VECTOR-BORNE DISEASES,SURVEILLANCE,PREVENTION Isolations of Potosi Virus from Mosquitoes (Diptera: Culicidae) Collected in Connecticut PHILIP M. ARMSTRONG, 1 THEODORE G. ANDREADIS, 1 JOHN F. ANDERSON, 1 AND ANDREW J. MAIN 1, 2 J. Med. Entomol. 42(5): 875Ð881 (2005) ABSTRACT Potosi virus (POTV) (Bunyaviridae: Orthobunyavirus) was Þrst isolated from Aedes albopictus (Skuse) collected in Potosi, MO, in 1989, and subsequent isolations were reported from Illinois, Michigan, Ohio, and the Carolinas. To determine whether the distribution of this virus extends into the northeastern United States, we analyzed arboviruses acquired from mosquitoes collected in Connecticut from 1998 to 2004. In 2001, a bunyavirus was isolated from Aedes vexans (Meigen) that was different from other arboviruses known to occur in Connecticut by cross-neutralization and reverse transcription-polymerase chain reaction (RT-PCR) assays. Nucleotide and encoded amino acid sequences of a portion of the G2 envelope gene were 99 and 100% similar to POTV, respectively, yet distinct from indigenous strains of Jamestown Canyon (JCV), Cache Valley (CVV), and Trivittatus virus (TVTV). Viral isolates obtained from the statewide surveillance program were retested by RT-PCR coupled with restriction enzyme analysis to distinguish POTV from other bunyaviruses. POTV isolates, previously typed by neutralization, were correctly identiÞed by RT-PCR; however, many isolates classiÞed as JCV or CVV by enzyme-linked immunosorbent assay proved to be POTV by molecular assays. In total, 92 strains of POTV were isolated from 12 mosquito species in 2000, 2001, and 2003, whereas POTV was not detected in mosquitoes sampled during 1998, 1999, 2002, and 2004. Viral isolation rates were highest for Anopheles punctipennis (Say) (3.2Ð11.3 infection rate per 1,000 mosquitoes), whereas the greatest number of isolates came from Ochlerotatus trivittatus (Coquillett) (8 Ð16 isolates). This Þnding represents the Þrst detection of POTV in the northeastern United States where it infects a diverse array of mosquito species. KEY WORDS Potosi virus, arbovirus, viral isolation, mosquitoes, Connecticut A FEW VIRUSES OF THE GENUS Orthobunyavirus (family Bunyaviridae) perpetuate in a cycle involving mos- quito vectors and deer hosts. Jamestown Canyon virus (JCV) and Cache Valley virus (CVV) Þll this ecolog- ical niche and are broadly distributed throughout the United States (Calisher et al. 1986). Human popula- tions are frequently exposed to these viruses where deer are abundant (Grimstad et al. 1986, Mayo et al. 2001), and infection occasionally results in meningitis or encephalitis (Grimstad et al. 1982, Srihongse et al. 1984, Sexton et al. 1997). In 1989, another bunyavirus, Potosi virus (POTV), was isolated from Aedes albop- ictus (Skuse) in Potosi, MO (Francy et al. 1990), and accumulating evidence suggests that it also circulates in a mosquitoÐ deer cycle. POTV infects a number of species of the genera Aedes, Anopheles, Coquillettidia, Culex, Ochlerotatus, and Psorophora (Mitchell et al. 1996), although only Ae. albopictus has been shown to be a competent vector in the laboratory (Mitchell et al. 1990, Heard et al. 1991). White-tailed deer, Odocoileus virginianus, are frequently infected by POTV in enzootic regions (McLean et al. 1996, Na- gayama et al. 2001) and develop viremias sufÞcient to infect susceptible mosquitoes (Blackmore and Grim- stad 1998). POTV has been found primarily in the central United States with isolations restricted to mosquitoes from Missouri, Illinois, Michigan, Ohio, and the Car- olinas (Francy et al. 1990, Harrison et al. 1995; Mitchell et al. 1996, 1998; Wozniak et al. 2001), and POTV antibodies were detected in deer from Arkansas, Mis- souri, Indiana, Iowa, and Colorado (McLean et al. 1996, Blackmore and Grimstad 1998). The geographic range of POTV may be much more extensive than reported previously. The involvement of deer hosts and a broad range of mosquito species suggest that other regions of North America also could support POTV transmission where these hosts are abundant. Indeed, the known distribution of related bunyavi- ruses, JCV and CVV, largely tracks that of their deer hosts and encompasses most of the continental United States, the southern provinces of Canada, and north- ern Mexico (Calisher et al. 1986). In Connecticut, deer populations have increased substantially in recent de- cades fueling the ampliÞcation of JCV and CVV (Main et al. 1979, Main 1981, Andreadis et al. 1994, Zamparo 1 The Connecticut Agricultural Experiment Station, 123 Hunting- ton St., New Haven, CT 06504. 2 American University in Cairo, 113 Kasr El-Aini, Cairo, Egypt. 0022-2585/05/0875Ð0881$04.00/0  2005 Entomological Society of America