ARBOVIRUS ACTIVITY IN
CONNECTICUT, 2008
John J. Shepard, Theodore G. Andreadis, Philip M.
Armstrong, and Michael C. Thomas
The Connecticut Agricultural Experiment Station
123 Huntington Street
PO Box 1106
New Haven, CT 06504
ABSTRACT
Statewide mosquito trapping was conducted from June 2
through October 23 at 92 fixed collection sites. Approximately one-third of the sites were
located in densely populated residential locales along an urban/suburban
corridor in the coastal southeastern corner of the state that also extended up
through the Connecticut River Valley.
Trap sites typically included parks, greenways, golf courses,
undeveloped wood lots, sewage treatment plants, dumping stations, and temporary
wetlands associated with waterways.
Trapping locations in the other regions of the state were established in
more sparsely populated rural settings that included permanent fresh-water
swamps (red maple/white cedar) and bogs, coastal salt marshes, horse stables,
and swamp-forest border environs.
Mosquito trapping was conducted with CO2 (dry
ice)-baited CDC miniature light traps equipped with aluminum domes, and gravid
mosquito traps baited with an albumin-hay infusion. Traps were placed in the field in the afternoon,
operated overnight, and retrieved the following morning. Trapping frequency was minimally made once
every ten days at each trap site over the course of the entire season. Adult mosquitoes were transported alive to
the laboratory each morning in an ice chest lined with cool packs. Mosquitoes were immobilized with dry ice and
transferred to chill tables where they were identified to species with the aid
of a stereo microscope (90X) based on morphological characters. Female mosquitoes were pooled in groups of 50
or fewer by species, collection date, and location and stored at -80oC until
processed for virus.
Aliquots of each mosquito pool were inoculated into
Vero cell cultures for detection of West Nile virus (WN)
and other mosquito-borne arboviruses of public health importance. Virus isolates from mosquito pools were
tested for WN, eastern equine encephalitis (EEE),
Flanders (FL), Jamestown Canyon (JC), Cache Valley (CV), Trivittatus (TVT), Highlands J (HJ), LaCrosse (LAC), and Potosi (POTV)
viruses. Isolated viruses were
identified by Real Time (TaqMan) polymerase chain
reaction (PCR) or standard RT-PCR using
virus-specific primers. All of the virus
isolation work was conducted in a certified Bio-Safety Level 3 laboratory at
the CAES.
In 2008, a total of 211,496 mosquitoes (15,055 pools)
representing 38 species were trapped and tested. A total of 191 isolations of WN virus were made from 9 mosquito species: Culex pipiens = 124, Culex restuans = 48, Culex salinarius =10, Culiseta melanura = 4, Aedes cinereus = 1, Culex territans = 1, Ochlerotatus japonicus = 1, Ochlerotatus
stimulans =1, and Ochlerotatus trivittatus =1 collected at 33 sites in 25 towns in 5 counties
(Fairfield, Hartford, Middlesex, New Haven, and New London). The first positive mosquitoes were collected
on June 11 representing the earliest date virus has been detected in mosquitoes
in the state, and the last on October 7.
Gravid trap collections accounted for 84% of all WN
virus isolates (n=160) and 93% of WN virus isolates
from Cx. pipiens (n = 115/124). As in
prior years, the majority of WN virus activity was
detected in densely populated urban and suburban regions in southwestern
(Fairfield and New Haven counties) and central (Hartford county) Connecticut.
Six locally acquired and one imported human cases of WN virus (encephalitis/meningitis= 4, fever = 3,
unspecified = 1) were reported to the State Department of Public Health with no
fatalities (age range = 12 to 87 yrs., median age = 49 yrs.). Dates of onset of symptoms ranged from June
21 to September 12. The June 21 date of
onset represented the earliest locally acquired WN
virus case in the state. Human cases
were correlated both temporally and spatially with the detection of WN-infected mosquitoes.
There was no activity of EEE in mosquitoes, humans or horses.
Other mosquito-borne viruses isolated included: JC =
19 isolates from 12 species (Jun. 2-Jul. 17); FL = 3 isolates from 1 species
(Jul. 7-21); POT = 63 isolates from 14 species (Jul. 17-Aug. 28); HJ = 7 isolates from 2 species (Aug. 11-Oct. 1); TVT = 4 isolates from 1 species (Aug. 13-28); and CV = 3
isolates from 3 species (Aug. 18-21).
Mosquito
species trapped and tested for arboviruses in Connecticut, 2008
Mosquito
Species
|
# Mosquitoes |
# Pools |
Virus |
||||||
|
CV |
FL |
HJ |
JC |
POT |
TVT |
WN |
|||
|
Aedes cinereus |
15,399 |
1,019 |
1 |
|
|
|
8 |
|
1 |
Ae. vexans
|
25,015 |
1,354 |
|
|
|
1 |
3 |
|
|
Anopheles barberi
|
9 |
9 |
|
|
|
|
|
|
|
An. crucians
|
25 |
14 |
|
|
|
|
|
|
|
|
An. punctipennis |
2,722 |
665 |
1 |
|
|
1 |
11 |
|
|
|
An. quadrimaculatus |
439 |
219 |
|
|
|
|
|
|
|
|
An. walkeri |
688 |
134 |
|
|
|
|
1 |
|
|
|
Coquillettidia
perturbans |
20,185 |
942 |
1 |
|
|
2 |
3 |
|
|
|
Culex pipiens |
19,200 |
1,448 |
|
|
|
|
|
|
124 |
|
Cx. restuans |
18,691 |
1,802 |
|
3 |
|
|
1 |
|
48 |
|
Cx. salinarius |
14,448 |
875 |
|
|
|
|
|
|
10 |
|
Cx. territans |
94 |
76 |
|
|
|
|
|
|
1 |
|
Culiseta melanura |
6,403 |
615 |
|
|
6 |
|
|
|
4 |
|
Cs. minnesotae |
11 |
4 |
|
|
|
|
|
|
|
|
Cs. morsitans |
166 |
71 |
|
|
|
|
|
|
|
|
Ochlerotatus abserratus |
2,993 |
158 |
|
|
|
2 |
|
|
|
|
Oc. atropalpus |
2 |
2 |
|
|
|
|
|
|
|
|
Oc. aurifer |
3,124 |
154 |
|
|
|
3 |
|
|
|
|
Oc. canadensis |
19,823 |
953 |
|
|
1 |
2 |
4 |
|
|
|
Oc. cantator |
4,070 |
333 |
|
|
|
3 |
1 |
|
|
|
Oc. communis |
34 |
3 |
|
|
|
|
|
|
|
|
Oc. excrucians |
421 |
59 |
|
|
|
1 |
|
|
|
|
Oc. grossbecki |
8 |
5 |
|
|
|
|
|
|
|
|
Oc. japonicus |
1,829 |
668 |
|
|
|
|
|
|
1 |
|
Oc. provocans |
69 |
7 |
|
|
|
|
|
|
|
|
Oc. sollicitans |
2,166 |
109 |
|
|
|
|
|
|
|
|
Oc. sticticus |
4,971 |
220 |
|
|
|
1 |
7 |
|
|
|
Oc. stimulans |
2,019 |
248 |
|
|
|
1 |
1 |
|
1 |
|
Oc. taeniorhynchus |
6,143 |
239 |
|
|
|
|
7 |
|
|
|
Oc. thibaulti |
7,482 |
312 |
|
|
|
1 |
|
|
|
|
Oc. triseriatus |
1,323 |
401 |
|
|
|
|
2 |
|
|
|
Oc. trivittatus |
17,317 |
947 |
|
|
|
|
13 |
4 |
1 |
|
Orthopodomyia signifera |
1 |
1 |
|
|
|
|
|
|
|
|
Psorophora columbiae |
1 |
1 |
|
|
|
|
|
|
|
|
Ps. ferox |
11,779 |
558 |
|
|
|
|
1 |
|
|
|
Ps. howardi |
1 |
1 |
|
|
|
|
|
|
|
|
Toxorhynchites rutilis |
1 |
1 |
|
|
|
|
|
|
|
|
Uranotaenia sapphirina |
2,424 |
428 |
|
|
|
|
|
|
|
|
TOTAL |
211,496 |
15,055 |
3 |
3 |
7 |
19 |
63 |
4 |
191 |
CV = Cache Valley, FL
= Flanders, HJ = Highlands J, JC = Jamestown Canyon, POT =
Potosi, TVT = Trivittatus, WN = West Nile