To Bite Or Not to Bite: Mosquitoes and Transmission of West Nile and Eastern Equine Encephalitis Viruses in Connecticut
To Bite Or Not To Bite: Mosquitoes and Transmission of West Nile and Eastern Equine Encephalitis Viruses in Connecticut
Goudarz Molaei, Ph.D. Center for Vector Biology & Zoonotic Diseases
The Connecticut Agricultural Experiment Station
CAES- Plant Science Day 2011 www.ct.gov/caes Connecticut Surveillance Program
• Primary Objectives – Quantify level of virus activity – Assess human risk – Provide early warning of epidemic threats • Goals – Prevent a sustained local outbreak – Reduce the risk of human and domesticated animals’ infections
CAES- Plant Science Day 2011 www.ct.gov/caes
Viruses Transmitted by Mosquitoes in Connecticut • West Nile Virus • Eastern Equine Encephalitis • Jamestown Canyon • Cache Valley
• La Crosse Human Disease • Highlands J • Potosi • Trivittatus Photographed by Michael Thomas • Flanders
CAES- Plant Science Day 2011 www.ct.gov/caes West Nile Virus Activity: 1999-2010
Human cases = 29,476 Fatalities = 1,152 (3.9%)
Estimated Connecticut: ~ 1.6 million Human cases = 80 people infected Fatality = 3
CDC/USGS
CAES- Plant Science Day 2011 www.ct.gov/caes Eastern Equine Encephalitis Virus • Geographic distribution – Eastern US – South America
• Disease
– Encephalitis in humans and CDC/USGS equines – 40% case fatality-rate – About 10 human cases each year in US
• Transmission – Maintained in a bird-mosquito cycle
– Occurs in fresh-water hardwood swamps CAES- Plant Science Day 2011 www.ct.gov/caes WNV and EEEV Transmission Cycle
Epidemic Transmission
Photographed by Michael Thomas ? Enzootic Cycle
Photographed by Michael? Thomas Incidental Infections Virus ?
Google images Wild Bird Reservoir
CAES- Plant Science Day 2011 www.ct.gov/caes Primary and Secondary Mosquito Vectors of WNV and EEEV WNV EEEV
Culex pipiens Culiseta melanura Culex restuans Culiseta morsitans Culex salinarius
Aedes vexans Coquillettidia perturbans Culiseta melanura Ochlerotatus canadensis
CAES- Plant Science Day 2011 www.ct.gov/caes Incriminating Evidence Against Mosquitoes
• Abundant
•Physiologically competent
Photographed by Michael Thomas
CAES- Plant Science Day 2011 www.ct.gov/caes Infection of Mosquito Feeding on a Viremic Animal
Courtesy of Stephen Higgs Lab. Virus particles in blood
CAES- Plant Science Day 2011 www.ct.gov/caes Digestion of Blood
Virus particles survive
Courtesy of Stephen Higgs Lab.
CAES- Plant Science Day 2011 www.ct.gov/caes Replication of Virus within Midgut
Courtesy of Stephen Higgs lab.
CAES- Plant Science Day 2011 www.ct.gov/caes Dissemination from the Midgut into Secondary Tissues
Fat body
Salivary glands Nervous system Hemocoel Courtesy of Stephen Higgs Lab.
CAES- Plant Science Day 2011 www.ct.gov/caes Virus Replication in Secondary Tissues in Body
Adequate virus titer required for transmission
(10,000 – 100,000 PFU’s) Courtesy of Stephen Higgs Lab.
CAES- Plant Science Day 2011 www.ct.gov/caes Transmission of Virus from Mosquito to New Host
Salivary glands
Courtesy of Stephen Higgs Lab.
CAES- Plant Science Day 2011 www.ct.gov/caes Incriminating Evidence Against Mosquitoes
• Abundant • Physiologically competent
Photographed by Michael Thomas • Frequent infection in nature
CAES- Plant Science Day 2011 www.ct.gov/caes Number and Percentage of Virus Isolates from Mosquito Vectors of WNV (1999-2010)
WNV
Culex pipiens (704, 70.3%)
Culex restuans (129, 12.9%)
Culex salinarius (74, 7.4%)
Aedes vexans (13, 1.3%)
Culiseta melanura (44, 4.4%)
CAES- Plant Science Day 2011 www.ct.gov/caes Number and Percentage of Virus Isolates from Mosquito Vectors of EEEV (1996-2010)
EEEV
Culiseta melanura (189, 57.6%)
Culiseta morsitans (5, 1.5%)
Coquillettidia perturbans (4, 1.2%)
Ochlerotatus canadensis (28, 8.5%)
CAES- Plant Science Day 2011 www.ct.gov/caes Incriminating Evidence Against Mosquitoes
• Abundant • Physiologically competent • Frequent infection in nature Photographed by Michael Thomas
• Acquire blood meals frequently from key vertebrate hosts
CAES- Plant Science Day 2011 www.ct.gov/caes Hartford Windham Litchfield Tolland
WNV Photographs by Michael Thomas EEE
New London New Haven Middlesex
Fairfield
CAES- Plant Science Day 2011 www.ct.gov/caes CO2 -baited CDC Light Trap
Gravid Trap
Backpack Aspirator
CAES- Plant Science Day 2011 www.ct.gov/caes Photographed by Michael Thomas Mosquito Resting Box
CAES- Plant Science Day 2011 www.ct.gov/caes Photographed by Michael Thomas Mosquito Resting Box (Nursery Pot)
CAES- Plant Science Day 2011 www.ct.gov/caes Mosquito Blood Feeding Studies-Materials and Methods • Abdomens were removed and used for DNA isolation. • DNAs from blooded abdomens were screened (by PCR) for a gene that is diagnostic for identification of birds and mammals. • Bird and mammal hosts were identified to species by comparing DNA sequences to the GenBank® sequence data base.
CAES- Plant Science Day 2011 www.ct.gov/caes
Percent 100 20 40 60 80 Blood CAES 0
- Culex pipiens
Plant Plant Science Day2011 92.6% 92.6% -
3.0% 3.0% Human Photographed by by Michael ThomasPhotographed Feeding of WNV Primary Feedingof WNVPrimary Vectors 0.5% 0.5%
3.6% 3.6%
0.8% 0.8%
Culex restuans
100.0% 100.0%
Culex salinarius 37.2% 37.2% 52.0% 52.0%
Bird Bird &Mammal Mammal Amphibian 10.8% 10.8%
Human
1.5% 1.5%
www.ct.gov/caes
Percent Blood CAES 100 20 40 60 80 0 -
Plant Plant Science Day2011 - Feedingof WNVSecondary Vectors Culiseta melanura 89.6% 89.6%
Photographed by by Michael ThomasPhotographed 4.2% 4.2%
Bird & Mammal Mammal Bird 6.2% 6.2%
7.6%` 7.6%` Aedesvexans
97.4% 97.4%
Human 3.2% 3.2% www.ct.gov/caes
Percentage of Bird-Derived Blood Meals 40
30 42 different species of birds identified
20
Percent of Total of Percent Google images 10
0 American Gray Catbird House Chickadee Mourning American Robin Sparrow Dove Crow
CAES- Plant Science Day 2011 www.ct.gov/caes Percentage of Bird-Derived Blood Meals 40 • Abundant • Frequently infected
30 • Reservoir competent
• Are likely to be a 20 very important
source of virus Percent of Total of Percent
Google image 10
0 American Gray Catbird House Chickadee Mourning American Robin Sparrow Dove Crow
CAES- Plant Science Day 2011 www.ct.gov/caes Percentage of Bird-Derived Blood Meals
• Crows acquire WNV through other means in addition to
mosquito bites • Crows are not likely ? to be the primary
Google image amplifying hosts Percent of Total of Percent
CAES- Plant Science Day 2011 www.ct.gov/caes Percentage of Mammal-Derived Blood Meals 80
70 • Most abundant large mammal in region 60 • Role in transmission unknown 50 • May divert feeding 40 from horses and humans
30 Percent of Total of Percent 20 Google image
10
0 Deer Horse Cat Raccoon Rabbit Human
CAES- Plant Science Day 2011 www.ct.gov/caes Percentage of Mammal-Derived Blood Meals 80
70 • Low level of feeding on humans 60
• Helps to explain
50 limited number of
40 human cases
30 Google image
Percent of Total of Percent 20
10
0 Deer Horse Cat Raccoon Rabbit Human
CAES- Plant Science Day 2011 www.ct.gov/caes Blood-Feeding of EEEV Primary Vectors
100 100.0% 89.2% Bird Mammal 80
Bird & Mammal
60
Percent 40
20
4.2% 6.2% 0 Culiseta melanura Culiseta morsitans
CAES- Plant Science Day 2011 www.ct.gov/caes
CAES
Percent 100 20 40 60 80 Blood 0 -
Plant Plant Science Day2011 Coquillettidia perturbans Human - 5.1% 5.1% Feeding of EEEV Secondary Vectors 11.8%
86.8% 86.8%
Photographed by by Michael ThomasPhotographed 1.4% 1.4% Reptile Bird &Mammal Mammal Bird
Ochlerotatus Ochlerotatus canadensis
1.0% 1.0%
98.0% 98.0%
Human 1.0% 1.0% 3.7% 3.7% www.ct.gov/caes
Bird-Derived Blood Meals in EEEV Vectors
18 different species
of birds identified
Percent of Total of Percent Google images
CAES- Plant Science Day 2011 www.ct.gov/caes Northeastern US WNV Transmission Cycle Overwinter Epidemic Transmission
Photographed by Michael Thomas Culex pipiens Culex salinarius Culex restuans Culex pipiens Culiseta melanura Aedes vexans June Enzootic to Cycle October Incidental Infections Virus Photographed by Michael Thomas
Google images August to October Wild Bird Reservoir and Amplifying Hosts CAES- Plant Science Day 2011 www.ct.gov/caes Northeastern US EEEV Transmission Cycle Overwinter ? Epidemic Transmission
Culiseta melanura Coquillettidia perturbans Culiseta morsitans Ochlerotatus canadensis
Enzootic June Incidental Infections Cycle to October Virus
Google images August to October Wild Bird Reservoir and Amplifying Hosts CAES- Plant Science Day 2011 www.ct.gov/caes CAES Center for Vector Biology & Zoonotic Diseases
Dr. John Dr. Philip Dr. Theodore Anderson Armstrong Andreadis
Michael John Shannon Thomas Shepard Finan
CAES- Plant Science Day 2011 www.ct.gov/caes CAES Center for Vector Biology & Zoonotic Diseases
Michael Vasil
Bonnie Hamid
Angela Bransfield
Michael Micensik
CAES- Plant Science Day 2011 www.ct.gov/caes Thank you
CAES- Plant Science Day 2011 www.ct.gov/caes Goudarz Molaei, Ph.D. Center for Vector Biology & Zoonotic Diseases The Connecticut Agricultural Experiment Station 123 Huntington Street P. O. Box 1106 New Haven, CT 06504
Phone: 203.974.8487 Email: [email protected] Website: www.ct.gov/caes
CAES- Plant Science Day 2011 www.ct.gov/caes