| Avian virulence and thermostable replication of the North American strain of West Nile virus | Kinney, R. M. | 2006 |
KeywordsWNV AbstractThe NY99 genotype of West Nile virus (WNV) introduced into North America has demonstrated high virulence for American crows (AMCRs), whilst a closely related WNV strain (KEN-3829) from Kenya exhibits substantially reduced virulence in AMCRs [Brault, A. C., Langevin, S. A., Bowen, R. A., Panella, N. A., Biggerstaff, B. J., Miller, B. R. & Nicholas, K. (2004). Emerg Infect Dis 10, 2161–2168]. Viruses rescued from infectious cDNA clones of both the NY99 and KEN-3829 strains demonstrated virulence comparable to that of their parental strains in AMCRs. To begin to define parameters that might explain the different virulence phenotypes between these two viruses, temperature-sensitivity assays were performed for both viruses at the high temperatures experienced in viraemic AMCRs. Growth curves of the two WNV strains were performed in African green monkey kidney (Vero; 37–42 °C) and duck embryonic fibroblast (DEF; 37–45 °C) cells cultured at temperatures that were tolerated by the cell line. Unlike the NY99 virus, marked decreases in KEN-3829 viral titres were detected between 36 and 120 h post-infection (p.i.) at temperatures above 43 °C. Replication of KEN-3829 viral RNA was reduced 6500-fold at 72 h p.i. in DEF cells incubated at 44 °C relative to levels of intracellular virus-specific RNA measured at 37 °C. In contrast, replication of virus derived from the NY99 infectious cDNA at 44 °C demonstrated only a 17-fold reduction in RNA level. These results indicated that the ability of WNV NY99 to replicate at the high temperatures measured in infected AMCRs could be an important factor leading to the increased avian virulence and emergence of this strain of WNV. AuthorsKinney, R. M., Huang, C. Y.-H., Whiteman, M. C., Bowen, R. A., Langevin, S. A., Miller, B. R. and Brault, A. C. Year Published2006 PublicationJournal of General Virology LocationsDOI10.1099/vir.0.82299-0 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17098976 |
| Behavioral Risks for West Nile Virus Disease, Northern Colorado, 2003 | Gujral, Indira B. | 2007 |
KeywordsWNV AbstractIn 2003, residents in 2 adjacent cities in northern Colorado (Loveland and Fort Collins) had severe outbreaks of human West Nile virus (WNV) disease. Unexpectedly, age-adjusted neuroinvasive disease rates were higher in Loveland (38.6 vs. 15.9 per 100,000), which had a more extensive mosquito control program and fewer mosquitoes. A survey was conducted to assess differences in personal protection and risk practices by each city's residents. During May and June 2004, a random-digit dial telephone survey was conducted among adults to assess personal protection behavioral practices used to prevent WNV infection during the 2003 outbreak. After we adjusted for identified risk factors, Loveland residents were 39% more likely to report seldom or never using N,N-diethyl-m-toluamide (DEET), and ≈30% were more likely to report being outdoors during prime mosquito-biting hours than Fort Collins residents. Personal protective practices may directly influence rates of WNV infection and remain important even when comprehensive community mosquito control measures are implemented. AuthorsGujral, Indira B., Zielinski-Gutierrez, Emily C., LeBailly, Adrienne and Nasci, Roger Year Published2007 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1303.060941 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17552095 |
| Bird Community Composition Linked to Human West Nile Virus Cases Along the Colorado Front Range | McKenzie, Valerie J. | 2010 |
KeywordsWNV AbstractIn the present study, we examined whether bird community composition can predict the annual number of human West Nile virus (WNV) cases on a per county basis in the Colorado Front Range, a region that experienced high numbers of human cases during the early part of the North American epidemic. We analyzed data sets pertaining to birds and human WNV cases from multiple existing databases between the years 2002 and 2008. Based on previous studies that used amplification fractions to compare the relative competence of different bird species, ten bird species that are common in Colorado were selected and categorized as high amplification birds, such as the American Robin (Turdus migratorius), or low amplification birds, such as the American Crow (Corvus brachyrhynchos). A general linear modeling analysis was used with an information theoretic (AIC) model sorting approach to examine which of the models best predicted the number of human WNV cases per county. Candidate models included year as a covariate and one of several bird community descriptors (e.g., richness, diversity, total bird abundance, high amplification abundance, or low amplification abundance). Results demonstrated that high amplification birds were a significant predictor of human WNV cases between 2002 and 2008. Our results suggest that a small subset of the bird community with high amplification fractions may drive the dynamics of human disease risk for West Nile. This study has implications for surveillance of West Nile and may offer insight into disease risk associated with other vector-borne zoonotic diseases. AuthorsMcKenzie, Valerie J. and Goulet, Nicolas E. Year Published2010 PublicationEcoHealth Locations- The range of this study spans counties on the Colorado and Wyoming Front Range, located directly east of the Rocky Mountains (105 39 2 to -104 3 1 W and 41 20 59 to 38 11 0 N). The counties include: Laramie, Larimer, Weld, Boulder, Denver, Arapahoe, Jefferson, Adams, Elbert, Park, Clear Creek, El Paso, Fremont, and Pueblo (40.0, -105.0)
DOI10.1007/s10393-010-0360-8 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21125307 |
| Bird-Baited Traps for Surveillance of West Nile Mosquito Vectors: Effect of Bird Species, Trap Height, and Mosquito Escape Rates | Darbro, Jonathan M. | 2006 |
KeywordsWest Nile virus, house sparrow, chicken, Culex p. pipiens, Culex restuans, WNV AbstractHost-seeking mosquitoes were sampled in bird-baited traps at four sites in New York state in 2003–2004. Trap placement and efficacy of chickens, Gallus gallus domesticus L., as bait compared with house sparrows, Passer domesticus L., an important reservoir of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), was evaluated. Each site had a chicken-baited trap near ground level (≈1.5 m) and in the tree canopy (≈9 m), and a house sparrow-baited trap at ground level and canopy level. Each trap allowed mosquito access to birds on one end, and an inner mesh screen blocked bird access on the other end. The two most abundant mosquitoes, Culex restuans Theobald and Culex pipiens pipiens L., were differentiated using molecular characters. In 2003, Cx. restuans and Cx. p. pipiens made up 88% of total mosquito catch. In 2004, Cx. restuans comprised 43% of total catch and Cx. p. pipiens comprised 33%. The remaining species representing at least 1% of total catch were Ochlerotatus trivittatus (Coquillett), Coquilletidia perturbans (Walker), and Culiseta morsitans (Theobald). Capture rates were similar for chicken and house sparrow-baited traps; however, significantly more mosquitoes were captured in the canopy for both bird species. Cx. restuans preferred canopy traps, whereas equal numbers of Cx. p. pipiens were captured at ground and canopy levels. Mosquitoes were more likely to escape (74%) when excluded from birds than when allowed free access to birds (54%). Sentinel bird surveillance for WNV can be improved by trapping in the tree canopy in addition to ground level to capture the most important avian vectors. AuthorsDarbro, Jonathan M. and Harrington, Laura C. Year Published2006 PublicationJournal of Medical Entomology Locations- Tompkins County, New York state. Four different field sites were sampled and included dairy farm hedgerow (42° 26.501′ N 076° 25.889′ W), nature trail (42° 28.532′ N 076° 27.044′ W), golf course (42° 27.486′ N 076° 27.594′ W), and private residence (42° 26.924′ N 076° 25.757′ W) (42.442, -76.431)
- Tompkins County, New York state. Four different field sites were sampled and included dairy farm hedgerow (42° 26.501′ N 076° 25.889′ W), nature trail (42° 28.532′ N 076° 27.044′ W), golf course (42° 27.486′ N 076° 27.594′ W), and private residence (42° 26.924′ N 076° 25.757′ W) (42.476, -76.451)
- Tompkins County, New York state. Four different field sites were sampled and included dairy farm hedgerow (42° 26.501′ N 076° 25.889′ W), nature trail (42° 28.532′ N 076° 27.044′ W), golf course (42° 27.486′ N 076° 27.594′ W), and private residence (42° 26.924′ N 076° 25.757′ W) (42.458, -76.46)
- Tompkins County, New York state. Four different field sites were sampled and included dairy farm hedgerow (42° 26.501′ N 076° 25.889′ W), nature trail (42° 28.532′ N 076° 27.044′ W), golf course (42° 27.486′ N 076° 27.594′ W), and private residence (42° 26.924′ N 076° 25.757′ W) (42.449, -76.429)
DOI10.1603/0022-2585(2006)043[0083:BTFSOW]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16506452 |
| Blood-Feeding Patterns of the Culex pipiens Complex in Sacramento and Yolo Counties, California | Montgomery, Matthew J. | 2011 |
KeywordsCulex pipiens, mosquito feeding, West Nile virus, WNV AbstractMosquitoes in the Culex pipiens complex are competent vectors of West Nile virus (WNV; family Flaviviridae, genus Flavivirus) in the laboratory, and field-collected mosquitoes have tested positive for the virus in California and elsewhere. A better understanding of Cx. pipiens complex blood-feeding patterns will help define the threat that these mosquitoes pose to human health and their role in WNV amplification in northern California. We collected blood-engorged Cx. pipiens complex mosquitoes from resting sites near and away from human habitation in Sacramento and Yolo Counties. Cytochrome c oxidase 1 gene sequences were used to identify the vertebrate species from which blood meals were taken. Of 330 engorged mosquitoes collected at 28 sites from June through August 2007 and May through August 2008, >99% fed on an avian host. Three mosquitoes contained bovine blood and none had fed on a human. American Robins (Turdus migratorius) were bitten most often, and the proportion of American Robin blood meals increased significantly over the summer. Other important avian hosts included House Finches (Carpodacus mexicanus), Barn Swallows (Hirundo rustica), Western Meadowlarks (Sturnella neglecta), and Mourning Doves (Zenaida macroura). In rural areas, Barn Swallows, Brewer's Blackbirds (Euphagus cyanocephalus), and House Sparrows (Passer domesticus) were frequent hosts. In settings near human habitation, Mourning Doves and Western Meadowlarks were common hosts. Our data indicate that in north central California mosquitoes in the Cx. pipiens complex may be more important as epiornitic than epidemic vectors of WNV. AuthorsMontgomery, Matthew J., Thiemann, Tara, Macedo, Paula, Brown, David A. and Scott, Thomas W. Year Published2011 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME10067 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21485380 |
| Bloodmeal Host Congregation and Landscape Structure Impact the Estimation of Female Mosquito (Diptera: Culicidae) Abundance Using Dry Ice-Baited Traps | Thiemann, Tara | 2011 |
KeywordsCulex tarsalis, Anopheles freeborni, dry ice-baited traps, abundance, California, WNV AbstractVegetation patterns and the presence of large numbers of nesting herons and egrets significantly altered the number of host-seeking Culex tarsalis Coquillett (Diptera: Culicidae) collected at dry ice-baited traps. The numbers of females collected per trap night at traps along the ecotone of Eucalyptus stands with and without a heron colony were always greater or equal to numbers collected at traps within or under canopy. No Cx. tarsalis were collected within or under Eucaplytus canopy during the peak heron nesting season, even though these birds frequently were infected with West Nile virus and large number of engorged females could be collected at resting boxes. These data indicate a diversion of host-seeking females from traps to nesting birds reducing sampling efficiency. AuthorsThiemann, Tara, Nelms, Brittany and Reisen, William K. Year Published2011 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME10273 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21661310 |
| Cerebrospinal fluid cytology in seasonal epidemic West Nile virus meningo-encephalitis | Rawal, Ajay | 2006 |
KeywordsWest Nile virus;cytology;cerebrospinal fluid;pleocytosis, WNV AbstractThe incidence of West Nile Virus (WNV) infection has progressively increased in North America since the first epidemic in 1999. Formal scholarly documentation of cerebrospinal fluid (CSF) cytology changes in patients with WNV infection is limited. We report our experience with CSF cytospins from a population of consecutive patients with documented CSF WNV-specific IgM. Thirty-two patients (12 male, 20 female) with a median age of 52 yr (range, 19–88) diagnosed with WNV meningo-encephalitis were studied. Symptoms were present for a mean of 5 days (range, 1–14) prior to lumbar puncture. CSF proteins were elevated in 94% of patients (30/32) with a mean value of 79 mg/dl (range, 36–185). CSF glucose was normal to elevated in all cases. All cytomorphologically adequate samples demonstrated a pleocytosis with a mean of 156 cells/mm3 (range, 13–683). Nearly, all (26/28) patients showed increased CSF neutrophils- mean 43% (range, 1–83). Mean lymphocyte and monocyte fractions were 44% (range, 8–85) and 14% (range, 2–27), respectively. Three cases showed 1–4% plasma cells. Mean total leukocyte counts (TLC) (197 cells/mm3) and mean neutrophil fractions (50%) were greater in patients sampled within the first 3 days of symptoms than in those sampled beyond day 3 (mean TLC, 126 cells/mm3; mean neutrophil fraction, 37%). Relative lymphocyte proportions increased from a mean of 39 to 48% after 3 days of illness. WNV should be considered as a potential etiology of infectious CSF pleocytosis in the North American late summer and early fall seasons. AuthorsRawal, Ajay, Gavin, Patrick J. and Sturgis, Charles D. Year Published2006 PublicationDiagnostic Cytopathology LocationsDOI10.1002/dc.20410 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16511849 |
| Characteristics of an outbreak of West Nile virus encephalomyelitis in a previously uninfected population of horses | Ward, Michael P. | 2006 |
KeywordsEquine; West Nile virus; Epidemiology; Outbreak; Risk factors; Geostatistical analysis, WNV AbstractEquine West Nile virus (WNV) encephalomyelitis cases – based on clinical signs and ELISA serology test results – reported to Texas disease control authorities during 2002 were analyzed to provide insights into the epidemiology of the disease within a previously disease-free population. The epidemic occurred between June 27 and December 17 (peaking in early October) and 1698 cases were reported. Three distinct epidemic phases were identified, occurring mostly in southeast, northwest and then central Texas. Significant (P < 0.05) disease clusters were identified in northwest and northern Texas. Most (91.1%) cases had no recent travel history, and most (68.9%) cases had not been vaccinated within the previous 12 months. One-third of cases did not survive, 71.2% of which were euthanatized. The most commonly reported presenting signs included ataxia (69%), abnormal gait (52%), muscle fasciculations (49%), depression (32%) and recumbency (28%). Vaccination status, ataxia, falling down, recumbency and lip droop best explained the risk of not surviving WNV disease. Results suggest that the peak risk period for encephalomyelitis caused by WNV may vary substantially among regions within Texas. Recumbent horses have a poor prognosis for survival. Vaccines, even if not administered sufficiently in advance of WNV infection within a district, may reduce the risk of death by at least 44%. AuthorsWard, Michael P., Schuermann, James A., Highfield, Linda D. and Murray, Kristy O. Year Published2006 PublicationVeterinary Microbiology LocationsDOI10.1016/j.vetmic.2006.07.016 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16971067 |
| Characterization of a small plaque variant of West Nile virus isolated in New York in 2000 | Jia, Yongqing | 2007 |
KeywordsWest Nile virus; Small plaque variant; Wild-type; Temperature sensitivity; Culex pipiens; Vector competence, WNV AbstractA small-plaque variant (SP) of West Nile virus (WNV) was isolated in Vero cell culture from kidney tissue of an American crow collected in New York in 2000. The in vitro growth of the SP and parental (WT) strains was characterized in mammalian (Vero), avian (DF-1 and PDE), and mosquito (C6/36) cells. The SP variant replicated less efficiently than did the WT in Vero cells. In avian cells, SP growth was severely restricted at high temperatures, suggesting that the variant is temperature sensitive. In mosquito cells, growth of SP and WT was similar, but in vivo in Culex pipiens (L.) there were substantial differences. Relative to WT, SP exhibited reduced replication following intrathoracic inoculation and lower infection, dissemination, and transmission rates following oral infection. Analysis of the full length sequence of the SP variant identified sequence differences which led to only two amino acid substitutions relative to WT, prM P54S and NS2A V61A. AuthorsKramer, Laura D., KAUFFMAN, ELIZABETH B., Franke, Mary A., Jia, Yongqing, Moudy, Robin M., Dupuis, Alan P., Ngo, Kiet A., Maffei, Joseph G. and Jerzak, Greta V.S. Year Published2007 PublicationVirology LocationsDOI10.1016/j.virol.2007.06.008 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17617432 |
| Climate-based models for West Nile Culex mosquito vectors in the Northeastern US | Gong, Hongfei | 2011 |
KeywordsWNV AbstractClimate-based models simulating Culex mosquito population abundance in the Northeastern US were developed. Two West Nile vector species, Culex pipiens and Culex restuans, were included in model simulations. The model was optimized by a parameter-space search within biological bounds. Mosquito population dynamics were driven by major environmental factors including temperature, rainfall, evaporation rate and photoperiod. The results show a strong correlation between the timing of early population increases (as early warning of West Nile virus risk) and decreases in late summer. Simulated abundance was highly correlated with actual mosquito capture in New Jersey light traps and validated with field data. This climate-based model simulates the population dynamics of both the adult and immature mosquito life stage of Culex arbovirus vectors in the Northeastern US. It is expected to have direct and practical application for mosquito control and West Nile prevention programs. AuthorsGong, Hongfei, DeGaetano, Arthur T. and Harrington, Laura C. Year Published2011 PublicationInternational Journal of Biometeorology Locations- Site 1, North Brunswick, Middlesex County, New Jersey (40.4°N,74.5°W) 1990–1993, 1997, 1999, 2001 (40.4, -74.5)
- Site 2, near Cambridge, Dorchester County, Maryland (38.56°N, 76.07°W ) (38.56, -76.07)
DOI10.1007/s00484-010-0354-9 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/20821026 |
