/j.heliyon.2020.e05063
PLoS Negl Trop Dis. 2020 Oct;14(10): e0008719

Impact of sars-cov-2 interventions on dengue transmission.

Jue Tao Lim, Borame Sue Lee Dickens, Lawrence Zheng Xiong Chew, Esther Li Wen Choo, Joel Ruihan Koo, Joel Aik, Lee Ching Ng, Alex R Cook.

An estimated 105 million dengue infections occur per year across 120 countries, where traditional vector control is the primary control strategy to reduce contact between mosquito vectors and people. The ongoing sars-cov-2 pandemic has resulted in dramatic reductions in human mobility due to social distancing measures; the effects on vector-borne illnesses are not known. Here we examine the pre and post differences of dengue case counts in Malaysia, Singapore and Thailand, and estimate the effects of social distancing as a treatment effect whilst adjusting for temporal confounders. We found that social distancing is expected to lead to 4.32 additional cases per 100,000 individuals in Thailand per month, which equates to 170 more cases per month in the Bangkok province (95% CI: 100-242) and 2008 cases in the country as a whole (95% CI: 1170-2846). Social distancing policy estimates for Thailand were also found to be robust to model misspecification, and variable addition and omission. Conversely, no significant impact on dengue transmission was found in Singapore or Malaysia. Across country disparities in social distancing policy effects on reported dengue cases are reasoned to be driven by differences in workplace-residence structure, with an increase in transmission risk of arboviruses from social distancing primarily through heightened exposure to vectors in elevated time spent at residences, demonstrating the need to understand the effects of location on dengue transmission risk under novel population mixing conditions such as those under social distancing policies.

DOI: https://doi.org/10.1371/journal.pntd.0008719
Insects. 2020 Oct 27. pii: E735. [Epub ahead of print]11(11):

Wolbachia's Deleterious Impact on Aedes aegypti Egg Development: The Potential Role of Nutritional Parasitism.

Megan J Allman, Johanna E Fraser, Scott A Ritchie, D Albert Joubert, Cameron P Simmons, Heather A Flores.

  The artificial introduction of the endosymbiotic bacterium, Wolbachia pipientis, into Aedes (Ae.) aegypti mosquitoes reduces the ability of mosquitoes to transmit human pathogenic viruses and is now being developed as a biocontrol tool. Successful introgression of Wolbachia-carrying Ae. aegypti into native mosquito populations at field sites in Australia, Indonesia and Malaysia has been associated with reduced disease prevalence in the treated community. In separate field programs, Wolbachia is also being used as a mosquito population suppression tool, where the release of male only Wolbachia-infected Ae. aegypti prevents the native mosquito population from producing viable eggs, subsequently suppressing the wild population. While these technologies show great promise, they require mass rearing of mosquitoes for implementation on a scale that has not previously been done. In addition, Wolbachia induces some negative fitness effects on Ae. aegypti. While these fitness effects differ depending on the Wolbachia strain present, one of the most consistent and significant impacts is the shortened longevity and viability of eggs. This review examines the body of evidence behind Wolbachia's negative effect on eggs, assesses nutritional parasitism as a key cause and considers how these impacts could be overcome to achieve efficient large-scale rearing of these mosquitoes.

Keywords:  Aedes aegypti; Wolbachia; biocontrol; nutritional parasitism

DOI:  https://doi.org/10.3390/insects11110735
J Med Entomol. 2020 Oct 27. pii: tjaa222. [Epub ahead of print]

Aedes albopictus (Diptera: Culicidae) Monitoring in the Lazio Region (Central Italy).

Federico Romiti, Arianna Ermenegildi, Adele Magliano, Pasquale Rombolà, Donatella Varrenti, Roberto Giammattei, Silvia Gasbarra, Simona Ursino, Luca Casagni, Andrea Scriboni, Vincenzo Puro, Amilcare Ruta, Laura Brignola, Oriano Fantasia, Daniela Corpolongo, Giuseppe Di Luzio, Claudio De Liberato.

  The Asian tiger mosquito Aedes albopictus (Skuse 1894) is assuming an ever-increasing importance as invasive species in Europe and consequently as human health and nuisance concern. In Central Italy, the species has been recently involved in a chikungunya outbreak. A 3 yr Ae. albopictus monitoring was carried out in 21 municipalities of the Lazio region (Central Italy), belonging to three provinces. Samplings were performed on a weekly basis using ovitraps, in order to investigate climatic and spatial variables driving egg abundance and Ae. albopictus period of activity. A temperature of 10.4°C was indicated as lower threshold for the onset of egg-laying activity, together with a photoperiod of 13:11 (L:D) h. The whole oviposition activity lasted 8 mo (May-December), with 95% of eggs laid between early June and mid-November and a peak at the end of August. Egg abundance was positively influenced by accumulated temperature (AT) of the 4 wk preceding sampling and negatively by precipitation during the week before. Egg-laying activity dropped with decreasing AT, increasing rainfall, and with a photoperiod below 10:14 (L:D) h. Our results pinpointed the importance of fine-scaled spatial features on egg abundance. Some of these fine-scaled characteristics have been highlighted, such as the presence of vegetation and human footprint index. Our model estimated an almost doubled maximum number of laid eggs for the maximum value of human footprint. Compelling evidence of the relevance of fine-scaled characteristics was reported, describing cases where human-made breeding sites driven the abundance of Ae. albopictus.

Keywords:  mosquito; ovitrap; phenology; rainfall; temperature

DOI:  https://doi.org/10.1093/jme/tjaa222
Int J Environ Res Public Health. 2020 Oct 27. pii: E7872. [Epub ahead of print]17(21):

ZanzaMapp: A Scalable Citizen Science Tool to Monitor Perception of Mosquito Abundance and Nuisance in Italy and Beyond.

Beniamino Caputo, Mattia Manica, Federico Filipponi, Marta Blangiardo, Pietro Cobre, Luca Delucchi, Carlo Maria De Marco, Luca Iesu, Paola Morano, Valeria Petrella, Marco Salvemini, Cesare Bianchi, Alessandra Della Torre.

  Mosquitoes represent a considerable nuisance and are actual/potential vectors of human diseases in Europe. Costly and labour-intensive entomological monitoring is needed to correct planning of interventions aimed at reducing nuisance and the risk of pathogen transmission. The widespread availability of mobile phones and of massive Internet connections opens the way to the contribution of citizen in complementing entomological monitoring. ZanzaMapp is the first mobile "mosquito" application for smartphones specifically designed to assess citizens' perception of mosquito abundance and nuisance in Italy. Differently from other applications targeting mosquitoes, ZanzaMapp prioritizes the number of records over their scientific authentication by requesting users to answer four simple questions on perceived mosquito presence/abundance/nuisance and geo-localizing the records. The paper analyses 36,867 ZanzaMapp records sent by 13,669 devices from 2016 to 2018 and discusses the results with reference to either citizens' exploitation and appreciation of the app and to the consistency of the results obtained with the known biology of main mosquito species in Italy. In addition, we provide a first small-scale validation of ZanzaMapp data as predictors of Aedes albopictus biting females and examples of spatial analyses and maps which could be exploited by public institutions and administrations involved in mosquito and mosquito-borne pathogen monitoring and control.

Keywords:  Aedes albopictus; biting activity; citizen science; mosquito; nuisance; tiger mosquito

DOI:  https://doi.org/10.3390/ijerph17217872
Front Microbiol. 2020 ;11 584846

The Role of Temperature in Shaping Mosquito-Borne Viruses Transmission.

Rachel Bellone, Anna-Bella Failloux.

  Mosquito-borne diseases having the greatest impact on human health are typically prevalent in the tropical belt of the world. However, these diseases are conquering temperate regions, raising the question of the role of temperature on their dynamics and expansion. Temperature is one of the most significant abiotic factors affecting, in many ways, insect vectors and the pathogens they transmit. Here, we debate the veracity of this claim by synthesizing current knowledge on the effects of temperature on arboviruses and their vectors, as well as the outcome of their interactions.

Keywords:  arboviruses; mosquitoes; temperature; vector-borne diseases; vectorial capacity

DOI:  https://doi.org/10.3389/fmicb.2020.584846
PLoS One. 2020 ;15(10): e0241235

Rapid spread and population genetics of Aedes japonicus japonicus (Diptera: Culicidae) in southeastern Europe (Croatia, Bosnia and Herzegovina, Serbia).

Nele Janssen, Nataša Graovac, Goran Vignjević, Mirta Sudarić Bogojević, Nataša Turić, Ana Klobučar, Mihaela Kavran, Dušan Petrić, Aleksandra Ignjatović Ćupina, Susanne Fischer, Doreen Werner, Helge Kampen, Enrih Merdić.

The Asian bush mosquito, Aedes japonicus japonicus (Theobald, 1901), a potential vector of several pathogens, has recently established in North America and Central Europe. In 2013, it was found on the Slovenian-Croatian border, and during the following years, it emerged in more and more counties of northwestern Croatia. Surveillance of Ae. j. japonicus and other invasive mosquito species was subsequently extended both spatially and temporally in Croatia and neighbouring Bosnia and Herzegovina and Serbia. Mosquito collections were conducted in 2017 and 2018, based on adult trapping through dry ice-baited CDC traps and BG-Lure-baited BG-Sentinel traps, larval sampling through dippers and nets, and ovitrapping. Aedes j. japonicus specimens from collected samples were subjected to population genetic analysis by comparing microsatellite signatures and nad4 DNA sequences between sampled locations and with data previously obtained from more western European distribution areas. Aedes j. japonicus immature stages were found at 19 sites in Croatia, two sites in Bosnia and Herzegovina and one site in Serbia. In Croatia, four new counties were found colonised, two in the east and two in the south of the previously known distribution area. A spread of 250 km could thus be documented within five years. The findings in Bosnia and Herzegovina and Serbia represent the first records of Ae. j. japonicus in these countries. Genetic analysis suggests at least two introduction events into the surveyed area. Among the locations analysed, Orahovica can be considered a genetic border. The individuals collected west of this point were found to be similar to samples previously collected in the border regions of Southeast Germany/Austria and Austria/Slovenia, while the specimens from more eastern Croatian localities, together with those from Bosnia and Herzegovina and Serbia, were genetically different and could not be assigned to a probable origin. Thus, introduction from Central Europe, possibly by vehicular traffic, into the study area is likely, but other origins, transportation routes and modes of entry appear to contribute. Further dispersal of Ae. j. japonicus to other parts of southeastern Europe is anticipated.

DOI: https://doi.org/10.1371/journal.pone.0241235
F1000Res. 2019 ;8 1217

The diversity of Anopheles blood feeding patterns suggests different malaria protection strategies in different localities.

Irfanul Chakim, Tepanata Pumpaibool.

  Background: Malaria is a significant health burden for many countries worldwide. Insecticide-treated bed nets and mosquito repellent are considered effective methods for preventing Anopheles bites. However, changes in the biological properties of the vector have led to a reduction in their effectiveness. Most published studies have only investigated the human population factor, not the dynamics of vector behavior. Therefore, this study aims to investigate the importance of primary vector activity for selecting an appropriate malaria protection strategy. Methods: Initially, active case detection (ACD) was carried out in western and eastern parts of Indonesia, Jambi and Sumba, to confirm their endemicity level. According to the 2016 national health report of Indonesia, Jambi has an annual parasite index (API) of 0.14 and Sumba has an API of 5.41. A series of entomological observations were carried out to compare the biting activity of Anopheles vector in two localities, with a total of 216 houses and catchers (108 in each study site). Results: The results indicated that endemicity at the sub-district level is higher than that at the provincial level. Only Anopheles balabacensi was found to be exophagic. Multiple comparisons found different biting times between the sites, suggesting that early evening (18.00-20.00) is most likely to be the time when mosquitos transmit the Plasmodium parasite in Jambi, while during sleeping hours (21.00-01.00) is the peak biting time of Anopheles mosquitos in Sumba. Conclusions: The study demonstrates the importance of Anopheles species blood feeding patterns in selecting an appropriate malaria protection strategy.

Keywords:  Anopheles; Malaria; blood feeding pattern; diversity; protective strategy

DOI:  https://doi.org/10.12688/f1000research.19341.1
Saudi J Biol Sci. 2020 Nov;27(11): 2917-2928

Entomofaunal survey and larvicidal activity of greener silver nanoparticles: A perspective for novel eco-friendly mosquito control.

Kuppusamy Elumalai, Shahid Mahboob, Khalid A Al-Ghanim, Fahad Al-Misned, Jeganathan Pandiyan, Putta Muralidharan Kousik Baabu, Kaliyamoorthy Krishnappa, Marimuthu Govindarajan.

  The entomofaunal survey and its toxicity of Blumea mollis (Asteraceae) leaf aqueous extract-mediated (Bm-LAE) silver nanoparticles (AgNPs) were assessed against selected human vector mosquitoes (HVMs). A total of 1800 individuals of 29 species belongs to 7 genera were identified. Month-wise and Genus-wise abundance of HVMs larval diversity were calculated and one-way ANOVA statistically analyzed the average physico-chemical characteristics. The relationship between physicochemical characteristics and HVMs larvae in KWS was interpreted. The total larval density and container index were 23530.18 and 1961.85 examined against 10 different containers. Various spectroscopic and microscopic investigation characterized Bm-AgNPs. The Bm- AgNPs tested against HVMs larvae, the predominant LC50/LC90 values of 18.17/39.56, 23.45/42.49 and 21.82/40.43 μg/mL were observed on An. subpictus Cx. vishnui and Ae. vittatus, respectively. The findings of this investigation, improperly maintained drainages, containers and unused things in study sites, are engaged to HVMs development. This will be essential for designing and implementing HVMs control. The larval toxic potentiality of Bm- AgNPs had a prompt, inexpensive and compelling synthesis of multi-disperse action against HVMs.

Keywords:  Blumea mollis; Green synthesis; Larval toxicity; Mosquito density and diversity; Physico-chemical characteristics

DOI:  https://doi.org/10.1016/j.sjbs.2020.08.046
Biol Cell. 2020 Oct 30.

Battleground midgut: the cost to the mosquito for hosting the malaria parasite.

Melika Hajkazemian, Clément Bossé, Raimondas Mozūraitis, S Noushin Emami.

  In eco-evolutionary studies of parasite-host interactions, virulence is defined as a reduction in host fitness as a result of infection relative to an uninfected host. Pathogen virulence may either promote parasite transmission, when correlated with higher parasite replication rate or decrease the transmission rate if the pathogen quickly kills the host. This evolutionary mechanism, referred to as 'trade-off' theory proposes that pathogen virulence evolves towards a level that most benefits the transmission. It has been generally predicted that pathogens evolve towards low virulence in their insect vectors, mainly due to the high dependence of parasite transmission on their vector-survival. Therefore the degree of virulence which malaria parasites impose on mosquito vectors may depend on several external and internal factors. Here we review briefly (I) the role of mosquito in parasite development, with a particular focus on mosquito midgut as the battleground between Plasmodium and the mosquito host. We aim to point out (II) the histology of the mosquito midgut epithelium and its role in host defence against parasite's countermeasures in the three main battle sites, namely a- the lumen (microbiota and biochemical environment) b- the peritrophic membrane (physical barrier), and c- the tubular epithelium including the basal membrane (physical and biochemical barrier). Lastly, (III) we describe the impact which malaria parasite and its virulence factors have on mosquito fitness. This article is protected by copyright. All rights reserved.

Keywords:  histology; host; mosquito; parasite; transmission; virulence

DOI:  https://doi.org/10.1111/boc.202000039