ARBOVIRUS ACTIVITY IN CONNECTICUT, 2012

John J. Shepard, Theodore G. Andreadis, Philip M. Armstrong, Michael C. Thomas and Shannon L. Finan

Center for Vector Biology & Zoonotic Diseases

The Connecticut Agricultural Experiment Station

123 Huntington Street

PO Box 1106

New Haven, CT 06504

John.Shepard@ct.gov

ABSTRACT

Statewide mosquito trapping was conducted from June 4 through October 19 at 91 fixed collection sites. Approximately one-third of the sites were located in densely populated residential locales along an urban/suburban corridor in the coastal southwestern corner of the state extending 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 a lactalbumin-yeast-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, trap type, and Collection site 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), eastern equine encephalitis (EEE), and other mosquito-borne arboviruses of public health importance. Virus isolates from mosquito pools were tested for WN, EEE, Flanders (FL), Jamestown Canyon (JC), Cache Valley (CV), Trivittatus (TVT), Highlands J (HJ), LaCrosse (LAC), St. Louis Encephalitis (SLE), and Potosi (POTV) viruses. Isolated viruses were identified by Real Time (TaqMan) reverse transcriptase polymerase chain reaction (RT-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 2012, a total of 189,193 mosquitoes (14,008 pools) representing 38 species were trapped and tested. A total of 234 isolations of WN virus were made from 7 mosquito species: Culex pipiens = 194, Cx. restuans = 17, Culiseta melanura = 11, Cx. salinarius = 7, Coquillettidia perturbans = 3, Aedes cinereus = 1, Ae. vexans = 1, collected at 51 sites in 44 towns in 5 counties (Fairfield, Hartford, Middlesex, New Haven, and New London). The first positive mosquitoes were collected on June 27, and the last on September 27. The majority of WN virus activity was detected in densely populated urban and suburban regions in southern Fairfield and New Haven counties. Twenty human cases of WN were locally acquired (8 = encephalitis/meningitis, 12 = fever) with no fatalities. The age range was 30 to 84 years, and the median age was 55 years. Date of onset ranged from July 12 to September 21. Human cases were temporally and spatially consistent with WN virus isolations from mosquito pools. Two horse cases of WN reported: one in Southbury (New Haven County) was treated and recovered, while one in South Windsor (Hartford County) was euthanized. Dates of onset were on August 27, and August 29.

Nine isolations of EEE were made from Culiseta melanura at a collection site in Chester (Middlesex County). The first positive mosquitoes were collected on August 8, and the last on September 8. There were no human, horse, or veterinary cases of EEE reported.

Other mosquito-borne viruses isolated included: Highlands J (HJ) = 3 isolates from 1 species (August 13 - August 21); Jamestown Canyon (JC) = 5 isolates from 3 species (June 12 – June 19)

Mosquito species trapped and tested for arboviruses in Connecticut, 2012

Species	Number Mossquitoes	Number Pools	Virus
			EEE	HJ	JC	WN
Aedes albopictus	245	102
Ae. cinereus	5,184	723				1
Ae. vexans	16,377	1,046				1
An. crucians	632	180
An. punctipennis	4,403	862
An. quadrimaculatus	838	311
An. walkeri	1,470	198
Coquillettidia perturbans	37,969	1,374				3
Culex erraticus	24	13
Cx. pipiens	26,014	1,691				194
Cx. restuans	4,152	773				17
Cx. salinarius	26,130	1,197			1	7
Cx. territans	94	73
Culiseta melanura	8,759	814	9	3		11
Cs. minnesotae	9	5
Cs. morsitans	13	11
Ochlerotatus abserratus	662	85
Oc. atropalpus	2	2
Oc. aurifer	493	50
Oc. canadensis	20,341	889
Oc. cantator	2,314	289			3
Oc. excrucians	68	37
Oc. grossbecki	2	2
Oc. japonicus	1,882	772
Oc. provocans	1	1
Oc. sollicitans	1,475	87
Oc. sticticus	893	69			1
Oc. stimulans	393	97
Oc. taeniorhynchus	10,251	324
Oc. thibaulti	6,893	299
Oc. triseriatus	1,559	446
Oc. trivittatus	3,428	372
Orthopodomyia signifera	4	4
Psorophora columbiae	2	1
Ps. ferox	3,225	339
Ps. howardii	4	4
Toxorhynchites r. septentionalis	2	2
Uranotaenia sapphirina	3,071	476
TOTAL	189,193	14,008	9	3	5	234

CV = Cache Valley, FL = Flanders, HJ = Highlands J, JC = Jamestown Canyon, PTV = Potosi, TVT = Trivittatus, WN = West Nile