Dispersal Of Ae Research Articles

High Wind Speed Prevents the Establishment of the Disease Vector Mosquito Aedes albopictus in Its Climatic Niche in Europe

Environmentally suitable habitats ofAedes albopictus(Ae. albopictus) in Europe are identified by several modeling studies. However, it is noticeable that even after decades of invasion process in Europe, the vector mosquito has not yet been established in all its environmentally suitable areas. Natural barriers and human-mediated transport play a role, but the potential of wind speed to explainAe. albopictus’absences and its inability to establish in its suitable areas are largely unknown. This study therefore evaluates the potential of wind speed as an explanatory parameter of the non-occurrence ofAe. albopictus. We developed a global ecological niche model with relevant environmental parameters including wind speed and projected it to current climatic conditions in Europe.Differences in average wind speed between areas of occurrence and non-occurrence ofAe. albopictuswithin its modeled suitable areas were tested for significance. A second global ecological niche model was trained with the same species records and environmental parameters, excluding windspeed parameters. Using multiple linear regression analyses and a test of average marginal effect, the effect of increasing wind speed on the average marginal effect of temperature and precipitation on the projected habitat suitability was estimated. We found that climatically suitable and monitored areas whereAe. albopictusis not established (3.12 ms-1 ± 0.04 SD) have significantly higher wind speed than areas where the species is already established (2.54 ms-1 ± 0.04 SD). Among temperature-related bioclimatic variables, the annual mean temperature was the most important variable contributing to the performance of both global models. Wind speed has a negative effect on the predicted habitat suitability ofAe. albopictusand reduces false-positive rates in model predictions. With increasing wind speed, the average marginal effect of annual mean temperatures decreases but that of the annual precipitation increases. Wind speed should be considered in future modeling efforts aimed at limiting the spread and dispersal ofAe. albopictusand in the implementation of surveillance and early warning systems. Local-scale data collected from fieldwork or laboratory experiments will help improve the state of the art on how wind speed influences the distribution, flight, and dispersal activity of the mosquito.

Update on the Dispersal of Aedes albopictus in Mexico: 1988–2021

The Asian tiger mosquito Aedes albopictus (Skuse) is one of the most important mosquito species in public health due to the variety of disease-causing viruses that this species can transmit. In Mexico, Ae. albopictus was reported for the first time in 1990 in the state of Tamaulipas, bordering to the state of Texas (USA). Since then, Ae. albopictus has been reported in 15 Mexican states. Currently, this species is present in all tropical and subtropical regions of the country and its presence is common in the states of the Gulf of Mexico and Chiapas. In the present study, the presence of Ae. albopictus is reported in six additional states: Colima, Guanajuato, Jalisco, Puebla, Oaxaca, and Querétaro. The rapid dispersal of Ae. albopictus in Mexico represents a risk to public health, and the surveillance of this species in regions where it has not yet been reported is essential as part of Mexican entomological surveillance programs.

Population genetic dynamics of dengue vectors Aedes aegypti and Aedes albopictus in Sri Lanka: baseline study for designing Wolbachia control method

Dengue is an arboviral disease transmitted principally by two vectors Aedes aegypti and Aedes albopictus. In the absence of a successful prophylaxis or treatment, the disease control relies solely on vector control. Therefore, the knowledge on vector population genetics can play an important role in designing efficient vector control strategies especially during the release of Wolbachia transinfected mosquitoes. As such, we investigated the population genetic structure of Ae. aegypti and Ae. albopictus in Sri Lanka covering seven (Colombo, Gampaha, Kalutara, Galle, Jaffna, Mullathivu and Kilinochchi) dengue endemic regions using six microsatellite markers specific for each species to provide baseline data to implement Wolbachia control method. According to the results, both species revealed small but significant population structure. The genetic structure observed for Ae. albopictus populations was more subtle compared to that of Ae. aegypti reflecting their comparatively high geneflow over long distances. Evidence for possible multiple invasions towards the northern part of the country from the southern Ae. albopictus populations facilitated by increased human activity and urbanization were also apparent. On the contrary, the dispersal of Ae. aegypti was observed to be more restricted especially between north and south parts of the country. The genetic diversity and effective population number was also greater for Ae. albopictus compared to Ae. aegypti indicating their relatively higher evolutionary potential and adaptability. As a whole, our study suggests that the scheduled dengue control measurers using Wolbachia infected mosquitoes need to cover both vector species based on their species specific geneflow patterns to yield an effective dengue control.

Will the yellow fever mosquito colonise Europe? Assessing the re-introduction of Aedes aegypti using a process-based population dynamical model

Aedes aegypti are feared invasive mosquitoes as they transmit pathogens which cause debilitating diseases in humans. Although mainland Europe has not yet witnessed re-establishment and dispersal of Ae. aegypti populations, several urban areas along coastlines represent suitable habitats for the species. In addition, European coastal areas are characterised by high exotic species propagule pressure, due to dense international ship traffic.To assess the likelihood of establishment in order to guide surveillance and control planning, we applied a process-based population dynamical model to simulate both the life cycle and dispersal of Ae. aegypti at the local scale after its introduction through ship traffic. We selected five European ports along a latitudinal gradient by considering both environmental conditions and the economical importance of ports: Algeciras and Barcelona in Spain; Venice and Genoa in Italy and Rotterdam in the Netherlands. The model was informed using parameters relevant for Ae. aegypti biology, fine-scale temperature time-series, urban structures and road networks.According to model results, the introduction of small quantities of Ae. aegypti eggs (10−1000) has the potential to cause species establishment, high local densities and slow initial dispersal in the two southernmost study areas, Algeciras and Barcelona, whereas Genoa is at the edge of suitability. Barcelona had the highest simulated mosquito densities (584 females/ha), whereas Algeciras densities were never more than 32 females/ha, but were higher during the colder seasons. The median spatial spread of the species varied between a few hundred meters to 2 km/year and was affected by the structure of the road network, topography and urban sprawl along the coast in the surrounding of the port of introduction. The study areas of Genoa, Venice and Rotterdam were found not suitable for establishment of this mosquito species, however, climate change could create conditions for Ae. aegypti invasion in these regions in the next decades.It is commonly accepted that targeted monitoring and early control actions are the most effective methods to hinder the establishment of invasive species in new areas. Our findings and model framework may support surveillance initiatives for those European coastal urban areas which are known to have high propagule pressure and a high modelled probability of Ae. aegypti establishment.

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

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.

Quantifying Aedes aegypti dispersal in space and time: a modeling approach

AbstractThe dispersal of the invasive mosquito Aedes aegypti in urbanized areas has received attention due to the hazard that this species poses to human health. However, we know little about this process at temperate latitudes, especially in recently colonized semi‐arid regions of the southwestern United States that differ ecologically from more typical habitats in the tropics. We collected data on Ae. aegypti dispersal through a mark–release–recapture (MRR) study in Central California. We employed stable isotopes of carbon and nitrogen to mark released mosquitoes. We characterized Ae. aegypti dispersal capacity using both traditional measures of central tendency and dispersal kernel theory coupled with space–time models, allowing for effects of environmental factors to provide more reliable dispersal estimates. Dispersal of Ae. aegypti was similar between females and males, and we found the mean distances traveled to be 224–240 m from the release location when estimated by conventional methods. Model‐based inference allowed for a more nuanced interpretation, with even greater dispersal distances possible depending on direction and environmental context. Our results showed that experimental conditions, such as spatial arrangement of traps and duration of the recapture period, as well as environmental conditions, such as wind speed and direction, altered the probability of recapturing marked mosquitoes, and therefore the observed dispersal pattern. This represents the first assessment of Ae. aegypti dispersal in the semi‐arid southwestern United States, which is unique among published studies in that the period of peak annual Ae. aegypti abundance coincides with cumulative precipitation close to zero. Results show that this species dispersed on average farther than commonly documented for other areas of the world. Our findings provide information for defining spatial control strategies, such as incompatible insect technique, which rely on a clear understanding of dispersal rates among neighboring areas.

Infection and transmission of Cache Valley virus by Aedes albopictus and Aedes aegypti mosquitoes

BackgroundCache Valley virus (CVV; Bunyavirales, Peribunyaviridae) is a mosquito-borne arbovirus endemic in North America. Although severe diseases are mainly observed in pregnant ruminants, CVV has also been recognized as a zoonotic pathogen that can cause fatal encephalitis in humans. Human exposures to CVV and its related subtypes occur frequently under different ecological conditions in the New World; however, neurotropic disease is rarely reported. High prevalence rates of neutralizing antibodies have been detected among residents in several Latin American cities. However, zoophilic mosquito species involved in the enzootic transmission are unlikely to be responsible for the transmission leading to human exposures to CVV. Mechanisms that lead to frequent human exposures to CVV remain largely unknown. In this study, competence of two anthropophilic mosquitoes, Aedes albopictus and Ae. aegypti, for CVV was determined using per os infection to determine if these species could play a role in the transmission of CVV in the domestic and peridomestic settings of urban and suburban areas.ResultsAedes albopictus were highly susceptible to CVV whereas infection of Ae. aegypti occurred at a significantly lower frequency. Whilst the dissemination rates of CVV were comparable in the two species, the relatively long period to attain maximal infectious titer in Ae. aegypti demonstrated a significant difference in the replication kinetics of CVV in these species. Detection of viral RNA in saliva suggests that both Ae. albopictus and Ae. aegypti are competent vectors for CVV under laboratory conditions.ConclusionsDifferential susceptibility to CVV was observed in Ae. albopictus and Ae. aegypti, reflecting their relatively different capacities for vectoring CVV in nature. The high susceptibility of Ae. albopictus to CVV observed in this study suggests its potential role as an efficient vector for CVV. Complemented by the reports of multiple CVV isolates derived from Ae. albopictus, our finding provides the basis for how the dispersal of Ae. albopictus across the New World may have a significant impact on the transmission and ecology of CVV.

A novel entomological index, Aedes aegypti Breeding Percentage, reveals the geographical spread of the dengue vector in Singapore and serves as a spatial risk indicator for dengue

BackgroundAedes aegypti is an efficient primary vector of dengue, and has a heterogeneous distribution in Singapore. Aedes albopictus, a poor vector of dengue, is native and ubiquitous on the island. Though dengue risk follows the dispersal of Ae. aegypti, the spatial distribution of the vector is often poorly characterized. Here, based on the ubiquitous presence of Ae. albopictus, we developed a novel entomological index, Ae. aegypti Breeding Percentage (BP), to demonstrate the expansion of Ae. aegypti into new territories that redefined the dengue burden map in Singapore. We also determined the thresholds of BP that render the specific area higher risk of dengue transmission.MethodsWe performed analysis of dengue fever incidence and Aedes mosquito breeding in Singapore by utilizing island-wide dengue cases and vector surveillance data from 2003 to 2013. The percentage of Ae. aegypti breeding among the total Aedes breeding habitats (BP), and the reported number of dengue fever cases in each year were calculated for each residential grid.ResultsThe BP of grids, for every year over the 11-year study period, had a consistent positive correlation with the annual case counts. Our findings suggest that the geographical expansion of Ae. aegypti to previously “non-dengue” areas have contributed substantially to the recent dengue fever incidence in Singapore. Our analysis further indicated that non-endemic areas in Singapore are likely to be at risk of dengue fever outbreaks beyond an Ae. aegypti BP of 20%.ConclusionsOur analyses indicate areas with increasing Ae. aegypti BP are likely to become more vulnerable to dengue outbreaks. We propose the usage of Ae. aegypti BP as a factor for spatial risk stratification of dengue fever in endemic countries. The Ae. aegypti BP could be recommended as an indicator for decision making in vector control efforts, and also be used to monitor the geographical expansion of Ae. aegypti.

Quantifying the Spatial Dimension of Dengue Virus Epidemic Spread within a Tropical Urban Environment

BackgroundDengue infection spread in naive populations occurs in an explosive and widespread fashion primarily due to the absence of population herd immunity, the population dynamics and dispersal of Ae. aegypti, and the movement of individuals within the urban space. Knowledge on the relative contribution of such factors to the spatial dimension of dengue virus spread has been limited. In the present study we analyzed the spatio-temporal pattern of a large dengue virus-2 (DENV-2) outbreak that affected the Australian city of Cairns (north Queensland) in 2003, quantified the relationship between dengue transmission and distance to the epidemic's index case (IC), evaluated the effects of indoor residual spraying (IRS) on the odds of dengue infection, and generated recommendations for city-wide dengue surveillance and control.Methods and FindingsWe retrospectively analyzed data from 383 DENV-2 confirmed cases and 1,163 IRS applications performed during the 25-week epidemic period. Spatial (local k-function, angular wavelets) and space-time (Knox test) analyses quantified the intensity and directionality of clustering of dengue cases, whereas a semi-parametric Bayesian space-time regression assessed the impact of IRS and spatial autocorrelation in the odds of weekly dengue infection. About 63% of the cases clustered up to 800 m around the IC's house. Most cases were distributed in the NW-SE axis as a consequence of the spatial arrangement of blocks within the city and, possibly, the prevailing winds. Space-time analysis showed that DENV-2 infection spread rapidly, generating 18 clusters (comprising 65% of all cases), and that these clusters varied in extent as a function of their distance to the IC's residence. IRS applications had a significant protective effect in the further occurrence of dengue cases, but only when they reached coverage of 60% or more of the neighboring premises of a house.ConclusionBy applying sound statistical analysis to a very detailed dataset from one of the largest outbreaks that affected the city of Cairns in recent times, we not only described the spread of dengue virus with high detail but also quantified the spatio-temporal dimension of dengue virus transmission within this complex urban environment. In areas susceptible to non-periodic dengue epidemics, effective disease prevention and control would depend on the prompt response to introduced cases. We foresee that some of the results and recommendations derived from our study may also be applicable to other areas currently affected or potentially subject to dengue epidemics.

A Scenario for Invasion and Dispersal ofAedes albopictus(Diptera: Culicidae) in New Zealand

To date, there has been no confirmed, indigenously acquired case of arthropod-borne viral disease in New Zealand, but this may change in the near future due to the presence of exotic vectors and regular influx of infected humans. The risk of a disease outbreak may be aggravated if other exotic mosquito vectors become established, in particular Aedes albopictus (Skuse), a species that has already been intercepted several times in New Zealand. In this study, the possible means of invasion and dispersal of Ae. albopictus in northern New Zealand are discussed, along with the factors that should facilitate its establishment in the event it evades border controls.