| Studies on Hibernating Populations of Culex pipiens from a West Nile Virus Endemic Focus in New York City: Parity Rates and Isolation of West Nile Virus | Andreadis, Theodore G. | 2010 |
KeywordsWNV AbstractA 3-year study was undertaken to examine the parity status, survival, and prevalence of West Nile virus (WNV) in overwintering populations of Culex pipiens pipiens collected from a hibernaculum located in a WNV endemic region in New York City. Nearly 6,000 females were collected from December through April. Parity rates were highest among females collected in December and January, ranging from 12.3% to 21.9%, depending on the year. In each year of the study, the proportion of parous females declined significantly during the course of the winter; the percentage of parous females found in April ranged from 0.9% to 10%. Results provide unequivocal evidence that parous Cx. p. pipiens females from this region of the northeastern US enter hibernacula in the fall in comparatively high proportions not previously recognized for this species, and while these females experience significant mortality during the winter, some survived to April to emerge in the spring. The absence of any detectible blood remnants in overwintering females reaffirms that blood feeding does not occur among diapausing females during the winter. The possibility that a portion of the diapausing population may be autogenous as a result of hybridization with sympatric belowground populations of Cx. p. pipiens "form molestus" is discussed. A single isolation of WNV was obtained in Vero cell culture from a pool of 50 females collected on January 11, 2007, representing an infection prevalence of 0.07% in the overwintering population in 2007 (n = 1,370 mosquitoes, 33 pools). No isolations of WNV were made from mosquitoes collected in 2008 (n = 1,870 mosquitoes, 190 pools) or 2009 (n = 1,767 mosquitoes, 184 pools). Findings provide further evidence for local overwintering of WNV in diapausing Cx. p. pipiens, albeit at very low rates, consistent with the paucity of WNV-positive mosquitoes detected in June and early July despite the emergence of females from hibernacula in early May in this region. AuthorsAndreadis, Theodore G., ARMSTRONG, PHILIP M. and Bajwa, Waheed I. Year Published2010 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/10-6004.1 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21033052 |
| West nile virus-associated optic neuritis and chorioretinitis | Anninger, William V. | 2003 |
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| Molecular evolution of West Nile virus in a northern temperate region: Connecticut, USA 1999–2008 | ARMSTRONG, PHILIP M. | 2011 |
KeywordsPhylogeny; Flaviviridae; Flavivirus; West Nile virus; Molecular epidemiology; Viral evolution, WNV AbstractWest Nile virus (WNV) has become firmly established in northeastern US, reemerging every summer since its introduction into North America in 1999. To determine whether WNV overwinters locally or is reseeded annually, we examined the patterns of viral lineage persistence and replacement in Connecticut over 10 consecutive transmission seasons by phylogenetic analysis. In addition, we compared the full protein coding sequence among WNV isolates to search for evidence of convergent and adaptive evolution. Viruses sampled from Connecticut segregated into a number of well-supported subclades by year of isolation with few clades persisting ≥ 2 years. Similar viral strains were dispersed in different locations across the state and divergent strains appeared within a single location during a single transmission season, implying widespread movement and rapid colonization of virus. Numerous amino acid substitutions arose in the population but only one change, V → A at position 159 of the envelope protein, became permanently fixed. Several instances of parallel evolution were identified in independent lineages, including one amino acid change in the NS4A protein that appears to be positively selected. Our results suggest that annual reemergence of WNV is driven by both reintroduction and local-overwintering of virus. Despite ongoing evolution of WNV, most amino acid variants occurred at low frequencies and were transient in the virus population. AuthorsARMSTRONG, PHILIP M., Vossbrinck, Charles R., Andreadis, Theodore G., Anderson, John F., Pesko, Kendra N., Newman, Ruchi M., Lennon, Niall J., Birren, Bruce W., Ebel, Gregory D. and Henn, Mathew R. Year Published2011 PublicationVirology LocationsDOI10.1016/j.virol.2011.06.006 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21723580 |
| Relationship Between Distance From Major Larval Habitats and Abundance of Adult Mosquitoes in Semiarid Plains Landscapes in Colorado | Barker, Christopher M. | 2009 |
KeywordsWNV AbstractWe examined the relationship between distance from major larval habitats and abundance of adult mosquitoes in the semiarid plains landscape characteristic of eastern Colorado. Mosquito collection was conducted from late June to early August 2007 and included trap locations at distances ranging from <10 m up to 20-150 m and 160-373 m from three major larval habitats: one area along a river corridor and two small reservoirs. The study yielded 65,140 mosquitoes of 14 species, and five species were sufficiently abundant to be included in statistical analyses: Aedes vexans (Meigen), Culex tarsalis Coquillett, Ochlerotatus dorsalis (Meigen) (=Ae. dorsalis), Ochlerotatus melanimon (Dyar) (=Ae. melanimon), and Culex pipiens L. Distance to nearest major larval habitat was not strongly related to Culex abundance within the approximately = 400-m range from larval habitats examined in this study. Abundance of Ae. vexans declined significantly with distance from the larval habitat, whereas abundance was significantly higher in the 20-150- and 160-373-m classes compared with areas within 10 m of the larval habitat for both Ochlerotatus species. Except for Ae. vexans, however, we did not find monotonic increasing or decreasing abundance trends associated with distance from larval habitats for the 400-m range examined. This, combined with a finding that fine-scale habitat heterogeneity influenced abundance for most of the mosquitoes examined, underscores the importance of considering not only distance from larval habitat but also fine-scale habitat heterogeneity to understand how important nuisance-biters and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) vectors use the landscape. We also discuss how these results relate to previous studies from western North America and explore their relevance to operational implementation of adulticides to suppress mosquito vectors during WNV disease outbreaks in the Great Plains. AuthorsBarker, Christopher M., Bolling, Bethany G., Moore, Chester G. and Eisen, Lars Year Published2009 PublicationJournal of Medical Entomology LocationsDOI10.1603/033.046.0606 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/19960672 |
| West Nile Virus in Host-Seeking Mosquitoes within a Residential Neighborhood in Grand Forks, North Dakota | Bell, Jeffrey A. | 2005 |
KeywordsWNV AbstractWest Nile virus (WNV) was first recovered in North Dakota near the city of Grand Forks in June 2002. During 2002, 2003, and 2004, we collected mosquitoes from Grand Forks using Mosquito Magnet™ traps and tested them for WNV. The seasonal abundance, species composition, and reproductive status of female mosquitoes were correlated with local environmental temperature and state surveillance data on WNV to determine the factors affecting local transmission of WNV. Over 90% of the mosquitoes collected were Aedes vexans, Ochlerotatus dorsalis, and Culex tarsalis, but WNV was detected only in Cx. tarsalis. Average summertime temperatures and relative abundance of mosquitoes were highest in 2002 but no WNV-positive mosquitoes were detected until the following summer. In 2003, nulliparous Cx. tarsalis appeared in mid-June (first summer brood), and parous Cx. tarsalis appeared in mid-July. The first WNV-positive pool occurred 21 July, and minimum daily infections rates increased thereafter until 27 August. The minimum infection rate (MIR) for Cx. tarsalis during the season was 5.7 infected mosquitoes per 1,000 tested, with the highest infection rates occurring at the end of the season as Cx. tarsalis populations started to decline. Mid-to-late August was identified as the period of highest risk for being bitten by a WNV-infected mosquito in Grand Forks during 2003. In 2004, viral activity in Grand Forks was low, due to very cool temperatures throughout the summer. To examine the genetic diversity of the 2003 WNV isolates from Grand Forks, we sequenced a 366-nucleotide region of the capsid and premembrane gene. Thirteen (46%) of the 28 WNV isolates contained at least one nucleotide substitution when compared to the homologous region of the progenitor WN NY-99 strain, and seven of these 13 substitutions coded for amino acid changes. Thus, WNV is established in North Dakota, it appears to be evolving and it is vectored primarily by Cx. tarsalis. Vector-Borne Zoonotic Dis. 5, 373–382. AuthorsBell, Jeffrey A., Mickelson, Nathan J. and Vaughan, Jefferson A. Year Published2005 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/vbz.2005.5.373 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16417433 |
| Serologic Survey of Select Infectious Diseases in Coyotes and Raccoons in Nebraska | Bischof, Richard | 2005 |
KeywordsCanine distemper virus, coyote, Francisella tularensis, Leptospira interrogans, Nebraska, raccoon, Rickettsia rickettsi, serology, West Nile virus, WNV AbstractTo obtain data about select zoonotic and other infectious diseases in free-ranging predators in five ecoregions in Nebraska, sera were collected from 67 coyotes (Canis la-trans) and 63 raccoons (Procyon lotor) from November 2002 through January 2003. For coyotes, antibodies were detected against canine distemper virus (CDV, 61%), Francisella tularensis (32%), Rickettsia rickettsi (13%), and flaviviruses (48%). None of the coyote sera had antibodies to Borrelia burgdorferi, Brucella canis, or six serovars of Leptospira interrogans. Because serologic cross-reactivity exists among flaviviruses, 14 sera from flavivirus-positive coyotes were also tested for St. Louis encephalitis virus (SLE) antibodies and two (14%) were positive, suggesting that up to 48% of coyotes tested had antibodies against West Nile virus (WNV). For raccoons, antibodies were detected against CDV (33%), F. tularensis (38%), and three serovars of L. interrogans (11%). AuthorsBischof, Richard and Rogers, Douglas G. Year Published2005 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-41.4.787 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16456169 |
| ENTOMOLOGICAL STUDIES ALONG THE COLORADO FRONT RANGE DURING A PERIOD OF INTENSE WEST NILE VIRUS ACTIVITY | BOLLING, B.G. | 2007 |
KeywordsWest Nile virus, vector ecology, Culex pipiens, Culex tarsalis, overwintering, WNV AbstractTo better understand the ecology of West Nile virus transmission in Northern Colorado, field studies were conducted in Larimer and Weld counties from September 2003 through March 2005. During summer studies, 18,540 adult mosquitoes were collected using light traps and gravid traps. West Nile virus RNA was detected in 24 of the 2,140 mosquito pools tested throughout the study area in 2003 and 2004. Culex tarsalis had the highest minimum infection rate (MIR) in both 2003 (MIR = 34.48) and in 2004 (MIR = 8.74). During winter studies, 9,391 adult mosquitoes were collected by aspirator from various overwintering sites including bridges and storm drains. The most frequently collected species was Culex pipiens. West Nile virus was not detected in our overwintering collections. The relationship between spring adult emergence and temperature inside and outside overwintering sites is described. Species composition of collections as well as the spatial and temporal distribution of West Nile virus detections are presented. AuthorsBOLLING, B.G., MOORE, C.G., ANDERSON, S.L., BLAIR, C.D. and BEATY, B.J. Year Published2007 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/8756-971X(2007)23[37:ESATCF]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17536366 |
| Seasonal Patterns for Entomological Measures of Risk for Exposure to Culex Vectors and West Nile Virus in Relation to Human Disease Cases in Northeastern Colorado | Bolling, Bethany G. | 2009 |
KeywordsCulex pipiens, Culex tarsalis, Colorado, seasonal risk, West Nile virus, WNV AbstractWe examined seasonal patterns for entomological measures of risk for exposure to Culex vectors and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) in relation to human WNV disease cases in a five-county area of northeastern Colorado during 2006–2007. Studies along habitat/ elevation gradients in 2006 showed that the seasonal activity period is shortened and peak numbers occur later in the summer for Culex tarsalis Coquillett females in foothills-montane areas > 1,600 m compared with plains areas 1,600 m. The vector index for abundance of WNV-infected Cx. tarsalis females for the plains sites combined exceeded 0.50 from mid-July to mid-August, with at least one site exceeding 1.00 from early July to late August. Finally, we found that abundance of Cx. tarsalis females and the vector index for infected females were strongly associated with weekly numbers of WNV disease cases with onset 4–7 wk later (female abundance) or 1–2 wk later (vector index). AuthorsBolling, Bethany G., Barker, Christopher M., Moore, Chester G., Pape, W. John and Eisen, Lars Year Published2009 PublicationJournal of Medical Entomology Locations- Sites along the Poudre River, South Platte River, and Big Thompson River in Larimer County, Weld County, Morgan County, Logan County, and Washington County, Colorado (40.6956, -105.594)
- Sites along the Poudre River, South Platte River, and Big Thompson River in Larimer County, Weld County, Morgan County, Logan County, and Washington County, Colorado (40.5266, -104.472)
- Sites along the Poudre River, South Platte River, and Big Thompson River in Larimer County, Weld County, Morgan County, Logan County, and Washington County, Colorado (40.2989, -103.729)
- Sites along the Poudre River, South Platte River, and Big Thompson River in Larimer County, Weld County, Morgan County, Logan County, and Washington County, Colorado (40.7056, -102.99)
- Sites along the Poudre River, South Platte River, and Big Thompson River in Larimer County, Weld County, Morgan County, Logan County, and Washington County, Colorado (40.0637, -102.99)
DOI10.1603/033.046.0641 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/19960707 |
| NONTARGET EFFECTS OF THE MOSQUITO ADULTICIDE PYRETHRIN APPLIED AERIALLY DURING A WEST NILE VIRUS OUTBREAK IN AN URBAN CALIFORNIA ENVIRONMENT | BOYCE, WALTER M. | 2007 |
KeywordsUltra-low volume adulticide, nontarget mortality, pyrethrins, WNV AbstractIn August 2006, a pyrethrin insecticide synergized with piperonyl butoxide (EverGreen® Crop Protection EC 60-6, McLaughlin Gormley King Company, Golden Valley, MN) was sprayed in ultra-low volumes over the city of Davis, CA, by the Sacramento–Yolo Mosquito and Vector Control District to control mosquitoes transmitting West Nile virus. Concurrently, we evaluated the impact of the insecticide on nontarget arthropods by 1) comparing mortality of treatment and control groups of sentinel arthropods, and 2) measuring the diversity and abundance of dead arthropods found on treatment and control tarps placed on the ground. We found no effect of spraying on nontarget sentinel species including dragonflies (Sympetrum corruptum), spiders (Argiope aurantia), butterflies (Colias eurytheme), and honeybees (Apis mellifera). In contrast, significantly higher diversity and numbers of nontarget arthropods were found on ground tarps placed in sprayed versus unsprayed areas. All of the dead nontarget species were small-bodied arthropods as opposed to the large-bodied sentinels that were not affected. The mortality of sentinel mosquitoes placed at the same sites as the nontarget sentinels and ground tarps ranged from 0% to 100%. Dead mosquitoes were not found on the ground tarps. We conclude that aerial spraying with pyrethrins had no impact on the large-bodied arthropods placed in the spray zone, but did have a measurable impact on a wide range of small-bodied organisms. AuthorsReisen, William K., BOYCE, WALTER M., LAWLER, SHARON P., SCHULTZ, JENNIFER M., McCAULEY, SHANNON J., KIMSEY, LYNN S., NIEMELA, MICHAEL K. and NIELSEN, CARRIE F. Year Published2007 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/8756-971X(2007)23[335:NEOTMA]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17939516 |
|
Surveillance for West Nile Virus and Vaccination of Free-Ranging Island Scrub-Jays (
Aphelocoma insularis
) on Santa Cruz Island, California
| BOYCE, WALTER M. | 2011 |
KeywordsWNV AbstractAbstract Transmission of West Nile virus (WNV) on mainland California poses an ongoing threat to the island scrub-jay (ISSJ, Aphelocoma insularis), a species that occurs only on Santa Cruz Island, California, and whose total population numbers 750 migrating and resident birds on the island from 2006 to 2009 indicated that WNV had not become established by the end of 2009. Several species of competent mosquito vectors were collected at very low abundance on the island, including the important mainland vectors Culex tarsalis and Culex quinquefasciatus. However, the island was generally cooler than areas of mainland California that experienced intense WNV transmission, and these lower temperatures may have reduced the likelihood of WNV becoming established because they do not support efficient virus replication in mosquitoes. A vaccination program was initiated in 2008 to create a rescue population of ISSJ that would be more likely to survive a catastrophic outbreak. To further that goal, we recommend managers vaccinate >100 ISSJ each year as part of ongoing research and monitoring efforts. AuthorsBOYCE, WALTER M., Vickers, Winston, Morrison, Scott A., Sillett, T. Scott, Caldwell, Luke, Wheeler, Sarah S., Barker, Christopher M., Cummings, Robert and Reisen, William K. Year Published2011 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/vbz.2010.0171 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21438695 |
