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Spatio-temporal diversity of the mosquito fauna (Diptera: Culicidae) in Switzerland

Authors:

Abstract

The spatio-temporal diversity of the Swiss mosquito fauna was investigated at eight locations distributed throughout the country (altitude between 198 and 1,255 meters above sea level) by five samplings over two years (July 2011 to September 2012). At each location at two sites (nature zone, suburban zone), mosquito immature stages were collected in 15-30 larval habitats (LH), and adults were trapped with CO2-baited traps. Mosquitoes were morphologically identified to species or sister taxa / species complex level. Mosquitoes were found at all sites. Among the 1,362 LHs inspections, 36.7% revealed the presence of mosquito immature stages, and around 9,000 specimens were identified. Adult trapping yielded around 2,000 mosquitoes. Fifteen mosquito species, 3 sibling species (of which all 6 species were confirmed) and the Anopheles maculipennis complex were collected. The nature zones showed the higher diversity (all species observed) but a lower relative abundance as compared to the suburban zones (overall 11 species and 2 sibling species identified). The most abundant species was Culex. pipiens/torrentium (61.2% of all specimens collected) occurring at all except two sites. Six species were frequently observed (Cx. hortensis, Aedes japonicus, An. maculipennis complex members, Ae. vexans, Ae. cinereus/geminus, and Ae. sticticus, accounting for 8.5% to 3.9%, respectively, of the individuals). Six of these seven most abundant species have a potential to act as vector. The highest relative abundances of the mosquito fauna, all species, were observed in June and July, for both nature and suburban zones, with peak abundances of different species varying from June to September. The experimental approach (repeated larval sampling and CO2-baited trapping) looks reliable for collecting most of the mosquito species. From the 36 mosquito species known to Switzerland, only 13 were not detected during the study: Ae. albopictus which is present in southern Ticino outside the study area only; 12 other species which are known to be rare or to occur at high altitudes. In addition to Ae. albopictus, the other invasive species Ae. japonicus shows a remarkable distribution, being highly abundant in north-eastern Switzerland (being the third most common species overall), but absent from western and southern parts of the country. All other species do not display any particular distribution. Further work to be accomplished includes the molecular identification within sibling species /complexes (e.g. Cx. pipiens/torrentium) by MALDI-TOF mass spectrometry, which has recently been established and which can be used as a high-throughput, cost-efficient and reliable tool for the identification of mosquito adults, larvae and eggs. Finally, extrapolation and modelling the potential distribution of the most common species for risk mapping will be done, using the VECMAP system modelling component which currently is in the finalization process.
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Spatio-temporal diversity of the mosquito fauna
(Diptera: Culicidae) in Switzerland
Research study
Final report
Commissioned by the Swiss Federal Office for the Environment
(Contract Number 10.0002.PJ / K222-2990)
Authors:
Francis Schaffner, Alexander Mathis
Institute of Parasitology
National Centre for Vector Entomology
University of Zürich, Winterthurerstr. 266a, 8057 Zürich
Telephone 044 635 85 01
E-mail: francis.schaffner@uzh.ch; alexander.mathis@uzh.ch
Study jointly performed with
Istituto Cantonale di Microbiologia (ICM), Bellinzona;
Musée Cantonal de Zoologie (MCZ), Lausanne;
Swiss Tropical and Public Health Institute (Swiss TPH), Basel.
August 2013
Page 2/19
Abstract
The spatio-temporal diversity of the Swiss mosquito fauna was investigated at eight locations
distributed throughout the country (altitude between 198 and 1,255 meters above sea level) by
five samplings over two years (July 2011 to September 2012). At each location at two sites
(nature zone, suburban zone), mosquito immature stages were collected in 15-30 larval
habitats (LH), and adults were trapped with CO2-baited traps. Mosquitoes were morphologically
identified to species or sister taxa / species complex level. Mosquitoes were found at all sites.
Among the 1,362 LHs inspections, 36.7% revealed the presence of mosquito immature stages,
and around 9,000 specimens were identified. Adult trapping yielded around 2,000 mosquitoes.
Fifteen mosquito species, 3 sibling species (of which all 6 species were confirmed) and the
Anopheles maculipennis complex were collected. The nature zones showed the higher
diversity (all species observed) but a lower relative abundance as compared to the suburban
zones (overall 11 species and 2 sibling species identified). The most abundant species was
Culex. pipiens/torrentium (61.2% of all specimens collected) occurring at all except two sites.
Six species were frequently observed (Cx. hortensis, Aedes japonicus, An. maculipennis
complex members, Ae. vexans, Ae. cinereus/geminus, and Ae. sticticus, accounting for 8.5%
to 3.9%, respectively, of the individuals). Six of these seven most abundant species have a
potential to act as vector. The highest relative abundances of the mosquito fauna, all species,
were observed in June and July, for both nature and suburban zones, with peak abundances of
different species varying from June to September.
The experimental approach (repeated larval sampling and CO2-baited trapping) looks reliable
for collecting most of the mosquito species. From the 36 mosquito species known to
Switzerland, only 13 were not detected during the study: Ae. albopictus which is present in
southern Ticino outside the study area only; 12 other species which are known to be rare or to
occur at high altitudes. In addition to Ae. albopictus, the other invasive species Ae. japonicus
shows a remarkable distribution, being highly abundant in north-eastern Switzerland (being the
third most common species overall), but absent from western and southern parts of the
country. All other species do not display any particular distribution.
Further work to be accomplished includes the molecular identification within sibling species
/complexes (e.g. Cx. pipiens/torrentium) by MALDI-TOF mass spectrometry, which has
recently been established and which can be used as a high-throughput, cost-efficient and
reliable tool for the identification of mosquito adults, larvae and eggs. Finally, extrapolation and
modelling the potential distribution of the most common species for risk mapping will be done,
using the VECMAP system modelling component which currently is in the finalization process.
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Contents
1.Introduction ............................................................................................................................ 4
2.Material and Methods ........................................................................................................... 5
3.Results ................................................................................................................................... 8
4.Discussion ........................................................................................................................... 13
5.Conclusions ......................................................................................................................... 17
6.References .......................................................................................................................... 17
Annex 1: Details on the selected locations and sites with situation maps.
Annex 2: Study protocol.
Annex 3: Identification quality check.
Abbreviations
Ae. Aedes
An. Anopheles
Cq. Coquillettidia
Cs. Culiseta
CSCF Centre Suisse de Cartographie de la Faune
Cx. Culex
ICM Istituto Cantonale di Microbiologia, Bellinzona
IPZ Institute of Parasitology, Zürich
LH Larval habitat
MCZ Musée Cantonal de Zoologie, Lausanne
Swiss TPH Swiss Tropical and Public Health Institute, Basel
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Introduction
Background
Mosquitoes are the most important insect vectors worldwide, and the epidemiology of many of
the infectious agents they transmit is changing, mainly due to environmental changes as well
as increase of trade and tourism [1]. In Switzerland, the significance of mosquitoes currently is
restricted to their role as nuisance and as vectors of few pathogens of veterinary importance
[2, 3], but this picture might change in the future (e.g. with regard to transmission of West Nile
virus which is emerging in neighbouring countries [4]). Further, invasive mosquitoes might pose
a hazard for biodiversity [5].
In order to gain an overview on the Swiss mosquito fauna, a recent pilot study [6] was done,
combining literature analysis with field investigations along transects in five regions in
Switzerland (northern Ticino, Midplains, Inner Alps, Pre-Alps, Jura) encompassing urban, peri-
urban, rural and nature zones. Hence, the literature revealed the report of 41 mosquito species
in Switzerland, two of them being recent invaders (Aedes albopictus, Ae. japonicus). However,
five species might be considered as doubtful records since only single observations have been
reported. Thus, the consolidated list of Swiss mosquitoes currently comprises 36 species.
Based on the transect study, the highest diversity of the mosquito fauna was observed in the
nature zones where all 13 species identified in this field study were present. In contrast, only 3-
4 species were occurring in the urban zones. Also, the spread of the invasive species Ae.
japonicus was further evaluated along other transects, revealing an expansion of 12 to 43 km
in different directions in 2010. Finally, the vector potentials of the mosquitoes of Switzerland
were assessed based on literature data, revealing that several of the identified species are
putative vectors for a number of pathogens (arboviruses and malaria of medical importance;
arboviruses, protozoa and nematodes of veterinary importance). By also including a score for a
potential threat to biodiversity, an overall classification of the Swiss mosquitoes with regard to
the global threat they pose is obtained (Table 1). Further investigations aiming at assessing the
hazard risk may focus on species showing a relevant score equal or higher to 3 in one of the
categories.
Framework
Here, we present the results of a research study implemented at the request of the Swiss
Federal Office for the Environment (FOEN), under Contract Number 10.0002.PJ / K222-2990.
This study aims at investigating the Swiss mosquito fauna by expanding the investigations
reported by the above-mentioned pilot study [6], focusing on the spatio-temporal diversity of
the mosquito fauna at eight locations distributed throughout the country as determined by
repeated sampling over two years.
As a result, we gain an overview on the Swiss mosquito fauna at country scale, which might
serve as a baseline for the assessment of risk hazards (for human or animal health,
biodiversity) posed by mosquito species.
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Table 1. Classification of Swiss mosquito species with regards to potential threat to human health
for 9 arboviruses (HHA), to human health for human malaria (HHM), to animal health for several
pathogens (avian malaria, 3 filarial nematodes and 3 arboviruses) (AH), and to biodiversity (TB).
Scoring for HH and AH is explained in the pilot study report [6], and scoring for TB is based
mainly on invasiveness of the species (see Box 1). A score equal or higher to 3 indicates
relevance for the category. Species are listed with descending total score which represents the
global potential threat. Species for which score = 0 are not listed.
HHA HHM AH TB Global threat
Ae. albopictus 553
13
An. claviger s.s. 345 12
Cx. modestus 55 10
Cx. pipiens 55 10
Ae. japonicus 333
9
An. maculipennis s.s. 135 9
Ae. vexans 35 8
An. plumbeus 232 7
Ae. caspius 15 6
Ae. dorsalis 33 6
Cs. longiareolata 24 6
Ae. punctor 32 5
Cs. annulata 14 5
Cs. morsitans 41 5
Cx. theileri 41 5
Ae. cinereus s.l. 44
Ae. geniculatus 22 4
An. messeae 13 4
Cq. richiardii 13 4
Cx. torrentium 44
Ae. communis 33
Ae. annulipes 11 2
Ae. cantans 11 2
Ae. excrucians s.l. 11 2
Ae. flavescens 22
Ae. sticticus 11
1. Material and Methods
Research plan
The pilot study investigating urban, suburban, rural and nature areas at different altitudes had
demonstrated that the methodology used was suitable to obtain data for a large spectrum of
mosquito species, the nature zone showing the highest diversity. Therefore, for the present
study, the spectrum of land-use units to be investigated was reduced, by selecting (1) the
nature zone for high diversity, and (2) the suburban zone for high mosquito-host (human, pets
and livestock) contact rate.
This study was performed in a collaboration with three other Swiss research groups: C.
Lengeler/P. Müller and team, Swiss Tropical and Public Health Institute (Swiss TPH), Basel; O.
Glaizot and team, Musée Cantonal de Zoologie (MCZ), Lausanne; and O. Petrini/M. Tonolla
and team, Istituto Cantonale di Microbiologia (ICM), Bellinzona. IPZ has taken over the project
co-ordination, training of investigators and quality control, global data analysis, reporting and
result dissemination.
Box 1. Scoring for TB is attributed as
follows:
5 – Exotic and invasive species,
suppressing indigenous species
4 – Exotic and invasive species, displacing
indigenous species
3 – Exotic species, invasive
2 – Exotic species, introduced and
established
1 – Indigenous species, expanding to new
areas or new larval habitats
0 – Indigenous species, no expansion
Page 6/19
Acquisition of new data based on a specific protocol (2011-2012)
Locations and sites
The spatio-temporal diversity of the mosquito fauna was investigated at eight locations
distributed throughout the country and at different altitudes (Fig. 1).
Figure 1. Situation of the selected 8 locations with 2 (nature, suburban) sites each. Red ovals:
areas already investigated in 2010 during the pilot study; Orange ovals: new areas.
At each location, two sites were selected, one in suburban/outskirts and one in nature zones,
based on land-use GIS maps. These transects were located in: northern Ticino, around
Biasca/Malvaglia (MT1); in central Ticino, around Locarno/Taverne (MT8); in the Midplains,
around Zürich/Bülach (MT2) and around Lausanne/Saint-George (MT7); in the Inner-Alps,
around Luzern/Engelberg (MT3); in Bas-Valais, around Villeneuve/Martigny (MT9): in the Jura,
around Bienne/Sonvillier (MT5); and in Basel around Basel/Langenbruck (MT6). Detail on
locations and sites with situation maps are given in Annex 1.
Locations/areas are attributed to the 4 teams involved in this study:
o ICM (project leader: Mauro Tonolla; in charge of field work: Evelin Casati): MT1
(Biasca/Malvaglia), MT8: (Locarno/Taverne)
o IPZ (project leader and global coordinator: Francis Schaffner; in charge of field
work: Stefanie Wagner): MT2 (Zürich/Bülach), MT3 (Luzern/Engelberg)
o MCZ (project leader: Olivier Glaizot; in charge of field work: Elodie Kuhnert,
2011, and Sébastien Biollay, 2012): MT7 (Lausanne/Saint-George), MT9
(Villeneuve/Martigny)
o Swiss TPH (Project leader: Pie Müller; in charge of field work: Tobias Sutter):
MT5 (Bienne/Sonvilier), MT6 (Basel/Langenbruck)
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Mosquito collection was performed during 5 periods (July 2011, September 2011, May 2012,
July 2012, and September 2012) and over 2 years, to reduce the impact of year-to-year
fluctuation due to global weather conditions. For each period, a window of 2 weeks was
suggested but most of the time these windows were a bit larger (2.5 to 3 weeks) because of
bad weather conditions or practical reasons. At one occasion, two sites were visited only 5
weeks later.
The focus was set on sampling of mosquito immature stages (larvae and pupae), as follows:
- Inspection of potential man-made and natural larval habitats (LH) such as swamps, tree
holes, flooded meadows, shallow and standing water bodies, etc. (see Table 3);
- Collection of larvae (also pupae when present) by visual search with a dipper or a net in
the water stratum;
- LH units were counted as a “whole LH” (e.g. container) or as “a physical/ecological part
of a LH” (e.g. large flooded area) with a maximum size of 20 m²;
- LH units1 were investigated starting from the central point of the site, spirally outwards,
and a minimum of 15 and a maximum of 30 LH units as well as a maximum of 5 LH
units per LH category (see Table 3) were sampled;
- Positive, negative (without any mosquitoes) and non-inspected (at the next visit) LH
units were reported and described.
In addition, at each visit, adult mosquitoes were trapped overnight at 2 places per site, with a
CO2-baited trap (CDC miniature trap or Biogents Sentinel trap), placed at least one hour before
sunset and recovered at least one hour after sunrise.
Geographic coordinates and altitude were collected by using a GPS device (specific or
included in a smartphone). Data were collected using the VECMAP system
(http://iap.esa.int/projects/health/vecmap) on a smartphone (Android platform, including GPS),
or on specific forms, including a field section (sampling) and a laboratory section
(identification), and then entered into a data base.
All larval specimens were stored in 70% ethanol and morphologically identified to species level
based on state-of-the-art morphological identification tools [8, 9]. Pupae were kept alive in a
sample bottle and reared in the laboratory until emergence of adults. These as well as the field
collected ones were killed by placing in a deep freezer for at least 15 minutes and
morphologically identified based on the previously mentioned tools.
All specimens will be kept at least for 1 year after the end of the study. Some specimens (at
least 2 specimens of each species from each location) are kept in the proper way for long-term
storage, i.e. larvae mounted on slide or in alcohol (in that case to be mounted later), adults
pinned with male genitalia mounted on slide or in alcohol (in that case to be mounted later),
and deposited in the reference collection of each institute and/or at a museum.
The study benefits from VECMAP system, mainly for (1) defining the sampling sites (i.e.
identifying geo-referenced sampling points/areas in the land-use units), (2) reporting data via a
smartphone-to-web system, (3) analysing the distribution data, and (3) modelling the potential
distribution of the most common species and mapping species richness in relation to earth
observation and climate data. This last task remains to be performed, as the modelling
software unit is still in the finalization process.
All data are associated to geo-referenced points and gathered in a central data base, and will
be shared with the Centre Suisse de Cartographie de la Faune (CSCF), for edition of
distribution maps of bloodsucking insects on the CSCF website.
1 The minimum number of LH to investigate is defined based on the statement that 70 visits/observations in a
defined area may allow to detect more than 90% of the mosquito species [7].
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Quality management
Field work was described in a detailed protocol (Annex 2), and a one-day training was
organized at the beginning of the project in Ticino for all investigators.
Mosquitoes were identified if possible by each partner and a one-day training was organized
for mosquito identification at IPZ, at the end of the first season.
A quality check (for at least 10% of the samples) of the identified samples was performed by an
expert at IPZ (F. Schaffner) (see Annex 3 for an example). This included (1) confirmation of the
identification of all samples of new species for a region, (2) identification of doubtful
diagnostics, and (3) checking of at least 10% of the samples, randomly selected. As not all
samples could be identified by the partners themselves, mainly due to the involvement of
temporary workers, the percentage of samples checked or identified by the expert varied from
25 to 100%.
2. Results
Potential larval habitats (LH) and the mosquito fauna were investigated at eight locations and
at two sites each (Table 2). The same LHs were repeatedly checked; if this was not possible
(e.g. container removed or LH no longer accessible), they were replaced by others, if possible
from the same category. A total of 1,362 LH observations are reported, ranging from 59 to 109
per site, with an approximately similar number for both nature and suburban zones (48.8 and
51.2%, respectively). The numbers of collected mosquitoes (immature or adult stages) varied
widely among the sites, with more adults being collected in the nature zones and more
immature in the suburban zones. Mosquito species diversity was higher in the nature zones.
Table 2. Numbers of larval habitats (LH) investigated, mosquitoes collected (larvae and adults)
and species identified*, each site (n=16), 2011-12. Adult trapping was performed at 10
occasions at each site. Land cover zones: N, nature; S, suburban.
Locations
Canton Muni cipa li ty Plac e ID Altitude
BE Biel/Bienne
ImRied
BMT5A S 445 75 928 65 8
BE Prêles
Châtillon
BMT5B N 805 85 528 6 6
BL Arlesheim
Öli
BMT6B N 315 59 217 6 8
BL Binningen
StMargreten
BMT6A S 375 75 925 33 6
LU Luzern
Friedental
LMT3A S 440 106 773 177 7
OW Engelberg
Gerschnial p
LMT3B N 1'255 82 661 0 4
TI Biasca
Quaresima
BMT1A S 295 85 355 30 4
TI Camignolo
Camignolo
LMT8B S 455 75 129 10 5
Ti Locarno
BollediMagadino
LMT8A N 198 108 52 546 10
TI Malvaglia
Lagiüna
BMT1B N 360 85 387 483 9
VD Lausanne
Montoi eBourdonette
LMT7A S 395 109 844 305 5
VD Mollens
Fermens
LMT7B N 675 81 169 80 10
VD Noville
LaTronchenaz
VMT9A N 375 88 257 181 14
VS CollombeyMuraz
Mura z
VMT9B S 415 93 597 21 5
ZH Oberglatt/Winkel
Hell
ZMT2B N 420 76 981 124 11
ZH Zürich
Irchel
ZMT2A S 490 80 1'162 0 3
TotalNature 664 3'252 1'426 22
TotalSu burban 698 5' 713 641 15
Grandtotal 1'362 8'965 2' 067 22
Land
cover
larval
habitats
adults
caught
mosquito
species
No.ofobservationsof
immatures
colle ct ed
* Species numbers include 3 pairs of sibling species and 1 species complex (An. maculipennis).
Page 9/19
Overall, the artificial (man-made) LHs are dominant (50.4%) over natural and semi-natural LHs
(37.1 and 12.5%, respectively) (Fig. 2, Table 3). They account for more than 84% of the larval
habitats in suburban zones, whereas natural LHs account for more than 65% in nature zones.
Within artificial LHs, catch basins, rain water barrels and plastic buckets are dominant (22.3,
19.0 and 12.7%, respectively). Within natural LHs, ponds, large pond borders, swamps and
flooded puddles in meadows account together for more than 81% (26.7, 23.9, 15.4, and 15.6%,
respectively).
Figure 2. Number of observations of larval habitat types, per land cover zone and overall, all
sites, 2011-12. Artificial = both substratum and source man-made; Semi-natural = substratum
natural but source man-made (and usually with significant impact of nature, e.g. presence of
vegetation); Natural = both substratum and source natural (and reduced direct impact of
human activities).
113
599
712
124
40
164
427
59
486
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Nature Suburban Overall
No.ofobservationsoflarvalhabitats
Landcoverzones
Natural
Seminatural
Artificial
n=1,362
Page 10/19
Among the 1,362 LHs inspections, 36.7% revealed the presence of mosquito immature stages
(larvae or pupae), with a higher proportion in artificial LHs (42.6%) compared to natural and
semi-natural LHs (30.7 and 30.4%, respectively) (Table 3, Fig. 3).
Table 3. Types and numbers of potential larval habitats (LH) and presence/absence of
mosquito larvae, per land cover zone, all sites (n=16), 2011-12. P: mosquito present; A:
absent.
PATotal PATotal
Artificial
Vase 24 26 50 50
Flowerpotdish 2 13 15 15
Bucket,metal 2 271017 19
Bucket,plastic 4 2 624 51 75 81
Pot,concrete 5 3 88
Container,concrete 2 1 34812 15
Catchbasin 4 11 15 64 63 127 142
Basin 5 8 13 13
Fountain 1 4 534 31 65 70
Drinkingtrough 6 16 22 16729
Rainwaterbarrel 10 5 15 55 51 106 121
Roofgutter 1 4 55
Tarpaulin 32 32 12 17 29 61
Trailer 2 22
Tyre 4 1 55
Seminatural
Puddle 41 77 118 4610 128
Rockpool 3 27 30 30
Natural
Ditch 9 16 25 25
Pond 22 49 71 13 41 54 125
Largepondborder 40 67 107 145112
Puddle,meadow 13 60 73 73
Floodedmeadow 1 2 33
Riverbed 2 18 20 20
Smallstream 9 11 20 20
Streampuddle 4 44
Swamp 30 42 72 72
Treehole 4 11 15 15
GrandTotal 200 430 630 263 370 633 1'263
Naturezone Suburbanzone Grand
Total
Larvalhabitattype
anddescription
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Figure 3. Number of reported presence/absence of mosquito immatures (larvae or pupae) in
potential LHs checked, per LH type, all sites, 2011-12.
271
48 144
463
365
110
325
800
0
200
400
600
800
1000
1200
1400
Artificial Seminatural Natural Overall
No.ofcheckedlarvalhabitats
Larvalhabitattypes
Absence
Presence
n=1,263
Overall, a total of 11,032 specimens (immature and adult stages) belonging to 15 mosquito
species, 3 sibling species (of which all 6 species were confirmed) and to the An. maculipennis
complex were collected (total 22 species; Table 4). The nature zones showed the highest
diversity (all species observed) but a lower relative abundance, accounting for 42.4 % of the
individuals, whereas the suburban zone revealed only 15 species (including 2 sibling species),
but 57.6% of the individuals. Mosquitoes were found at all sites (range 139 - 1,149).
The most abundant species was Cx. pipiens/torrentium (not distinguishable at larval stage;
61.2% of all specimens collected) occurring at all except two sites. Six species were frequently
observed, i.e. Cx. hortensis, Ae. japonicus, An. maculipennis complex members, Ae. vexans,
Ae. cinereus/geminus (both species, not distinguishable as larva or adult female), and Ae.
sticticus, accounting each for 8.5 to 3.9% of the individuals. The remaining species were rarely
found, accounting each for less than 1%.
Page 12/19
Table 4. Numbers of immature and adult individuals collected, per land cover zone, all sites,
2011-12. (*Sibling species pairs and members of the Maculipennis complex are counted
together, as not all specimens have been identified to species level yet).
Immatures Adults Immatures Adults Immatures Adults GrandTotal
Aedesannulipes/cantans* 55 50155 661
Ae.caspius 0100011
Ae.cinereus/geminus* 341 174 03341 177 518
Ae.geniculatus 1119210 12
Ae.japonicus 92 0684 0776 0776
Ae.punctor 1000101
Ae.rusticus 47 10047 148
Ae.sticticus 62 366 0162 367 429
Ae.vexans 126 455 08126 463 589
Anophelesclaviger 65006511
An.maculipenniscomplex* 556 105 3
0
559 105 664
An.plumbeus 29 28937 11 48
Coquillettidiarichiardii 011 08019 19
Culexhortensis 31 0912 0943 0943
Cx.pipiens/torrentium* 1'780 297 4'074 600 5'854 897 6' 751
Cx.territans 36 01037 037
Culisetaannulata 77 15282 385
Cs.longiareolata 12 025 037 037
Cs.morsitans 0200022
Total 3'252 1'426 5'713 641 8'965 2'067 11'032
Overall
Mosquitospecies
observed
Naturezone Suburbanzone
A total of 160 CO2-baited trapping nights were implemented, and 70 of them provided a total of
2,067 mosquito specimens (Table 2, Table 4). The nature zone showed the highest relative
abundance, with 69.0% of the individuals, whereas only 31.0% were caught in the suburban
zone. The highest number of adult mosquitoes was obtained at site MT8A, Locarno (Bolle di
Magadino) (Table 2), in nature zone, with more than 60% of the mosquitoes belonging to either
Ae. vexans or Ae. sticticus. The second site in terms of adult relative abundance was MT1A,
Malvaglia (Lagiüna), also in nature zone, with the two species mentioned above almost
reaching 85% of the collected adults. The third site was MT7A, Lausanne (Montoie-
Bourdonette), in suburban zone, with Cx. pipiens/torrentium accounting for more than 98% of
the caught adults. At two sites, one in nature zone, MT3B, Engelberg (Gershnialp) and on in
suburban zone, MT2A, Zurich (Irchel), no adult mosquitoes were caught at all with the CO2-
baited traps.
Highest relative abundances of the mosquito fauna, all species, were observed in June and
July, for both nature and suburban zones (Fig. 4). Container-breeding mosquitoes showed
either a peek in June (Cx. hortensis), July (Cx. pipiens/torrentium) or August (Ae. japonicus).
The floodland/marshland mosquitoes Ae. vexans and Ae. sticticus peeked in June, but not Ae.
cinereus/geminus. Among the less abundant species (not shown), Cq. richiardii showed a
relative short presence period (June-August), with a peek in June, whereas Ae.
annulipes/cantans and Ae. rusticus showed a peek early in the season (April), and An.
plumbeus late in the season (September).
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Figure 4. Seasonal relative abundance of mosquitoes (both immatures and adults) for each
sampling period (n=5), all sites, 2011-12. A. All species, grouped by genus. B. The two most
abundant species Cx. pipiens/torrentium and Cx. hortensis. C. Two frequently collected
species, Ae. japonicus and An. maculipennis complex. D. Three other frequently collected
species, Ae. vexans, Ae. cinereus/geminus, and Ae. sticticus.
A. B.
C. D.
3. Discussion
The consolidated list of Swiss mosquitoes currently comprises 36 species [6], of which eight
species belonging to three sibling species pairs and to one species complex were not
systematically distinguished in this study (Ae. annulipes/cantans, Ae. cinereus/geminus, An.
maculipennis complex, Cx. pipiens/torrentium). However, all members of the sibling pairs could
be identified in the study by morphology at one stage (male), together with 15 other species,
resulting in the observation of a total of 21 species and one species complex (which will be
further characterized by molecular analysis).
Compared to the Pilot Study (2010) which relied on single samplings in August/September at
five locations, seven additional species were collected in the present study in which eight
locations were repeatedly sampled covering the whole season. Of these seven species, three
occur strictly (Ae. rusticus, Cs. morsitans) or mainly (Ae. punctor) early in the season (when no
investigations were done in the 2010 study) or at sites (single sites only for each species) that
were not investigated in 2010. A single adult of one additional species (Ae. caspius) was
caught at a site that was not investigated in 2010. Another species, Cq. richiardii, was collected
as adults in both new and former sites (four sites). The species relies on LHs in wetlands and
is almost impossible to collect as larvae, and occurs as adult (single generation) only over a
few summer weeks. Two species (Cs. annulata, Cs. longiareolata) were collected at both new
and former sites, and the increasing number of sampling could explain the specific finding in
this study.
Page 14/19
Thirteen species from the Swiss mosquito list were not found during this study: Ae. albopictus,
Ae. cataphylla, Ae. communis, Ae. dorsalis, Ae. excrucians, Ae. flavescens, Ae. pullatus, Ae.
refiki; Cq. buxtoni, Cx. modestus, Cx. martinii, Cs. fumipennis, Cs. alaskaensis. About the
reasons why they escaped their detection in this study can be speculated as follow:
- Ae. albopictus: this invasive mosquito is spreading into Switzerland from northern Italy;
to date, it is only reported from southern Ticino [10], and is not known to be present at
the time of the study at the four sites investigated in Ticino.
- Ae. cataphylla, Ae. communis, Ae. pullatus: these three snow-melt mosquitoes occur
mainly at high altitudes in the Alps and the Jura [6]. We had expected to find them (in
particular Ae. communis) in this study at some nature sites, and the reason for their
absence remains unclear.
- Ae. refiki: this other snow-melt mosquito with strictly only one generation per year is
scarce in Europe and is found only at a limited number of places [9, 11]. More sampling
in spring has to be performed over the country to detect this species in Switzerland.
- Ae. dorsalis and Ae. flavescens breed mainly in halophilic LH; both species have been
collected only at one occasion in Switzerland [11]. Specific investigations should be
performed around salt extraction sites (Aargau, Basel-Landschaft, and Vaud cantons) to
determine whether suitable larval habitats are still available in Switzerland.
- Ae. excrucians: this species complex is rarely found in central Europe, but known to
occur nearby one of our sites (MT2B) [6]. The absence of flooding in 2012 of the known
LH and the performance of trapping late in the season in 2011 could explain the non-
detection in this study. However, the species cannot be distinguished from Ae.
annulipes/cantans as adult, and therefore molecular analysis should be performed to
confirm its absence.
- Cq. buxtoni: As for Cq. richiardii, larvae live submerged and are therefore almost
impossible to collect. Adults are found together with Cq. richiardii but always in very low
numbers compared to Cq. richiardii. So far, the species has only been detected as
adults in southern Ticino [12], nearby one of our sites (MT8-A), but more trappings will
probably be needed in July-August to collect the species.
- Cx. modestus was reported so far only once in Switzerland, from Ticino [12], but it is not
uncommon in the neighbouring French regions Rhône-Alpes [13] and Alsace (F.
Schaffner, personal observations). Specific searches in favourable environments (e.g.
reed beds) might lead to new findings of this species which is regarded as the main
vector of West Nile virus in some European wetlands such as the Camargue [14].
- Cx. martini, Cs. fumipennis, Cs. alaskaensis. These rare species in central Europe have
been collected so far at few places only in Switzerland [6, 11, 15], but more samplings
would probably allow to identify new places.
In this study, some differences in immature sampling and adult trapping can be pinpointed:
- Three species caught as adults were not collected as immatures: Ae. caspius, caught
as a single specimen, probably flying from a distant LH (not sampled in the study); Cq.
richiardii which breeds in permanent water with immature stages submerged and fixed
on plant stems (and not surfacing for breathing) and therefore almost impossible to
collect as larvae except by using specific techniques; and Cs. morsitans, of which two
females were caught in Mollens, August 2012. This species is abundant in early spring
only [8] but a second generation, reduced in number, can be develop at the end of the
summer (F. Schaffner, personal observation).
- Five species collected as immatures were not caught as adults: Cx. hortensis, Cx.
territans, Cs. longiareolata, which are known to be not or only very weakly attracted to
CO2-baited traps used in the study. Similarly, Ae. japonicus is only well attracted to
CO2-baited traps when using an additional chemical lure [16]. Aedes punctor is known
to be well attracted but most probably is very scarce in the surveyed sites (and a single
immature specimens was collected).
The experimental approach (larval sampling and CO2-baited trapping) looks reliable for
collecting most of the mosquito species, and in particular the vector species. Association of
Page 15/19
larval sampling and adult trapping has allowed to enlarge the collected species spectrum, as
eight species among 22 were collected by only one of the two methods. Only rare species,
which because of their scarcity might have no or little impact on mosquito-borne disease
transmissions, were not collected in our study. As for invasive mosquitoes (Ae. albopictus, Ae.
japonicus), additional trapping techniques increase the chances to detect their presence and
estimate their abundances, by using ovitraps, infusion-baited gravid traps, or BG-Sentinel™
traps with Traptech™ lure [16, 17]. However, modelling the distribution of the mosquito species
remains to be performed in order to validate the experimental design for risk mapping.
In this study, we performed, per location, five investigations at two sites instead of only one at
five sites as in the Pilot Study, 2010. When comparing the results in terms of species present
at sites that were investigated during both studies (Table 5), congruent results were obtained in
26 instances (XX in Table 5). The present study identified the presence of mosquito species in
25 instances more than the Pilot Study, whereas the inverse occurred in 3 cases only. When
comparing the results at locations (all 4 sites in the Pilot Study, 2 in this study, per location),
mosquito species were detected in both studies in 22 cases, and a species was found only in
this study in 18 cases, whereas the inverse happened in 5 cases only (data not shown). This
confirms the higher sensitivity of the field experimental design of this study, as compared to the
Pilot Study.
Table 5. Mosquito species detected at sites investigated in both the Pilot Study (2010) and this
study (2011-12). Species detection: X, in Pilot Study only; XX, in both studies; XXX, in this
study only.
2010 201112 2010 201112 2010 201112 2010 201112 2010 201112 2010 201112 2010 201112 2010 201112
Aedesannulipes/cantans X XXX XXX X
Ae.caspius
Ae.cinereus/geminus XXX XXX
Ae.geniculatus XX XX
Ae.japonicus XXX XXX XXXXXXXXXXXX
Ae.punctor XXX
Ae.rusticus
Ae.sticticus XXX XX XX XXX
Ae.vexans XX XX XX XX XXX XXX XX XX
Anophelesclaviger X XXXX XXXX
An.maculipenniscomplex XXX XX XX XX XX XXX
An.plumbeus XXX XX XX
Coq uillettidia richiardii XXX XXX
Culexhortensis XX XX XXX XXX XXX XXX XX XX
Cx.pipiens/torrentium XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX XX
Cx.territans XX XX XX XX XX XX XXX
Culisetaannulata XXX XXX
Cs.longiareolata XXX
Cs.morsitans XXX
Total no.ofspecies 68461361114386724
BMT5A LMT3A ZMT2A
Naturezone Suburbanzone
BMT1B BMT5B LMT3B ZMT2B BMT1A
Mosquitospecies
observed
Considering the geographical distribution of the collected species, solid conclusions can only
be stated for Ae. japonicus which was collected in high numbers at all places in northeaster
Switzerland, but not in western and southern Switzerland. This confirms that this species had
been introduced in northern Switzerland and was spreading from there [18]. The most westerly
confirmed occurrence in Switzerland is Biel, and is not clear why the species, which rapidly
spread after its introduction [18] is not invading western Switzerland. The recently published
presence of this mosquito in Germany at two places (around Stuttgart and Bonn [19]) therefore
might originate from separate introductions, not from unnoticed continuous expansion of the
Swiss population northwards.
Page 16/19
Other data suggesting that some species might have limited geographical distributions are too
weak for any conclusions to be drawn (except for Ae. albopictus which is restricted to southern
Ticino which was outside our study area). Indeed, Ae. caspius and Ae. punctor were found only
southern to the Alps, and Cs. morsitans only in Western Switzerland, but the two last species
are known to also occur in other regions of the country. All other species do not show any
particular distribution.
All 22 mosquito species were found in nature zone, and five of them (Ae. caspius, Ae. punctor,
Ae. rusticus, An. claviger, and Cs. morsitans) where not found in the suburban zone. However,
four additional species (Ae. cantans/annulipes, Ae. cinereus/geminus, Ae. vexans, and An.
claviger) were found in the suburban zone only as adults, and therefore could have flown into
these sites from distant LHs. These results confirm the higher diversity in nature zone as
compared to suburban zone, already suggested in our Pilot Study.
From collected data, seasonal dynamic tendencies can be suggested a follows:
- Ae. vexans and Ae. sticticus breed in wetlands and are usually abundant after flooding
(from spring to fall); in our study, they were highly abundant in June (Fig. 4D). Aedes
cinereus and Ae. geminus have similar LHs and therefore could be expected to show a
similar dynamic, but this was not the case in this study. Rather, their populations were
more abundant in April and July, with less marked peaks of abundance. All four species
can fly over some distances to disperse and seek hosts.
- Ae. japonicus, which was shown to be a vector under laboratory conditions for a number
of pathogens, including West Nile and Dengue virus [20-24], was more abundant in
summer (August; Fig. 4C), when high temperatures would favour virus amplification,
thus rendering this species a potential vector. When established for several years, the
species seems to become the most abundant one in the suburban zone, as shown at
Zürich, Irchel, where it was more abundant than Cx. pipiens/torrentium in three of the
five investigated periods (but the Culex species prevailed overall).
- Among malaria vectors, An. plumbeus whose populations have increased over the last
years and which was shown to be an efficient vector [25], becomes abundant late in the
season, in August-September, whereas species form the Maculipennis complex were
abundant over the whole summer, from June to September (Fig. 4C).
- Cq. richiardii shows one peak in June which is in agreement with its univoltine
characteristic.
- Ae. rusticus, Ae. cantans, and Ae. annulipes were mostly found in April, confirming their
classification as spring mosquitoes with only one generation (Ae. rusticus) or showing
occasionally a weak second generation or staggered secondary cohorts.
- Cx. pipiens and Cx. torrentium (Fig. 4B) show a weak population in spring, which
corresponds to the first generation produced by the overwintering females; later,
populations are abundant all over the summer and fall, in particular in June and July;
they are the most abundant mosquitoes at almost all places, except two nature
locations (Locarno, Bolle di Magadino and Noville, La Tronchenaz).
Overall (Fig. 4A), the highest abundance of mosquitoes occur in a period less favourable for
pathogen transmission (June, lower temperature), but high abundance were observed in July,
which looks to be the highest risk period with regard to vector abundance and suitability of
pathogen replication.
Some in-depth investigations remain to be performed: molecular identification within
complexes and sibling species (larvae and females of Ae. cinereus/geminus, Ae.
annulipes/cantans, Cx. pipiens/torrentium; larvae and adults of the Maculipennis complex) by
PCR or MALDI-TOF MS technique (recently established by IPZ and Mabritec, Riehen [26, 27]),
together with samples of the Pilot Study 2010); statistical analysis; and finally extrapolation and
modelling for risk mapping using the VECMAP modelling component which currently is in the
finalization process.
Page 17/19
4. Conclusions
The chosen approach to characterize the spatio-temporal diversity of the mosquito fauna in
Switzerland, repeated larval sampling and CO2-baited trapping at eight nature and suburban
locations, was successful for collecting most of the Swiss mosquito species, including the
vector species. From the known 36 species from Switzerland, only 13 were not identified in the
collected mosquitoes, mainly species known to be rare or having halophilic or thermophilic
requirements. The seven most common mosquitoes (Ae. cinereus/geminus; Ae. japonicus, Ae.
sticticus, Ae. vexans, An. maculipennis complex, Cx. hortensis, Cx. pipiens/torrentium)
accounted for around 97% of the collected specimens, all but Cx. hortensis (second most
common) being described as having a potential to act as vector (Table 1). As virtually no adults
of these vector species were collected in suburban areas (with the exception of Cx.
pipiens/torrentium), specific vector surveillance could abstain from using adult collection in
these areas. Laboratory vector competence studies under realistic Swiss climate conditions are
required to assess the vector competence of the Swiss mosquito populations, and such studies
are currently being performed at IPZ (Zürich) for West Nile virus.
Morphological identification of mosquitoes is in many instances a time-consuming and
sometimes difficult task, and the capacity for large scale surveillances is not available in
Switzerland (identification was often done by temporary, semi-skilled collaborators, requiring
extensive quality control). The recently developed MALDI-TOF MS database, currently
containing spectra of immature and adult stages of 35 European species [27], can be used as
a high-throughput, cost-efficient and highly reliable identification tool. The technique also is
suitable to identify several species in pools of eggs, and thus is particularly useful for the
surveillance of invasive container breeding Aedes species. Aedes albopictus was not detected
in the study (the known distribution area in southern Ticino was not included) but is expected to
spread further. Indeed, very few specimens (adults or larvae) of Ae. albopictus have repeatedly
been detected in summer in Germany and Austria north of the Alps [28, 29].
The invasive species Ae. japonicus was overall the third most common species, being the
prevailing species in late summer. To answer the question whether this species is a threat to
biodiversity by reducing resident container breeding species requires further investigations. In
North America, where the species has also been introduced, this issue is controversially
discussed [30-32].
Finally, as already stated in the Pilot Study, a nation-wide surveillance could be extended to
include also other arthropod vectors (sand flies, biting and sucking flies, ticks). More
knowledge on vector distribution and capacity in Switzerland will allow to develop a risk
assessment and management for vector-borne diseases that might emerge under
environmental and climate changes.
Page 18/19
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Annex 1. Details on the selected locations and sites with situation maps.
o MT1 (Fig. 1): Ticino (northern), from Biasca towards north-east (Malvaglia)
MT1A: District Riviera, Municipality Biasca, Location Quaresima; Central point Lat.
46.351114°, Lon. 8.967637°, Alt. 294m; Land-use Suburban.
MT1B: District Blenio, Municipality Malvaglia, Location Lagiüna; Central point Lat.
46.383771°, Lon. 8.983422°, Alt. 360m; Land-use Nature.
o MT2 (Fig. 2): Midland, from Zürich towards north (Bülach)
MT2A: District Zürich, Municipality Zürich, Location Irchel; Central point Lat. 47.398992°,
Lon. 8.551096°, Alt. 488m; Land-use Suburban.
MT2B: District Dielsdorf/Bülach, Municipalities Oberglatt/Winkel; Central point Lat.
47.483587°, Lon. 8.540984°, Alt. 418m; Land-use Nature/Agriculture.
o MT3 (Fig. 3): Inner-Alps, from Luzern towards south (Engelberg)
MT3A: District Luzern, Municipality Luzern, Location Friedental; Central point Lat.
47.061441°, Lon. 8.298851°, Alt. 442m; Land-use Suburban.
MT3B: District Obwalden, Municipality Engelberg, Location Gershnialp; Central point Lat.
46.809905°, Lon. 8.399895°, Alt. 1255m; Land-use Nature/Agriculture.
o MT5 (Fig. 4): Jura, from Biel/Bienne towards west (Sonvilier)
MT5A: District Biel, Municipality Biel; Central point Lat. 47.128079°, Lon. 7.263576°, Alt.
445m; Land-use Suburban.
MT5B: District La Neuveville, Municipality Prêles, Location Châtillon; Central point Lat.
47.099628°, Lon. 7.103412°, Alt. 810m; Land-use Nature/Agriculture.
o MT6 (Fig. 5): Basel, from Basel towards south-east (Langenbruck)
MT6A: District Arlesheim, Municipality Binningen, Location St Margreten; Central point
Lat. 47.541406°, Lon. 7.579974°, Alt. 314m; Land-use Suburban.
MT6B: District Arlesheim, Municipality Arlesheim, Location Öli; Central point Lat.
47.490991°, Lon. 7.632468°, Alt. 373m; Land-use Suburban.
o MT7 (Fig. 6): Vaud, from Lausanne towards west (Saint-George)
MT7A: District Lausanne, Municipality Lausanne, Location Montoie-Bourdonette; Central
point Lat. 46.523040°, Lon. 6.594694°, Alt. 393m; Land-use Suburban.
MT7B: District Morges, Municipality Mollens, Location Fermens; Central point Lat.
46.574357°, Lon. 6.386388°, Alt. 670m; Land-use Nature.
o MT8 (Fig. 7): Ticino (southern), from Locarno towards south (Taverne)
MT8A: District Locarno, Municipality Locarno, Location Bolle di Magadino; Central point
Lat. 46.160338°, Lon. 8.864050°, Alt. 195m; Land-use Nature/Agriculture.
MT8B: District Lugano, Municipality Camignolo; Central point Lat. 46.106023°, Lon.
8.937104°, Alt. 443m; Land-use Suburban.
o MT9 (Fig. 8): Bas-Valais, Villeneuve towards south (Martigny)
MT9A: District Aigle, Municipality Noville, Location La Tronchenaz; Central point Lat.
46.391857°, Lon. 6.916904°, Alt. 375m; Land-use Nature.
MT9B: District Monthey, Municipality Collombey-Muraz, Location Muraz; Central point Lat.
46.279608°, Lon. 6.924871°, Alt. 413m; Land-use Suburban.
Note: MT4 (around Fribourg) of the pilot study (2010) was not used for the present study.
Figure 1. Situation of the 2 sites of MT1 (Biasca/Malvaglia)
Figure 2. Situation of the 2 sites of MT2 (Zürich/Bülach)
Figure 3. Situation of the 2 sites of MT3 (Luzern/Engelberg)
Figure 4. Situation of the 2 sites of MT5 (Bienne/Sonvilier)
Figure 5. Situation of the 2 sites of MT6 (Basel/Langenbruck)
Figure 6. Situation of the 2 sites of MT7 (Lausanne/Saint-George)
Figure 7. Situation of the 2 sites of MT8 (Locarno-Taverne)
Figure 8. Situation of the 2 sites of MT9 (Villeneuve/Martigny)
Working document Page 1/8 Mosquito Diversity Protocol
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
Annex 2
Research project Spatio-temporal diversity of mosquito fauna in Switzerland,
BAFU, 2011-12
Study protocol
This study aims to investigate the spatio-temporal diversity of the Swiss mosquito fauna as
follows:
At 8 locations distributed throughout the country at different altitudes (Annex 1).
For each location, 2 sites are selected, one in suburban/outskirts and one in nature zones,
based on land-use GIS maps.
Each site is investigated based on (1) larval (juvenile) collection in potential larval habitats and
(2) adult trapping by CO2-baited traps.
All sites will be investigated at 5 occasions: July 2011, September 2011, May 2012, July 2012,
and September 2012.
1. FIELD EXPERIMENT DESIGN
a. Locations and sites
8 locations/areas (see Annex 1) attributed to the 4 teams gathered for this study:
ICM – Project leader: Mauro Tonolla – In charge of field work:
Evelin Casati
o B-MT1: Ticino (northern), from Biasca towards north-east
o L-MT8: Ticino (southern), From Locarno towards south (Taverne)
IPZ – Project leader (also global coordinator): Francis Schaffner – In charge of
field work: Stefanie Wagner
o Z-MT2: Midland, from Zurich towards north (Bülach)
o L-MT3: Inner-Alps, from Luzern towards south (Engelberg)
MCZ – Project leader: Olivier Glaizot – In charge of field work:
Elodie Kuhnert
o L-MT7: Vaud, from Lausanne towards west (Saint-George)
o V-MT9: Bas-Valais, Villeneuve towards south (Martigny)
STPH – Project leader: Pie Müller – In charge of field work: Tobias Sutter
o B-MT5: Jura, from Biel/Bienne towards west (Sonvilier)
o B-MT6: Basel, from Basel towards south-east (Langenbruck)
b. Sampling methods
Adult trapping with CO2-baited traps (CDC light-trap or Biogents Sentinel trap),
overnight, 2 traps per site.
Filling in one trapping field form per trap-night [FORM 1]
Larval sampling (also pupae) in all potential larval habitats (LH), collected with a
dipper or a net:
- LH are man-made and natural breeding habitats such as swamps, tree holes,
floodplains, shallow and standing water bodies, etc.
- LH units are defined as a whole LH (e.g. container) or a physical/ecological part
of it (e.g. large flooded area) with a maximum size of 20 m².
- LH units are investigated starting from the central point of the site, spirally
outwards; A minimum of 15 and a maximum of 30 LH units as well as a
maximum of 5 LH units per LH category are sampled.
Working document Page 2/8 Mosquito Diversity Protocol
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
- Positive, negative (without any mosquitoes) and not checked LH units are
reported and described as well as the environment.
Report on samples field form [FORM 2]
See details in Chapter 2
c. Sampling frequency
All sites will be investigated at 5 occasions: July 2011 (week 30), September 2011
(week 37 or 38), May 2012, July 2012, and September 2012; 2012: weeks still to be
defined.
d. Specimens identification and conservation
Collected larvae (or pupae) are stored in 70% ethanol.
When only pupae are present, they are kept alive in a sample bottle and are reared
in the lab to identify the emerged adults.
Adults females are kept frozen by -20°C, adult males in 70% ethanol.
All specimens are identified to species by morphology; For complex species,
molecular tools will be used (e.g. Culex pipiens and Anopheles maculipennis
complexes).
When a sample contains more than 50 individuals, they are ‘grouped’ based on their
morphological overall aspect, and at least 5 individuals per group are identified to
species.
All specimens are kept at least for 1 year after the end of the study; Some
specimens (at least 2 specimens of each species from each location) are kept in
proper way for long-term storage, i.e. larvae mounted on slide or in alcohol (in that
case to be mounted later), adults pinned with male genitalia mounted on slide or in
alcohol (in that case to be mounted later), and deposited in the reference collection
of each institute and/or at a museum.
Mosquitoes are identified by each partner and training will be organized for
mosquito identification at IPZ, at the end of the first season, including a quality
check (around 10 % of the samples) of the identified samples by an expert;
Identification by molecular tools is made at IPZ.
Report on trapping identification form [FORM 3] or sample identification form
[FORM 4]
e. Other issues
Data will be validated (quality check as described above) and stored in a central
data base at IPZ.
The study benefits from VECMAP system, mainly for (1) defining the sampling sites
(i.e. identifying geo-referenced sampling points/areas in the land-use units), (2)
reporting data via a smartphone-to-web system (at least in 2012), (3) analysing the
distribution data, and (3) modelling the potential distribution of the most common
species and mapping species richness in relation to earth observation and climate
data.
All data will be associated to geo-referenced points and reported in a central data
base, and shared with the Centre Suisse de Cartographie de la Faune, for real-time
update of web-edited distribution maps of bloodsucking insects (at least in 2012).
After data analysis of the first field work season, the project might be adjusted (e.g.
to include further sites).
Working document Page 3/8 Mosquito Diversity Protocol
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
FIELD PROTOCOL
f. Preparation
Light traps
Charge the batteries (up to 6.2-6.4 volts)
Order 5 kg of dry-ice (for 4 traps)
g. Field material checklist
Larval (juveniles) sampling
Aquatic net or dipper
1 litter white plastic tray
3 transfer pipettes
Labeled small plastic bottles (red lid; X ml)
Adult trapping with CO2-baited light traps
4 complete CO2-baited CDC light traps (or BG Sentinel traps)
- central piece (plastic plate + tube + ventilator + electric system); with the light bulb
taken off
- net with plastic box
- battery (6 V, 12 Ah)
- blue isotherm bottle
Dry-ice
Gloves for manipulation of dry-ice (-80°C)
String, knife
Other
Paper, pencil, waterproof pencil
GPS device
Project field forms
h. Larval sampling
1. Sampling:
Small containers: pour the whole content into the white plastic tray.
Small fixed containers (i.e. tree holes): take the water out with a pipe by sucking
up or with a small cup, into the plastic tray.
Large LH units:
2. Take the mosquitoes out of the tray with the transfer pipette into a labeled plastic
vial.
3. If only pupae, add water form LH up to 2/3 of the plastic vial; If larvae and pupae,
take the water out and replace by 70% alcohol.
i. Adult traps pose
CO2-baited traps
At least 2 hours before sunset:
1. Hang the trap with the insect entrance at about 1.5 m from ground level; take the
light bulb off if not done before.
Working document Page 4/8 Mosquito Diversity Protocol
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
2. Hang the isotherm bottle (previously filled with dry-ice up to 2/3, 800 gr.) above
the trap.
3. Add the net with a label inside (site and dates).
4. Connect the battery (cable to battery terminal connection: red to red, black to black;
With photoswitch activated for the fan running continuously), pose the battery on the
ground, protected from rain.
j. Adult traps taking off
CO2-baited traps
At least 2 hours after sun rise:
1. Disconnect the battery (both cables).
2. Take the net off, close it, and store it in a large isotherm box if air temperature is
higher than 22°C (label inside).
3. Take the trap, the isotherm bottle and the battery off.
k. Samples handling
Larvae (and pupae)
Keep the sample vial in a cold storage room at 4/10°C.
Pupae (from LH units showing no larvae)
Keep the pupae in sample bottles (with water from LH) at room temperature (not
higher than 25°C) until emerging of adults (maximum 3 days).
Take the adults off a few hours after emerging with a mouth aspirator, to be handled
as below.
Adults
Place the trap net in the freezer (-20°C) for at least 10 minutes, to kill the
mosquitoes.
Take the net off the freezer, take the label and the mosquitoes carefully out.
They can now be identified under the binocular; store the males apart in a labeled
70% alcohol tube, and keep the females in a labeled sample tube in the freezer
(-20°C). Part of them can be pinned (and labeled) in an insect box for long-term
conservation.
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
Municipality:
Location: Starting of trapping
Ending of trapping
Site environnement:
* Trapping ID = SiteID_YYMMDD
Time:Date:
Trapping field form
Mosquitoes, BAFU project 2011-2012
FORM 1
Canton:
Georeference coordinates: Altitude:
Trapping ID*:
To be filled out on the first visit
Site information Trapping information
Meteo:
Trap ID:
T. model/no.:
Site ID: Date: Time:
Meteo:
Manipulator(s):
Presence of hosts on the site: yes / no
List of hosts:
Comments:
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
HB= Human Bait
LS=Larval Sampling
CT=CO2-baited Trap
Catch information
Larval habitat Sampling
Municipality Place Altitude Type Description LH
surface Water
surface LH
depth Water
depth
presence/
absence not
checked
Date Time Trap_
Type
TI B-MT1A N name name m NxN or D (cm) cm cm F/M/L/P/- N 10/07/2010 9:00 LS
Mosquitoes, BAFU project
2011-2012
FORM 2 Samples field form Filled by:
Degree decimal: N,NNNN
Latitude
Google Earth
WGS84
Longitude
Google Earth
WGS84
Site information
Canton Location
ID LH unit
ID
Mosquitoes
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
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











Identification :
1
Tentative
2
Definitive
Total other insects: Total sample: Sub-sample: proportion: Database entry: 
Other biting insects
Culicidae
FORM 3 Trapping identification form
Mosquitoes, BAFU project
2011-2012
Species
Site ID:
Trapping ID:
Protocol reference: BAFU 2011-12 Date of first insect sorting:
Manipulator for first sorting:
Date of identification:
Manipulator for identification:
D
2
Total
females
Date of trapping:
Total
males Sample
total T
1
Uni-Zürich-CH / IPZ / FS Edition: 25/07/2011
Culicidae species No. larvae No. pupae
B-MT1A N Culex pipiens NNNN
FORM 4
Comments
Samples identification form
Filled by:
Site information
Location ID LH unit
ID No. females No. males
Mosquitoes, BAFU pro
j
ect
2011-2012
... Recent studies of the Swiss mosquito fauna revealed a consolidated list of 36 species, several of which can play a role in pathogen transmission (Schaffner & Mathis, 2013). Solid data exist on the presence and seasonal abundance of the invasive species Aedes albopictus (Skuse) (Diptera: Culicidae) (Flacio et al., 2016), a potential vector of the dengue, Chikungunya and Zika viruses, and targeted control measures against this species have been implemented (Flacio et al., 2015a). ...
... Samplings were based on baited adult CDC traps run over the mosquito season in 2013, which yielded a collection of 29 715 specimens, with complementary monitoring performed in 2012 and 2014, as well as JS and ovitrapping to complete the trapping results. A total of 122 831 mosquito specimens were gathered in this study, representing a quantity unsurpassed in similar studies (Schaffner & Mathis, 2013;Flacio et al., 2014) carried out in Switzerland. A combined literature and field pilot study in 2010 revealed a consolidated list of 36 mosquito species in Switzerland . ...
... Cx. pipiens, Ae. vexans and Ae. sticticus (Schaffner & Mathis, 2013;Flacio et al., 2014)], and two invasive species found either south (Ae. albopictus) or north (Ae. ...
Article
Pathogens of medical or veterinary significance that are transmitted by mosquitoes (Diptera: Culicidae) are (re-)emerging in Europe [e.g. West Nile virus (WNV), Dirofilaria nematodes]. Little is known about the spatiotemporal abundances of mosquito species in Switzerland. Therefore, mosquito population dynamics were investigated, focusing on areas of risk for sylvatic or synanthropic transmission, such as natural sites and suburban sites on either side of the Alpine crest. Repeated collections were made using Centers for Disease Control (CDC) traps, juvenile sampling and ovitrapping. A total of 122 831 mosquito specimens of 21 taxa were identified. Levels of mosquito species richness were similar at suburban sites and in natural zones in Switzerland. Mosquito abundances and seasonality were analysed with generalized linear mixed models based on 382 CDC trap samples (29 454 females) and revealed Aedes annulipes/cantans, Aedes geniculatus, Aedes japonicus, Aedes sticticus, Aedes vexans, Coquillettidia richiardii and Culex pipiens/torrentium as the dominant species overall. Abundances of these species were season-dependent in most cases. There was an effect of site with regard to abundance (higher in natural zones), but not with respect to seasonality. Together with data on vector competence and the host preferences of different species, the present data contribute to assessments of risk for pathogen transmission. For example, both natural and suburban environments seem feasible as sites for amplification cycles of WNV and transmission to mammals.
... As CO 2 is a general host-seeking cue for blood-feeding arthropods, only CO 2 was chosen as an attractant for this study. Larval sampling could further complement adult female trapping to study mosquito diversity (Rueda, 2008;Lundström et al., 2013;Schaffner & Mathis, 2013). Furthermore, the number of trapped species and specimens can fluctuate substantially depending on the year (Osório et al., 2008). ...
... Although diversity indices did not show a clear pattern for habitats (Table 2), species diversity was always higher in (semi-) natural areas (farms and wetlands) when compared to peri-urban habitats in all countries. This corresponds with other studies that found higher diversity in wet, inundated or heterogenic natural areas with a high vegetation index (Schäfer et al., 2004;Foley et al., 2007;Chaves et al., 2011;Marí & Jiménez-Peydró, 2011;Schaffner & Mathis, 2013;Versteirt et al., 2013;Roiz et al., 2015). This probably reflects the fact that natural areas offer more diversity in breeding habitats, resting places, and available hosts for mosquitoes. ...
... Culex pipiens was trapped in large numbers in all three countries and most of the habitats. Other studies in Europe also found Cx. pipiens to be one of the most dominant species (Aranda et al., 2009;Marí & Jiménez-Peydró, 2011;Schaffner & Mathis, 2013;Versteirt et al., 2013;Roiz et al., 2015;Boukraa et al., 2016). Culex pipiens is a known vector for WNV, which already circulates in some parts of Europe (Han et al., 1999;Turell et al., 2005). ...
... As CO 2 is a general host-seeking cue for bloodfeeding arthropods, only CO 2 was chosen as an attractant for this study. Larval sampling could further complement adult female trapping to study mosquito diversity [17,40,41]. Furthermore, the number of trapped species and specimens can fluctuate substantially depending on the year [19]. ...
... Although diversity indices did not show a clear pattern for habitats (Table 2), species diversity was always higher in (semi-) natural areas (farms and wetlands) when compared to peri-urban habitats in all countries. This corresponds with other studies that found higher diversity in wet, inundated or heterogenic natural areas with a high vegetation index [14,16,21,23,41,44,45]. This probably reflects the fact that natural areas offer more diversity in breeding habitats, resting places, and available hosts for mosquitoes. ...
... Culex pipiens was trapped in large numbers in all three countries and most of the habitats. Other studies in Europe also found Cx. pipiens to be one of the most dominant species [16,23,41,44,48,49]. Culex pipiens is a known vector for WNV, which already circulates in some parts of Europe [2,50]. ...
Article
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Background Studies on mosquito species diversity in Europe often focus on a specific habitat, region or country. Moreover, different trap types are used for these sampling studies, making it difficult to compare and validate results across Europe. To facilitate comparisons of trapping sites and community analysis, the present study used two trap types for monitoring mosquito species diversity in three habitat types for three different countries in Europe. Methods Mosquitoes were trapped using Biogents Sentinel (BGS), and Mosquito Magnet Liberty Plus (MMLP) traps at a total of 27 locations in Sweden, the Netherlands and Italy, comprising farm, peri-urban and wetland habitats. From July 2014 to June 2015 all locations were sampled monthly, except for the winter months. Indices of species richness, evenness and diversity were calculated, and community analyses were carried out with non-metric multidimensional scaling (NMDS) techniques. Results A total of 11,745 female mosquitoes were trapped during 887 collections. More than 90% of the mosquitoes belonged to the genera Culex and Aedes, with Culex pipiens being the most abundant species. The highest mosquito diversity was found in Sweden. Within Sweden, species diversity was highest in wetland habitats, whereas in the Netherlands and Italy this was highest at farms. The NMDS analyses showed clear differences in mosquito communities among countries, but not among habitat types. The MMLP trapped a higher diversity of mosquito species than the BGS traps. Also, MMLP traps trapped higher numbers of mosquitoes, except for the genera Culex and Culiseta in Italy. Conclusions A core mosquito community could be identified for the three countries, with Culex pipiens as the most abundant species. Differences in mosquito species communities were more defined by the three countries included in the study than by the three habitat types. Differences in mosquito community composition across countries may have implications for disease emergence and further spread throughout Europe. Future research should, therefore, focus on how field data of vector communities can be incorporated into models, to better assess the risk of mosquito-borne disease outbreaks. Electronic supplementary material The online version of this article (10.1186/s13071-017-2481-1) contains supplementary material, which is available to authorized users.
... Centers for Disease Control traps activated with CO 2 showed different levels of attractiveness for different species of mosquito according to the environments and the added attractants (light, chemical lure). In these trapping trials, eight of the 13 mosquito species common in the study area ( Schaffner & Mathis, 2013) were collected. The mean number of specimens collected per night was generally rather low (4.4 ± 0.4 mosquitoes per night), but was comparable with previous results obtained in a study conducted in the same area ( Schaffner & Mathis, 2013). ...
... In these trapping trials, eight of the 13 mosquito species common in the study area ( Schaffner & Mathis, 2013) were collected. The mean number of specimens collected per night was generally rather low (4.4 ± 0.4 mosquitoes per night), but was comparable with previous results obtained in a study conducted in the same area ( Schaffner & Mathis, 2013). Aedes vexans and Cx. ...
... No eggs of this univoltine species were identified in the present study. Aedes geniculatus is usually present in low densities ( Schaffner & Mathis, 2013), which was confirmed by CDC adult trap collections (0.3% of total mosquitoes caught). In both infusion and oviposition substrate evaluation tests, the largest collections of eggs were obtained in the cemetery, where adult trapping of Ae. j. japonicus was low. ...
... Among the 10 taxa found in the BG-Sentinel traps the most dominant one was the sibling species pair Culex pipiens/torrentium. Culex pipiens/torrentium has frequently been described as the most abundant mosquito taxon in Switzerland [66,67]. Further MALDI-TOF MS analysis of a subset of specimens taken from one site in Ticino and three sites north of the Swiss Alps identified Cx. pipiens s.s. ...
... japonicus. These species have also been observed at higher frequencies in Switzerland in previous studies [36,67]. ...
Article
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Over the past three decades, Europe has witnessed an increased spread of invasive aedine mosquito species, most notably Aedes albopictus, a key vector of chikungunya, dengue and Zika virus. While its distribution in southern Europe is well documented, its dispersal modes across the Alps remain poorly investigated, preventing a projection of future scenarios beyond its current range in order to target mosquito control. To monitor the presence and frequency of invasive Aedes mosquitoes across and beyond the Alps we set oviposition and BG-Sentinel traps at potential points of entry with a focus on motorway service areas across Switzerland. We placed the traps from June to September and controlled them for the presence of mosquitoes every other week between 2013 and 2018. Over the six years of surveillance we identified three invasive Aedes species, including Ae. albopictus, Ae. japonicus and Ae. koreicus. Based on the frequency and distribution patterns we conclude that Ae. albopictus and Ae. koreicus are being passively spread primarily along the European route E35 from Italy to Germany, crossing the Alps, while Ae. japonicus has been expanding its range from northern Switzerland across the country most likely through active dispersal.
... Consequently, this peak will probably have no consequences regarding a local transmission. During the March-April peak, DENV and CHIKV can be transmitted by Ae. japonicus [23], and ZIKV by Ae. vexans if European mosquitoes appear to be competent (such as Canadian ones do) [30]. The summer peak is highly correlated with the activity of Ae. albopictus. ...
... Number of mosquito species recorded per country[16,[19][20][21][22][23][24][25]. ...
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Background: The intensification of trade and travel is linked to the growing number of imported cases of dengue, chikungunya or Zika viruses into continental Europe and to the expansion of invasive mosquito species such as Aedes albopictus and Aedes japonicus. Local outbreaks have already occurred in several European countries. Very little information exists on the vector competence of native mosquitoes for arboviruses. As such, the vectorial status of the nine mosquito species largely established in North-Western Europe (Aedes cinereus and Aedes geminus, Aedes cantans, Aedes punctor, Aedes rusticus, Anopheles claviger s.s., Anopheles plumbeus, Coquillettidia richiardii, Culex pipiens s.l., and Culiseta annulata) remains mostly unknown. Objectives: To review the vector competence of both invasive and native mosquito populations found in North-Western Europe (i.e., France, Belgium, Germany, United Kingdom, Ireland, The Netherlands, Luxembourg and Switzerland) for dengue, chikungunya, Zika, West Nile and Usutu viruses. Methods: A bibliographical search with research strings addressing mosquito vector competence for considered countries was performed. Results: Out of 6357 results, 119 references were related to the vector competence of mosquitoes in Western Europe. Eight species appear to be competent for at least one virus. Conclusions: Aedes albopictus is responsible for the current outbreaks. The spread of Aedes albopictus and Aedes japonicus increases the risk of the autochthonous transmission of these viruses. Although native species could contribute to their transmission, more studies are still needed to assess that risk.
... Die asiatische Buschmücke, die häufig mit der asiatischen Tigermücke (Ae. albopictus) verwechselt wird (Abbildung 11), wurde bereits vermehrt im schweizerischen Mittelland gefunden [8,12,14] ...
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Despite the eradication of malaria across most European countries in the 1960s and 1970s, the anopheline vectors are still present. Most of the malaria cases that have been reported in Europe up to the present time have been infections acquired in endemic areas by travelers. However, the possibility of acquiring malaria by locally infected mosquitoes has been poorly investigated in Europe, despite autochthonous malaria cases having been occasionally reported in several European countries. Here we present an update on the occurrence of potential malaria vector species in Europe. Adopting a systematic review approach, we selected 288 papers published between 2000 and 2021 for inclusion in the review based on retrieval of accurate information on the following Anopheles species: An. atroparvus, An. hyrcanus sensu lato (s.l.), An. labranchiae, An. maculipennis sensu stricto (s.s.), An. messeae/daciae, An. sacharovi, An. superpictus and An. plumbeus. The distribution of these potential vector species across Europe is critically reviewed in relation to areas of major presence and principal bionomic features, including vector competence to Plasmodium. Additional information, such as geographical details, sampling approaches and species identification methods, are also reported. We compare the information on each species extracted from the most recent studies to comparable information reported from studies published in the early 2000s, with particular reference to the role of each species in malaria transmission before eradication. The picture that emerges from this review is that potential vector species are still widespread in Europe, with the largest diversity in the Mediterranean area, Italy in particular. Despite information on their vectorial capacity being fragmentary, the information retrieved suggests a re-definition of the relative importance of potential vector species, indicating An. hyrcanus s.l., An. labranchiae, An. plumbeus and An. sacharovi as potential vectors of higher importance, while An. messeae/daciae and An. maculipennis s.s. can be considered to be moderately important species. In contrast, An. atroparvus and An. superpictus should be considered as vectors of lower importance, particularly in relation to their low anthropophily. The presence of gaps in current knowledge of vectorial systems in Europe becomes evident in this review, not only in terms of vector competence but also in the definition of sampling approaches, highlighting the need for further research to adopt the appropriate surveillance system for each species. Graphical Abstract
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The Asian bush mosquito Aedes japonicus japonicus (Theobald, 1901) [=Ochlerotatus japonicus (sensu Reinert et al., 2004) =Hulecoeteomyia japonica (sensu Reinert et al., 2006)], has invaded large parts of North America and has recently started to spread in Central-Western Europe. The species is suspected to act as a bridge vector of West Nile virus but nothing or very little is known about its vector competence for Chikungunya and Dengue viruses. Here, we report on experiments of laboratory infections of Ae. japonicus with CHIKV and DENV, demonstrating that the species has a vector potential for both viruses. Considering the high abundance of the species in urban environments and its ability to feed on human, these results plead to include this species when processing risk assessments for mosquito-borne diseases.
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Background The recent notifications of autochthonous cases of dengue and chikungunya in Europe prove that the region is vulnerable to these diseases in areas where known mosquito vectors (Aedes albopictus and Aedes aegypti) are present. Strengthening surveillance of these species as well as other invasive container-breeding aedine mosquito species such as Aedes atropalpus, Aedes japonicus, Aedes koreicus and Aedes triseriatus is therefore required. In order to support and harmonize surveillance activities in Europe, the European Centre for Disease Prevention and Control (ECDC) launched the production of ‘Guidelines for the surveillance of invasive mosquitoes in Europe’. This article describes these guidelines in the context of the key issues surrounding invasive mosquitoes surveillance in Europe. Methods Based on an open call for tender, ECDC granted a pan-European expert team to write the guidelines draft. It content is founded on published and grey literature, contractor’s expert knowledge, as well as appropriate field missions. Entomologists, public health experts and end users from 17 EU/EEA and neighbouring countries contributed to a reviewing and validation process. The final version of the guidelines was edited by ECDC (Additional file 1). Results The guidelines describe all procedures to be applied for the surveillance of invasive mosquito species. The first part addresses strategic issues and options to be taken by the stakeholders for the decision-making process, according to the aim and scope of surveillance, its organisation and management. As the strategy to be developed needs to be adapted to the local situation, three likely scenarios are proposed. The second part addresses all operational issues and suggests options for the activities to be implemented, i.e. key procedures for field surveillance of invasive mosquito species, methods of identification of these mosquitoes, key and optional procedures for field collection of population parameters, pathogen screening, and environmental parameters. In addition, methods for data management and analysis are recommended, as well as strategies for data dissemination and mapping. Finally, the third part provides information and support for cost estimates of the planned programmes and for the evaluation of the applied surveillance process. Conclusion The ‘Guidelines for the surveillance of invasive mosquitoes in Europe’ aim at supporting the implementation of tailored surveillance of invasive mosquito species of public health importance. They are intended to provide support to professionals involved in mosquito surveillance or control, decision/policy makers, stakeholders in public health and non-experts in mosquito surveillance. Surveillance also aims to support control of mosquito-borne diseases, including integrated vector control, and the guidelines are therefore part of a tool set for managing mosquito-borne disease risk in Europe.
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The success of an invasive species in a new region depends on its interactions with ecologically similar resident species. Invasions by disease vector mosquitoes are important as they may have ecological and epidemiological consequences. Potential interactions of a recent invasive mosquito, Aedes japonicus Theobald, with resident species in Virginia were evaluated by sampling larvae from containers and trapping adults. Distinct species compositions were observed for artificial containers and rock pools, with Ae. albopictus most abundant in the former and Ae. japonicus in the latter. However, these two species were found to co-occur in 21.2% of containers sampled. Among the six mosquito species most common in containers from May through September, 2006, only interspecific associations of Ae. japonicus with Aedes albopictus (Skuse) and Aedes triseriatus (Say) were significant, and both were negative. In addition to differences in habitat preference, mean crowding estimates suggest that interspecific repulsion may contribute to the significant negative associations observed between these species. High relative abundances of late instars and pupae of Ae. japonicus seem to provide this species with a mechanism of evading competition with Ae. albopictus, facilitating their coexistence in artificial containers. Although annual fluctuations were observed, trends in adult populations over a 6-yr period provide no evidence of declines. In summary, this survey of diverse container types and all life stages provided only limited evidence for competitive displacements or reductions of resident container species by Ae. japonicus, as observed elsewhere in its invasive range.
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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.
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