ARBOVIRUS ACTIVITY IN CONNECTICUT, 2011

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

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 May 31 through October 26 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 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, trap type, 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), St. Louis Encephalitis (SLE), 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 2011, a total of 334,371 mosquitoes (19,283 pools) representing 37 species were trapped and tested. A total of 163 isolations of WN virus were made from 5 mosquito species: Culex pipiens = 117, Cx. restuans = 26, Cx. salinarius = 12, Culiseta melanura = 2, Coquillettidia perturbans = 2, collected at 44 sites in 35 towns in 7 counties (Fairfield, Hartford, Litchfield, Middlesex, New Haven, New London, and Tolland). The first positive mosquitoes were collected on June 21, and the last on September 26. The majority of WN virus activity was detected in densely populated urban and suburban regions in southern Fairfield and New Haven counties. Nine human cases of WN were locally acquired (8 = encephalitis/meningoencephalis, 1 = fever) with no fatalities. The age range was 45 to 87 years and the median age was 73 years. Date of onset ranged from August 17, to September 15. There was one horse cases of WN reported in Suffield (Hartford County).

Three isolations of EEE were made from Culiseta melanura at collections sites in Stonington (New London County) and Plainfield (Windham County). The first positive mosquitoes were collected on September 15, and the last on October 12. There were no human, horse, or veterinary cases of EEE reported.

Other mosquito-borne viruses isolated included: Highlands J (HJ) = 16 isolates from 3 species (August 25 - October 12); Jamestown Canyon (JC) = 53 isolates from 10 species (June 1 – June 28)

Mosquito species trapped and tested for arboviruses in Connecticut, 2011

Mosquito Species	# Mosquitoes	# Pools	Virus
			CV	EEE	FL	HJ	JC	TVT	WN
Aedes albopictus	12	11
Ae. cinereus	16,774	1,217
Ae. vexans	39,509	1,682				1	1
Anopheles barberi	6	6
An. crucians	42	27
An. punctipennis	4,338	833					4
An. quadrimaculatus	950	316
An. walkeri	4,603	304
Coquillettidia perturbans	33,790	1,238							2
Culex pipiens	24,920	1,612							117
Cx. restuans	10,743	1,443							26
Cx. salinarius	27,415	1,282							12
Cx. territans	215	148
Culiseta melanura	13,324	895		3		14			6
Cs. minnesotae	132	31
Cs. morsitans	107	54
Ochlerotatus abserratus	4,190	200					3
Oc. atropalpus	1	1
Oc. aurifer	4,019	213					3
Oc. canadensis	51,183	1,671					8
Oc. cantator	5,465	383					10
Oc. communis	162	15
Oc. excrucians	886	109
Oc. grossbecki	18	13
Oc. japonicus	1,841	638
Oc. provocans	545	16					7
Oc. sollicitans	2,258	129
Oc. sticticus	3,551	298					4
Oc. stimulans	2,761	300					2
Oc. taeniorhynchus	17,322	473
Oc. thibaulti	13,383	442
Oc. triseriatus	1,475	463
Oc. trivittatus	24,771	1,288				1	11
Orthopodomyia signifera	5	5
Psorophora ferox	20,121	1,021
Ps. howardii	1	1
Uranotaenia sapphirina	3,533	505
TOTAL	334,371	19,283	0	3	0	16	53	0	163

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