Mosquito Surveillance for EEE
and Other Arboviruses in CT
Philip Armstrong
Department of Environmental Sciences
Center for Vector Biology & Zoonotic Diseases
The Connecticut Agricultural Experiment Station
New Haven, CT
Connecticut Mosquito Management Program
• Established 1997 by Public Act 97-289
• Comprised of 5 State Agencies
• The CT Agricultural Experiment Station (mosquito surveillance, virus
testing)
• Department of Public Health (epidemiology of human, veterinary cases)
• Department of Energy & Environmental Protection (mosquito control,
habitat restoration)
• Department of Agriculture (veterinary cases)
• Pathobiology Department at UCONN (necropsy, initial veterinary testing)
• Rural Areas
• Permanent swamps and bogs
• Marsh areas (fresh and salt)
Mosquito Trapping Locations
• Urban / Suburban Sites
• Neighborhood parks and
schools
• Along waterways and
streams
• Sewage treatment plants
• Horse stables
(92)
LitchfieldHartford
Tolland
Windham
New LondonMiddlesexNew Haven
Fairfield
WNV EEEEEE
• Mosquito trapping from June – October
• 92 permanent trapping stations (ADD 15 in 2020)
• 91 Sites maintained by CAES
• 1 Site maintained by US Navy
• Trap on a Rotational Basis (about every 10 days)
• If WNV or EEE isolates from mosquitoes
•Trap Weekly (twice if possible)
• 2 or 3 types of trap per location
Detect virus in mosquitoes prior to human or animal
cases
Mosquito Surveillance
• Host seeking females
• Out for blood
• Collects a large & diverse
number of mosquitoes
• Aedes/Ochlerotatus
• Coquillettidia
• Culex
• Culiseta
• Psorophora
CDC Light Trap
CO2
• Host seeking females
• Out for blood
• Collects a large & diverse
number of mosquitoes
• Aedes/Ochlerotatus
• Coquillettidia
• Culex
• Culiseta
• Psorophora
CDC Light Trap
CO2
• Hay-yeast-lactalbumin infusion
• Culex pipiens & Cx. restuans• Ready to lay eggs• Obtained blood meal• More Likely to be WNV (+)• 90% of collection
• Accounts for >75% of WNV (+) isolates from Cx. pipiens and Cx. restuans
CDC Gravid Trap
• Designed for Ae. albopictus• Used at sites to evaluate
population size
• Small populations in CT•Coastal Fairfield and New Haven counties
• Invasive Species
• Aggressive Human Biter• Secondary vector of Zika,
Chikungunya and Dengue
BG Sentinel Trap
scent
• Females identified to species
- 43 species collected in 2019
• Completed on day of collection
- 6 identifiers during peak season
• Pooled by species, site and trap type
- Maximum of 50 / pool
• All species tested for arboviruses
Mosquito Identification
• Biosafety Level 3 Laboratory
– Incubate for 7 days at 37oC in 5%CO2
– Examine daily for virus growth
• Virus isolation in Vero cell cultures
(African Green Monkey)
Virus Isolation & Identification
• Virus identification by
Real time PCR, RT-PCR,
molecular techniques
• West Nile Virus
• Eastern Equine Encephalitis
• Jamestown Canyon
• Cache Valley
• La Crosse
• Trivittatus
• Potosi
• Highlands J
• Flanders
• Can detect Zika, Chikungunya,
or other exotic viruses
Mosquito-Borne Viruses in Connecticut
Cause Human
Disease
Human Disease Causing Mosquito-Borne Viruses in CT
VirusNo.
isolations*
No. locations
*Reservoir Age Group Human disease
West Nile 2,440 106 Bird ElderlyModerate to severe, fever, encephalitis
Eastern Equine Encephalitis
534 48 BirdChildren, Elderly
Severe, encephalitis
Jamestown Canyon
557 88 White-tailed deer All agesFever, meningitis,
encephalitis
Cache Valley 226 71 Deer, horse, sheep All agesFever, meningitis,
encephalitis
Trivittatus 104 25Rabbit, squirrel,
raccoon, opossumAll ages Febrile illness
La Crosse 5 3 Squirrel, chipmunk Children Severe, encephalitis
* = 1997-2019
• EEE, WNV, or exotic virus identified
• Notify CT DPH, DEEP
• DPH contacts local Health Dept.
• Report to CDC (ArboNet)
• Post on CAES/Mosquito Management Website• www.portal.ct.gov/caes
• www.portal.ct.gov/mosquito
• Map
• Weekly & Cumulative Results Tables
• Press Release may be issued (state or local)
Reporting of Results
SEARCH: “CAES Mosquito Testing”
Northeastern US EEE Virus Transmission Cycle
Culiseta melanura
Virus
EnzooticCycle
Wild Passerine Bird
Reservoir and Amplifying
Hosts
JulytoOctober
Northeastern US EEE Virus Transmission Cycle
Culiseta melanura
Virus
EnzooticCycle
Wild Passerine Bird
Reservoir and Amplifying
Hosts
“Incidental”
Infections
Coquillettidia perturbans
Culiseta melanura
Aedes and
Ochlerotatus species
Epidemic / Epizootic
Transmission
JulytoOctober
August to October
Eastern Equine Encephalitis Actvivity, 1999-2017
0
50
100
150
'96 '98 '00 '02 '04 '06 '08 '10 '12 '14 '16 '18
Virus Isolations per Year
Total = 534
Eastern Equine Encephalitis Activity, 1996-2019
0
40
80
120
7/1 7/8 7/15 7/22 7/29 8/5 8/12 8/19 8/24 9/2 9/9 9/16 9/23 9/30 10/7 10/14 10/21 10/28
No
. E
EE
vir
us
is
ola
tio
ns
Week
1996-2018
2013
Weekly Isolations of EEE virus
from field collected mosquitoes
in Connecticut
0
10
20
30
40
506
/2-6
/8
6/9
-6/1
5
6/1
6-6
/22
6/2
3-6
/29
6/3
0-7
/6
7/7
-7/1
3
7/1
4-7
/20
7/2
1-7
/27
7/2
8-8
/3
8/4
-8/1
0
8/1
1-8
/17
8/1
8-8
/24
8/2
5-8
/31
9/1
-9/7
9/8
-9/1
4
9/1
5-9
/21
9/2
2-9
/28
9/2
9-1
0/5
10
/6-1
0/1
2
10
/13
-10
/19
10
/20
-10
/26
10
/28
-11
/3
EEE
Iso
late
s p
er
We
ek
2019 Eastern Equine Encephalitis Activity per WeekNon-mammalian biter (n=90)
Mammalian biter (n=32)= Human Case* (n=4) = Horse Case* (n=6) = Pheasant or Partridge* (n=2)
* = onset of illness symptoms
EEE Isolations from Mosquito Pools - CT 1996-2019
Cs. melanura63%
Oc. canadensis7%
Ae. cinereus4%
Ae. vexans3%
Cx. salinarius3%
Ur. sapphirina3%
Cx. pipiens2%
Other Species
11%
Cs. melanura
2%
Species Isolates
Culiseta melanura 344
Ochlerotatus canadensis 37
Aedes cinereus 20
Aedes vexans 19
Uranotaenia sapphirina 19
Culex salinarius 16
Coquillettidia perturbans 10
Culex pipiens 10
Other Species (11) 58
TOTAL 534
Culex pipiens
Culex restuans
Culiseta melanura
Wild Passerine Bird Reservoir
and Amplifying Hosts
Virus
EnzooticCycle
JunetoOctober
Northeastern US West Nile Virus Transmission Cycle
Northeastern US West Nile Virus Transmission Cycle
Culex pipiens
Culex restuans
Culiseta melanura
Wild Passerine Bird Reservoir
and Amplifying Hosts
Virus
EnzooticCycle
“Incidental”
Infections
Culex salinarius
Culex pipiens
Aedes vexans
Epidemic / Epizootic
Transmission
July to October
JunetoOctober
West Nile Virus Isolates from Mosquitoes, 1999-2019
0
100
200
300
400
'99 '01 '03 '05 '07 '09 '11 '13 '15 '17 '19
Virus Isolations per Year
Total = 2.440
West Nile Virus Human Infections, 1999-2019
0
10
20
30
'99 '01 '03 '05 '07 '09 '11 '13 '15 '17 '19
Human Infections per Year
Total = 158
WNV Isolations from Mosquito Pools, CT 1999-2019
Culex pipiens69%
Culex restuans
14%
Culex salinarius
7%
Culiseta melanura
5%
Species Isolates
Culex pipiens 1,695
Culex restuans 341
Culex salinarius 171
Culiseta melanura 118
Aedes vexans 19
Aedes cinereus 13
Coquillettidia perturbans 14
Ochlerotatus japonicus 10
Oc. canadensis 12
Oc. taeniorhynchus 6
Other Species (14) 52
TOTAL 2,440
Other species (19) 5%
0
0.5
1
1.5
2
0
5
10
15
20
25
6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10 8/17 8/24 8/31 9/7 9/14 9/21 9/28 10/5 10/12 10/19 10/26
No
. W
NV
Is
ola
tes
Week
10 yr Mean Human
10 yr Mean Mosq.
WNV Epidemic Curve
Jamestown Canyon Virus
Human Case – CT, 2018• Meningitis
• Bethlehem (Litchfield County)
• Onset of Symptoms on September 4th
• 1st CT case documented since 2001
Human Symptoms• Mild
• Flu-like
• Fever, headache, fatigue
• Severe
• Meningitis, encephalitis
• All ages affected
Neurological illness in humans is rare• 4-10% of the CT residents have antibody to the virus
• About ~1 case/year reported in US prior to 2013
• 181 human cases reported 2013-2018
• Neuroivasive cases in Northeast (CT, MA, ME, NH, NJ, NY, RI)c
Jamestown Canyon Virus
• 23 Virus Isolations – CT, 2019• 15 sites in 15 towns
• June 4th – September 9th
• 9 species
• Enzootic Cycle between deer and
mammal-biting mosquitoes• Wide-spread distribution in CT (88 sites)
• 557 isolates (1997-2019)
• Higher prevalence in June & July
• 25 species
• “Snow-pool” Ochlerotaus, Aedes species
Weekly Jamestown Canyon Virus Isolations from Mosquitoes
Jun Jul Aug Sept
No
. viru
s iso
latio
ns
0
5
10
15
20
25
30
35
40
45
Me
an
no
. m
osq
uito
es / lig
ht tr
ap
0
40
80
120
160
200
240
280
Virus isolations
Mosquitoes
0.03
0.19
0.37
0.39
0.12
0.25
0.13
0.22
0.20
0.060.05
0.10
0.030.09
0.07
MLE = 0.03 - 0.39
The Connecticut Agricultural Experiment Station
Mosquito Collection and Identification
John Shepard
Tanya Petruff
Virus Isolation and Identification (BSL-3)Angela Bransfield
Michael Misencik
Station Director
Dr. Theodore Andreadis
CT Department of Public Health
Dr. Matthew Cartter
Dr. Jocelyn Mullins
Brenda Esponda-Morrison
CT Dept. of Energy & Environmental Protection
Roger Wolfe
Steve Rosa
Acknowledgements
Seasonal StaffCatherine Cleary Noelle Khalil
Caroline Cullen Alyssa Marini
Will Cutrone Joey Miller
Andrew Donnellycolt Anthony Perugini
Patrick Daly Mike Olson
Ron Ferrucci Demi Rodriguez
Aiden Florio Bill Sennett
Joshua Stumpf
CT Department of Agriculture
Dr. Mary Jane Lis
U.S. Navy, Groton Sub Base
HM3 Ervin Jimenez
HM3 Hunter Baughman
HM1 James Limer
Questions?
Philip Armstrong
Connecticut Mosquito and Arbovirus Surveillance Program
The Connecticut Agricultural Experiment Station
New Haven, CT
203-974-8510
Mosquito Surveillance: www.portal.ct.gov/caes
Mosquito Management Program: www.portal.ct.gov/mosquito
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