Cryptic species Anopheles daciae (Diptera: Culicidae) found in the Czech Republic and Slovakia

We report the distribution of mosquitoes of the maculipennis complex in two distinct areas of the Czech Republic (Bohemia and South Moravia) and in one locality of neighbouring Slovakia with emphasis on the detection of the newly described cryptic species Anopheles daciae (Linton, Nicolescu & Harbach, 2004). A total of 691 mosquitoes were analysed using a species-specific multiplex PCR assay to differentiate between the members of the maculipennis complex. In the Czech Republic, we found Anopheles maculipennis (with a prevalence rate of 1.4%), Anopheles messeae (49.0%) and Anopheles daciae (49.6%). In Slovakia, only An. messeae (52.1%) and An. daciae (47.9%) were detected. In this study, An. daciae was documented for the first time in the two countries where it represented a markedly higher proportion of maculipennis complex species (with an overall prevalence almost reaching 50%) in comparison to previous reports from Germany, Romania and Poland. The determination of the differential distribution of maculipennis complex species will contribute to assessing risks of mosquito-borne diseases such as malaria or dirofilariasis.

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.

The Nuisance Mosquito Anopheles plumbeus (Stephens, 1828) in Germany-A Questionnaire Survey May Help Support Surveillance and Control

The mosquito species Anopheles plumbeus is an aggressive biter and a potential vector of malaria parasites and West Nile virus. It occurs naturally at low population densities, as its larval development is adapted to the specific water qualities found in tree holes. However, probably owing to environmental changes, it has recently been observed in several European countries to use increasingly often artificial breeding habitats that may lead to mass development and severe annoyance to humans living close by. The perception of mosquito nuisance, however, is very subjective, and breeding habitats are not always known, thus impeding targeted surveillance and control. To relate nuisance by An. plumbeus to specific environmental conditions, a questionnaire survey was carried out addressing persons who had submitted specimens of this particular mosquito species to the German citizen science project “Mueckenatlas”, an instrument of passive mosquito surveillance. The questionnaire was intended to find out whether a nuisance situation linked to An. plumbeus had existed, whether mosquito breeding habitats could be identified and whether control measures had been conducted. Despite some efforts, the participants who claimed to suffer from an An. plumbeus nuisance problem had rarely identified the source of the mosquitoes. Once control measures had been performed on abandoned manure pits, however, the nuisance problem disappeared or mosquito abundance was at least significantly reduced. Nevertheless, no significant effect of abandoned manure pits on the probability of an An. plumbeus nuisance could be demonstrated in a multivariate logistic regression model testing various variables. Instead, a significant positive effect of a disused farm nearby was found. The reason is probably that manure pits as the most frequent source of An. plumbeus mass development are often located on disused farms, without most people’s knowledge about their existence. Disused farms are therefore appropriate candidates to consider when it comes to public health issues connected to An. plumbeus such as surveillance of mass development and implementation of control measures.

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.

Evaluation of blowfly larvae (Diptera: Calliphoridae) as possible reservoirs and mechanical vectors of African swine fever virus

In 2014, highly virulent African swine fever virus (ASFV) was introduced into the Baltic States and Poland, with new cases being reported almost every week from wild boar and also from domestic pigs. Contrary to initial predictions that the disease would either die out due to the high virulence of the virus strain or spread rapidly in westerly direction, the infection became endemic and spread slowly. The unexpected disease epidemiology led to the hypothesis that hitherto unconsidered factors might contribute to virus persistence and dispersal. To check whether arthropod species feeding and developing on infected carcasses might be involved, larvae of two commonly found blowfly species, Lucilia sericata and Calliphora vicina, were experimentally bred on ASFV-infected spleen tissue. After different time intervals, developing larvae and pupae were tested for infectious virus and viral DNA. By qPCR, contamination of the blowfly larvae and pupae with ASFV-DNA could be demonstrated even after several washing steps, proving the uptake of virus during feeding in the larval stage. However, infectious virus could never be isolated. By contrast, the larvae appeared to have inactivated ASFV in the offered tissue, which might be explained by the known anti-biotic effect of salivary secretions. It is concluded that immature blowfly stages do not play a relevant role as reservoirs or mechanical vectors of ASFV.

Closely-related Borrelia burgdorferi (sensu stricto) strains exhibit similar fitness in single infections and asymmetric competition in multiple infections

Background

Wild hosts are commonly co-infected with complex, genetically diverse, pathogen communities. Competition is expected between genetically or ecologically similar pathogen strains which may influence patterns of coexistence. However, there is little data on how specific strains of these diverse pathogen species interact within the host and how this impacts pathogen persistence in nature. Ticks are the most common disease vector in temperate regions with Borrelia burgdorferi, the causative agent of Lyme disease, being the most common vector-borne pathogen in North America. Borrelia burgdorferi is a pathogen of high public health concern and there is significant variation in infection phenotype between strains, which influences predictions of pathogen dynamics and spread.

Methods

In a laboratory experiment, we investigated whether two closely-related strains of B. burgdorferi (sensu stricto) showed similar transmission phenotypes, how the transmission of these strains changed when a host was infected with one strain, re-infected with the same strain, or co-infected with two strains. Ixodes scapularis, the black-legged tick, nymphs were used to sequentially infect laboratory-bred Peromyscus leucopus, white-footed mice, with one strain only, homologous infection with the same stain, or heterologous infection with both strains. We used the results of this laboratory experiment to simulate long-term persistence and maintenance of each strain in a simple simulation model.

Results

Strain LG734 was more competitive than BL206, showing no difference in transmission between the heterologous infection groups and single-infection controls, while strain BL206 transmission was significantly reduced when strain LG734 infected first. The results of the model show that this asymmetry in competition could lead to extinction of strain BL206 unless there was a tick-to-host transmission advantage to this less competitive strain.

Conclusions

This asymmetric competitive interaction suggests that strain identity and the biotic context of co-infection is important to predict strain dynamics and persistence.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1964-9) contains supplementary material, which is available to authorized users.

The invasive Asian tiger mosquito Aedes albopictus (Diptera: Culicidae) in Germany: Local reproduction and overwintering

Within the framework of a German mosquito monitoring programme, the 'Mueckenatlas' (mosquito atlas) has been established as an instrument of citizen participation in mosquito mapping. In 2015, a strikingly large number of Aedes albopictus, which had not been considered established in Germany, was submitted. Three of six collection sites showed local reproduction, with demonstration of developmental stages over three months at two sites. The third populated site was checked only once in October. Developmental stages of Ae. albopictus were found again at these three sites in spring 2016, including one site in southeastern Germany where reproduction had already been documented in 2014. Although population genetic analyses performed on specimens collected at the latter locality in 2014 and 2015 did not provide proof for hibernation, the finding of developmental stages at this and two other very same sites as in the year before and at very early times in the season strongly suggest accomplished overwintering of Ae. albopictus in Germany. Obviously, the second extremely mild winter in Germany in a row and ongoing adaptation of Ae. albopictus to the temperate European climate allow the species to push northwards from endemic regions in the south. Due to the vector competence of Ae. albopictus for numerous pathogens, including dengue, chikungunya and Zika viruses, action should be taken immediately after the detection of local reproduction to eliminate the populations.

Activity of Culicoides spp. (Diptera: Ceratopogonidae) inside and outside of livestock stables in late winter and spring

Culicoides Latreille, 1809 midge species are the putative vectors of Bluetongue virus (BTV) and Schmallenberg virus (SBV) in Europe. To gain a better understanding of the epidemiology of the diseases, basic knowledge about the overwintering of the vectors is needed. Therefore, we investigated culicoid activity in relation to air temperature at livestock stables during late winter and spring season. Ceratopogonids were captured weekly indoors and outdoors on three cattle farms, three horse farms and one sheep farm in the federal state of Brandenburg, Germany between January and May, 2015 by BG-Sentinel UV-light suction traps. First seasonal activity was measured inside a sheep barn and cattle stables in mid-March, suggesting the existence of a preceding vector-free period. The first species at all trapping sites were members of the Obsoletus Complex followed by Culicoides punctatus (Meigen), 1804 and Culicoides pulicaris (Linnaeus), 1758 simultaneously. In total, 160 collections were made, including 3465 Culicoides specimens with 2790 (80.6%) of them being members of the Obsoletus Complex. The remaining 675 individuals belonged to six other culicoid species. 59.8% of all Culicoides were collected indoors, and almost five times as many midges were sampled on cattle farms as on horse farms. Cattle farms harboured seven species while only two species were found on the horse and the sheep farms, respectively. Temperatures, husbandry practises and the presence/quality of potential breeding sites might be responsible for the difference in species and numbers of caught specimens between livestock holdings.

Vernachlässigte, neue und wiederkehrende Parasitosen in Deutschland – bedeutend für die Großtierpraxis?

In der tierärztlichen Praxis spielen Parasitosen und deren Bekämpfung nach wie vor eine wesentliche Rolle. Die vergangenen Jahre haben Veränderungen der Rahmenbedingungen mit sich gebracht, unter denen sich auch Parasitosen entwickeln und verbreiten können. Hier sind vor allem die fortschreitende Globalisierung mit weltweit zunehmendem Tier- und Warenverkehr sowie die längerfristig wirkenden klimatischen Veränderungen zu nennen. An je zwei Beispielen aus der Protozoologie, der Helminthologie und der Entomologie wird der aktuelle Kenntnisstand dargestellt, wobei neu auftretende und wiederkehrende, ebenso wie längst bekannte, aber wenig beachtete Parasitosen Berück sichtigung finden.

Anopheles plumbeus (Diptera: Culicidae) in Germany: updated geographic distribution and public health impact of a nuisance and vector mosquito

OBJECTIVES

The aim of this study was to map the current spatial distribution of Anopheles plumbeus in Germany, a potential vector of malaria parasites and West Nile virus. Reports of mass occurrence and nuisance connected with artificial breeding site usage by this species were analysed.

METHODS

Distribution data were collected from 2011 to 2014 mainly through trapping and submissions of adult mosquito specimens to a citizen science project. In the framework of the latter, additional information was gathered on recent nuisance incidents caused by An. plumbeus, including a longitudinal analysis of mosquito occurrence and the impact of management measures at a nuisance site in south-western Germany.

RESULTS

Based on the most comprehensive set of collection data obtained during the last decades, An. plumbeus is shown to be widely distributed over Germany. The data also indicate a continuing extension of the breeding site repertoire of the species from natural to artificial habitats that facilitate mass development. Increasing incidents of persistent nuisance suggest that this mosquito species is rarely diagnosed correctly and managed adequately.

CONCLUSIONS

As An. plumbeus is both a serious nuisance pest and a potential vector species, awareness of this species and the public health problems linked to it should be raised among pest managers and public health personnel.

Indoor development of Aedes aegypti in Germany, 2016

In spring 2016, a German traveller returning from Martinique cultivated imported plant offsets in her home, and accidentally bred Aedes aegypti. Thirteen adult mosquito specimens submitted for identification and the traveller were tested for Zika, dengue and chikungunya virus infections, with negative results. The detection of Ae. aegypti by the 'Mueckenatlas' project demonstrates the value of this passive surveillance scheme for potential public health threats posed by invasive mosquitoes in Germany.

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.

Culicoides vector species on three South American camelid farms seropositive for bluetongue virus serotype 8 in Germany 2008/2009

Palearctic species of Culicoides (Diptera, Ceratopogonidae), in particular of the Obsoletus and Pulicaris complexes, were identified as putative vectors of bluetongue virus serotype 8 (BTV-8) on ruminant farms during the epizootic in Germany from 2006 to 2009. BTV may cause severe morbidity and mortality in ruminants and sporadically in South American camelids (SAC). However, the fauna of Culicoides spp. on SAC farms has not been investigated. Therefore, the ceratopogonid fauna was monitored on three farms with BTV-seropositive SAC in Germany. Black-light traps were set up on pastures and in stables from summer 2008 to autumn 2009. Additionally, ceratopogonids were caught in emergence traps mounted on llama dung and dung-free pasture from spring to autumn 2009. After morphological identification, selected Culicoides samples were analysed for BTV-RNA by real-time RT-PCR. The effects of the variables 'location', 'temperature' and 'humidity' on the number of Culicoides caught in black-light traps were modelled using multivariable Poisson regression. In total, 26 species of Culicoides and six other genera of biting midges were identified. The most abundant Culicoides spp. collected both outdoors and indoors with black-light traps belonged to the Obsoletus (77.4%) and Pulicaris (16.0%) complexes. The number of Culicoides peaked in summer, while no biting midges were caught during the winter months. Daily collections of Culicoides were mainly influenced by the location and depended on the interaction of temperature and humidity. In the emergence traps, species of the Obsoletus complex predominated the collections. In summary, the absence of BTV-RNA in any of the analysed Culicoides midges and in the BTV-seropositive SAC on the three farms together with the differences in the pathogenesis of BTV-8 in SAC compared to ruminants suggests a negligible role of SAC in the spread of the virus. Although SAC farms may provide similar suitable habitats for putative Culicoides vectors than ruminant farms, the results suggest that geographic and meteorological factors had a stronger influence on Culicoides abundance than the animal species.

An entomological review of invasive mosquitoes in Europe

Among the invasive mosquitoes registered all over the world, Aedes species are particularly frequent and important. As several of them are potential vectors of disease, they present significant health concerns for 21st century Europe. Five species have established in mainland Europe, with two (Aedes albopictus and Aedes japonicus) becoming widespread and two (Ae. albopictus and Aedes aegypti) implicated in disease transmission to humans in Europe. The routes of importation and spread are often enigmatic, the ability to adapt to local environments and climates are rapid, and the biting nuisance and vector potential are both an ecomonic and public health concern. Europeans are used to cases of dengue and chikungunya in travellers returning from the tropics, but the threat to health and tourism in mainland Europe is substantive. Coupled to that are the emerging issues in the European overseas territorities and this paper is the first to consider the impacts in the remoter outposts of Europe. If entomologists and public health authorities are to address the spread of these mosquitoes and mitigate their health risks they must first be prepared to share information to better understand their biology and ecology, and share data on their distribution and control successes. This paper focusses in greater detail on the entomological and ecological aspects of these mosquitoes to assist with the risk assessment process, bringing together a large amount of information gathered through the ECDC VBORNET project.

A comparison of four light traps for collecting Culicoides biting midges

Epidemiological analyses of vector-associated diseases such as bluetongue (BT), African horse sickness, or epizootic hemorrhagic disease require substantiated data on the species diversity and activity patterns of vector species. To this end, Spain and Italy implemented extensive Culicoides biting midge monitoring programs since 2000, as several other countries did after the arrival of BT in northern Europe in 2006. The seasonal occurrence, spatial distribution, and abundance of Culicoides species, as the major results of such monitoring programs, are used as parameters for assessing the risk of virus introduction and transmission in a given area. However, the quality of entomological monitoring results fundamentally depends on the collection techniques. In this publication, we describe a Latin Square design trial carried out in Germany under field conditions in 2009/2010 to compare the efficacy of four commonly used light baited/suction traps in collecting Culicoides. A total of 2651 Culicoides were caught over 18 nights. In both years, the Onderstepoort and BG-Sentinel traps caught significantly more Culicoides than the Rieb and the CDC trap. Most specimens were caught by the Onderstepoort trap (1246, i.e., 76 % in 2009 and 819, i.e., 82 % in 2010). Most were classified as midges of the Culicoides obsoletus group.

Recently discovered Aedes japonicus japonicus (Diptera: Culicidae) populations in The Netherlands and northern Germany resulted from a new introduction event and from a split from an existing population

Background

Originally 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.

Methods

To 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.

Results

A 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.

Conclusion

As 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.

Approaches to passive mosquito surveillance in the EU

The recent emergence in Europe of invasive mosquitoes and mosquito-borne disease associated with both invasive and native mosquito species has prompted intensified mosquito vector research in most European countries. Central to the efforts are mosquito monitoring and surveillance activities in order to assess the current species occurrence, distribution and, when possible, abundance, in order to permit the early detection of invasive species and the spread of competent vectors. As active mosquito collection, e.g. by trapping adults, dipping preimaginal developmental stages or ovitrapping, is usually cost-, time- and labour-intensive and can cover only small parts of a country, passive data collection approaches are gradually being integrated into monitoring programmes. Thus, scientists in several EU member states have recently initiated programmes for mosquito data collection and analysis that make use of sources other than targeted mosquito collection. While some of them extract mosquito distribution data from zoological databases established in other contexts, community-based approaches built upon the recognition, reporting, collection and submission of mosquito specimens by citizens are becoming more and more popular and increasingly support scientific research. Based on such reports and submissions, new populations, extended or new distribution areas and temporal activity patterns of invasive and native mosquito species were found. In all cases, extensive media work and communication with the participating individuals or groups was fundamental for success. The presented projects demonstrate that passive approaches are powerful tools to survey the mosquito fauna in order to supplement active mosquito surveillance strategies and render them more focused. Their ability to continuously produce biological data permits the early recognition of changes in the mosquito fauna that may have an impact on biting nuisance and the risk of pathogen transmission associated with mosquitoes. International coordination to explore synergies and increase efficiency of passive surveillance programmes across borders needs to be established.

Aedes albopictus breeding in southern Germany, 2014

Larvae, pupae and eggs of the Asian tiger mosquito Aedes albopictus were found in Freiburg, southern Germany, after submission of an adult mosquito specimen from that area to the 'Mückenatlas', a German instrument of passive mosquito surveillance. While previously collected Ae. albopictus in Germany were trapped on, or close to, service stations on motorways, suggesting introduction by vehicles from southern Europe, these new specimens were out of flight distance from the motorway on the one hand and indicate local reproduction on the other. The findings call for a thorough active and passive surveillance in exposed geographic regions such as the relatively warm German Upper Rhine Valley to prevent Ae. albopictus from establishing.

Unexpected patterns of admixture in German populations of Aedes japonicus japonicus (Diptera: Culicidae) underscore the importance of human intervention

The mosquito Aedes japonicus japonicus, originally restricted to temperate East Asia, is now widespread in North America and more recently has become established in Europe. To ascertain the putative number of separate introductions to Europe and examine patterns of expansion we analyzed the genetic makeup of Ae. j. japonicus populations from five cemeteries in North Rhine-Westphalia and Rhineland-Palatinate, two western German federal states, as well as of specimens from populations in Belgium, Switzerland, and Austria/Slovenia. To do so, we genotyped individual specimens at seven pre-existing polymorphic microsatellite loci and sequenced part of the nad4 mitochondrial locus. We found evidence of two different genotypic signatures associated with different nad4 mitochondrial haplotypes, indicating at least two genetically differentiated populations of Ae. j. japonicus in Europe (i.e. two distinct genotypes). Belgian, Swiss, and Austrian/Slovenian populations all share the same genotypic signature although they have become differentiated since isolation. Contrary to expectations, the German Ae. j. japonicus are not closely related to those in Belgium which are geographically nearest but are also highly inbred. German populations have a unique genotype but also evidence of mixing between the two genotypes. Also unexpectedly, the populations closest to the center of the German infestation had the highest levels of admixture indicating that separate introductions did not expand and merge but instead their expansion was driven by punctuated human-mediated transport. Critically, the resulting admixed populations have higher genetic diversity and appear invasive as indicated by their increased abundance and recent spread across western Germany.

Dirofilaria repens and Dirofilaria immitis DNA findings in mosquitoes in Germany: temperature data allow autochthonous extrinsic development

After the repeated demonstration of Dirofilaria repens infections in German dogs, D. repens and Dirofilaria immitis DNA was detected in mosquitoes trapped in 2011, 2012 and 2013 in northeastern and southwestern Germany within the framework of culicid monitoring projects. As temperature is the most important factor dictating the extrinsic development of dirofilarial larvae in the potential vector, data of the German Weather Service (DWD) were analysed for the regions where the positive mosquitoes had been collected. Based on the mean daily temperatures recorded by weather stations most closely to the collection sites of the mosquitoes, it can be concluded that the mosquitoes were trapped in time periods that allowed for the completion of the developmental cycle of the worms in the mosquitoes and a subsequent transmission to a vertebrate host. The results of this study confirm the principal climatic suitability of certain German regions for the establishment of natural dirofilarial transmission cycles. Moreover, the theoretical climatic considerations, together with findings of D. repens infections in German dogs and mosquitoes, strongly suggest that the continuing spread of at least D. repens from its traditional habitats in the Mediterranean has reached southwestern and northeastern Germany.

Towards the PCR-based identification of Palaearctic Culicoides biting midges (Diptera: Ceratopogonidae): results from an international ring trial targeting four species of the subgenus Avaritia

Background

Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are biological vectors of internationally important arboviruses. To understand the role of Culicoides in the transmission of these viruses, it is essential to correctly identify the species involved. Within the western Palaearctic region, the main suspected vector species, C. obsoletus, C. scoticus, C. dewulfi and C. chiopterus, have similar wing patterns, which makes it difficult to separate and identify them correctly.

Methods

In this study, designed as an inter-laboratory ring trial with twelve partners from Europe and North Africa, we assess four PCR-based assays which are used routinely to differentiate the four species of Culicoides listed above. The assays based on mitochondrial or ribosomal DNA or microarray hybridisation were tested using aliquots of Culicoides DNA (extracted using commercial kits), crude lysates of ground specimens and whole Culicoides (265 individuals), and non-Culicoides Ceratopogonidae (13 individuals) collected from across Europe.

Results

A total of 800 molecular assays were implemented. The in-house assays functioned effectively, although specificity and sensitivity varied according to the molecular marker and DNA extraction method used. The Obsoletus group specificity was overall high (95-99%) while the sensitivity varied greatly (59.6-100%). DNA extraction methods impacted the sensitivity of the assays as well as the type of sample used as template for the DNA extraction.

Conclusions

The results are discussed in terms of current use of species diagnostic assays and the future development of molecular tools for the rapid differentiation of cryptic Culicoides species.