| Rainfall Influences Survival of Culex pipiens (Diptera: Culicidae) in a Residential Neighborhood in the Mid-Atlantic United States | Jones, Christy E. | 2012 |
KeywordsCulex pipiens, dispersal, mosquito, survival, West Nile virus, WNV AbstractMeasurement of the survival and dispersal rates of mosquito vectors is an important step in designing and implementing control strategies. Vector survival plays a key role in determining the intensity of pathogen transmission, and vector movement determines the spatial scale on which control efforts must operate to be effective. We provide the first estimates of field survival and dispersal rates for Culex pipiens L. in North America, an important enzootic and bridge vector for West Nile virus (WNV). We conducted mark-release-recapture studies in a residential area near Washington, DC, in two consecutive years and fit nonlinear regression models to the recapture data that incorporate weather information into survival and recapture probabilities. We found that daily survival rates were not significantly different between the 2 yr but were negatively affected by rainfall. The daily survival rate was 0.904 ± 0.037 (SE), which implies an average longevity of 10.4 d. As with other vector-borne pathogens, the measured survival rate suggests that at our site the majority of WNV-infected Cx. pipiens mosquitoes may perish before becoming infectious (being able to transmit WNV to hosts). We found relatively little evidence of dispersal after the initial night after release. Our results suggest that transmission of WNV and other pathogens transmitted by Cx. pipiens may be highly local and they highlight the importance of factors that influence survival of mosquito vectors. AuthorsJones, Christy E., Lounibos, L. Philip, Marra, Peter P. and Kilpatrick, A. Marm Year Published2012 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME11191 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/22679852 |
| Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States | Chuang, Ting-Wu | 2012 |
KeywordsWNV AbstractThe northern Great Plains (NGP) of the United States has been a hotspot of West Nile virus (WNV) incidence since 2002. Mosquito ecology and the transmission of vector-borne disease are influenced by multiple environmental factors, and climatic variability is an important driver of inter-annual variation in WNV transmission risk. This study applied multiple environmental predictors including land surface temperature (LST), the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa) derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) products to establish prediction models for WNV risk in the NGP. These environmental metrics are sensitive to seasonal and inter-annual fluctuations in temperature and precipitation, and are hypothesized to influence mosquito population dynamics and WNV transmission. Non-linear generalized additive models (GAMs) were used to evaluate the influences of deviations of cumulative LST, NDVI, and ETa on inter-annual variations of WNV incidence from 2004-2010. The models were sensitive to the timing of spring green up (measured with NDVI), temperature variability in early spring and summer (measured with LST), and moisture availability from late spring through early summer (measured with ETa), highlighting seasonal changes in the influences of climatic fluctuations on WNV transmission. Predictions based on these variables indicated a low WNV risk across the NGP in 2011, which is concordant with the low case reports in this year. Environmental monitoring using remote-sensed data can contribute to surveillance of WNV risk and prediction of future WNV outbreaks in space and time. AuthorsChuang, Ting-Wu and Wimberly, Michael C. Year Published2012 PublicationPLOS One LocationsDOI10.1371/journal.pone.0046882 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23071656 |
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West Nile virus cluster analysis and vertical transmission in
Culex pipiens
complex mosquitoes in Sacramento and Yolo Counties, California, 2011
| Fechter-Leggett, Ethan | 2012 |
KeywordsCalifornia, California: epidemiology, Culex, West Nile virus: pathogenicity, West Nile virus, West Nile Fever: transmission, West Nile Fever, Infectious Disease Transmission, Vertical, Female, Culex: virology, Animals AbstractWest Nile virus (WNV) is now endemic in California, with annual transmission documented by the statewide surveillance system. Although much is known about the horizontal avian-mosquito transmission cycle, less is known about vertical transmission under field conditions, which may supplement virus amplification during summer and provide a mechanism to infect overwintering female mosquitoes during fall. The current study identified clusters of WNV-infected mosquitoes in Sacramento and Yolo Counties, CA, during late summer 2011 and tested field-captured ovipositing female mosquitoes and their progeny for WNV RNA to estimate the frequency of vertical transmission. Space-time clustering of WNV-positive Culex pipiens complex pools was detected in the northern Elk Grove area of Sacramento County between July 18 and September 18, 2011 (5.22 km radius; p<0.001 and RR=7.80). Vertical transmission by WNV-infected females to egg rafts was 50% and to larvae was 40%. The estimated minimal filial infection rate from WNV-positive, ovipositing females was 2.0 infected females/1,000. The potential contribution of vertical transmission to WNV maintenance and amplification are discussed. AuthorsFechter-Leggett, Ethan, Nelms, Brittany M., Barker, Christopher M. and Reisen, William K. Year Published2012 PublicationJournal of Vector Ecology LocationsDOI10.1111/j.1948-7134.2012.00248.x Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23181869 |
| Prevalence of West Nile Virus Antibodies in a Breeding Population of American Kestrels (Falco sparverius) in Pennsylvania | Medica, Darcy L. | 2007 |
KeywordsWNV AbstractWest Nile virus (WNV) has been identified in nearly 300 species of wild birds, including raptors, in North America since its introduction in New York City in 1999. American Kestrels (Falco sparverius) are susceptible to WNV infection, and the numbers of these birds have declined along the Atlantic coast in recent years. We examined the population biology and WNV exposure of kestrels breeding in the area surrounding Hawk Mountain Sanctuary in Kempton, Pennsylvania, USA. The reproductive biology of kestrels in this area was studied from 1992 until 2004. The number of kestrels breeding in nestboxes in 2004 was only 44% of the 6-yr mean observed prior to 1999. During the 2004 nesting season (study period: 8 June through 22 July 2004), adult kestrels were trapped near the site of their nestboxes. Blood samples were obtained, and serum antibodies specific to WNV were quantified using a plaque reduction neutralization test. Of 22 birds tested, 21 exhibited serum antibodies to WNV, suggesting that most (95%) of the adult kestrels in the population had been exposed to WNV. AuthorsMedica, Darcy L., Clauser, Rachael and Bildstein, Keith Year Published2007 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-43.3.538 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17699096 |
| PATHOLOGY AND EPIDEMIOLOGY OF NATURAL WEST NILE VIRAL INFECTION OF RAPTORS IN GEORGIA | Ellis, Angela E. | 2007 |
KeywordsWNV AbstractCarcasses from 346 raptors found between August 2001 and December 2004 were tested for West Nile virus (WNV) using virus isolation and immunohistochemistry; 40 were positive for WNV by one or both methods. Of these 40 birds, 35 had histologic lesions compatible with WNV infection, one had lesions possibly attributable to WNV, and four had no histologic evidence of WNV. The most common histologic lesions associated with WNV infection were myocardial inflammation, necrosis, and fibrosis; skeletal muscle degeneration, inflammation, and fibrosis; and lymphoplasmacytic encephalitis. Other lesions included hepatitis, lymphoid depletion in spleen and bursa, splenic and hepatic hemosiderosis, pancreatitis, and ganglioneuritis. Gross lesions included calvarial and leptomeningeal hemorrhage, myocardial pallor, and splenomegaly. Red-tailed hawks (Buteo jamaicensis) (10/56), sharp-shinned hawks (Accipiter striatus) (8/40), and Cooper's hawks (Accipiter cooperii) (10/103) were most commonly affected. Also affected were red-shouldered hawks (Buteo lineatus) (2/43), an osprey (Pandion haliaetus) (1/5), barred owls (Strix varia) (4/27), a great horned owl (Bubo virginianus) (1/18), and eastern screech owls (Megascops asio) (4/42). Although birds were examined throughout the year, positive cases occurred only during the summer and late fall (June–December). Yearly WNV mortality rates ranged from 7–15% over the four years of the study. This study indicates trends in infection rates of WNV in raptorial species over a significant time period and supports the available information regarding pathology of WNV infection in Strigiformes and Falconiformes. Although many species tested were positive for WNV infection, severity of lesions varied among species. AuthorsEllis, Angela E., Mead, Daniel G., Allison, Andrew B., Stallknecht, David E. and Howerth, Elizabeth W. Year Published2007 PublicationJournal of Wildlife Diseases LocationsDOI10.7589/0090-3558-43.2.214 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17495305 |
