First establishment of Aedes japonicus japonicus (Theobald, 1901) (Diptera: Culicidae) in France in 2013 and its impact on public health

Using geometric wing morphometrics to distinguish Aedes japonicus japonicus and Aedes koreicus

BACKGROUND

Aedes japonicus japonicus (Theobald, 1901) and Aedes koreicus (Edwards, 1917) have rapidly spread in Europe over the last decades. Both species are very closely related and occur in sympatry. Females and males are difficult to distinguish. However, the accurate species discrimination is important as both species may differ in their vectorial capacity and spreading behaviour. In this study, we assessed the potential of geometric wing morphometrics as alternative to distinguish the two species.

METHODS

A total of 147 Ae. j. japonicus specimens (77 females and 70 males) and 124 Ae. koreicus specimens (67 females and 57 males) were collected in southwest Germany. The left wing of each specimen was removed, mounted and photographed. The coordinates of 18 landmarks on the vein crosses were digitalised by a single observer. The resulting two-dimensional dataset was used to analyse the differences in the wing size (i.e. centroid size) and wing shape between Ae. j. japonicus and Ae. koreicus using geometric morphometrics. To analyse the reproducibility of the analysis, the landmark collection was repeated for 20 specimens per sex and species by two additional observers.

RESULTS

The wing size in female Ae. koreicus was significantly greater than in Ae. j. japonicus but did not differ significantly for males. However, the strong overlap in wing size also for the females would not allow to discriminate the two species. In contrast, the wing shape clustering was species specific and a leave-one-out validation resulted in a reclassification accuracy of 96.5% for the females and 91.3% for the males. The data collected by different observers resulted in a similar accuracy, indicating a low observer bias for the landmark collection.

CONCLUSIONS

Geometric wing morphometrics provide a reliable and robust tool to distinguish female and male specimens of Ae. j. japonicus and Ae. koreicus.

Emergence of the invasive Asian bush mosquito Aedes (Hulecoeteomyia) japonicus (Theobald, 1901) in the Czech Republic

BACKGROUND

Aedes japonicus is a mosquito species native to North-East Asia that was first found established outside its original geographic distribution range in 1998 and has since spread massively through North America and Europe. In the Czech Republic, the species was not reported before 2021.

METHODS

Aedes invasive mosquitoes (AIM) are routinely surveyed in the Czech Republic by ovitrapping at potential entry ports. This surveillance is supported by appeals to the population to report uncommon mosquitoes. The submission of an Ae. japonicus specimen by a citizen in 2021 was followed by local search for aquatic mosquito stages in the submitter's garden and short-term adult monitoring with encephalitis virus surveillance (EVS) traps in its surroundings. Collected Ae. japonicus specimens were subjected to nad4 haplotype and microsatellite analyses.

RESULTS

Aedes japonicus was detected for the first time in the Czech Republic in 2021. Aquatic stages and adults were collected in Prachatice, close to the Czech-German border, and eggs in Mikulov, on the Czech-Austrian border. Morphological identification was confirmed by molecular taxonomy. Genetic analysis of specimens and comparison of genetic data with those of other European populations, particularly from Germany, showed the Prachatice specimens to be most closely related to a German population. The Mikulov specimens were more distantly related to those, with no close relatives identifiable.

CONCLUSIONS

Aedes japonicus is already widely distributed in Germany and Austria, two countries neighbouring the Czech Republic, and continues to spread rapidly in Central Europe. It must therefore be assumed that the species is already present at more than the two described localities in the Czech Republic and will further spread in this country. These findings highlight the need for more comprehensive AIM surveillance in the Czech Republic.

Laboratory Evaluation of Flight Capacities of Aedes japonicus (Diptera: Culicidae) Using a Flight Mill Device

Dispersion expands the distribution of invasive species and as such, it is a key factor of the colonization process. Aedes japonicus japonicus (Theobald, 1901) is an invasive species of mosquito and a vector of various viruses. It was detected in the northeast of France in 2014. The population of this species can expand its distribution by several kilometers per year. However, though flight capacities play an active part in the dispersion of Ae. japonicus, they remain unknown for this species. In this study, we investigated the flight capacities of Ae. japonicus in a laboratory setting using the flight mill technique. We evaluated the influence of age on flight. We recorded videos of individual flights with a camera mounted on Raspberry Pi. We extracted data on distance, duration, and speed of flight using the Toxtrac and Boris software. Our analysis showed a median flight distance of 438 m with a maximum of 11,466 m. Strong flyers, which represented 10% of the females tested, flew more than 6,115 m during 4 h and 28 min at a speed of 1.7 km per h. As suspected, Ae. japonicus is a stronger flyer than the other invasive species Aedes albopictus (Skuse, 1894) (Diptera: Culicidae). To our knowledge, this is the first flight mill study conducted on Ae. japonicus and therefore the first evaluation of its flight capacity. In the future, the flight propensity of Ae. japonicus determined in this study can be included as a parameter to model the colonization process of this invasive vector species.

At the tip of an iceberg: citizen science and active surveillance collaborating to broaden the known distribution of Aedes japonicus in Spain

BACKGROUND

Active surveillance aimed at the early detection of invasive mosquito species is usually focused on seaports and airports as points of entry, and along road networks as dispersion paths. In a number of cases, however, the first detections of colonizing populations are made by citizens, either because the species has already moved beyond the implemented active surveillance sites or because there is no surveillance in place. This was the case of the first detection in 2018 of the Asian bush mosquito, Aedes japonicus, in Asturias (northern Spain) by the citizen science platform Mosquito Alert.

METHODS

The collaboration between Mosquito Alert, the Ministry of Health, local authorities and academic researchers resulted in a multi-source surveillance combining active field sampling with broader temporal and spatial citizen-sourced data, resulting in a more flexible and efficient surveillance strategy.

RESULTS

Between 2018 and 2020, the joint efforts of administrative bodies, academic teams and citizen-sourced data led to the discovery of this species in northern regions of Spain such as Cantabria and the Basque Country. This raised the estimated area of occurrence of Ae. japonicus from < 900 km2 in 2018 to > 7000 km2 in 2020.

CONCLUSIONS

This population cluster is geographically isolated from any other population in Europe, which raises questions about its origin, path of introduction and dispersal means, while also highlighting the need to enhance surveillance systems by closely combining crowd-sourced surveillance with public health and mosquito control agencies' efforts, from local to continental scales. This multi-actor approach for surveillance (either passive and active) shows high potential efficiency in the surveillance of other invasive mosquito species, and specifically the major vector Aedes aegypti which is already present in some parts of Europe.

Diapause characterisation and seasonality of Aedes japonicus japonicus (Diptera, Culicidae) in the northeast of France

The invasive mosquito Aedes japonicus japonicus (Theobald, 1901) settled in 2013 in the Alsace region, in the northeast of France. In this temperate area, some mosquito species use diapause to survive cold winter temperatures and thereby foster settlement and dispersal. This study reports diapause and its seasonality in a field population of Ae. japonicus in the northeast of France. For two years, eggs were collected from May to the beginning of November. They were most abundant in summer and became sparse in late October. Diapause eggs were determined by the presence of a fully developed embryo in unhatched eggs after repeated immersions. Our study showed effective diapause of Ae. japonicus in this part of France. At the start of the egg-laying period (week 20), we found up to 10% of eggs under diapause, and this rate reached 100% in October. The 50% cut-off of diapause incidence was determined by the end of summer, leading to an average calculated maternal critical photoperiod of 13 h 23 min. Interestingly, diapause was shown to occur in part of the eggs even at the earliest period of the two seasons, i.e. in May of each year. Even though we observed that the size of eggs was positively correlated with diapause incidence, morphology cannot be used as the unique predictive indicator of diapause status due to overlapping measurements between diapausing and non-diapausing eggs. This study provides new knowledge on diapause characterisation and invasive traits of Ae. japonicus.

Emergence of the invasive Asian bush mosquito, Aedes (Finlaya) japonicus japonicus, in an urban area, Romania

Background

A study conducted at the International Airport of Cluj-Napoca, Romania, with the aim of investigating the presence/absence of invasive Aedes mosquito species resulted in finding Aedes japonicus japonicus (Theobald 1901) eggs in one of the ovitraps placed on site.

Methods

The study was carried out between 30 June and 29 September 2020. On 24 August, 26 eggs were collected and later hatched at the University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca’s insectary. On 15 October another adult female Ae. japonicus was caught entering a building in the center of the city, about 7 km from the first sampling spot.

Results

The mosquitoes were identified morphologically and confirmed by molecular analysis, based on the genetic analysis of the mitochondrial gene cytochrome c oxidase subunit 1 (COI).

Conclusion

This is the first report of the species in Romania, highlighting the need for surveillance and implemented control methods. However, in Romania to our knowledge only Aedes albopictus has been established; further studies are required to learn about this new invasive species' status in Romania.

Population genetic structure of the Asian bush mosquito, Aedes japonicus (Diptera, Culicidae), in Belgium suggests multiple introductions

BACKGROUND

Aedes japonicus japonicus has expanded beyond its native range and has established in multiple European countries, including Belgium. In addition to the population located at Natoye, Belgium, locally established since 2002, specimens were recently collected along the Belgian border. The first objective of this study was therefore to investigate the origin of these new introductions, which were assumed to be related to the expansion of the nearby population in western Germany. Also, an intensive elimination campaign was undertaken at Natoye between 2012 and 2015, after which the species was declared to be eradicated. This species was re-detected in 2017, and thus the second objective was to investigate if these specimens resulted from a new introduction event and/or from a few undetected specimens that escaped the elimination campaign.

METHODS

Population genetic variation at nad4 and seven microsatellite loci was surveyed in 224 and 68 specimens collected in Belgium and Germany, respectively. German samples were included as reference to investigate putative introduction source(s). At Natoye, 52 and 135 specimens were collected before and after the elimination campaign, respectively, to investigate temporal changes in the genetic composition and diversity.

RESULTS

At Natoye, the genotypic microsatellite make-up showed a clear difference before and after the elimination campaign. Also, the population after 2017 displayed an increased allelic richness and number of private alleles, indicative of new introduction(s). However, the Natoye population present before the elimination programme is believed to have survived at low density. At the Belgian border, clustering results suggest a relation with the western German population. Whether the introduction(s) occur via passive human-mediated ground transport or, alternatively, by natural spread cannot be determined yet from the dataset.

CONCLUSION

Further introductions within Belgium are expected to occur in the near future, especially along the eastern Belgian border, which is at the front of the invasion of Ae. japonicus towards the west. Our results also point to the complexity of controlling invasive species, since 4 years of intense control measures were found to be not completely successful at eliminating this exotic at Natoye.

Identification of Aedes mosquitoes by MALDI-TOF MS biotyping using protein signatures from larval and pupal exuviae

BACKGROUND

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) biotyping is an innovative strategy, applied successfully for the identification of numerous arthropod families including mosquitoes. The effective mosquito identification using this emerging tool was demonstrated possible at different steps of their life-cycle, including eggs, immature and adult stages. Unfortunately, for species identification by MS, the euthanasia of the mosquito specimen is required.

METHODS

To avoid mosquito euthanasia, the present study assessed whether aedine mosquitoes could be identified by MALDI-TOF MS biotyping, using their respective exuviae. In this way, exuviae from the fourth-instar and pupal stages of Aedes albopictus and Aedes aegypti were submitted to MALDI-TOF MS analysis.

RESULTS

Reproducible and specific MS spectra according to aedine species and stage of exuviae were observed which were objectified by cluster analyses, composite correlation index (CCI) tool and principal components analysis (PCA). The query of our reference MS spectra database (DB) upgraded with MS spectra of exuviae from fourth-instar larvae and pupae of both Aedes species revealed that 100% of the samples were correctly classified at the species and stage levels. Among them, 93.8% (135/144) of the MS profiles reached the threshold log score value (LSV > 1.8) for reliable identification.

CONCLUSIONS

The extension of reference MS spectra DB to exuviae from fourth-instar and pupal stages made now possible the identification of mosquitoes throughout their life-cycle at aquatic and aerial stages. The exuviae presenting the advantage to avoid specimen euthanasia, allowing to perform complementary analysis on alive mosquitoes.

Active dispersion, habitat requirements and human biting behaviour of the invasive mosquito Aedes japonicus japonicus (Theobald, 1901) in Hungary

Aedes japonicus japonicus is endemic in a number of countries in eastern Asia but has been accidently introduced into many regions of the world including Europe. It was first detected in Hungary in 2012. In 2017, robust populations of the species were found at Lake Balaton, one of the most important tourist destinations in Central Europe. Based on the experience gathered in the above localities, habitat requirements, dispersion abilities and human biting behaviour of the species were studied in western Hungary during 2017 and 2018. Our results show that (a) a few years after its detection at the Slovenian-Hungarian border, Ae. j. japonicus is widespread in at least two-thirds of the western half of Hungary; (b) the species spreads quickly in ecological corridors formed by mosaics of rural areas, detached houses, gardens and small forest patches; (c) Ae. j. japonicus occupies artificial containers; (d) expansion of the species into new areas is slowed by extensive closed forest patches.

The Asian bush mosquito Aedes japonicus japonicus (Diptera: Culicidae) in Europe, 17 years after its first detection, with a focus on monitoring methods

After the first detection of the Asian bush mosquito Aedes japonicus japonicus in the year 2000 in France, its invasive nature was revealed in 2008 in Switzerland and Germany. In the following years, accumulating reports have shown that Ae. j. japonicus succeeded in establishing in several European countries. Surveillance efforts suggest that there are currently four populations in Europe, with the largest one, formed by the recent fusion of several smaller populations, ranging from West Germany, with extensions to Luxembourg and French Alsace, southwards to Switzerland and continuing westwards through Liechtenstein to western Austria. This paper summarises the present distribution of Ae. j. japonicus in Europe, based on published literature and hitherto unpublished findings by the authors, and critically reviews the monitoring strategies applied. A proposal for a more standardised monitoring approach is provided, aiming at the harmonisation of future data collections for improving the comparability between studies and the suitability of collected data for further research purposes, e.g. predictive modelling approaches.

First detection of Aedes japonicus in Spain: an unexpected finding triggered by citizen science

BACKGROUND

Aedes japonicus is an invasive vector mosquito from Southeast Asia which has been spreading across central Europe since the year 2000. Unlike the Asian Tiger mosquito (Aedes albopictus) present in Spain since 2004, there has been no record of Ae. japonicus in the country until now.

RESULTS

Here, we report the first detection of Ae. japonicus in Spain, at its southernmost location in Europe. This finding was triggered by the citizen science platform Mosquito Alert. In June 2018, a citizen sent a report via the Mosquito Alert app from the municipality of Siero in the Asturias region (NW Spain) containing pictures of a female mosquito compatible with Ae. japonicus. Further information was requested from the participant, who subsequently provided several larvae and adults that could be classified as Ae. japonicus. In July, a field mission confirmed its presence at the original site and in several locations up to 9 km away, suggesting a long-time establishment. The strong media impact in Asturias derived from the discovery raised local participation in the Mosquito Alert project, resulting in further evidence from surrounding areas.

CONCLUSIONS

Whilst in the laboratory Ae. japonicus is a competent vector for several mosquito-borne pathogens, to date only West Nile virus is a concern based on field evidence. Nonetheless, this virus has yet not been detected in Asturias so the vectorial risk is currently considered low. The opportunity and effectiveness of combining citizen-sourced data to traditional surveillance methods are discussed.

The new European invader Aedes (Finlaya) koreicus: a potential vector of chikungunya virus

Arthropod-borne disease outbreaks, facilitated by the introduction of exotic mosquitoes, pose a significant public health threat. Recent chikungunya virus (CHIKV) epidemics in Europe highlight the importance of understanding the vector potential of invading mosquitoes. In this paper we explore the potential of Aedes koreicus, a mosquito new to Europe, to transmit CHIKV. Mosquitoes were challenged with CHIKV and maintained at two temperatures: 23 °C and a fluctuating temperature. Total CHIKV infection rates at 3, 10 and 14 days post-feeding were low for both temperature treatments (13.8% at 23 °C; 6.2% at fluctuating T). A low percentage (6.1%, n = 65) of mosquitoes maintained at a constant 23 °C showed dissemination of the virus to the wings and legs. Infection of mosquito saliva, with live virus, occurred in 2 mosquitoes. No dissemination was noted under the fluctuating temperature regime. Based on these results we conclude that CHIKV transmission by this species is possible.

The Citizen Science Project 'Mueckenatlas' Helps Monitor the Distribution and Spread of Invasive Mosquito Species in Germany

The citizen science project 'Mueckenatlas' (mosquito atlas) was implemented in early 2012 to improve mosquito surveillance in Germany. Citizens are asked to support the spatiotemporal mapping of culicids by submitting mosquito specimens collected in their private surroundings. The Mueckenatlas has developed into an efficient tool for data collection with close to 30,000 mosquitoes submitted by the end of 2015. While the vast majority of submissions included native mosquito species, a small percentage represented invasive species. The discovery of Aedes albopictus (Skuse) (Diptera: Culicidae), Aedes japonicus japonicus (Theobald) (Diptera: Culicidae) and Aedes koreicus (Edwards) (Diptera: Culicidae) specimens via the Mueckenatlas project prompted targeted monitoring activities in the field which produced additional information on the distribution of these species in Germany. Among others, Mueckenatlas submissions led to the detection of three populations of Ae. j. japonicus in West, North and Southeast Germany in 2012, 2013, and 2015, respectively. As demonstrated by on-site monitoring, the origins of Ae. j. japonicus specimens submitted to the Mueckenatlas mirror the distribution areas of the four presently known German populations as found by active field sampling (the fourth population already reported prior to the launch of the Mueckenatlas). The data suggest that a citizen science project such as the Mueckenatlas may aid in detecting changes in the mosquito fauna and can therefore be used to guide the design of more targeted field surveillance activities.

Emerging mosquito species in Germany-a synopsis after 6 years of mosquito monitoring (2011-2016)

Globalisation and climate change are the main drivers of invasion of non-endemic regions by mosquitoes. Mass transportation of people, animals and goods facilitate accidental long-distance displacement while climate warming supports active spread and establishment of thermophilic species. In the framework of a mosquito-monitoring programme, eight non-indigenous culicid species have been registered in Germany since 2011, with four of them being more or less efficient vectors of disease agents and another four now considered established. The eight newly emerged species include Aedes albopictus, Ae. japonicus, Ae. aegypti, Ae. koreicus, Ae. berlandi, Ae. pulcritarsis, Anopheles petragnani and Culiseta longiareolata. We here review recent findings and at the same time present new findings of specimens of non-native mosquito species in Germany.

Development of Dirofilaria immitis and Dirofilaria repens in Aedes japonicus and Aedes geniculatus

Background

The mosquito-borne filarial nematodes Dirofilaria immitis and Dirofilaria repens primarily affect dogs but also cats, causing heartworm disease or subcutaneous dirofilariosis, respectively, and both may also cause zoonotic diseases in humans. Several mosquito species have been reported as competent vectors for these nematodes, but no data are available for the invasive mosquito species Aedes japonicus (Theobald, 1901). The objective of this study was to describe the development of both D. immitis and D. repens under standardised experimental laboratory conditions in mosquitoes.

Methods

For this purpose, both a laboratory strain and field-collected individuals of the invasive mosquito species Ae. japonicus and, for comparative purposes, a laboratory strain of Aedes geniculatus, a rare indigenous species sharing habitats with Ae. japonicus, and of the tropical species Aedes aegypti were used. Anticoagulated microfilariaemic blood was fed at a density of 3000 mf/ml to mosquitoes with a hemotek system. Blood-fed mosquitoes were incubated at 27 °C and 85% relative humidity, and specimens were dissected under the microscope at pre-set time points to observe developmental stages of both Dirofilaria species. Additionally, real-time PCRs were carried out in some microscopically negative samples to determine the infection rates.

Results

In field-collected Ae. japonicus infectious L3 larvae of both D. immitis and D. repens developed, rendering this mosquito species an efficient vector for both filarial species. Additionally, Ae. geniculatus was shown to be an equally efficient vector for both filarial species. Aedes japonicus mosquitoes from a laboratory colony were refractory to D. immitis but susceptible to D. repens, whereas Ae. aegypti was refractory to both filarial species.

Conclusions

To our knowledge, Aedes japonicus was for the first time shown to be an efficient vector for both D. immitis and D. repens, indicating that this invasive and locally highly abundant species may contribute to a transmission of filarial worms. The data emphasize the necessity to perform vector competence studies with local mosquito populations as basis for risk assessments. We further demonstrated that detection of filarial DNA in a mosquito species alone does not allow to draw reliable conclusions with regard to its vector competence.

Occurrence and Spread of the Invasive Asian Bush Mosquito Aedes japonicus japonicus (Diptera: Culicidae) in West and North Germany since Detection in 2012 and 2013, Respectively

The invasive Asian bush mosquito Aedes japonicus japonicus was first recognised as established in Germany in 2008. In addition to the first known and quickly expanding population in the southwestern part of the country, three separate populations were discovered in West, North and southeastern Germany in 2012, 2013 and 2015, respectively, by means of the ‘Mueckenatlas’, a German instrument of passive mosquito surveillance. Since the first findings of mosquito specimens in West and North Germany, these regions were checked annually for continuing colonisation and spread of the species. Both affected areas were covered by a virtual 10x10km² grid pattern in the cells of which cemeteries were screened for immature stages of the mosquito. The cells were considered populated as soon as larvae or pupae were detected, whereas they were classified as negative when no mosquito stages were found in the cemeteries of at least three different towns or villages. Presence was also recorded when Ae. j. japonicus adults were submitted to the ‘Mueckenatlas’ from the respective cell or when there was evidence of local occurrence in localities other than cemeteries. Based on this approach, a significant expansion of the populated area was documented in West Germany since the first detection of Ae. j. japonicus in 2012 (increase in positive grid cells by more than 400%), while the North German population appears not to be expanding so far (reduction of positive grid cells by ca. 30% since 2013). As Ae. j. japonicus finds suitable climatic and ecological conditions in Germany, the differential expansion of the two populations might be attributed to the West German population being older and thus more firmly established than the closely related but younger North German population that might still be in its founder phase. However, geographic spread of all German populations in the future is anticipated. Continuous surveillance is recommended, as Ae. j. japonicus is a competent vector of several pathogens in the laboratory.

Aedes albopictus and Aedes japonicus - two invasive mosquito species with different temperature niches in Europe

BACKGROUND

Aedes albopictus and Ae. japonicus are two of the most widespread invasive mosquito species that have recently become established in western Europe. Both species are associated with the transmission of a number of serious diseases and are projected to continue their spread in Europe.

METHODS

In the present study, we modelled the habitat suitability for both species under current and future climatic conditions by means of an Ensemble forecasting approach. We additionally compared the modelled MAXENT niches of Ae. albopictus and Ae. japonicus regarding temperature and precipitation requirements.

RESULTS

Both species were modelled to find suitable habitat conditions in distinct areas within Europe: Ae. albopictus within the Mediterranean regions in southern Europe, Ae. japonicus within the more temperate regions of central Europe. Only in few regions, suitable habitat conditions were projected to overlap for both species. Whereas Ae. albopictus is projected to be generally promoted by climate change in Europe, the area modelled to be climatically suitable for Ae. japonicus is projected to decrease under climate change. This projection of range reduction under climate change relies on the assumption that Ae. japonicus is not able to adapt to warmer climatic conditions. The modelled MAXENT temperature niches of Ae. japonicus were found to be narrower with an optimum at lower temperatures compared to the niches of Ae. albopictus.

CONCLUSIONS

Species distribution models identifying areas with high habitat suitability can help improving monitoring programmes for invasive species currently in place. However, as mosquito species are known to be able to adapt to new environmental conditions within the invasion range quickly, niche evolution of invasive mosquito species should be closely followed upon in future studies.

Sterilization of Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Theobald, 1901) by high-energy photon irradiation: implications for a sterile insect technique approach in Europe

Hulecoeteomyia japonica japonica (= Aedes japonicus japonicus) (Diptera: Culicidae) (Theobald 1901), a container-breeding invasive species in North America and Europe, is attracting particular attention for its high local abundances and possible roles in the transmission of human and animal pathogens. The preferential habitats of this species are forested and bushy areas, which renders control measures extremely inefficient. Use of the sterile insect technique (SIT) may contribute to the implementation of area-wide integrated pest management strategies, as has been successfully proven with other aedine mosquito species. The present study investigates the effects of irradiation at a dose of 40 Gy on fitness parameters in H. j. japonica. Irradiation was performed on 16-24-h-old pupae from a colonized strain (PA) using a TrueBeam linear accelerator. Males from the PA strain were crossed with females of the same colony or with field-collected females. Irradiation induced a slight increase in mortality in male pupae, but did not alter the survival and mating abilities of emerging adult males. Rates of blood feeding and fertility were lower when PA strain males were kept with field-collected females rather than PA females. Irradiated males induced reductions in fertility (residual fertility: 2.6%) and fecundity in mated females. The data indicate that the SIT is a suitable technique to enhance the control of this species.

Spread of Aedes japonicus japonicus (Theobald, 1901) in Austria, 2011-2015, and first records of the subspecies for Hungary, 2012, and the principality of Liechtenstein, 2015

Background

The Asian bush mosquito, Aedes (Hulecoeteomyia) japonicus japonicus (Theobald, 1901) (Diptera: Culicidae), was first identified in Austria in August 2011 in the federal state of Styria at the border to Slovenia.

Methods

Between 2011 and 2015 the spread of Ae. j. japonicus was monitored in southern, eastern and western Austrian provinces as well as in neighbouring countries by checking natural and man-made container habitats for the aquatic stages. The search concentrated around the most recent occurrence of Ae. j. japonicus and extended up to several kilometres until the subspecies could not be found anymore.

Results

Between May and July 2012 the distribution area of Ae. j. japonicus was found to be extended westwards into Carinthia, and eastwards towards the federal state of Burgenland. In August 2012, the subspecies was found in Hungary, representing the first record of an invasive mosquito species in this country. In 2013 its expansion was confirmed at several sites in Austria. Additionally, between April and July 2015, the subspecies was detected in all districts of the westernmost Austrian state Vorarlberg reaching the alpine Montafon valley at the end of October 2015, at all three examined sites in southern Bavaria bordering Vorarlberg, and in the adjacent Principality of Liechtenstein, for which it also represents the first record of an invasive mosquito species. One remarkable finding of the subspecies was located close to the city of Kufstein in the lower Inn valley of the Tyrol in September 2015, which is an isolated occurrence without spatial connection to any known established population.

Conclusions

Our findings demonstrate the ongoing spread of Ae. j. japonicus towards all directions within Austria and beyond. Together with the absence of supposed natural barriers, e.g. high mountain chains, at the borders of the current subspecies’ distribution area in south-eastern Austria, these findings suggest a further spread to the Austrian capital Vienna and the Hungarian tourist region of Lake Balaton within the upcoming few years. The observed intrusions in western Austria represent most probably extensions of the population established and spreading in eastern Switzerland and southern Germany. The putative role of the subspecies in pathogen transmission together with its rapid spread observed argues for the implementation of comprehensive nation-wide surveillance and response preparedness.

Newly discovered population of Aedes japonicus japonicus (Diptera: Culicidae) in Upper Bavaria, Germany, and Salzburg, Austria, is closely related to the Austrian/Slovenian bush mosquito population

Background

The German mosquito surveillance instrument ‘Mueckenatlas’ requests the general public to collect and submit mosquito specimens. Among these, increasing numbers of individuals of invasive species have been registered. Specimens of the Asian bush mosquito Aedes japonicus japonicus submitted from German Upper Bavaria, where this species had not previously been recorded, triggered regional monitoring in mid-2015.

Methods

The search for Ae. j. japonicus breeding sites and developmental stages concentrated on cemeteries in the municipality of origin of the submitted specimens and, subsequently, in the whole region. A virtual grid consisting of 10 × 10 km² cells in which up to three cemeteries were checked, was laid over the region. A cell was considered positive as soon as Ae. j. japonicus larvae were detected, and regarded negative when no larvae could be found in any of the cemeteries inspected. All cells surrounding a positive cell were screened accordingly. A subset of collected Aedes j. japonicus specimens was subjected to microsatellite and nad4 sequence analyses, and obtained data were compared to individuals from previously discovered European populations.

Results

Based on the grid cells, an area of approximately 900 km² was populated by Ae. j. japonicus in Upper Bavaria and neighbouring Austria. Genetic analyses of microsatellites and nad4 gene sequences generated one genotype out of two previously described for Europe and three haplotypes, one of which had previously been found in Europe only in Ae. j. japonicus samples from a population in East Austria and Slovenia. The genetic analysis suggests the new population is closely related to the Austrian/Slovenian population.

Conclusion

As Ae. j. japonicus is well adapted to temperate climates, it has a strong tendency to expand and to colonise new territories in Central Europe, which is facilitated by human-mediated, passive transportation. The new population in Upper Bavaria/Austria is the seventh separate population described in Europe. According to our data, it originated from a previously detected population in eastern Austria/Slovenia and not from an introduction event from abroad. The dispersal and population dynamics of Ae. j. japonicus should be thoroughly surveyed, as this species is a potential vector of disease agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1447-z) contains supplementary material, which is available to authorized users.