| Mosquito Larval Habitat Mapping Using Remote Sensing and GIS: Implications of Coalbed Methane Development and West Nile Virus | Zou, Li | 2006 |
KeywordsCulex tarsalis, risk, discharge water, WNV AbstractPotential larval habitats of the mosquito Culex tarsalis (Coquillett), implicated as a primary vector of West Nile virus in Wyoming, were identified using integrated remote sensing and geographic information system (GIS) analyses. The study area is in the Powder River Basin of north central Wyoming, an area that has been undergoing a significant increase in coalbed methane gas extractions since the late 1990s. Large volumes of water are discharged, impounded, and released during the extraction of methane gas, creating aquatic habitats that have the potential to support immature mosquito development. Landsat TM and ETM+ data were initially classified into spectrally distinct water and vegetation classes, which were in turn used to identify suitable larval habitat sites. This initial habitat classification was refined using knowledge-based GIS techniques requiring spatial data layers for topography, streams, and soils to reduce the potential for overestimation of habitat. Accuracy assessment was carried out using field data and high-resolution aerial photography commensurate with one of the Landsat images. The classifier can identify likely habitat for ponds larger than 0.8 ha (2 acres) with generally satisfactory results (72.1%) with a lower detection limit of ≈0.4 ha (1 acre). Results show a 75% increase in potential larval habitats from 1999 to 2004 in the study area, primarily because of the large increase in small coalbed methane water discharge ponds. These results may facilitate mosquito abatement programs in the Powder River Basin with the potential for application throughout the state and region. AuthorsMiller, Scott N., Zou, Li and Schmidtmann, Edward T. Year Published2006 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585(2006)43[1034:MLHMUR]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17017244 |
| Seasonal variation in susceptibility to West Nile virus infection in Culex pipiens pipiens (L.) (Diptera: Culicidae) from San Joaquin County, California | Vaidyanathan, Rajeev | 2006 |
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| Overwintering of West Nile Virus in Southern California | Reisen, William K. | 2006 |
KeywordsWest Nile virus, overwintering, southern California, Culex tarsalis, Culex pipiens quinquefasciatus, WNV AbstractWest Nile virus (family Flaviviridae, genus Flavivirus, WNV) invaded southern California during 2003, successfully overwintered, amplified to epidemic levels, and then dispersed to every county in the state. Although surveillance programs successfully tracked and measured these events, mechanisms that allowed the efficient overwintering and subsequent amplification of WNV have not been elucidated. Our current research provided evidence for three mechanisms whereby WNV may have persisted in southern California during the winters of 2003–2004 and 2004–2005: 1) continued enzootic transmission, 2) vertical transmission by Culex mosquitoes, and 3) chronic infection in birds. WNV was detected in 140 dead birds comprising 32 species, including 60 dead American crows, thereby verifying transmission during the November–March winter period. Dead American crows provide evidence of recent transmission because this species always succumbs rapidly after infection. However, WNV RNA was not detected concurrently in 43,043 reproductively active female mosquitoes comprising 11 species and tested in 1,258 pools or antibody in sera from 190 sentinel chickens maintained in 19 flocks. Although efficient vertical transmission by WNV was demonstrated experimentally for Culex tarsalis Coquillett infected per os, 369 females collected diapausing in Kern County and tested in 32 pools were negative for WNV. Vertical transmission was detected in Culex pipiens quinquefasciatus Say adults reared from field-collected immatures collected from Kern County and Los Angeles during the summer transmission period. Chronic infection was detected by finding WNV RNA in 34 of 82 birds that were inoculated with WNV experimentally, held for >6 wk after infection, and then necropsied. Frequent detection of WNV RNA in kidney tissue in experimentally infected birds >6 wk postinfection may explain, in part, the repeated detection of WNV RNA in dead birds recovered during winter, especially in species such as mourning doves that typically do not die after experimental infection. In summary, our study provides limited evidence to support multiple modes of WNV persistence in southern California. Continued transmission and vertical transmission by Culex p. quinquefasciatus Say seem likely candidates for further study. AuthorsReisen, William K., Fang, Ying, Martinez, Vincent M., Cahoon-Young, Barbara, Carney, Ryan, Lothrop, Hugh D., Wilson, Jennifer, O’Connor, Paul, Shafii, Marzieh and Brault, Aaron C. Year Published2006 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585(2006)043[0344:OOWNVI]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16619621 |
| Aquatic Effects of Aerial Spraying for Mosquito Control over an Urban Area | Weston, Donald P. | 2006 |
KeywordsWNV AbstractIn an effort to combat West Nile Virus, planes dispersed insecticide over Sacramento, CA, treating nearly 50,000 hectares with pyrethrins and the synergist piperonyl butoxide (PBO). Widespread dispersal of insecticide over a metropolitan area, coupled with extensive pretreatment data on the area's urban creeks, provided a unique opportunity to study effects of mosquito control agents on aquatic habitats within an urban setting. There was no evidence of aquatic toxicity from the two active ingredients in the product applied. However, PBO concentrations were high enough to enhance toxicity of pyrethroids already existing in creek sediments from general urban pesticide use. PBO concentrations of 2−4 μg/L were high enough to nearly double the toxicity of sediments to the amphipod Hyalella azteca. Though the increase in toxicity was modest, it was unexpected to find environmental synergy at all. Risk assessments for mosquito control agents have focused on the active ingredients but have failed to recognize the potential for interactions with pesticides previously existing in the environment, which in this case appeared to represent a risk to aquatic life greater than that of the active ingredients themselves. AuthorsWeston, Donald P., Amweg, Erin L., Mekebri, Abdou, Ogle, R. Scott and Lydy, Michael J. Year Published2006 PublicationEnvironmental Science & Technology LocationsDOI10.1021/es0601540 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17007146 |
| SUSCEPTIBILITY OF GREATER SAGE-GROUSE TO EXPERIMENTAL INFECTION WITH WEST NILE VIRUS | Clark, Larry | 2006 |
KeywordsCentrocercus urophasianus, experimental infection, greater sage-grouse, vaccine, West Nile virus, WNV AbstractPopulations of greater sage-grouse (Centrocercus urophasianus) have declined 45– 80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (103.2 plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 106.4 PFUs/ml (±100.2 PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival time was increased (50% survival=9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) with no signs of illness. Mean peak viremia for the vaccinated birds was 102.3 PFUs/ml (±100.6 PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV. AuthorsKlenk, Kaci, Bowen, Richard, Clark, Larry, Hall, Jeffrey, McLean, Robert, Dunbar, Michael and Smeraski, Cynthia A. Year Published2006 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-42.1.14 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16699144 |
| HEMATOLOGY, PLASMA BIOCHEMISTRY, AND ANTIBODIES TO SELECT VIRUSES IN WILD-CAUGHT EASTERN MASSASAUGA RATTLESNAKES (SISTRURUS CATENATUS CATENATUS) FROM ILLINOIS | Allender, Matthew C. | 2006 |
KeywordsBiochemistry, hematology, massasauga, ophidian paramyxovirus, rattlesnake, serology, Sistrurus catenatus catenatus, West Nile virus, WNV AbstractDuring the 2004 field season, blood was collected from Eastern massasauga rattlesnakes (Sistrurus catenatus catenatus) in the Carlyle Lake (Carlyle, Illinois, USA) and Allerton Park (Monticello, Illinois, USA) populations to derive baseline complete blood count and plasma biochemistry data and to assess the prevalence of antibodies to West Nile virus (WNV) and ophidian paramyxovirus (OPMV). Massasaugas were located for sampling through visual encounter surveys. Body weight, snout–vent length, total protein, globulins, sodium, and potassium were normally distributed among the survey population. Aspartate aminotransferase, creatine kinase, albumin, calcium, uric acid, white blood cell count, heterophils, lymphocytes, monocytes, eosinophils, and basophils were non-normally distributed within these animals. Female snakes had significantly shorter tail lengths; lower blood glucose, packed cell volumes, and absolute azurophil counts; and higher plasma calcium and phosphorus concentrations than did males. None of the snakes tested (n=21) were seropositive for WNV, whereas all (n=20) were seropositive for OPMV. AuthorsAllender, Matthew C., Mitchell, Mark A., Phillips, Christopher A., Gruszynski, Karen and Beasley, Val R. Year Published2006 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-42.1.107 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16699153 |
| West Nile Virus from Female and Male Mosquitoes (Diptera: Culicidae) in Subterranean, Ground, and Canopy Habitats in Connecticut | Anderson, John F. | 2006 |
KeywordsWest Nile virus, Culex restuans, Culex salinarius, Aedes vexans, Culex pipiens, WNV AbstractIn total, 93,532 female mosquitoes (Diptera: Culicidae) were captured in traps placed in subterranean (catch basin), ground (≈ 1.5 m above ground), and canopy (≈7.0 m above ground) habitats in Stamford and Stratford, CT, during 2003–2005. Culex pipiens L. was the most abundant (64.8%) of the 31 species identified. Significantly greater numbers of Cx. pipiens were captured in canopy-placed mosquito magnet experimental traps, and significantly greater numbers were collected in catch basin-placed (Centers for Disease Control) CDC traps than in CDC traps placed elsewhere. Culex restuans Theobald was captured in significantly greater numbers in traps placed in catch basins. Aedes vexans (Meigen), Aedes cinereus Meigen, and Aedes cantator (Coquillett) were significantly more abundant in ground traps. In total, 429 isolations of West Nile virus (WNV) were made from seven species of mosquitoes from late June through the end of October during 2003 through 2005. Three hundred ninety-eight (92.8%) isolates were from Cx. pipiens. Others were from Cx. restuans (n = 16), Culex salinarius Coquillett (n = 5), Ae. vexans (n = 4), Ae. cantator (n = 3), Aedes triseriatus (Say) (n = 2), and Ae. cinereus (n = 1). Multiple isolates from Cx. pipiens were made each week, primarily during the later part of July through the end of September. Weekly minimum infection rates (MIRs) were lower in 2004 (highest weekly MIR = 7.1) when no human cases were reported in Connecticut in comparison with 2003 and 2005 (highest weekly MIR = 83.9) when human cases were documented. Frequencies of infected pools were significantly higher in Cx. pipiens captured in traps in the canopy and significantly higher in catch basin placed traps than in traps at ground level. The physiological age structure of Cx. pipiens captured in the canopy was significantly different from that of Cx. pipiens collected in catch basins. Invariably, Cx. pipiens captured in the canopy were nulliparous or parous with ovaries in Christophers’ stage 2, whereas 58.7% of the females captured in catch basins possessed ovaries filled with mature oocytes in Christophers’ stage 5. Our results suggest that females in the canopy are seeking hosts, and after digestion of the bloodmeal and development of mature oocytes, they descend to catch basins for shelter and deposition of eggs. WNV was isolated from three, one, and two pools of male Cx. pipiens captured in catch basin-, ground-, and canopy-placed traps, respectively, and from six nulliparous Cx. pipiens females collected in the canopy. Weekly MIR ranged from 1.2 to 31.1 per 1,000 male specimens. These data show that mosquitoes become infected by means other than by blood feeding, possibly by transovarial transmission. The placement of traps in tree canopies and in catch basins can be used to augment current practices of placement of traps near the ground for surveillance of mosquitoes infected with WNV and for studies of the ecology of WNV. AuthorsAndreadis, Theodore G., Anderson, John F., Vossbrinck, Charles R., Main, Andy J. and Ferrandino, Francis J. Year Published2006 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585(2006)43[1010:WNVFFA]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17017241 |
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West Nile Virus Antibody Prevalence in Red-Winged Blackbirds (
Agelaius phoeniceus
) from North Dakota, USA (2003–2004)
| Sullivan, Heather | 2006 |
KeywordsWNV AbstractThis study was designed to explore the role that red-winged blackbirds (Agelaius phoeniceus) may have played in disseminating West Nile virus (WNV) across the United States. Using enzyme-linked immunosorbent assays designed to detect WNV antibodies in avian species we were able to determine the WNV antibody prevalence in a cohort of red-winged blackbirds in central North Dakota in 2003 and 2004. The peak WNV antibody prevalence was 22.0% in August of 2003 and 18.3% in July of 2004. The results of this study suggest that red-winged blackbird migratory populations may be an important viral dispersal mechanism with the ability to spread arboviruses such as WNV across the United States. AuthorsLinz, George, Clark, Larry, Sullivan, Heather and Salman, Mo Year Published2006 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/vbz.2006.6.305 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16989570 |
| 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 |
| DEMOGRAPHIC AND SPATIAL ANALYSIS OF WEST NILE VIRUS AND ST. LOUIS ENCEPHALITIS IN HOUSTON, TEXAS | RIOS, JANELLE | 2006 |
KeywordsWest Nile virus, St. Louis encephalitis, geospatial analysis, environment, demographics, WNV AbstractThis descriptive prevalence study describes the relationships between mosquito density and the presence of arboviruses (in mosquitoes and humans) with various socioeconomic and environmental factors present near the time of the arbovirus outbreak in Harris County, Texas, in 2002. This study suggests that mosquito density increased if the trap was located in an area with a large number of containers that may inadvertently retain rainwater (P = 0.056). When considering only virus-positive mosquitoes, significant relationships were observed if the trap was located near waste materials (P < 0.001) or near containers that may inadvertently retain rainwater (P = 0.037). Furthermore, the presence of arbovirus activity (in mosquitoes or humans) in a geographic area tended to be associated with the socioeconomic status of the local community. Although the results of the socioeconomic comparisons were not significant, they were suggestive, demonstrating an interesting trend. Compared with communities where virus activity was not observed, the socioeconomic status of the arbovirus-positive community was consistently lower. Specifically, results showed that the populations residing in virus-positive census tracts attained less education, earned less income per household, and were more likely to be below the poverty level. In addition, this study found that virus-positive mosquitoes were randomly distributed throughout the study area, whereas severe human infection cases were clustered. Based on the results of this study, we conclude that the health outcome of a local community as it relates to West Nile virus and St. Louis encephalitis is dependent on many factors, including the socioeconomic and environmental characteristics of the community. AuthorsRIOS, JANELLE, HACKER, CARL S., HAILEY, CHRISTINA A. and PARSONS, RAY E. Year Published2006 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/8756-971X(2006)22[254:DASAOW]2.0.CO;2 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17019771 |
