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A new focus of Aedes japonicus japonicus (Theobald, 1901) (Diptera, Culicidae) distribution in Western Germany: rapid spread or a further introduction event?

ABSTRACT: BACKGROUND: The Asian bush mosquito, Aedes japonicus japonicus, a potential vector of several viruses, was first detected in Germany in 2008 on the Swiss-German border. In the following years, this invasive species apparently succeeded in establishing populations in southern Germany and in spreading northwards. In 2011, its distribution area already covered large areas of the federal state of Baden-Wurttemberg, and its northernmost German collection point was reported to be close to Stuttgart. Several independent submissions to our laboratories of Ae. j. japonicus specimens in July 2012, originating from the same area in the federal state of North Rhine-Westphalia, western Germany, prompted us to carry out an immediate surveillance in this region in the expectation of finding a further distribution focus of Ae. j. japonicus in Germany. METHODS: After inspecting the places of residence of the collectors of the submitted mosquito specimens, all kinds of water containers in 123 cemeteries in surrounding towns and villages were checked for mosquito developmental stages. These were collected and kept to produce adults for morphological species identification. One specimen per collection site was identified genetically by COI sequence analysis. RESULTS: Aedes j. japonicus adults and immature stages were found in 36 towns/villages that were checked (29%) over an area of approximately 2,000 km2 in southern North Rhine-Westphalia and northern Rhineland Palatinate. The species could not be demonstrated further south when monitoring towards the northernmost previous collection sites in southern Germany. It therefore remains to be elucidated whether the species has entered western Germany from the south, from Belgium in the west where it has been demonstrated to occur locally since 2002, or through a new introduction. CONCLUSIONS: Aedes j. japonicus is obviously much more widely distributed in Germany than previously thought. It appears to be well adapted, to have a strong expansion tendency and to replace indigenous mosquito species. Thus, a further spread is anticipated and elimination seems hardly possible anymore. The vector potency of the species should be reason enough to thoroughly monitor its future development in Germany.

SUBMITTER: Kampen H

PROVIDER: S-EPMC3533968 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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A new focus of Aedes japonicus japonicus (Theobald, 1901) (Diptera, Culicidae) distribution in Western Germany: rapid spread or a further introduction event?

Kampen Helge H Zielke Dorothee D Werner Doreen D

Parasites & vectors 20121207

<h4>Background</h4>The Asian bush mosquito, Aedes japonicus japonicus, a potential vector of several viruses, was first detected in Germany in 2008 on the Swiss-German border. In the following years, this invasive species apparently succeeded in establishing populations in southern Germany and in spreading northwards. In 2011, its distribution area already covered large areas of the federal state of Baden-Wurttemberg, and its northernmost German collection point was reported to be close to Stutt ...[more]

PMID: 23216741

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Project description: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.

Project description:Background Invasive mosquitoes of the genus Aedes are quickly spreading around the world. The presence of these alien species is concerning for both their impact on the native biodiversity and their high vector competence. The surveillance of Aedes invasive mosquito (AIM) species is one of the most important steps in vector-borne disease control and prevention. Methods In 2020, the monitoring of AIM species was conducted in five areas (Bratislava, Zvolen, Banská Bystrica, Prešov, Košice) of Slovakia. The sites were located at points of entry (border crossings with Austria and Hungary) and in the urban and rural zones of cities and their surroundings. Ovitraps were used at the majority of sites as a standard method of monitoring. The collected specimens were identified morphologically, with subsequent molecular identification by conventional PCR (cox1) and Sanger sequencing. The phylogenetic relatedness of the obtained sequences was inferred by the maximum likelihood (ML) method. The nucleotide heterogeneity of the Slovak sequences was analysed by the index of disparity. Results A bush mosquito, Aedes japonicus japonicus, was found and confirmed by molecular methods in three geographically distant areas of Slovakia—Bratislava, Zvolen and Prešov. The presence of AIM species is also likely in Košice; however, the material was not subjected to molecular identification. The nucleotide sequences of some Slovak strains confirm their significant heterogeneity. They were placed in several clusters on the ML phylogenetic tree. Moreover, Ae. j. japonicus was discovered in regions of Slovakia that are not close to a point of entry, where the mosquitoes could find favourable habitats in dendrothelms in city parks or forests. Conclusion Despite being a first record of the Ae. j. japonicus in Slovakia, our study indicates that the established populations already exist across the country, underlining the urgent need for intensified surveillance of AIM species as well as mosquito-borne pathogens. Graphical Abstract

Project description: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.

Project description:BackgroundOriginally native to East Asia, Aedes japonicus japonicus, a potential vector of several arboviruses, has become one of the most invasive mosquito species in the world. After having established in the USA, it is now spreading in Europe, with new populations emerging. In contrast to the USA, the introduction pathways and modes of dispersal in Europe are largely obscure.MethodsTo find out if two recently detected populations of Ae. j. japonicus in The Netherlands and northern Germany go back to new importations or to movements within Europe, the genetic makeup of mosquito specimens from all known European populations was compared. For this purpose, seven microsatellite loci from a representative number of mosquito specimens were genotyped and part of their mitochondrial nad4 gene sequenced.ResultsA novel nad4 haplotype found in the newly discovered Dutch population of Ae. j. japonicus suggests that this population is not closely related to the other European populations but has emanated from a further introduction event. With five nad4 haplotypes, the Dutch population also shows a very high genetic diversity indicating that either the founder population was very large or multiple introductions took place. By contrast, the recently detected North German population could be clearly assigned to one of the two previously determined European Ae. j. japonicus microsatellite genotypes and shows nad4 haplotypes that are known from West Germany.ConclusionAs the European populations of Ae. j. japonicus are geographically separated but genetically mixed, their establishment must be attributed to passive transportation. In addition to intercontinental shipment, it can be assumed that human activities are also responsible for medium- and short-distance overland spread. A better understanding of the processes underlying the introduction and spread of this invasive species will help to increase public awareness of the human-mediated displacement of mosquitoes and to find strategies to avoid it.

Project description:BACKGROUND:The invasive temperate mosquito Aedes japonicus japonicus is a potential vector for various infectious diseases and therefore a target of vector control measures. Even though established in Germany, it is unclear whether the species has already reached its full distribution potential. The possible range of the species, its annual population dynamics, the success of vector control measures and future expansions due to climate change still remain poorly understood. While numerous studies on occurrence have been conducted, they used mainly presence data from relatively few locations. In contrast, we used experimental life history data to model the dynamics of a continuous stage-structured population to infer potential seasonal densities and ask whether stable populations are likely to establish over a period of more than one year. In addition, we used climate change models to infer future ranges. Finally, we evaluated the effectiveness of various stage-specific vector control measures. RESULTS:Aedes j. japonicus has already established stable populations in the southwest and west of Germany. Our models predict a spread of Ae. j. japonicus beyond the currently observed range, but likely not much further eastwards under current climatic conditions. Climate change models, however, will expand this range substantially and higher annual densities can be expected. Applying vector control measures to oviposition, survival of eggs, larvae or adults showed that application of adulticides for 30 days between late spring and early autumn, while ambient temperatures are above 9 °C, can reduce population density by 75%. Continuous application of larvicide showed similar results in population reduction. Most importantly, we showed that with the consequent application of a mixed strategy, it should be possible to significantly reduce or even extinguish existing populations with reasonable effort. CONCLUSION:Our study provides valuable insights into the mechanisms concerning the establishment of stable populations in invasive species. In order to minimise the hazard to public health, we recommend vector control measures to be applied in 'high risk areas' which are predicted to allow establishment of stable populations to establish.

Project description:BackgroundAedes japonicus japonicus, first detected in Europe in 2000 and considered established in Germany 10 years later, is of medical importance due to its opportunistic biting behaviour and its potential to transmit pathogenic viruses. Its seasonal phenology, temperature and land use preference related to oviposition in newly colonised regions remain unclear, especially in the context of co-occurring native mosquito species.MethodsFocussing on regions in Germany known to be infested by Ae. japonicus japonicus, we installed ovitraps in different landscapes and their transition zones and recorded the oviposition activity of mosquitoes in relation to season, temperature and land use (arable land, forest, settlement) in two field seasons (May-August 2017, April-November 2018).ResultsAe. japonicus japonicus eggs and larvae were encountered in 2017 from June to August and in 2018 from May to November, with a markedly high abundance from June to September in rural transition zones between forest and settlement, limited to water temperatures below 30 °C. Of the three native mosquito taxa using the ovitraps, the most frequent was Culex pipiens s.l., whose offspring was found in high numbers from June to August at water temperatures of up to 35 °C. The third recorded species, Anopheles plumbeus, rarely occurred in ovitraps positioned in settlements and on arable land, but was often associated with Ae. japonicus japonicus. The least frequent species, Aedes geniculatus, was mostly found in ovitraps located in the forest.ConclusionsThe transition zone between forest and settlement was demonstrated to be the preferred oviposition habitat of Ae. japonicus japonicus, where it was also the most frequent container-inhabiting mosquito species in this study. Compared to native taxa, Ae. japonicus japonicus showed an extended seasonal activity period, presumably due to tolerance of colder water temperatures. Higher water temperatures and arable land represent distribution barriers to this species. The frequently co-occurring native species An. plumbeus might be useful as an indicator for potentially suitable oviposition habitats of Ae. japonicus japonicus in hitherto uncolonised regions. The results contribute to a better understanding of mosquito ecology and provide a basis for more targeted monitoring, distribution modelling and risk management of mosquitoes.

Dataset Information

A new focus of Aedes japonicus japonicus (Theobald, 1901) (Diptera, Culicidae) distribution in Western Germany: rapid spread or a further introduction event?

Publications

A new focus of Aedes japonicus japonicus (Theobald, 1901) (Diptera, Culicidae) distribution in Western Germany: rapid spread or a further introduction event?

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