Arbovirus circulation, temporal distribution, and abundance of mosquito species in two Carolina bay habitats.

Carolina bays, a type of geomorphic feature, may be important in the ecology of mosquito vectors in South Carolina. Their hydrology varies from wetland habitats with marked flooding/drying regimes to permanently flooded spring-fed lakes. Moreover, they possess characteristics that contribute to the support of a particularly abundant and diverse invertebrate fauna. Although it has been estimated that 2,700+ bays exist in South Carolina, approximately 97% have been altered; < or = 200 bays remain intact, and only 36 are protected by state-funded conservation projects. We conducted a study in two distinct Carolina bay habitats, Savage Bay Heritage Preserve (SBHP) and Woods Bay State Park (WBSP), from June 1997 to July 1998 to determine mosquito temporal distribution, species composition, and the occurrence of arbovirus activity. The largest mosquito collection was obtained at WBSP (n = 31,172) representing 25 species followed by SBHP (n = 3,940) with 24 species. Anopheles crucians complex were the most common species encountered in both bays. Two virus isolates were obtained from SBHP in 1997: Keystone (KEY) virus from Ochlerotatus atlanticus-tormentor and Cache Valley (CV) virus from Oc. canadensis canadensis. Twenty-nine (29) arbovirus-positive pools were obtained from WBSP: 28 in 1997 and one in 1998. KEY virus was isolated from three pools of Oc. atlanticus-tormentor and Tensaw (TEN) virus was isolated from two pools of An. crucians complex; 10 isolates could not be identified with the sera available. Additionally, 14 pools of An. crucians complex tested positive for Eastern equine encephalitis (EEE) virus antigen. These represent the first record of KEY and CV viruses in South Carolina. Our data indicate the presence of high mosquito density and diversity in both Carolina bay habitats, which may be influenced, in part, by seasonal changes in their hydroperiods. The study of mosquito and arbovirus ecology in Carolina Bay habitats could provide more information on the transmission dynamics of arboviruses and its impact on human and animal arboviral disease occurrence in South Carolina.

Bat rabies in South Carolina, 1970-90.

This retrospective study examines the geographic and temporal distribution of bat species submitted for rabies testing in South Carolina (USA) from 1970 to 1990. Histories of human or animal exposures to rabid and nonrabid bats submitted during this time period were compared. Two hundred and thirty-one bats were found to be rabid from the 2,657 bats submitted over this 20 yr period. The two species most frequently submitted for testing were Lasiurus borealis with 785 specimens (30% of the total) and Nycticeius humeralis with 607 specimens (22% of the total). Lasiurus borealis also had the highest prevalence of rabies (18%) while N. humeralis had the lowest prevalence (3%). Fifty-one percent (1,259) of the bats received for testing were submitted from June through August. The majority (54%) of rabid bats were received from August through October.

Arbovirus surveillance in South Carolina, 1996-98.

Arboviruses isolated and identified from mosquitoes in South Carolina (USA) are described, including new state records for eastern equine encephalitis virus (EEE), St. Louis encephalitis virus (SLE), Flanders virus, Tensaw virus (TEN), and a variant of Jamestown Canyon virus (JC). Mosquitoes were collected at 52 locations in 30 of 46 South Carolina counties beginning in June 1996, and ending in October 1998, and tested for arboviruses. Of 1,329 mosquito pools tested by virus isolation (85,806 mosquitoes representing 34 mosquito species or complexes), 15 pools were positive. Virus isolations included EEE from 1 pool each of Anopheles crucians complex and Culex erraticus; a variant of JC from 1 pool of An. crucians complex; a California serogroup virus from 1 pool of Aedes atlanticus/tormentor; TEN from 5 pools of An. crucians complex and 1 pool each of Culex salinarius and Psorophora ciliata; Flanders virus from 1 pool of Culiseta melanura; and Potosi virus from 1 pool each of Aedes vexans, Coquillettidia perturbans, and Psorophora columbiae. Of 300 mosquito pools tested by antigen-capture assay for EEE and SLE (14,303 mosquitoes representing 16 mosquito species or complexes), 21 were positive for EEE and I was positive for SLE. Positive EEE mosquito pools by antigen-capture assay included An. crucians complex (14 pools), Anopheles punctipennis (1 pool), Anopheles quadrimaculatus (1 pool), Cq. perturbans (4 pools), and Cs. melanura (1 pool). One pool of Cx. salinarius was positive for SLE by antigen-capture assay. Arbovirus-positive mosquito pools were identified from 12 South Carolina counties, all located in the Atlantic Coastal Plain, and from 4 of 8 Carolina bays surveyed.