Populations Of Ae Research Articles

Invazivne vrste komaraca (Diptera: Culicidae) u Srbiji

Invasive mosquito species surveillance has been carried out in Europe since late 1990s, and the results revealed that their distribution range and population density have been increasing every year (ECDC, 2020). Majority of European countries are affected by at least one of invasive mosquito species, which are considered as important vector species of public health concern. Aedes invasive species are very aggressive daily biters and highly competitive with native mosquito species coexisting in the same breeding sites. Although pathogens transmitted by mosquitoes are much bigger problem in tropical areas, imported and autothonous cases of these diseases have been recorded every year in Europe. International and intercontinental transport of humans and goods increase the likely-hood of outbreaks caused by vector-borne pathogens. Cases of imported invasive mosquito species and cases of imported human infection (with Dengue and Chikungunya virus, imported and autohtonous) are increasing every year. Together with the presence of invasive mosquito species, outbreaks caused by vector-borne pathogens are significantly driven by human behaviour, ecosystem and climat changes. Two invasive mosquito species were present in Serbia so far: Aedes albopictus (Asian tiger mosquito) and Aedes japonicus (Japaneese bush mosquito). Populations of Ae. albopicus has been succesfully spreading in many urban and suburban areas in our country, while Ae. japonicus was identified in only two localities up today. According to the experience from Croatia, where this mosquito species is widely spread, similar scenario could be expected in Serbia as well.

Typical Gastroesophageal Reflux Disease in the General Adult Population in Cotonou: Prevalence and Associated Socio-Demographic Factors

Introduction: Gastroesophageal Reflux Disease (GERD) is a common benign condition with a worldwide prevalence of between 5% and 45% in the adult population. Its prevalence in the general population is little known in Africa. The aim of this work was to study the prevalence of typical GERD in the general adult population of a large city and the associated socio-demographic factors. Patients and Methods: This was a prospectively collected, descriptive and analytical cross-sectional study that was conducted over a one-month period (June 2018). We included any person residing in the city of Cotonou for at least 6 months, aged 15 years or older, who had given consent for the study. The two-stage cluster sampling technique was used. The dependent variable was the typical gastroesophageal reflux defined by the heatburn-regurgitation association. Results: We had included 728 subjects. Of these, 255 had a typical GERD, i.e. a prevalence of 35%. The mean age of the respondents was 31.9 ± 13.2 years with extremes of 15 and 88 years. There were 379 men (52.1%) with a sex ratio of 1.08. The study population was represented respectively by artisans (29.3%), students (26.6%) and traders/dealers (20.3%). In terms of marital status, there were as many married and single subjects (48.2%). In addition, 47% of the study population had a body mass index of less than 25 kg/m2. In univariate analysis, the sociodemographic factors associated with typical GERD were: age (60 years and older): OR: 0.220 [95% CI 07 - 0.63], p = 0.005 and marital status divorced/separated/widowed: OR: 0.32 [0.11 - 0.97], p = 0.04. Older age and divorced/separated/widowed status appear to be protective of the occurrence of GERD. Conclusion: Typical GERD was common in the adult population of Cotonou. It readily affected young (under 60 years of age), single or married subjects.

Ovitrap Surveillance of the Dengue Vectors Aedes aegypti and Aedes albopictus in Selected Endemic Areas in Sandakan, Sabah

Ovitrap technique could be considered an efficient tool for monitoring of Aedes populations. This study aimed to monitor the dengue vector population and to provide baseline data of vector density in selected endemic areas. 1600 ovitraps were placed indoor and outdoor randomly in selected houses from January till July 2014 at eight selected localities. 96%–100% of ovitraps were recovered after seven days. In total, 9399 larvae were examined of which 2674 (28.2%) were Ae. Aegypti and 6752 (71.8%) Ae. albopictus. Ae. albopictus were dominant than Ae. aegypti in every locality. Highest collection of Ae. albopictus was recorded in Kampung Air (total larvae = 1357), followed by Kampung Bokara (total larvae = 1165) and Taman Fajar (total larvae = 846). Three main localities that recorded highest collection of Ae. aegypti were Kampung Bokara (total larvae = 504), Kampung Air (total larvae = 457) and Taman Fajar (total larvae = 341). Ae. albopictus was found more abundant compared to Ae. aegypti. The ovitrap index recorded in all localities (ranged 18.0% - 59.0%) was more than the transmission threshold (10%). Mix breeding of Ae. aegypti and Ae. albopictus were also detected for outdoor ovitraps. In conclusion, this study found that selected localities in Sandakan district have a high risk for transmission and outbreaks of dengue. Furthermore, this study also provided a baseline data of Aedes density for further planning of prevention and control activities.

Monitoring Aedes Population using Ovitrap Index and Larval Abundance in an Urban University Residence

Autocidal ovitraps have played a significant role in surveillance and control of dengue vectors, Aedes aegypti and Aedes albopictus. Malaysia has witnessed the deployment of several types of autocidal ovitraps, which includes the Mosquito Larvae Trapping Device (MLTD) introduced by Kuala Lumpur City Hall. This study aimed to assess Aedes larval abundance and local meteorological variables in a university residence, in Cheras, Kuala Lumpur. MLTD (n=30) baited with organic NPK fertiliser (5:5:5) solutions were deployed. Larvae collection and trap servicing were performed weekly for a duration of eight weeks. Rearing and species identification for larvae were conducted in the laboratory. Out of 2,152 Aedes larvae, 85% of them were Ae. albopictus whilst the remaining were Ae. aegypti. Outdoor collection of Ae. albopictus surpassed its indoor collection (mean larvae per trap of 9.28 versus 6.08). Conversely, an indoor collection of Ae. aegypti was greater than its outdoor collection (mean larvae per trap of 1.72 versus 0.86). The highest ovitrap indices were observed in Week 5 and 6 which were 90% and 93%, respectively. Week 1 had the lowest ovitrap index, 30%. Our analyses revealed a positive correlation between Aedes larval abundance and maximum temperature (r=0.830, p=0.011) whereas minimum relative humidity was shown to have a negative correlation (r=-0.778, p=0.023), with the larval abundance. Routine monitoring of dengue vectors at its immature stages can provide information on the density and fluctuation of the local mosquito population. Coupled with concurrent meteorological variables, it can guide vector control operations as part of dengue prevention strategies.

Detection of Cell-Fusing Agent virus across ecologically diverse populations of Aedes aegypti on the Caribbean island of Saint Lucia.

Background. Outbreaks of mosquito-borne arboviral diseases including dengue virus (DENV), Zika virus (ZIKV), yellow fever virus (YFV) and chikungunya virus (CHIKV) have recently occurred in the Caribbean. The geographical range of the principal vectors responsible for transmission, Aedes (Ae.) aegypti and Ae. albopictus are increasing and greater mosquito surveillance is needed in the Caribbean given international tourism is so prominent. The island of Saint Lucia has seen outbreaks of DENV and CHIKV in the past five years but vector surveillance has been limited with the last studies dating back to the late 1970s. Natural disasters have changed the landscape of Saint Lucia and the island has gone through significant urbanisation. Methods. In this study, we conducted an entomological survey of Ae. aegypti and Ae. albopictus distribution across the island and analysed environmental parameters associated with the presence of these species in addition to screening for medically important arboviruses and other flaviviruses. Results. Although we collected Ae. aegypti across a range of sites across the island, no Ae. albopictus were collected despite traps being placed in diverse ecological settings. The number of Ae. aegypti collected was significantly associated with higher elevation, and semi-urban settings yielded female mosquito counts per trap-day that were five-fold lower than urban settings. Screening for arboviruses revealed a high prevalence of cell-fusing agent virus (CFAV). Conclusions. Outbreaks of arboviruses transmitted by Ae. aegypti and Ae. albopictus have a history of occurring in small tropical islands and Saint Lucia is particularly vulnerable given the limited resources available to undertake vector control and manage outbreaks. Surveillance strategies can identify risk areas for predicting future outbreaks. Further research is needed to determine the diversity of current mosquito species, investigate insect-specific viruses, as well as pathogenic arboviruses, and this should also be extended to the neighbouring smaller Caribbean islands.

Detection of Cell-Fusing Agent virus across ecologically diverse populations of Aedes aegypti on the Caribbean island of Saint Lucia

Background. Outbreaks of mosquito-borne arboviral diseases including dengue virus (DENV), Zika virus (ZIKV), yellow fever virus (YFV) and chikungunya virus (CHIKV) have recently occurred in the Caribbean. The geographical range of the principal vectors responsible for transmission, Aedes (Ae.) aegypti and Ae. albopictus are increasing and greater mosquito surveillance is needed in the Caribbean given international tourism is so prominent. The island of Saint Lucia has seen outbreaks of DENV and CHIKV in the past five years but vector surveillance has been limited with the last studies dating back to the late 1970s. Natural disasters have changed the landscape of Saint Lucia and the island has gone through significant urbanisation. Methods. In this study, we conducted an entomological survey of Ae. aegypti and Ae. albopictus distribution across the island and analysed environmental parameters associated with the presence of these species in addition to screening for medically important arboviruses and other flaviviruses. Results. Although we collected Ae. aegypti across a range of sites across the island, no Ae. albopictus were collected despite traps being placed in diverse ecological settings. The number of Ae. aegypti collected was significantly associated with higher elevation, and semi-urban settings yielded female mosquito counts per trap-day that were five-fold lower than urban settings. Screening for arboviruses revealed a high prevalence of cell-fusing agent virus (CFAV). Conclusions. Outbreaks of arboviruses transmitted by Ae. aegypti and Ae. albopictus have a history of occurring in small tropical islands and Saint Lucia is particularly vulnerable given the limited resources available to undertake vector control and manage outbreaks. Surveillance strategies can identify risk areas for predicting future outbreaks. Further research is needed to determine the diversity of current mosquito species, investigate insect-specific viruses, as well as pathogenic arboviruses, and this should also be extended to the neighbouring smaller Caribbean islands.

RADIAL METAPHYSIS FRACTURES;

Greenstick / torus fracture of distal radial metaphysis are quite common inchildren. It has been seen that these fractures are stable and splintage is necessary for comfort and pain relief.Objectives: To reduce the number of visits to clinics, which is logistically difficult in a rural community population ofa large catchment’s area. Design Prospectively Setting: Accident , Emergency and orthopaedics Departments,General Hospital Letterkenny. Patients & Materials: 65 cases with green stick fractures treated with Soft cast, whichwas easily removable at home. Results: All patients in this study showed good results with no complications. Theparent satisfaction rate was 97.3%. Conclusions: Our findings suggest that it is clinically safe, cost effective andconvenient to parents to treat undisplaced green stick fractures within the community.

Vector–Borne infections in Pakistan do not come alone

Background: From 1995 till 2019, around 147,200 cases of dengue infection and more than 800 deaths are reported from Pakistan. Vector of dengue virus is mosquito Aedes which is capable of transmitting other viral infections like Chikungunya, Zika, and Yellow Fever. From 2016–2018, Chikungunya infection was reported in 776 patients. With exponential increase in population and utilization of resources, it is important to eradicate this mosquito. Methods and materials: The present study provides an in-depth analysis on the factors, both virological and environmental, responsible for making dengue infection and its vector Aedes endemic in Pakistan. For this study, phylogeographic analysis of dengue, and Chikungunya virus was conducted using BEAST program. Coalescent GMRF Bayesian Skyride and Brownian Random Walk model was selected as continuous traits substitution model. Data was collected to relate vector distribution, and conditions responsible in increasing Aedes population. Results: The Chikungunya virus in Pakistan originated from the nodes of Madhya Pradesh and Rajasthan, India in 2015. This virus spread in Malir, Karachi and in Bahawalpur, Punjab, Pakistan in 2016. CHIKV strains of Pakistan resemble Indian strains due to their origin. Dengue strains are closely related to Indian and Chinese isolates. Pakistan being the fifth most populous country with density population of 281, Comoros2, the main cities of Karachi and Hyderabad in Sind province; Lahore and Faisalabad in Punjab province; and Islamabad/Rawalpindi of federal area and Peshawar of KP make up 22 million of population. Climatic change is not the only factor responsible for increased vector population in areas. Other global change factors including, growing population, agriculture, deforestation, and urbanization equally and significantly contribute to spread of mosquitoes. All these factors add to breeding of Aedes mosquito in any region. Previously a dweller of greenery, this mosquito became domesticated through extensive travel and trade in different areas of Pakistan. Conclusion: First dengue became endemic in Pakistan, then Chikungunya was isolated form Pakistan. Each year resurfacing of dengue infection points towards future danger of spreading of other Aedes borne infections in Pakistan. It is not impossible to say that soon Zika infections will be reported from Pakistan.

Insecticide resistance status of Aedes aegypti in Bangladesh

BackgroundArboviral diseases, including dengue and chikungunya, are major public health concerns in Bangladesh where there have been unprecedented levels of transmission reported in recent years. The primary approach to control these diseases is to control the vector Aedes aegypti using pyrethroid insecticides. Although chemical control has long been practiced, no comprehensive analysis of Ae. aegypti susceptibility to insecticides has been conducted to date. The aim of this study was to determine the insecticide resistance status of Ae. aegypti in Bangladesh and investigate the role of detoxification enzymes and altered target site sensitivity as resistance mechanisms.MethodsEggs of Aedes mosquitoes were collected using ovitraps from five districts across Bangladesh and in eight neighborhoods of the capital city Dhaka, from August to November 2017. CDC bottle bioassays were conducted for permethrin, deltamethrin, malathion, and bendiocarb using 3- to 5-day-old F0–F2 non-blood-fed female mosquitoes. Biochemical assays were conducted to detect metabolic resistance mechanisms, and real-time PCR was performed to determine the frequencies of the knockdown resistance (kdr) mutations Gly1016, Cys1534, and Leu410.ResultsHigh levels of resistance to permethrin were detected in all Ae. aegypti populations, with mortality ranging from 0 to 14.8% at the diagnostic dose. Substantial resistance continued to be detected against higher (2×) doses of permethrin (5.1–44.4% mortality). Susceptibility to deltamethrin and malathion varied between populations while complete susceptibility to bendiocarb was observed in all populations. Significantly higher levels of esterase and oxidase activity were detected in most of the test populations as compared to the susceptible reference Rockefeller strain. A significant association was detected between permethrin resistance and the presence of Gly1016 and Cys1534 homozygotes. The frequency of kdr (knockdown resistance) alleles varied across the Dhaka Aedes populations. Leu410 was not detected in any of the tested populations.ConclusionsThe detection of widespread pyrethroid resistance and multiple resistance mechanisms highlights the urgency for implementing alternate Ae. aegypti control strategies. In addition, implementing routine monitoring of insecticide resistance in Ae. aegypti in Bangladesh will lead to a greater understanding of susceptibility trends over space and time, thereby enabling the development of improved control strategies.Graphical

Vector Competence of Aedes aegypti Populations from Entebbe, Uganda, for Zika Virus.

We evaluated the vector competence of three strains of Aedes aegypti formosus from Entebbe, Uganda, for Zika virus (ZIKV). The aim was to find out if these strains were competent or incompetent vectors for ZIKV, to explain the lack of ZIKV outbreaks in the city of Entebbe. We observed transmission rates ranging from 33% to 78%; however, these rates were not statistically significantly different, suggesting that there were no real differences among the strains. Nonetheless, this showed that populations of Ae. aegypti formosus in Entebbe are competent vectors for ZIKV. The reason why there is no detectable transmission of ZIKV to humans in Entebbe is currently unknown. The lack of detectable transmission despite Ae. aegypti formosus competence for ZIKV suggests that other parameters, such as preference for nonhuman blood, may be limiting its ability to serve as a vector.

Mosquito Diversity and Population Genetic Structure of Six Mosquito Species From Hainan Island.

Hainan is a tropical island in southern China with abundant mosquito species, putting Hainan at risk of mosquito-borne virus disease outbreaks. The population genetic diversity of most mosquito species on Hainan Island remains elusive. In this study, we report the diversity of mosquito species and the genetic diversity of the predominant species on Hainan. Field populations of adults or larvae were collected from 12 regions of Hainan Island in 2018 and 2019. A fragment of the mitochondrial cytochrome c oxidase subunit I (coxI) gene was sequenced from 1,228 mosquito samples and used for species identification and genetic diversity analysis. Twenty-three known mosquito species from the genera Aedes, Armigeres, Culex, Mansonia, and Anopheles and nine unconfirmed mosquito species were identified. Aedes albopictus, Armigeres subalbatus, and Culex pipiens quinquefasciatus were the most prevalent mosquito species on Hainan. The regions north of Danzhou, Tunchang, and Qionghai exhibited high mosquito diversity (26 species). The order of the total haplotype diversity and nucleotide diversity of the populations from high to low was as follows: Culex tritaeniorhynchus, Ar. subalbatus, Culex pallidothorax, Culex gelidus, Ae. albopictus, and C. p. quinquefasciatus. Tajima’s D and Fu’s Fs tests showed that Ae. albopictus, C. p. quinquefasciatus, C. tritaeniorhynchus, and C. gelidus had experienced population expansion, while the Ar. subalbatus and C. pallidothorax populations were in genetic equilibrium. Significant genetic differentiation existed in the overall populations of Ae. albopictus, Ar. subalbatus, C. p. quinquefasciatus, and C. pallidothorax. The Ae. albopictus populations on Hainan were characterized by frequent gene exchange with populations from Guangdong and four other tropical countries, raising the risk of viral disease outbreaks in these regions. Two subgroups were reported in the Ar. subalbatus populations for the first time. Our findings may have important implications for vector control on Hainan Island.

Variation in the susceptibility of urban Aedes mosquitoes infected with a densovirus

Urban Aedes mosquitoes are vectors of many viruses affecting human health such as dengue, chikungunya and Zika viruses. Insecticide resistance and environmental toxicity risks hamper the effectiveness of chemical control against these mosquito vectors. Alternative control methods, such as the use of mosquito-specific entomopathogenic viruses should be explored. Numerous studies have focused on evaluating the potential of different densoviruses species as biological control agents. However, knowledge on the extent of inter- and intra-specific variations in the susceptibility of Aedes mosquitoes to infection by different densoviruses remains insufficient. In this study, we compared infection and mortality rates induced by the Aedes albopictus densovirus 2 in different strains of Aedes albopictus and Aedes aegypti mosquitoes. The two Aedes species were different in terms of susceptibility to viral infection. Under laboratory conditions, Aedes albopictus densovirus 2 appeared more virulent for the different strains of Aedes aegypti tested than for those of Aedes albopictus. In addition, we also found significant intra-specific variation in infection and mortality rates. Thus, although even if Aedes albopictus densoviruses could be powerful biocontrol agents used in the management of urban Aedes populations, our results also call into question the use of single viral isolate as biocontrol agents.

Landscape and Anthropogenic Factors Associated with Adult Aedes aegypti and Aedes albopictus in Small Cities in the Southern Great Plains.

Simple SummaryMosquito-borne diseases are a growing human health concern in the United States. While recent studies have updated the distribution of Aedes aegypti in southern Great Plains, little is known about what factors can be used to predict where important mosquito species thrive in the region. The aim of the study assessed different factors associated with encountering adult container-breeding mosquitoes in small cities in southern Oklahoma. Collections using two types of traps were carried out over a ten week period from June to August 2017 along two geographical transects, each consisting of three cities, equally distant from the Red River/Texas border. After five rounds of collection, 6628 female mosquitoes were collected from 242 commercial or residential sites in six cities. Of the mosquitoes collected, 80% consisted of container-breeding species. Regionally, Ae. aegypti was most likely to be collected in cities closest to the Texas border while Aedes albopictus was spread throughout the region. In general, Ae. aegypti and Ae. albopictus were more associated with residential sites or sites featuring no or low vegetation. The study highlighted important factors involved in the distribution of Ae. aegypti and Ae. albopictus in small cities in the southern Great Plains.As mosquito-borne diseases are a growing human health concern in the United States, the distribution and potential arbovirus risk from container-breeding Aedes mosquitoes is understudied in the southern Great Plains. The aim of the study was to assess landscape and anthropogenic factors associated with encountering adult container-breeding mosquitoes in small cities in southern Oklahoma. Collections were carried out over a 10 week period from June to August 2017 along two geographical transects, each consisting of three cities, equally distant from the Red River/Texas border. Mosquitoes were collected weekly using two trap types along with data for 13 landscape, vegetation, and anthropogenic variables. After five rounds of collection, 6628 female mosquitoes were collected over 2110 trap-nights involving 242 commercial or residential sites in six cities. Of the mosquitoes collected, 80% consisted of container-breeding species: Aedes albopictus (72%), Culex pipiens complex (16%) and Aedes aegypti (8%). Regionally, Aedes aegypti was more likely present in cities closest to the Texas border while Ae. albopictus was spread throughout the region. In general, Ae. aegypti and Ae. albopictus were significantly more present in sites featuring no or low vegetation and residential sites. Variables associated with Ae. albopictus presence and abundance varied between cities and highlighted the urban nature of the species. The study highlighted the distribution of Ae. aegypti geographically and within the urban context, indicated potential habitat preferences of container-breeding mosquito species in small towns, and demonstrated the usefulness of Gravid Aedes traps (GAT) traps for monitoring Aedes populations in urban habitats in small cities.

Mechanisms associated with pyrethroid resistance in populations of Aedes aegypti (Diptera: Culicidae) from the Caribbean coast of Colombia.

Aedes aegypti is the main vector of dengue, chikungunya, and Zika viruses, which are of great public health importance in Colombia. Aedes control strategies in Colombia rely heavily on the use of organophosphate and pyrethroid insecticides, providing constant selection pressure and the emergence of resistant populations. In recent years, insecticide use has increased due to the increased incidence of dengue and recent introductions of chikungunya and Zika. In the present study, pyrethroid resistance was studied across six populations of Ae. aegypti from the Caribbean coast of Colombia. Susceptibility to λ-cyhalothrin, deltamethrin, and permethrin was assessed, and resistance intensity was determined. Activity levels of enzymes associated with resistance were measured, and the frequencies of three kdr alleles (V1016I, F1534C, V410L) were calculated. Results showed variations in pyrethroid susceptibility across Ae. aegypti populations and altered enzyme activity levels were detected. The kdr alleles were detected in all populations, with high variations in frequencies: V1016I (frequency ranging from 0.15–0.70), F1534C (range 0.94–1.00), and V410L (range 0.05–0.72). In assays of phenotyped individuals, associations were observed between the presence of V1016I, F1534C, and V410L alleles and resistance to the evaluated pyrethroids, as well as between the VI1016/CC1534/VL410 tri-locus genotype and λ-cyhalothrin and permethrin resistance. The results of the present study contribute to the knowledge of the mechanisms underlying the resistance to key pyrethroids used to control Ae. aegypti along the Caribbean coast of Colombia.

Observations of an unexpected abundance of estuarine mosquitoes associated with an urban freshwater wetland

ABSTRACT Urban freshwater wetlands have been identified as a potential source of mosquitoes of pest and public health concern in Australia. Mosquitoes most commonly associated with these habitats include Anopheles annulipes, Culex annulirostris, Culex quinquefasciatus, Coquillettidia linealis and Mansonia uniformis. However, adaptive management of freshwater wetlands for wildlife conservation or vegetation management can alter the local environmental conditions and may provide opportunities for other mosquito species to exploit these habitats. A series of small wetlands at Sydney Olympic Park, NSW, were drained in spring 2016 and allowed to refill via rainfall to improve conditions for the endangered green and golden bell frog Litoria aurea. Below-average rainfall was experienced that summer and the wetlands did not fully refill until early autumn. Surprisingly, immature stages of the estuarine mosquito, Aedes vigilax, were observed in the freshwater wetlands in exceptional abundances during this period. Adjacent to these freshwater wetlands there are extensive saltmarsh and mangrove habitats where highly abundant populations of Ae. vigilax are common. Observations of use of freshwater habitats by this estuarine mosquito have implications for urban freshwater wetland management and rehabilitation strategies, which currently do not consider the potential pest and public health issues associated with estuarine mosquitoes.

Assessing the role of two populations of Aedes japonicus japonicus for Zika virus transmission under a constant and a fluctuating temperature regime

BackgroundSince the huge epidemic of Zika virus (ZIKV) in Brazil in 2015, questions were raised to understand which mosquito species could transmit the virus. Aedes aegypti has been described as the main vector. However, other Aedes species (e.g. Ae. albopictus and Ae. japonicus) proven to be competent for other flaviviruses (e.g. West Nile, dengue and yellow fever), have been described as potential vectors for ZIKV under laboratory conditions. One of these, the Asian bush mosquito, Ae. japonicus, is widely distributed with high abundances in central-western Europe. In the present study, infection, dissemination and transmission rates of ZIKV (Dak84 strain) in two populations of Ae. japonicus from Switzerland (Zürich) and France (Steinbach, Haut-Rhin) were investigated under constant (27 °C) and fluctuating (14–27 °C, mean 23 °C) temperature regimes.ResultsThe two populations were each able to transmit ZIKV under both temperature regimes. Infectious virus particles were detected in the saliva of females from both populations, regardless of the incubation temperature regime, from 7 days post-exposure to infectious rabbit blood. The highest amount of plaque forming units (PFU) (400/ml) were recorded 14 days post-oral infection in the Swiss population incubated at a constant temperature. No difference in terms of infection, dissemination and transmission rate were found between mosquito populations. Temperature had no effect on infection rate but the fluctuating temperature regime resulted in higher dissemination rates compared to constant temperature, regardless of the population. Finally, transmission efficiency ranged between 7–23% and 7–10% for the constant temperature and 0–10% and 3–27% under fluctuating temperatures for the Swiss and the French populations, respectively.ConclusionsTo the best of our knowledge, this is the first study confirming vector competence for ZIKV of Ae. japonicus originating from Switzerland and France at realistic summer temperatures under laboratory conditions. Considering the continuous spread of this species in the northern part of Europe and its adaptation at cooler temperatures, preventative control measures should be adopted to prevent possible ZIKV epidemics.

Analysis of a stage-dependent epidemic model based on a non-Markov random process

We present some stochastic model of an infection spread among the adult population of a certain region. The model bases on a random birth and death process supplemented by the point distributions that reflect the durations of stay of individuals at various stages of the disease. The durations of some stages of the disease are assumed constant. The model is a stochastic analog of a system of delay differential equations and convolution integral equations describing the infection spread in the deterministic approach. We address the problem of the infection eradication over a time span comparable to the average lifetime of several generations of individuals. The results of computational experiments are presented, where the dynamics of mathematical expectations of the size of certain groups of individuals is studied and the probability of the infection eradication over a finite time span is estimated using the Monte Carlo method.

Sunshine versus gold: The effect of population age on genetic structure of an invasive mosquito.

The genetic diversity and structure of invasive species are affected by the time since invasion, but it is not well understood how. We compare likely the oldest populations of Aedes aegypti in continental North America with some of the newest to illuminate the range of genetic diversity and structure that can be found within the invasive range of this important disease vector. Aedes aegypti populations in Florida have probably persisted since the 1600‐1700s, while populations in southern California derive from new invasions that occurred in the last 10 years. For this comparison, we genotyped 1,193 individuals from 28 sites at 12 highly variable microsatellites and a subset of these individuals at 23,961 single nucleotide polymorphisms (SNPs). This is the largest sample analyzed for genetic structure for either region, and it doubles the number of southern California populations previously analyzed. As predicted, the older populations (Florida) showed fewer indicators of recent founder effect and bottlenecks; in particular, these populations have dramatically higher genetic diversity and lower genetic structure. Geographic distance and driving distance were not good predictors of genetic distance in either region, especially southern California. Additionally, southern California had higher levels of genetic differentiation than any comparably sized documented region throughout the worldwide distribution of the species. Although population age and demographic history are likely driving these differences, differences in climate and transportation practices could also play a role.

Gravitrap deployment for adult Aedes aegypti surveillance and its impact on dengue cases

House Index, Container Index, and Breteau Index are the most commonly used indices for dengue vector surveillance. However, these larval indices are a poor proxy for measuring the adult population—which is responsible for disease transmission. Information on the adult distribution and density are important for assessing transmission risk as well as for developing effective control strategies. This study introduces a new entomological index, Gravitrap aegypti index (GAI), which estimates the adult female Aedes aegypti population in the community and presents its association with dengue cases. Gravitraps were deployed across 34 treatment sites in Singapore from September 2013 to September 2016. The GAI, derived from the Gravitrap surveillance data, was analysed to investigate the spatio-temporal patterns of the Ae. aegypti population in Singapore. The index was further categorised into low, moderate, and high-risk groups and its association with dengue cases were examined. A Before-After Control Impact analysis was performed to evaluate the epidemiology impact of Gravitrap system on dengue transmission. The Ae. aegypti population exhibits a seasonal pattern, and spatial heterogeneity in Ae. aegypti abundance was observed among treatment sites. The Ae. aegypti population was also found to be unevenly distributed among floors of an apartment block, with low floors (floors 1–4) having a higher abundance of mosquitoes trapped than mid (floors 5–8) and high (floors ≥9) floors. Areas with high GAI were shown to have higher dengue case count. Gravitrap has also demonstrated to be a good dengue control tool. The contribution of cases by treatment sites to the national numbers was lower after Gravitraps deployment. The GAI, which is of better relevance to dengue transmission risk, could be recommended as an indicator for decision making in vector control efforts, and to monitor the spatio-temporal variability of the adult Aedes population in the country. In addition, findings from this study indicate that Gravitraps can be used as a dengue control tool to reduce dengue transmission.

Genome-Wide Screening of Aedes aegypti (Culicidae: Diptera) Populations From Northwestern Argentina: Active and Passive Dispersal Shape Genetic Structure.

Aedes aegypti is the primary vector of arboviruses of great impact on human health. Our goal was to assess the spatial genetic structure of Ae. aegypti at the regional and local levels in Northwestern Argentina, an area with high prevalence of dengue fever. We analyzed 59 Ae. aegypti individuals collected from six locations in Northwestern Argentina using nuclear genome-wide Single Nucleotide Polymorphisms (SNPs) generated with double digest Restriction-site Associated DNA Sequencing. We also performed an entomological survey in 70 households in the cities of Orán and Tartagal. An analysis at the regional level indicated that the populations of Ae. aegypti in Northwestern Argentina are spatially structured and present a significant IBD pattern. Our results suggest that passive transport of eggs/immature stages, in both northward and southward directions, plays an important role in structuring Ae. aegypti populations at a regional scale and also as a source for the introduction of novel genetic variants through migration events into established populations. At a local level, we found neither spatial genetic structure nor significant isolation by distance (IBD) in Tartagal, indicating high gene flow within the city and active dispersal. In contrast, samples from Orán formed two clusters with a significant IBD pattern, although weaker than that at a regional level. Both populations showed signs of recent bottleneck events, probably coincident with past eradication campaigns. The entomological survey revealed a high prevalence of Ae. aegypti in both cities, although significantly higher in Tartagal.