Center for Vector Biology and Zoonotic Diseases

New Haven, CT, United States

Center for Vector Biology and Zoonotic Diseases

New Haven, CT, United States
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Armstrong P.M.,Center for Vector Biology and Zoonotic Diseases | Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases
Vector-Borne and Zoonotic Diseases | Year: 2012

Disease outbreaks caused by eastern equine encephalitis virus (EEEV; Togaviridae, Alphavirus) may be prevented by implementing effective surveillance and intervention strategies directed against the mosquito vector. Methods for EEEV detection in mosquitoes include a real-time reverse transcriptase PCR technique (TaqMan assay), but we report its failure to detect variants isolated in Connecticut in 2011, due to a single base-pair mismatch in the probe-binding site. To improve the molecular detection of EEEV, we developed a multi-target TaqMan assay by adding a second primer/probe set to provide redundant targets for EEEV detection. The multi-target TaqMan assay had similar performance characteristics to the conventional assay, but also detected newly-evolving strains of EEEV. The approach described here increases the reliability of the TaqMan assay by creating back-up targets for virus detection without sacrificing sensitivity or specificity. © Mary Ann Liebert, Inc. 2012.


Anderson J.F.,Center for Vector Biology and Zoonotic Diseases | Main A.J.,American University in Cairo | Cheng G.,Yale University | Ferrandino F.J.,U.S. Department of Soil and Water | Fikrig E.,Howard Hughes Medical Institute
American Journal of Tropical Medicine and Hygiene | Year: 2012

Culex tarsalis is a superior horizontal and vertical vector of West Nile virus (WNV) compared with Culex salinarius. Culex salinarius transmitted WNV genotype NY99 (CT 2741-99 strain) horizontally to suckling mice at significantly lower rates than Cx. tarsalis on Days 8, 9, 10, and 12 post-infection, and Cx. salinarius transmitted WNV genotype NY99 to offspring at a lower vertical transmission infection rate than Cx. tarsalis. Culex tarsalis transmitted WNV genotypes NY99 and WN02 (CT S0084-08 strain) with equal efficiency. Daily percent horizontal transmission of genotype NY99 by Cx. tarsalis-infected per os and by intra-thoracic infection was not significantly different from daily transmission of genotype WN02 from Days 5-23 and Days 2-9 post-infection, respectively. Our findings do not support the previously published hypothesis that genotype NY99 was replaced in the New World by WN02 because of a shorter extrinsic incubation of WN02. Copyright © 2012 by The American Society of Tropical Medicine and Hygiene.


Anderson J.F.,Center for Vector Biology and Zoonotic Diseases | Main A.J.,Center for Vector Biology and Zoonotic Diseases | Armstrong P.M.,Center for Vector Biology and Zoonotic Diseases | Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases | Ferrandino F.J.,U.S. Department of Soil and Water
American Journal of Tropical Medicine and Hygiene | Year: 2015

To investigate arbovirus transmission in North Dakota, we collected and screened mosquitoes for viral infection by Vero cell culture assay. Seven viruses were isolated from 13 mosquito species. Spatial and temporal distributions of the important vectors of West Nile virus (WNV), Cache Valley virus, Jamestown Canyon virus (JCV), and trivittatus virus are reported. Snowshoe hare virus, Potosi virus, and western equine encephalomyelitis virus were also isolated. The risks of Culex tarsalis and Aedes vexans transmitting WNV to humans were 61.4% and 34.0% in 2003-2006, respectively, but in 2003 when the largest epidemic was reported, risks for Ae. vexans and Cx. tarsalis in Cass County were 73.6% and 23.9%, respectively. Risk of humans acquiring an infectious bite was greatest from about the second week of July through most of August. West Nile virus sequences were of the WN02 genotype. Most JCV strains belonged to a single clade of genetically related strains. Cache Valley virus and JCV were prevalent during August and early September and during July and August, respectively. Copyright © 2015 by The American Society of Tropical Medicine and Hygiene.


Anderson J.F.,Center for Vector Biology and Zoonotic Diseases | Cowles R.S.,U.S. Department of Soil and Water
Journal of Economic Entomology | Year: 2012

Relative increases of bed bug, Cimex lectularius L., populations are probably due in large measure to their resistance to pyrethroids, which have been used extensively against urban pests. A Connecticut population of bed bugs was assessed for sensitivity to pyrethroids and exposed to commonly-used commercial insecticides applied to various substrates on which the residues were allowed to age for 024 wk. Type I and type II pyrethroids differed in toxicity when applied at a high dosage (1 g) per bed bug. Some type II pyrethroids (cyfluthrin, -cyhalothrin, cis-cypermethrin, and deltamethrin) caused >80% mortality, whereas exposure to type I pyrethroids caused <5% mortality over 72 h (with one exception, pyrethrins caused 23% mortality). Dust products were not affected by residue aging; mortality response over time of exposure closely fit (R2 > 0.95) an exponential rise to a maximum model from which the survival half-life (S1/2) was calculated directly. Tempo Dust (Bayer Environmental Science, Montvale, NJ) killed bed bugs relatively quickly, as did Syloid 244 (Grace Davison, Columbia, MD) and Drione (Bayer Environmental Science, Montvale, NJ) on hardboard and mattress fabric substrates (S1/2 < 1 d); DeltaDust (Bayer Environmental Science, Montvale, NJ) provided a relatively slow kill (S1/2 ≈ 3.5 d). The sprayable pyrethroids, Cyonara 9.7 (Insecticide Control solutions, Pasadena, TX) and D-Force HPX Aerosol 0.06% (Waterbury Companies, Waterbury, CT), displayed reduced residual toxicity as they aged; the mortality was <50% on some substrates after 4 d. Desiccant dusts, with their physical mode of action and long residual activity, appear to be superior to sprayable pyrethroid products for killing bed bugs. © 2012 Entomological Society of America.


Magnarelli L.A.,Center for Vector Biology and Zoonotic Diseases | Williams S.C.,Center for Vector Biology and Zoonotic Diseases | Fikrig E.,Yale University
Journal of Wildlife Diseases | Year: 2010

Whole-blood samples were obtained from 214 white-tailed deer (Odocoileus virginianus) representing 44 sites in Connecticut (USA) during 1992, 1993, 1996, 1999, and 2000 through 2006. Sera were analyzed for total antibodies to whole-cell or recombinant antigens of Borrelia burgdorferi sensu stricto and Anaplasma phagocytophilum, the respective causative agents of Lyme borreliosis and human granulocytic anaplasmosis. Deer sera contained antibodies to both bacteria during different seasons and throughout the 11-yr study. Of the 224 sera tested, 141 (63%) contained antibodies to whole-cell B. burgdorferi in a polyvalent enzyme-linked immunosorbent assay, whereas 124 (55%) were positive to whole-cell A. phagocytophilum by indirect fluorescent antibody staining. Use of highly specific recombinant antigens (VlsE of B. burgdorfert and protein 44 of A. phagocytophilum) provided strong confirmatory results of past or current infections. There was coexistence of antibodies to whole-cell or recombinant antigens of both agents in 72 (32%) sera. Analyses of 18 sera from eight deer that were marked, released, and recaptured, showed minimal changes in antibody titer over sampling time intervals ranging from 17 days to 5.1 yr. Relatively high antibody prevalences for both bacterial agents in different seasons and years reaffirm that there are well-established foci for both tick-borne infections and probably reflect frequent exposure of deer to infected Ixodes scapularis ticks. November and December is a suitable period to obtain blood samples from deer to conduct serosurveillanoe for both bacteria. © Wildlife Disease Association 2010.


Anderson J.F.,Center for Vector Biology and Zoonotic Diseases | Armstrong P.M.,Center for Vector Biology and Zoonotic Diseases
American Journal of Tropical Medicine and Hygiene | Year: 2012

A total of 30 Powassan virus (POWV) isolates from Ixodes scapularis collected from Bridgeport and North Branford, CT in 2008, 2010, 2011, and 2012 and one earlier isolate from Ixodes cookei collected in Old Lyme, CT in 1978 were characterized by phylogenetic analysis of their envelope gene sequences. Powassan virus sequences segregated into two major groups termed the deer tick virus (DTV) and Powassan (POW) lineages. The lineage from I. cookei was POW. The remaining viruses from I. scapularis grouped with the DTV lineage. Powassan viruses from Bridgeport were nearly identical and clustered with a virus strain from a human in New York. Viruses from North Branford were homogeneous and grouped with viruses from Massachusetts, northwestern Connecticut, and Ontario. These findings suggest that POWV was independently introduced into these geographical locations in Connecticut and maintained focally in their respective environments. An improved method of isolation of POWV in vitro is described. Copyright © 2012 by The American Society of Tropical Medicine and Hygiene.


Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases | Armstrong P.M.,Center for Vector Biology and Zoonotic Diseases | Anderson J.F.,Center for Vector Biology and Zoonotic Diseases | Main A.J.,Center for Vector Biology and Zoonotic Diseases
Vector-Borne and Zoonotic Diseases | Year: 2014

Cache Valley virus (CVV) is a mosquito-borne bunyavirus (family Bunyaviridae, genus Orthobunyavirus) that is enzootic throughout much of North and Central America. White-tailed deer (Odocoileus virginianus) have been incriminated as important reservoir and amplification hosts. CVV has been found in a diverse array of mosquito species, but the principal vectors are unknown. A 16-year study was undertaken to identify the primary mosquito vectors in Connecticut, quantify seasonal prevalence rates of infection, and define the spatial geographic distribution of CVV in the state as a function of land use and white-tailed deer populations, which have increased substantially over this period. CVV was isolated from 16 mosquito species in seven genera, almost all of which were multivoltine and mammalophilic. Anopheles (An.) punctipennis was incriminated as the most consistent and likely vector in this region on the basis of yearly isolation frequencies and the spatial geographic distribution of infected mosquitoes. Other species exhibiting frequent temporal and moderate spatial geographic patterns of virus isolation within the state included Ochlerotatus (Oc.) trivittatus, Oc. canadensis, Aedes (Ae.) vexans, and Ae. cinereus. New isolation records for CVV were established for An. walkeri, Culiseta melanura, and Oc. cantator. Other species from which CVV was isolated included An. quadrimaculatus, Coquillettidia perturbans, Culex salinarius, Oc. japonicus, Oc. sollicitans, Oc. taeniorhynchus, Oc. triseriatus, and Psorophora ferox. Mosquitoes infected with CVV were equally distributed throughout urban, suburban, and rural locales, and infection rates were not directly associated with the localized abundance of white-tailed deer, possibly due to their saturation throughout the region. Virus activity in mosquitoes was episodic with no consistent pattern from year-to-year, and fluctuations in yearly seasonal infection rates did not appear to be directly impacted by overall mosquito abundance. Virus infection in mosquitoes occurred late in the season that mostly extended from mid-August through September, when adult mosquito populations were visibly declining and were comparatively low. Findings argue for a limited role for vertical transmission for the perpetuation of CVV as occurs with other related bunyaviruses. © Mary Ann Liebert, Inc.


Huang S.,Center for Vector Biology and Zoonotic Diseases | Molaei G.,Center for Vector Biology and Zoonotic Diseases | Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases
American Journal of Tropical Medicine and Hygiene | Year: 2011

Mosquitoes in the Culex pipiens complex are important vectors of several disease-causing pathogens, including West Nile virus. In North America, the complex consists of Cx. pipiens pipiens form pipiens, Cx. pipiens pipiens form molestus, Cx. pipiens quinquefasciatus, and their hybrids that exhibit substantial diversity in physiology, behavior, and geographic range. Hybridization among these mosquitoes is of concern because of potential implications for disease transmission. Currently, several morphological and molecular markers exist for differentiating members of the Cx. pipiens complex; however, these markers have specific limitations. We report here two highly reliable ribosomal DNA-based single nucleotide polymorphism (SNP) markers, CxpG2T and CxpA2d, for detecting Cx. pipiens complex mosquitoes containing Cx. p. quinquefasciatus alleles. Both CxpG2T and CxpA2d contain one allele that is present in all members of the Cx. pipiens complex, and the other allele is specific to Cx. p. quinquefasciatus. Testing of field populations from the eastern United States showed that these two SNP markers are capable of identifying a south to north gradient of Cx. p. quinquefasciatus and hybrids. The northern limit of detection of Cx. p. quinquefasciatus alleles in this study was in Fort Totten, NY (40.79°N), whereas the southern boundary was determined between Atlanta, GA (33.81°N) and Gainesville, FL (29.64°N). CxpG2T and CxpA2d were more accurate than the ACE-2 marker, and they may conceivably provide comparable resolution with microsatellite markers for detecting Cx. p. quinquefasciatus alleles. Copyright © 2011 by The American Society of Tropical Medicine and Hygiene.


Hardstone M.C.,Center for Vector Biology and Zoonotic Diseases | Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases
Journal of Medical Entomology | Year: 2012

The spread of exotic mosquito species into new environments can introduce shifts in mosquito populations and potentially alter public health risks to mosquito-borne diseases. The successful establishment of exotic species may occur due to their competitive advantage over other cohabitating species. We hypothesized that the recently introduced exotic mosquito Aedes japonicus japonicus (Theobald) would be a more effective competitor than Aedes atropalpus (Coquillett) and Aedes triseriatus (Say), and an equal competitor to Culex pipiens (L.) based on larval abundance data within tire habitats. Impacts of competition were measured using the larval developmental rate and survival of larvae, adult mortality, wing length, and sex ratio. We found that intraspecific competition acted strongest against Ae. japonicus versus the other three resident mosquito species by delaying larval development and increasing adult mortality. Interspecific competition was generally weak and significant main effects were only detected for species and density. Overall, our results show that larval competition between Ae. japonicus and the three resident species was weak when present, indicating that other ecological or behavioral factors may be influencing the invasion success for Ae. japonicus in North America. © 2012 Entomological Society of America.


Andreadis T.G.,Center for Vector Biology and Zoonotic Diseases
Journal of the American Mosquito Control Association | Year: 2012

Mosquitoes within the Culex pipiens complex have been implicated as major vectors of West Nile virus (WNV) in North America due to their seasonal abundance, vector competence and high field infection rates. However, the role of Cx. p. pipiens complex mosquitoes in enzootic amplification of WNV among avian hosts and epidemic transmission to humans varies throughout its geographical distribution. In the northeastern United States, Cx. p. pipiens is recognized as the primary enzootic vector responsible for amplification of virus among wild bird populations. However, because this mosquito is strongly ornithophilic, its role in transmission to humans appears to be more limited in this region. In the north central and Mid-Atlantic States by contrast, Cx. p. pipiens shows an increased affinity for human hosts and has been incriminated as a key bridge vector. In southern regions of the United States, Culex p. quinquefasciatus are more opportunistic feeders, and are thought to be principal enzootic and epidemic vectors. In western regions of the United States where Culex tarsalis predominates, especially in rural areas, Cx. p. pipiens and Cx. p. quinquefasciatus play roles that are more limited and are recognized as secondary vectors. In the southwestern United States Cx. p. quinquefasciatus also appears to be the predominant vector in urban habitats, but only a secondary vector in more rural environs. The direct involvement of Cx. p. pipiens form molestus in WNV transmission is largely unknown, but human-biting Cx. p. pipiens are more likely to have a probability of genetic ancestry with Cx. p. pipiens form molestus. The detection of WNV from overwintering populations of diapausing Cx. p. pipiens and non-diapausing Cx. p. quinquefaciatus and their role in local overwintering of WNV are addressed. © 2012 by The American Mosquito Control Association, Inc.

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