Large-scale performance assessment of the BG-Counter 2 used with two different mosquito traps.

BACKGROUND: Mosquitoes are important vectors of pathogens. They are usually collected with CO2-baited traps and subsequently identified by morphology. This procedure is very time-consuming. Automatic counting traps could facilitate timely evaluation of the local risk for mosquito-borne pathogen transmission or decision-making on vector control measures, but the counting accuracy of such devices has rarely been validated in the field. METHODS: The Biogents (BG)-Counter 2 automatically counts mosquitoes by discriminating the size of captured objects directly in the field and transmits the data to a cloud server. To assess the accuracy of this counting device, 27 traps were placed at 19 sampling sites across Germany and used in daily, weekly or bimonthly intervals from April until October 2021. The BG-Counter 2 was attached to a CO2-trap (BG-Pro trap = CO2-Pro) and the same trap was converted to also attract gravid mosquitoes (upside-down BG-Pro trap with a water container beneath = CO2-Pro-gravid). All captured mosquitoes were identified by morphology. The number of females (unfed and gravid), mosquito diversity and the number of identified specimens in relation to the counting data of the BG-Counter were compared between the two trapping devices to evaluate sampling success and counting accuracy. RESULTS: In total 26,714 mosquitoes were collected during 854 trap days. The CO2-Pro-gravid trap captured significantly more mosquitoes per trap day for all specimens, gravid females and non-gravid females, while there was no difference in the mosquito diversity. The linear model with the captured mosquitoes as a response and the counted specimens as a predictor explained only a small degree of the variation within the data (R2 = 0.16), but per individual trap the value could reach up to 0.62 (mean R2 = 0.23). The counting accuracy for the daily samples had a significant positive correlation with sample size, resulting in higher accuracy for the CO2-Pro-gravid trap and higher accuracy for sites and sampling months with high mosquito abundance. CONCLUSIONS: While the accuracy of the BG-Counter 2 is quite low, the device is able to depict mosquito phenology and provide information about local population dynamics.

Assessment of Genotoxicity of Zinc Oxide Nanoparticles Using Mosquito as Test Model.

The widespread applications of ZnO NPs in the different areas of science, technology, medicine, agriculture, and commercial products have led to increased chances of their release into the environment. This created a growing public concern about the toxicological and environmental effects of the nanoparticles. The impact of these NPs on the genetic materials of living organisms is documented in some cultured cells and plants, but there are only a few studies regarding this aspect in animals. In view of this, the present work regarding the assessment of the genotoxicity of zinc oxide nanoparticles using the mosquito Culex quinquefaciatus has been taken up. Statistically significant chromosomal aberrations over the control are recorded after the exposure of the fourth instar larvae to a dose of less than LD20 for 24 h. In order to select this dose, LD20 of ZnO NPs for the mosquito is determined by Probit analysis. Lacto-aceto-orcein stained chromosomal preparations are made from gonads of adult treated and control mosquitoes. Both structural aberrations, such as chromosomal breaks, fragments, translocations, and terminal fusions, resulting in the formation of rings and clumped chromosomes, and numerical ones, including hypo- and hyper-aneuploidy at metaphases, bridges, and laggards at the anaphase stage are observed. The percentage frequency of abnormalities in the shape of sperm heads is also found to be statistically significant over the controls. Besides this, zinc oxide nanoparticles are also found to affect the reproductive potential and embryo development as egg rafts obtained from the genetic crosses of ZnO nanoparticle-treated virgin females and normal males are small in size with a far smaller number of eggs per raft. The percentage frequencies of dominant lethal mutations indicated by the frequency of unhatched eggs are also statistically significant (p < 0.05) over the control. The induction of abnormalities in all of the three short-term assays studied during the present piece of work indicates the genotoxic potential of ZnO NPs, which cannot be labeled absolutely safe, and this study pinpoints the need to develop strategies for the protection of the environment and living organisms thriving in it.

Assessment Heartworm Disease in the Canary Islands (Spain): Risk of Transmission in a Hyperendemic Area by Ecological Niche Modeling and Its Future Projection.

Heartworm disease is a vector-borne zoonotic disease caused by Dirofilaria immitis. The Canary Islands (Spain), geolocated close to the coast of Western Sahara, is an archipelago considered hyperendemic where the average prevalence in domestic dogs is high, heterogeneous, and non-uniform. In addition, Culex theileri has been reported as a vector of the disease on two of the most populated islands. Our aim was to develop a more accurate transmission risk model for dirofilariosis for the Canary Islands. For this purpose, we used different variables related to parasite transmission; the potential distribution of suitable habitats for Culex spp. was calculated using the ecological niche model (ENM) and the potential number of generations of D. immitis. The resulting model was validated with the geolocation of D. immitis-infected dogs from all islands. In addition, the impact of possible future climatic conditions was estimated. There is a risk of transmission on all islands, being high in coastal areas, moderate in midland areas, and minimal in higher altitude areas. Most of the dogs infected with D. immitis were geolocated in areas with a high risk of transmission. In 2080, the percentage of territory that will have been gained by Culex spp. is small (5.02%), although it will occur toward the midlands from coastal areas. This new model provides a high predictive power for the study of cardiopulmonary dirofilariosis in the Canary Islands, as a hyperendemic area of the disease, and can be used as a tool for its prevention and control.

Assessment of Truck-Mounted Area-Wide S-methoprene Applications to Manage West Nile Virus Vector Species in the Suburbs of Chicago, IL, USA.

West Nile virus remains the leading cause of arboviral neuroinvasive disease in the United States, despite extensive efforts to control the mosquito vectors involved in transmission. In this study, we evaluated the effectiveness of Altosid SR-20 (active ingredient, S-methoprene 20%) larvicide applications using truck-mounted ultra-low volume (ULV) dispersal equipment to target Culex pipiens Linnaeus (Diptera: Culicidae) and Cx. restuans (Theobald)larvae. A combination of emergence bioassays, open-field measurements of deposited S-methoprene and spray distribution using gas chromatography-mass spectrometry, and assessments of adult Culex spp. populations in response to applications were conducted over the summer of 2020 within the North Shore Mosquito Abatement District (IL, USA). Open-field applications revealed that dispersed Altosid SR-20 using ULV equipment was effective (75% emergence inhibition in susceptible lab strain Cx. pipiens larvae) up to 53 m. In suburban neighborhood applications, we found that S-methoprene deposition and larval emergence inhibition (EI) in front yards did not differ significantly from backyards. An overall EI of 46% and 28% were observed for laboratory strain Cx. pipiens and wild Cx. restuans larvae respectively, and both had an EI significantly higher than the untreated control group. The EI of exposed wild Cx. pipiens larvae did not differ from the untreated controls, suggesting an increased tolerance to S-methoprene. No difference in abundance of gravid or host-seeking adult Culex spp. post-application was detected between treated and untreated sites. These results document the ability of area-wide application to distribute S-methoprene, but this strategy will need further modifications and evaluation for Culex spp. management.

Honey-baited FTA cards in box gravid traps for the assessment of Usutu virus circulation in mosquito populations in Germany.

Usutu virus (USUV) is becoming increasingly important to veterinary and human health in Germany. USUV has been implicated in mass die-off events of birds, especially of blackbirds (Turdus merula), and has experienced significant range expansion in the years since its first detection in 2010. Current detection methods rely primarily on dead bird surveillance or mass mosquito collection using CO2 as the main attractant. Dead bird surveillance can result in detection of disease circulation past the point at which control efforts would be most impactful. Vector surveillance offers the opportunity to detect disease circulation before significant outbreaks occur. However, current methods result in collections of extremely large numbers of predominantly nulliparous female mosquitoes who have not yet taken a blood meal. This study sought to test whether box gravid traps could successfully trap USUV infected gravid Culex mosquitoes, and if viral RNA could be successfully transferred and stabilised on an FTA card. During the month of August 2020, 18 Reiter-Cummings style box gravid traps with honey-baited FTA cards were set in a region of known USUV circulation around the southern border of Hesse, Germany. Four 48-hour trapping rounds were conducted. All mosquitoes and FTA cards were collected and stored during transport to the laboratory on dry ice. Samples and FTA cards were then transferred and stored in a freezer at -5 °C until identification. Identification was carried out on a chill plate before being sent with overnight courier in a styrofoam box with cooling elements for virus detection with a modified generic flavivirus RT-PCR. Mosquitoes were separated into pools by trap, date, species and feeding status. 2003 mosquitoes were caught in four rounds of trapping, 1834 or 88% of which were female Culex mosquitoes used for examination. 13 pools of mosquitoes and four FTA cards tested positive for USUV. No positive FTA cards were found in traps with positive mosquitoes and no positive mosquitoes were found in traps with positive FTA cards. Although fewer FTA cards than expected returned a positive result, this may have been a result of the extreme conditions experienced in the field and highlights the need to establish the temperature and humidity boundaries such a collection method can withstand. Box gravid traps however, provided a highly effective and targeted approach for capturing gravid female Culex mosquitoes, the most appropriate subpopulation for testing for USUV. Additionally, the simplicity and effectiveness of this trapping and surveillance method make it an attractive option for use as an early warning system, including for large scale surveillance programmes.

Bio-fabricated silver nanoparticles for controlling dengue and filaria vectors and their characterization, as well as toxicological risk assessment in aquatic mesocosms.

The present study is focused on synthesis of silver nanoparticles from weeds and an assessment of their mosquito larvicidal efficacy. This study also presented the toxicological effects as well as the stability of these nanoparticles in aquatic mesocosms. The weed Digiteria sanguinallis was first time used for the synthesis of silver nanoparticles. The synthesized nanoparticles were characterized by various analytical techniques, such as UV-VIS, TEM, FESEM, EDX, XRD, FTIR, and zeta potential study. The result revealed that the nanoparticles are crystalline, spherical shape with band gap 2.44 eV, and average size 18 nm. The LC50 value of synthesized AgNPs were recorded as 7.47 and 6.31 mg/L at 24 h against Cx. quinquefasciatus and A. albopictus respectively. In contrast, larvicidal activity of weed extract was insignificant against two target species. In aquatic mesocosm study, AgNPs (LC50 dose) does not alter the nature of water parameters within experimental period. However only EC % and ORP were changes because of silver ion oxidation. In biochemical parameters, only stress enzymes for animal and plant species were moderately altered under long term exposure. But glycogen, protein, and AchE of two mosquito species were significantly changed under same mesocosm setup within short exposure. Comparatively, in control mesocosm, synthesized AgNPs are naturally change their nano form within 20 days with the presence of all non-target species and pond sediment. Therefore, it can be concluded that biosynthesized AgNPs could be used as a larvicidal agent in near future with negligible effects on aquatic organisms.

Assessment of larvicidal and genotoxic potentials of extracts of Hyptis suaveolens against Culex quinquefasciatus based on enzyme profile and RAPD-PCR assay.

Vector control strategies have focused on the development of effective and ecofriendly alternatives. In the present study, investigation of larvicidal and genotoxic effects of leaves of Hyptis suaveolens from four different extraction solvents (aqueous, hexane, methanol and acetone) on fourth instar larvae of Culex quinquefasciatus was carried out. Extraction was done using soxhlet apparatus and the characteristics functional group of active constituents were identified using Fourier Transform Infrared spectrophotometer. Larvicidal activities were screened using three different concentrations (50, 150 and 250 mg/mL) following WHO standard protocol and mortality was recorded after 24, 48 and 72 hr. Hexane extract showed the highest mortality (27.92, 38.75, 90.42 %; LC50: 272.5, 191.3, 114.8 mg/mL), followed by aqueous extract (20.83, 34.58, 59.58 %; LC50: 496.6, 392.9, 208.1 mg/mL) and acetone extract (20.83, 32.08, 59.58 %; LC50: 1111.2, 393.6, 266.1 mg/mL) and methanol extract (17.92, 29.17, 52.92 %; LC50: 466.0, 400.1, 272.3 mg/mL). Enzyme profile such as superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase (CAT), glutathione (GSH) and alkaline phosphatase (ALP) were significantly altered in the larvae exposed to the four extracts. Phytochemical screening of all solvents extract revealed the presence of saponins, flavonoids, terpenoids and alkaloids as common constituents. Random Amplified Polymorphic DNA-Polymerase Chain Reaction (RAPD-PCR) profile implied hexane and aqueous extracts altered the DNA of larvae. Furthermore, FTIR Spectroscopic analysis revealed phenols, alcohols, aliphatic primary amines and saponins as the major groups in the extracts. Conclusively, this study established the lethal potential of extracts of H. suaveolens as alternative plant-based and eco-friendly larvicide against Cx. quinquefasciatus.

Assessment of susceptible Culex quinquefasciatus larvae in Indonesia to different insecticides through metabolic enzymes and the histopathological midgut.

Filariasis and virus diseases that are transmitted by Culex quinquefasciatus are still a global health problem. Control of mosquito vectors with synthetic insecticides causes resistance to these mosquitoes to insecticides so that detection of susceptibility of the mosquito larval stage to insecticides is important for evaluating mosquito control programs. The aim of this study was to evaluate the susceptibility of wild-caught Cx. quinquefasciatus larvae in Jakarta, Indonesia, following exposure to temephos, malathion, cypermethrin, and deltamethrin; this was done by examining the detoxifying enzyme activities and histological damage to the larval midgut. Cx. quinquefasciatus larvae were collected from five fields in Jakarta and exposed for 24 h to temephos (1.25, 6.25, 31.25, and 156.25 ppm), malathion (0.5 ppm), cypermethrin (0.25 ppm), and deltamethrin (0.35 ppm). The larvae were then examined for acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase activities using biochemical methods. Histological damage to the larval midgut was examined using routine histopathological methods and transmission electron microscopy (TEM). After 24 h, temephos and deltamethrin led to 100% mortality in the Cx. quinquefasciatus larvae. Temephos and malathion significantly inhibited the activity of AChE, while cypermethrin and deltamethrin significantly inhibited oxidase activity. Histologically, all insecticides damaged the larval midgut, as indicated by irregularities in the epithelial cell (ECs), microvilli (Mv), food boluses (FBs), peritrophic membranes (PMs), and cracked epithelial layers (Ep). The TEM findings confirmed that temephos and cypermethrin damage to the midgut ECs included damage to the cell membrane, nucleus, nucleoli, mitochondria, and other cell organelles. Overall, Cx. quinquefasciatus larvae in Jakarta were completely susceptible to temephos and deltamethrin. Synthetic insecticides may kill Cx. quinquefasciatus larvae through their actions on the metabolic enzyme activities and histopathological midgut.

A Temperature Conditioned Markov Chain Model for Predicting the Dynamics of Mosquito Vectors of Disease.

Understanding and predicting mosquito population dynamics is crucial for gaining insight into the abundance of arthropod disease vectors and for the design of effective vector control strategies. In this work, a climate-conditioned Markov chain (CMC) model was developed and applied for the first time to predict the dynamics of vectors of important medical diseases. Temporal changes in mosquito population profiles were generated to simulate the probabilities of a high population impact. The simulated transition probabilities of the mosquito populations achieved from the trained model are very near to the observed data transitions that have been used to parameterize and validate the model. Thus, the CMC model satisfactorily describes the temporal evolution of the mosquito population process. In general, our numerical results, when temperature is considered as the driver of change, indicate that it is more likely for the population system to move into a state of high population level when the former is a state of a lower population level than the opposite. Field data on frequencies of successive mosquito population levels, which were not used for the data inferred MC modeling, were assembled to obtain an empirical intensity transition matrix and the frequencies observed. Our findings match to a certain degree the empirical results in which the probabilities follow analogous patterns while no significant differences were observed between the transition matrices of the CMC model and the validation data (ChiSq = 14.58013, df = 24, p = 0.9324451). The proposed modeling approach is a valuable eco-epidemiological study. Moreover, compared to traditional Markov chains, the benefit of the current CMC model is that it takes into account the stochastic conditional properties of ecological-related climate variables. The current modeling approach could save costs and time in establishing vector eradication programs and mosquito surveillance programs.

Mosquito Vector Production across Socio-Economic Divides in Baton Rouge, Louisiana.

We investigated the role of socio-economic factors in the proliferation of mosquito vectors in two adjacent but socio-economically contrasting neighborhoods in Baton Rouge, LA, USA. We surveyed mosquito larvae habitat, mosquito larvae, and adult mosquitoes during the summer of 2020. We also evaluated the number of requests for mosquito abatement services in the years preceding the study for each area. While we did not find differences in terms of the most abundant species, Culex quinquefasicatus (F1,30 = 0.329, p = 0.57), we did find a higher abundance of mosquito habitats, particularly discarded tires, as well as larvae (z = 13.83, p < 0.001) and adults (F1,30 = 4.207, p = 0.049) of the species Aedes albopictus in the low-income neighborhood. In contrast, mosquito abatement requests were significantly higher in the high socio-economic neighborhood (z = -8.561, p < 0.001). This study shows how factors such as adjudicated properties, discarded tires and pest abatement requests can influence the abundance of mosquito vectors, disproportionately affecting low-income groups. This study also highlights how Aedes spp. may be better indicators than Culex spp. of socio-economic differences between nearby neighborhoods, due to their short flight range and habitat preferences, and this should be considered in future studies attempting to detect such disparities in the future.

Assessment the Changing Trend of Susceptibility to Two Insecticides among Field-Population Culex quinquefasciatus Compared with the Same Population Undergoing to Multiple Colonization.

BACKGROUND: During the past decade, rapid development of insecticide resistance have been reported among many species of mosquito vectors against four main categories of insecticides worldwide. The aim of the research was to assess the variation trend of susceptibility levels of Culex quinquefasciatus to two insecticides separately for the field population compared with subsequent generations of the same sample after multiple colonization. METHODS: Larvae and pupae of Cx. quinquefasciatus were collected from house sewages and reared to adult which blood-fed on roosters. Ten percent sucrose fed female mosquitoes aged 2-3 days were used for susceptibility tests with DDT and deltamethrin. Susceptibility levels was assessed in the adult stage of field stran Cx. quinquefasciatus against DDT 4.0% and deltamethrin 0.05% and continued up to next six generations undergoing multiple rearing at insectary condition. RESULTS: The susceptibility levels to DDT 4.0% did not change compared to the field with the lab population to six generations. Regarding deltamethrin 0.05%, no significant difference was shown between field strain (58.3%) and 3rd generation (52.7%) compared to the 6th one (33.8%). CONCLUSION: This finding may reflect the role of the kdr gene in resistance to organochlorine which has cross-resistance with pyrethroid insecticides. The results of this study clearly showed the irreversible trend of pyrethroid resistance among colonized mosquitoes. This is the first study of the resistance status of Cx. quinquefasciatus in Iran.

Elimination of Lymphatic Filariasis in Shandong Province, China, 1957-2015.

China used to be one of the most heavily endemic countries for lymphatic filariasis (LF) in the world. Bancroftian filariasis, which is caused by the filarioid nematode Wuchereria bancrofti, is the only filariasis in Shandong Province. A total of 864 endemic counties (cities) in 16 provinces/autonomous regions/municipalities with a total population of 330 million people were at risk of infection. Shandong Province was a highly LF-endemic area in the 1950s, the epidemiological investigation of LF conducted in 1957 indicated that the disease was endemic in 74 counties and the highest microfilaria rate was up to 26%. There were ∼5 million people in the province infected with LF; among which almost 2.5 million people had lymphedema, elephantiasis, or hydrocele. Through vigorous prevention and scientific research, Shandong Province was the first to propose to treat LF with fortified diethylcarbamazine salt, more than 25 million people in the province had taken the salt, and more than 3 million people took intermittent medication. After more than 50 years of unremitting efforts, Shandong Province basically eliminated LF in 1983 and became the first province in China that successfully eradicated LF in 2004, which has played an important role in accelerating the elimination of filariasis in the country in 2007 and has made tremendous contributions to social and economic development of China. Since 1980, Shandong Province has carried out extensive international cooperation as the WHO Collaborating Center for Lymphatic Filariasis. This article is intended to share the experience in eliminating LF to other parts of the world and improve public health capacity in regions such as Africa and Oceania where the disease is still endemic for interest.

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

BACKGROUND: The insecticidal efficacy of selected mosquito larvicides [teflubenzuron, S-methoprene, diflubenzuron, temephos, Bacillus thuringiensis var. israelensis (Bti) and polydimethylsiloxane (PDMS)], applied alone or in combination, against two Culex pipiens biotypes, Cx. p. pipiens and Cx. p. molestus, was compared under laboratory and semi-field conditions. Registered larvicides were evaluated at the label dose, whereas those not registered for mosquito control were tested at the label dose per area, i.e. as plant protection products. Teflubenzuron and temephos were also evaluated at half the label dose, alone or in combination with a non-ionic surfactant. Larval mortality and adult emergence were assessed after 1, 3, 5, 7, 9, 11, 16 and 20 days of exposure. RESULTS: In all cases, PDMS showed complete (100%) larval control after 3 days of exposure against both biotypes. With temephos, all larvae were dead after 1 day of exposure, even at half the label dose. For teflubenzuron, mortality reached 100% at the end of the bioassays and adult emergence was avoided completely, whereas for diflubenzuron, mortality was close to 100% at the end of the trials. By contrast, in S-methoprene-treated water, control was below the 90% mortality threshold for both biotypes. In semi-field trails, in all treatments with Bti, all larvae of both biotypes were dead after 1 day of exposure. CONCLUSIONS: Based on our data, and with the exception of S-methoprene, the larvicides tested remained below the threshold for effective treatment against larvae of Cx. p. pipiens and Cx. p. molestus for the entire duration of the study. Most of the larvicides tested showed high levels of efficacy against Cx. p. pipiens and Cx. p. molestus larvae in laboratory and semi-field bioassays. © 2020 Society of Chemical Industry.

Entomological Assessment of the Status and Risk of Mosquito-borne Arboviral Transmission in Ghana.

Entomological surveillance is one of the tools used in monitoring and controlling vector-borne diseases. However, the use of entomological surveillance for arboviral infection vector control is often dependent on finding infected individuals. Although this method may suffice in highly endemic areas, it is not as effective in controlling the spread of diseases in low endemic and non-endemic areas. In this study, we examined the efficiency of using entomological markers to assess the status and risk of arbovirus infection in Ghana, which is considered a non-endemic country, by combining mosquito surveillance with virus isolation and detection. This study reports the presence of cryptic species of mosquitoes in Ghana, demonstrating the need to combine morphological identification and molecular techniques in mosquito surveillance. Furthermore, although no medically important viruses were detected, the importance of insect-specific viruses in understanding virus evolution and arbovirus transmission is discussed. This study reports the first mutualistic relationship between dengue virus and the double-stranded RNA Aedes aegypti totivirus. Finally, this study discusses the complexity of the virome of Aedes and Culex mosquitoes and its implication for arbovirus transmission.

Effects of Mosquito Microbiota on the Survival Cost and Development Success of Avian Plasmodium.

Both intrinsic and extrinsic factors affect the capacity of mosquitoes for the transmission of vector-borne pathogens. Among them, mosquito microbiota may play a key role determining the development of pathogens in mosquitoes and the cost of infections. Here, we used a wild avian malaria-mosquito assemblage model to experimentally test the role of vector microbiota on the cost of infection and their consequences for parasite development. To do so, a cohort of Culex pipiens mosquitoes were treated with antibiotics, including gentamicin sulfate and penicillin-streptomycin, to alter their microbiota, and other cohort was treated with sterilized water as controls. Subsequently, both cohorts were allowed to feed on Plasmodium infected or uninfected house sparrows (Passer domesticus). The antibiotic treatment significantly increased the survival rate of mosquitoes fed on infected birds while this was not the case of mosquitoes fed on uninfected birds. Additionally, a higher prevalence of Plasmodium in the saliva of mosquitoes was found in antibiotic treated mosquitoes than in mosquitoes of the control group at 20 days post exposure (dpe). Analyses of the microbiota of a subsample of mosquitoes at 20 dpe suggest that although the microbiota diversity did not differ between individuals of the two treatments, microbiota in control mosquitoes had a higher number of unique features and enriched in biochemical pathways related to the immune system than antibiotic treated ones. In sum, this study provides support for the role of mosquito microbiota on mosquito survival and the presence of parasite DNA in their saliva.

Assessment of Synthetic Membranes for Artificial Blood Feeding of Culicidae.

Potential pathogen transmission through hematophagy in Culicidae is a major public-health problem, and several studies have been performed to better understand this phenomenon. Research on these insects often requires the maintenance of colonies in the laboratory. Due to the hematophagic habits of these organisms, blood must be provided in order to guarantee the reproduction of individuals that constitute the colonies. Some species of mammals and birds are used as a direct blood source in many laboratories. Due to current bioethical parameters, the direct use of animals has been replaced by artificial blood feeding by using synthetic membranes to simulate animal skin. In this study, the efficiency of collagen and latex in the artificial feeding of mosquitoes of the Aedes aegypti and Culex quinquefasciatus species was evaluated and compared with Parafilm®, a standard membrane that is frequently used for this purpose. Important aspects of the feeding and reproduction of these insects were considered. For both species, latex showed the poorest performance. Collagen membrane performed well in most parameters, but was not as efficient as Parafilm® for fecundity in Aedes aegypti, and for the percentage of engorged females in Culex quinquefasciatus. We concluded that, although collagen is more resistant and easier to handle, Parafilm® was the most efficient among the three evaluated membranes for the artificial blood feeding of mosquitoes.

Assessment of Culex pipiens bioforms in the world's southernmost distribution limit

The mosquito Culex pipiens s.s. L. occurs as two bioforms that differ in physiology and behaviour affecting virus transmission cycles. To assess the occurrence of Cx. pipiens bioforms in the southernmost limit of its distribution, specimens were collected aboveground in southern Buenos Aires Province and east Patagonia, Argentina. Ten larvae and 25 adults were individually processed and identified by polymerase chain reaction (PCR) amplification of Ace-2 and CQ11 loci. Culex quinquefasciatus Say (one larva, two adults), Cx. pipiens f. molestus (one larva, one adult) and one adult of hybrid origin were identified in Buenos Aires Province; only Cx. pipiens f. molestus was recorded in Patagonia (eight larvae, 21 adults). The potential absence of bioform pipiens and its implications in arbovirus enzootic cycles is discussed.

Environmental and Sociological Factors Associated with the Incidence of West Nile Virus Cases in the Northern San Joaquin Valley of California, 2011-2015.

Environmental and socioeconomic risk factors associated with the incidence of human West Nile virus (WNV) cases were investigated in the Northern San Joaquin Valley region of California, a largely rural area. The study included human WNV cases from the years 2011 to 2015 in the three-county area of San Joaquin, Stanislaus, and Merced Counties, and used census tracts as the unit of analysis. Environmental factors included temperature, precipitation, and WNV-positive mosquito pools. Socioeconomic variables included age, housing age, housing foreclosures, median income, and ethnicity. Chi-square independence tests were used to examine whether each variable was associated with the incidence of WNV cases using data from the three counties combined. In addition, negative binomial regression revealed that the environmental factors of temperature and precipitation were the strongest predictors of the incidence of human WNV cases, while the socioeconomic factor of ethnicity was a significant predictor as well, and is a factor to consider in prevention efforts. Source reduction of mosquito breeding sites and targeted prevention and education remain key in reducing the risk associated with WNV.

Isolation and growth inhibition potential of entomopathogenic nematodes against three public health important mosquito vectors.

The prevalence of mosquito vector borne diseases and the resistance of mosquitoes to conventional pesticides have been of important public concern to the mosquito endemic countries. Present study was conducted to identify the native bio-larvicidal potential of the entomopathogenic nematodes; Steinernema siamkayai (KPR-4) Heterohabditis indica (KPR-8), Steinernema glaseri and Steinernema abbasi. The isolated nematodes were subsequently cultured and evaluated their larvicidal potential against the larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Among the tested four different nematode species, the S. abassi exerted the highest mortality against A. aegypti (97.33%), the H. indica (KPR-8) against A. stephensi (97.33%) and the S. siamkayai (KPR-4) against C. quinquefasciatus (98.67%). The maximal mosquito-larvicidal property of EPNs was found with the LC50 and LC90 values (IJs/larvae): S. abbasi = 12.47 & 54.35 on A. aegypti; H. indica KPR-8 = 19.88 & 66.81 on A. stephensi and S. siamkayai KPR-4 = 16.69 & 58.97 on C. quinquefasciatus, respectively. The presently generated data on the molecular and larvicidal characteristics of the entomopathogenic nematodes form an important baseline data that upon further research would lead to the development of eco-friendly mosquito-control agent.

Assessment of vector competence of UK mosquitoes for Usutu virus of African origin.

BACKGROUND: Usutu virus (USUV) is an emerging zoonotic virus originally from sub-Saharan Africa. It has been introduced into Europe on multiple occasions, causing substantial mortality within the Eurasian blackbird (Turdus merula) population. It is transmitted by the mosquito species Culex pipiens in Europe and Africa. Vector competence studies indicate that European strains of USUV are readily transmitted by indigenous Cx. pipiens. However, there is limited information on the ability of an African strain to infect European mosquitoes. METHODS: We evaluated the ability of African strain SAAR-1776 to infect two lines of Cx. pipiens colonised within the United Kingdom (UK). Mosquitoes were fed blood meals containing this virus and maintained at 25 °C for up to 21 days. Individual mosquitoes were tested for the presence of virus in the body, legs and an expectorate saliva sample. Changes to the consensus of the virus genome were monitored in samples derived from infected mosquitoes using amplicon based next generation sequencing. RESULTS: Infection, dissemination and the presence of virus in saliva in one mosquito line was observed, but no evidence for dissemination in the second mosquito line. This suggests a strong barrier to infection in UK Cx. pipiens for this strain of USUV. When comparing the genome of input virus within the blood meal with USUV recovered from an infected mosquito, we observed limited changes in the consensus genome sequence. CONCLUSIONS: The evaluation of vector competence of UK populations of Cx. pipiens for Usutu virus suggests a limited susceptibility to infection with USUV strain SAAR-1776 of African origin. However, within a single mosquito there was complete dissemination and expectoration of USUV, indicating that infection, and potentially transmission, is possible. Sequence changes were observed that may represent early adaption to the mosquito host and could reflect the early events of USUV establishment in European mosquito populations.