| Achieving Operational Hydrologic Monitoring of Mosquitoborne Disease | Shaman, Jeffrey | 2005 |
KeywordsWNV AbstractMosquitoes and mosquitoborne disease transmission are sensitive to hydrologic variability. If local hydrologic conditions can be monitored or modeled at the scales at which these conditions affect the population dynamics of vector mosquitoes and the diseases they transmit, a means for monitoring or modeling mosquito populations and mosquitoborne disease transmission may be realized. We review how hydrologic conditions have been associated with mosquito abundances and mosquitoborne disease transmission and discuss the advantages of different measures of hydrologic variability. We propose that the useful application of any measure of hydrologic conditions requires additional consideration of the scales for both the hydrologic measurement and the vector control interventions that will be used to mitigate an outbreak of vectorborne disease. Our efforts to establish operational monitoring of St. Louis encephalitis virus and West Nile virus transmission in Florida are also reviewed. AuthorsDay, Jonathan F. and Shaman, Jeffrey Year Published2005 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1109.050340 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16229760 |
| Alligators as West Nile Virus Amplifiers | Klenk, Kaci | 2004 |
KeywordsWNV AbstractRecent evidence suggests that American alligators (Alligator mississippiensis) may be capable of transmitting West Nile virus (WNV) to other alligators. We experimentally exposed 24 juvenile alligators to WNV parenterally or orally. All became infected, and all but three sustained viremia titers >5.0 log10 PFU/mL (a threshold considered infectious for Culex quinquefasciatus mosquitoes) for 1 to 8 days. Noninoculated tankmates also became infected. The viremia profiles and multiple routes of infection suggest alligators may play an important role in WNV transmission in areas with high population densities of juvenile alligators. AuthorsKlenk, Kaci, Snow, Jamie, Morgan, Katrina, Bowen, Richard, Stephens, Michael, Foster, Falicia, Gordy, Paul, Beckett, Susan, Komar, Nicholas, Gubler, Duane and Bunning, Michel Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1012.040264 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15663852 |
| An examination of the effect of landscape pattern, land surface temperature, and socioeconomic conditions on WNV dissemination in Chicago | Liu, Hua | 2009 |
KeywordsWNV AbstractThis paper developed an approach by the synthesis of remote sensing, landscape metrics, and statistical methods to examine the effects of landscape pattern, land surface temperature, and socioeconomic conditions on the spread of West Nile virus (WNV) caused by mosquitoes and animal hosts in Chicago, USA. Land use/land cover and land surface temperature images were derived from Terra's Advanced Spaceborne Thermal Emission and Reflection Radiometer imagery. An analytical procedure using landscape metrics was developed, applying configuration analysis of landscape patterns in the study area. The positive reports of mosquitoes and animal hosts for WNV in fall, 2001-2006, were collected from the Cook County Public Health Department. Forty-nine municipalities were found to have WNV-positive records in mosquitoes and animal hosts in fall 2004. Socioeconomic data were obtained from the 2000 US Census. Statistical analysis was applied to WNV data in fall 2004 to identify the relationship between potential predictors and WNV spread. As a result, landscape factors, such as landscape aggregation index and the urban areas and areas of grass and water, showed strong correlations with the WNV-positive records. Socioeconomic conditions, such as the population over 65 years old, also showed a strong correlation with WNV-positive records. Thermal conditions of water showed a less but still considerable correlation to WNV-positive records. This research offers an opportunity to explore the effects of landscape pattern, land surface temperature, and socioeconomic conditions on the spread of WNV caused by mosquitoes and animal hosts. Results can contribute to public health and environmental management in the study area. AuthorsLiu, Hua and Weng, Qihao Year Published2009 PublicationEnvironmental Monitoring and Assessment LocationsDOI10.1007/s10661-008-0618-6 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/19107566 |
| Antibody Prevalence of West Nile Virus in Birds, Illinois, 2002 | Ringia, Adam M. | 2004 |
KeywordsWNV AbstractAntibodies to West Nile virus were detected in 94 of 1,784 Illinois birds during 2002. Captive and urban birds had higher seropositivity than did birds from natural areas, and northern and central Illinois birds’ seropositivity was greater than that from birds from the southern sites. Adult and hatch-year exposure rates did not differ significantly. AuthorsRingia, Adam M., Blitvich, Bradley J., Koo, Hyun-Young, Van de Wyngaerde, Marshall, Brawn, Jeff D. and Novak, Robert J. Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1006.030644 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15207067 |
| 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 |
| Assessment of arbovirus vector infection rates using variable size pooling | Gu, W. | 2004 |
KeywordsCulex pipiens;Cx. restuans;arbovirus vector;maximum likelihood estimation;minimum infection rate;pool testing;variable size pooling;West Nile virus;Chicago;U.S.A, WNV AbstractPool testing of vector samples for arboviruses is widely used in surveillance programmes. The proportion of infected mosquitoes (Diptera: Culicidae) is often estimated from the minimum infection rate (MIR), based on the assumption of only one infected mosquito per positive pool. This assumption becomes problematic when pool size is large and/or infection rate is high. By relaxing this constraint, maximum likelihood estimation (MLE) is more useful for a wide range of infection levels that may be encountered in the field. We demonstrate the difference between these two estimation approaches using West Nile virus (WNV) surveillance data from vectors collected by gravid traps in Chicago during 2002. MLE of infection rates of Culex mosquitoes was as high as 60 per 1000 at the peak of transmission in August, whereas MIR was less than 30 per 1000. More importantly, we demonstrate roles of various pooling strategies for better estimation of infection rates based on simulation studies with hypothetical mosquito samples of 18 pools. Variable size pooling (with a serial pool sizes of 5, 10, 20, 30, 40 and 50 individuals) performed consistently better than a constant size pooling of 50 individuals. We conclude that variable pool size coupled with MLE is critical for accurate estimates of mosquito infection rates in WNV epidemic seasons. AuthorsGu, W., Lampman, R. and Novak, R. J. Year Published2004 PublicationMedical and Veterinary Entomology LocationsDOI10.1111/j.0269-283X.2004.00482.x Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15189246 |
| Assessment of methods for prediction of human West Nile virus (WNV) disease from WNV-infected dead birds | Veksler, Anna | 2009 |
KeywordsWNV AbstractBACKGROUND: West Nile virus (WNV) is currently the leading cause of arboviral-associated encephalitis in the U.S., and can lead to long-term neurologic sequelae. Improvements in dead bird specimen processing time, including the availability of rapid field laboratory tests, allows reassessment of the effectiveness of using WNV-positive birds in forecasting human WNV disease. METHODS: Using New York State integrated WNV surveillance data from transmissions seasons in 2001-2003, this study determined which factors associated with WNV-positive dead birds are most closely associated with human disease. The study also addressed the 'delay' period between the distribution of the dead bird variable and the distribution of the human cases. In the last step, the study assessed the relative risk of contracting WNV disease for people who lived in counties with a 'signal' value of the predictor variable versus people who lived in counties with no 'signal' value of the predictor variable. RESULTS: The variable based on WNV-positive dead birds [(Positive/Tested)*(Population/Area)] was identified as the optimum variable for predicting WNV human disease at a county level. The delay period between distribution of the variable and human cases was determined to be approximately two weeks. For all 3 years combined, the risk of becoming a WNV case for people who lived in 'exposed' counties (those with levels of the positive dead bird variable above the signal value) was about 2 times higher than the risk for people who lived in 'unexposed' counties, but risk varied by year. CONCLUSION: This analysis develops a new variable based on WNV-positive dead birds, [(Positive/Tested)*(Population/Area)] to be assessed in future real-time studies for forecasting the number of human cases in a county. A delay period of approximately two weeks between increases in this variable and the human case onset was identified. Several threshold 'signal' values were assessed and found effective at indicating human case risk, although specific thresholds are likely to vary by region and surveillance system differences. AuthorsVeksler, Anna, Eidson, Millicent and Zurbenko, Igor Year Published2009 PublicationEmerging Themes in Epidemiology LocationsDOI10.1186/1742-7622-6-4 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/19500367 |
| Association of West Nile virus illness and urban landscapes in Chicago and Detroit | Ruiz, Marilyn O | 2007 |
KeywordsWNV AbstractBackground
West Nile virus infection in humans in urban areas of the Midwestern United States has exhibited strong spatial clustering during epidemic years. We derived urban landscape classes from the physical and socio-economic factors hypothesized to be associated with West Nile Virus (WNV) transmission and compared those to human cases of illness in 2002 in Chicago and Detroit. The objectives were to improve understanding of human exposure to virus-infected mosquitoes in the urban context, and to assess the degree to which environmental factors found to be important in Chicago were also found in Detroit.
Results
Five urban classes that partitioned the urban space were developed for each city region. The classes had many similarities in the two settings. In both regions, the WNV case rate was considerably higher in the urban class associated with the Inner Suburbs, where 1940–1960 era housing dominates, vegetation cover is moderate, and population density is moderate. The land cover mapping approach played an important role in the successful and consistent classification of the urban areas.
Conclusion
The analysis demonstrates how urban form and past land use decisions can influence transmission of a vector-borne virus. In addition, the results are helpful to develop hypotheses regarding urban landscape features and WNV transmission, they provide a structured method to stratify the urban areas to locate representative field study sites specifically for WNV, and this analysis contributes to the question of how the urban environment affects human health. AuthorsRuiz, Marilyn O, Walker, Edward D, Foster, Erik S, Haramis, Linn D and Kitron, Uriel D Year Published2007 PublicationInternational Journal of Health Geographics LocationsDOI10.1186/1476-072X-6-10 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/17352825 |
| Avian diversity and West Nile virus: testing associations between biodiversity and infectious disease risk | Ezenwa, V. O | 2006 |
KeywordsWest Nile virus, vector-borne disease, zoonoses, dilution effect, biodiversity, birds, WNV AbstractThe emergence of several high profile infectious diseases in recent years has focused attention on our need to understand the ecological factors contributing to the spread of infectious diseases. West Nile virus (WNV) is a mosquito-borne zoonotic disease that was first detected in the United States in 1999. The factors accounting for variation in the prevalence of WNV are poorly understood, but recent ideas suggesting links between high biodiversity and reduced vector-borne disease risk may help account for distribution patterns of this disease. Since wild birds are the primary reservoir hosts for WNV, we tested associations between passerine (Passeriform) bird diversity, non-passerine (all other orders) bird diversity and virus infection rates in mosquitoes and humans to examine the extent to which bird diversity is associated with WNV infection risk. We found that non-passerine species richness (number of non-passerine species) was significantly negatively correlated with both mosquito and human infection rates, whereas there was no significant association between passerine species richness and any measure of infection risk. Our findings suggest that non-passerine diversity may play a role in dampening WNV amplification rates in mosquitoes, minimizing human disease risk. AuthorsEzenwa, V. O, Godsey, M. S, King, R. J and Guptill, S. C Year Published2006 PublicationProceedings of the Royal Society B: Biological Sciences LocationsDOI10.1098/rspb.2005.3284 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/16519242 |
| Avian Host-Selection by Culex pipiens in Experimental Trials | Simpson, Jennifer E. | 2009 |
KeywordsWNV AbstractEvidence from field studies suggests that Culex pipiens, the primary mosquito vector of West Nile virus (WNV) in the northeastern and north central United States, feeds preferentially on American robins (Turdus migratorius). To determine the contribution of innate preferences to observed preference patterns in the field, we conducted host preference trials with a known number of adult female C. pipiens in outdoor cages comparing the relative attractiveness of American robins with two common sympatric bird species, European starling, Sternus vulgaris and house sparrow, Passer domesticus. Host seeking C. pipiens were three times more likely to enter robin-baited traps when with the alternate host was a European starling (n = 4 trials; OR = 3.06; CI [1.42-6.46]) and almost twice more likely when the alternative was a house sparrow (n = 8 trials; OR = 1.80; CI = [1.22-2.90]). There was no difference in the probability of trap entry when two robins were offered (n = 8 trials). Logistic regression analysis determined that the age, sex and weight of the birds, the date of the trial, starting-time, temperature, humidity, wind-speed and age of the mosquitoes had no effect on the probability of a choosing a robin over an alternate bird. Findings indicate that preferential feeding by C. pipiens mosquitoes on certain avian hosts is likely to be inherent, and we discuss the implications innate host preferences may have on enzootic WNV transmission. AuthorsSimpson, Jennifer E., Folsom-O'Keefe, Corrine M., Childs, James E., Simons, Leah E., Andreadis, Theodore G. and Diuk-Wasser, Maria A. Year Published2009 PublicationPLOS One LocationsDOI10.1371/journal.pone.0007861 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/19924251 |
