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Diversity of mosquito fauna and risk assessment for Switzerland

Institute of Parasitology, Vector Entomology [email protected]

Francis Schaffner

Mosquitoes as vectors of diseases in Europe…

YesterdayMalaria,Dengue,Yellow fever…

TodayChikungunya,West Nile,Usutu…

?

TomorrowDengue?Rift Valley fever?Malaria?

Swiss mosquito fauna and risk – 1. Introduction

2007-091914

Mosquitoes in the European context

2010 events:

First introduction and control of Aedes aegypti in NL

Autochthonous Dengue and Chikungunya cases (FR, HR)

West Nile outbreaks in southern and eastern Europe (AU, GR, HU, PO, RO, RU, SP)

Autochthonous Malaria case in Spain



2011 events

West Nile outbreaks

Mosquitoes of Switzerland – 1. Introduction

http://ecdc.europa.eu


2011 events

Malaria outbreak in Greece 63 cases, 33 were Greek citizens without travel history to an endemic country


Map: Municipality of residence of Plasmodium vivax malaria cases, Greece, as of 15 November, 2011 (n=63)

http://ecdc.europa.eu


2011 events

Further spread and new introductions of invasive species


Updated distributions of invasive mosquitoes in Europe

Aedes albopictusSouthern Europe, since 1979

Aedes japonicusFR 2000 (†), BE 2002 (localized), CH 2008, DE 2008, AT+SLO 2011

Aedes atropalpusIT 1996 (†), FR 2003 (†), NL 2009 (localized)

Aedes aegyptiRU 2001, PT (Madeira) 2004, GE 2007, NL 2010 (localized)

Aedes koreicusBE 2008 (localized), IT 2011 Decembe


Status of invasive species and relevant actions

VBORNET (ECDC): updated vector distribution maps, risk assessment and fact sheets

ECDC: Guidelines for the surveillance of invasive mosquitoes in Europe

EMCA/WHO: Guidelines for the control of invasive mosquitoes and associated vector-borne diseases on the European continent

WHO: Handbook on vector surveillance and control at points of entry (IHR 2005)


Mosquitoes as vectors in Switzerland?

Mosquitoes are major vectors worldwide

In Switzerland: Malaria has been endemic in Switzerland until the early last century Pest species: severe nuisance problems in several regions Invasive species: pest and putative vectors

International context: Exotic pathogens emerging in Europe Some old world pathogens circulating more frequently

and in new areas Introduction and spread of invasive mosquitoes

Which are the hazardous species in Switzerland?


What makes a mosquito a good vector?

1. Vector competence Ability to acquire a pathogen from a reservoir host

and later transmit it to a susceptible host Extrinsic cycle

2. Vector capacity Evaluate the efficiency for a vector to transmit a pathogen Determined by

• Vector competence• Vector population density (abundance)• Vector age and longevity• Host preferences (blood meal)• Biting rate• These factors are related to climatic and environmental conditions and

to the host cultural and sanitary environment


Assessing risk induced by mosquitoes in Switzerland

Research study 2010 (BAFU)

‘Mosquitoes and related hazards in Switzerland’

Research study 2011-12 (BAFU)

‘Spatio-temporal diversity of mosquito fauna in Switzerland’

Collaborative project (ICMB, IPZ, MCZL, Swiss TPH)

Other research programmes (EMIDA-ERA NET; BVET)

Abundance and vector competence of Swiss mosquitoes

Swiss mosquito fauna and risk – 2. Study results

Research study 2010‘Mosquitoes and related hazards in Switzerland’

Pilot study 2010 funded by BAFUDiscussed at ‘vector management’ group (BABS, BAFU, BAG, BVET)

Aims: To investigate the Swiss mosquito fauna at selected places along transects in order to gain an overview on the species present and to validate the approach and the trapping methods

Expected outcomes: Based on literature data, the mosquito species which pose a hazard (for human, animal and biodiversity) will be identified for a specific surveillance in a further long-term study

Mosquitoes of Switzerland – 3. Research study 2010

Larval sampling and adult trapping

Along transects encompassing urban, rural and nature zones

Inspection and report of all potential larval habitats within a 250m square

In 5 locations in Jura, Midland, Pre-Alps, Inner Alps, Ticino

Morphological identification

Occasional genetic analysis for species complexes (Anopheles maculipennis s.l., Culex pipiens/torrentium)


Research study 2010 – Field observations‘Mosquitoes and related hazards in Switzerland’

Transect 1 : Ticino

Transect 2 (Zurich), Site 4

Larval habitats:

Positive

Negative

Research study 2010 – Field observations

Results

20 sites, from 3 to 205 larval habitats per site

586 potential larval habitats, man-made largely dominant (95%)

24 CO2-baited trapping nights

13 observed species, all by larval sampling and 10 of them by adult trapping

Mosquitoes present in all altitudinal zones

Highest diversity observed in the nature zones (all species)

In contrast, only 3-4 species occurring in the urban zones


Number and type of larval habitats per land cover zone and overall

Number of pos/neg potential larval habitats checked, for the most abundant artificial larval habitats

Total number of potential larval habitats checked, per altitudinal zone

0

100

200

300

400

500

600

700

Urban Peri‐urban Rural Nature Overall

No. of larval h

abita

ts

Land cover zones

Natural

Semi‐natural

Artificial

245 225

89

27

586

n=586

0

100

200

300

400

500

600

700

Urban Peri‐urban Rural Nature Overall

No. of larval h

abita

ts

Land cover zones

Natural

Semi‐natural

Artificial

245 225

89

27

586

n=586

14

48

19 165

7931

48

18

14

0102030405060708090100

vase, XS catch basin, S container, S barrel, S fountain, M

No. of che

cked

larval habita

ts

Main artificial larval habitats

Negative

Positive

93

79

34

67

19

n=292

14

48

19 165

7931

48

18

14

0102030405060708090100

vase, XS catch basin, S container, S barrel, S fountain, M

No. of che

cked

larval habita

ts

Main artificial larval habitats

Negative

Positive

93

79

34

67

19

n=292

0

50

100

150

200

250

300

350

400

450

Colin Submontane Montane Subalpine

No. of larval h

abita

ts

Natural

Semi‐natural

Artificial

n = 586

0

50

100

150

200

250

300

350

400

450

Colin Submontane Montane Subalpine

No. of larval h

abita

ts

Natural

Semi‐natural

Artificial

n = 586

Field observations 2010

Nature zone

Peri-urban zone

Rural zone

Urban zone

All zones

Ae. annulipes/cantans 1 1Ae. cinereus 1 1Ae. cinereus/geminus 2 2 1Ae. geniculatus 2 3 5Ae. japonicus 3 31 13 13 60 1Ae. sticticus 1 1 1Ae. vexans 2 2 2An. claviger 3 3 1An. maculipennis s.s. 4 3 7An. plumbeus 3 3 2Cx. hortensis 2 4 4 10 20Cx. pipiens/torrentium 6 33 23 26 88 6Cx. territans 6 6

No. of positive

light traps

No. of positive larval habitats per land cover zoneMosquito spp.

Positive larval habitats (n=131) and CO2-baited traps

at all sites, 5 transects: 13 mosquito spp.

Consolidated list of 36 mosquito spp. in Switzerland

Literature: 41 spp. (2 invasive spp.)

7 spp. being considered doubtful (single observations), but 3 of them are confirmed: Ae. geminus, Cs. longiareolata, Cx. martinii

36 spp. plus 5 ‘doubtful’ spp. (Ae. intrudens is added)

Aedes (Aedes) cinereusAe. (Aedes) geminusAe. (Aedimorphus) vexansAe. (Stegomyia) albopictusAe. (Fin.) geniculatusAe. (Fin.) japonicusAe. (Ochlerotatus) annulipesAe. (Och.) cantansAe. (Och.) caspius caspiusAe. (Och.) cataphyllaAe. (Och.) communisAe. (Och.) dorsalisAe. (Och.) excrucians Ae. (Och.) flavescensAe. (Och.) intrudens

Culiseta (Allotheobaldia) longiareolataCs. (Culicella) fumipennisCs. (Cuc.) morsitansCs. (Culiseta) alaskaensisCs. (Cus.) annulataCs. (Cus.) glaphyroptera

Culex (Barraudius) modestusCx. (Cx.) pipiensCx. (Cx.) theileriCx. (Cx.) torrentiumCx. (Maillotia) hortensis hortensisCx. (Neoculex) martiniiCx. (Ncx.) territans

Orthopodomyia pulcripalpis

Ae. (Och.) pullatusAe. (Och.) punctorAe. (Och.) ripariusAe. (Och.) sticticusAe. (Rusticoidus) refikiAe. (Rus.) rusticus

Anopheles (Anopheles) clavigerAn. (Ano.) maculipennis s.s. An. (Ano.) messeaeAn. (Ano.) plumbeus

Coquillettidia (Coquillettidia) buxtoniCq. (Coq.) richiardii

Species with relevant vector potential

9

Potential vector role of mosquitoes – Public health

Classification of mosquito species of Switzerland with regards to their potential vector role for 9 arboviruses

(Batai, Dengue, Chikungunya, Inkoo, Lednice, Sindbis, Tahyna, Usutu, West Nile)

Vector in central-western Europe

Vector outside central-western Europe

Infected in nature and competent

Competent in laboratory

Infected in nature

No information or not implicated

5: Vector in central-western Europe4: Infected in nature and competent3: Infected in nature and competent2: Competent in laboratory1: Infected in nature0: No information or not implicated

Potential vector role of mosquitoes - West Nile virus

Very rare species observed only before 2000 have been excluded from the list* = Rare species

Classification of mosquito species of northern or southern Switzerland with regard to their potential vector role for West Nile virus

5: Vector in central-western Europe4: Infected in nature and competent3: Infected in nature and competent2: Competent in laboratory1: Infected in nature0: No information or not implicated

Northern Switzerland

Southern Switzerland

Species with relevant vector potential

9

Potential vector role of mosquitoes – Human malaria

Classification of mosquito species of Switzerland (suspected and confirmed to occur) with regards to their potential vector role

Primary vector in the past in central-western Europe

Primary vector outside central-western Europe

Secondary vector in central-western Europe

2: Secondary vector outside c-w Europe3: Competent in laboratory

Not implicated

Mosquito vectors in Switzerland

Speculative risk scales: Several mosquitoes are putative vectors (indigenous, invasive species)

CH: proven recent vector transmission: Avian malaria and …

Mosquito-borne diseases in Switzerland?

Summer 2006/07: high mortality (peracute) among Passeriformesand Strigiformes; wild and zoo birds.

Local (around 2 km of Zoo Zürich)Usutu Virus (Flavivirus, Jap. encephalitis group)Other such outbreaks: Vienna 2001, Budapest 2005, south Germany 2011

Mosquito vectors in Switzerland

Speculative risk scales: Several mosquitoes are putative vectors (indigenous, invasive species)

CH: proven recent vector transmission: Avian malaria and …

Neighbouring countries: High competence and capacity for Ae. albopictus, Cx. pipiens

Need for further studieso Spatio-temporal occurrence and abundance of relevant mosquito spp.o Their vector competence under realistic climatic conditions

Research study 2011-2012‘Spatio-temporal diversity of mosquito fauna in Switzerland’

Methodology Focus on 2 land use units (sites): nature (highest diversity) and

suburban (highest mosquito-host contact rate), at 8 locations throughout Switzerland

Sites (250m squares): Inspection and report of all potential larval habitats; Larval sampling; Adult trapping

Investigate 5 times: Jul-11, Sep-11, Apr-12, Jun-12, Aug-12

Morphological identification and occasional genetic analysis for species complexes

Collaborative work: IPZ (coordination); Istituto Cantonale di Microbiologia – Bellinzona; Musée Cantonal de Zoologie – Lausanne; Swiss Tropical and Public Health Institute – Basel.

Mosquitoes of Switzerland – 4. Research study 2011-12

L-MT-7

Z-MT2

B-MT6

B-MT5

B-MT1

L-MT8

L-MT3

S-MT9

Vector role of Swiss mosquitoes

Risk assessment requires evaluation of vector competence

Invasive species but also indigenous mosquitoes: Aedes japonicus for Chikungunya and Dengue viruses Anopheles plumbeus for Plasmodium falciparum

Collaborative studies with Institut Pasteur, Paris

Subsequent studies at Uni Zurich

Vector competence of Ae. japonicus for DENV and CHIKV

First results: Swiss population of Ae. japonicus shows

vector potential for both dengue and chikungunya viruses Field collected

larval populations

Reared females

Experimental infection in BSL3

CHIK: 107 pfu/mlRVF: 109 pfu/ml14 days at 28°C

Dissemination rates:

91.0% (10/11) for DENV-2

13.3% (2/15) for CHIKV 6-21

Effective transmission potential:

Both DEN and CHIK viral particles present in saliva

Schaffner et al., EMB 2011

Vector competence of Ae. japonicus for DENV and CHIKV

First results: Swiss population of Ae. japonicus shows

vector potential for both dengue and chikungunya viruses

Rapid spread in Switzerland 2008-2010 Most abundant mosquito in Zürich

Schaffner et al., EMB 2011

Vector competence of An. plumbeus for P. falciparum

Main vectors of malaria in Europe are members of Maculipennis complex

An. plumbeus suspected to contribute occasionally

This tree hole breeder can proliferate in abandoned cesspits

Common in CH, including urban areas and around airports


Main vectors of malaria in Europe are members of Maculipennis complex

An. plumbeus suspected to contribute occasionally

This tree hole breeder can proliferate in abandoned cesspits

Common in CH, including urban areas and around airports

Need to assess its vector competence for possibly introduced Plasmodia.

4 series of 200-250 Swiss An plumbeus experimentally infected

Experimental protocol

Mosquito survey

D 8 Oocystes detection, midgut

D 15

2) Sporozoite countin salivary gland

D 0Pf Infection ♀

Selection starved ♀D-1

25/26°C

Fresh human blood

D-15 in vitroP. falciparum culture

Mature gametocytes

Control: An gambiae5 days-old

An. plumbeusMosquito field populations

received 5-6 daysprior infection

1) Oocystdetection, midgut

3) PCR sporozoitedetection in head/thorax

37°C


A significant number of females could be infected (277/900)

An. plumbeus is highly susceptible to P. falciparum

P. falciparum can complete sporogony in European Anopheles

Schaffner et al., in prep.

D15 An. gambiae Ngousso An. plumbeusReplicates 1 2 3 4 1 2 3 4

Prevalencemidgut (%) 100 100 66.7 70.0 75.0 15.4 43.1 11.1

Oocysts/female(mean no.) 22 44 26 8 5 2 29 3

Sporozoites/female(mean no.) 11,178 25,623 15,755 950 1,620 nd 108 nd

PCR sporozoitesdetection (%) 96.8 87.5 66.6 70.0 83.3 30.7 88.6 57.1

Results: Oocyst load and intensity of infection

Highlights

Increasing needs for pest and vector risk assessment Invasive species but also indigenous mosquitoes

Need for collaborative studies Vector distribution (including modelling) Vector capacity

■ Need for risk management Early warning systems for M-borne diseases Network for surveillance and control

Acknowledgments…

Institute of ParasitologyWinterthurerstrasse 266a

CH-8057 ZürichDir.: Pr. Dr Peter Deplazes

Vector entomology unit:Jeannine Hauri

Dr. Christian KaufmannPr. Alexander MathisDr. Francis Schaffner

Stefanie [email protected]

BVET - Referenzlabor für tierseuchenassoziierte Vektoren

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