Browsing by Subject "West nile virus"
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Item Analyses of relationships of human West Nile virus, confined livestock operations, and playa lakes in the Texas Panhandle and South Plains region(2010-12) Stephens, Christena; Presley, Steven; Dixon, Ken; Gao, Weimin; Salice, Christopher J.A total of 432 human West Nile virus (WNV) cases have occurred with 28 fatalities in the Panhandle and South Plains region from 2002 to 2008 in 41 counties. Of significant interest was determining if these WNV cases were spatially clustered near major ecological and economic features of playa lakes and confined livestock operations (CLOs). Another research interest was to identify chemicals used in mosquito control in regional cities to determine if mosquito control increased during the years of the initial WNV outbreak in the region. An important role of spatial statistics is to account for spatial dependence and search for spatial patterns in geographical data. Cluster investigations have long been an important tool in epidemiology and spatial statistics. To quantify WNV prevalence in the region for clustering around CLOs and playa lakes, SaTScan™ and ArcGIS™ were used in conjunction to determine spatial clustering. Spatial clustering results indicate that a spatial correlation and dependence exists in the geographical data between human WNV cases, beef cattle operations and playa lakes. Malathion was identified as the most common pesticide used in the region from 2002 – 2009.Item Effects of weather on mosquito biology, behavior, and potential for West Nile virus transmission on the Southern High Plains of Texas(2005-08) Bradford, Carrie M.; Presley, Steven; Nisbett, Richard; McIntyre, Nancy E.; Cox, Stephen B.; Anderson, ToddThe threat of emerging and resurgent vector-borne diseases associated with weather conditions, global climate change, and biologic attacks is of major concern. West Nile virus (WNV) first appeared in the United States in the summer of 1999. Since then it has spread rapidly across the nation and continues to be a threat to humans, domestic animals (particularly horses), and wildlife. The goal of this project was to model the factors involved in the WNV maintenance and transmission cycle. Mosquito surveillance to determine mosquito community dynamics and WNV infection in mosquito populations has been ongoing in Lubbock County, TX (33.65°N; 101.81°W; 975 m elevation), since the summer of 2002. West Nile virus was first detected in Lubbock County in late summer 2002 and has continued to appear each summer. The occurrence of WNV in mosquitoes collected over a three-year period was determined and related to very diverse annual weather conditions during those years in order to determine trends in WNV occurrence. Differences in weather conditions between study years was reflected in differences in mosquito collections and WNV maintenance and transmission. In the Lubbock area, 2003 was a drought year, and Culex tarsalis Coquillett dominated mosquito collections due to an abundance of stagnant pools that allowed for the proliferation of this species. Additionally, a large number of mosquito pools tested positive for WNV. The following year, however, was a wet year, and Aedes vexans Meigen, a floodwater species, dominated mosquito collections. During 2004, the number of WNV-positive mosquito pools was reduced by two-thirds, despite testing approximately the same number of pools. Modeling mosquito populations and WNV occurrence in relation to weather patterns revealed interesting trends. Both of these were predicted by weather conditions, typically rainfall and temperature, in the weeks prior to collection of WNV infected mosquitoes. By understanding the factors that drive mosquito populations and the occurrence of WNV, future patterns of disease occurrence can be predicted and efficient mosquito control operations can be initiated prior to a major disease outbreak. Models which explain when and why disease transmission occurred are important as related to effective surveillance and control activities as well as with respect to climate change and the potential for biologic attacks. Climate change is expected to increase the geographic distribution of many vector-borne diseases, and especially mosquito-borne diseases. Malaria, among other diseases, has already reappeared in regions in which it had previously been eradicated. Global warming that is projected to occur with climate change will allow for the geographic range of many mosquito species to be expanded, with the potential for these species to carry new diseases into naïve areas. Additionally, climate change is expected to increase the frequency of extreme events such as floods and droughts, which have previously been shown to facilitate the outbreak of various mosquito-borne diseases. Models of disease transmission will help public health officials initiate effective surveillance and proactive control strategies to prevent the further spread of disease. Acts of terrorism involving biologics is also of major concern. Models of disease transmission will aid in distinguishing between natural outbreaks of disease and a biologic attack. Understanding how a disease outbreak was initiated is also critical for effective surveillance and control operations, since biologic attacks could involve genetically altered pathogens, thus potentially requiring a different means of disease treatment or control.Item Effects of weather on mosquito biology, behavior, and potential for West Nile virus transmission on the Southern High Plains of Texas(Texas Tech University, 2005-08) Bradford, Carrie M.; Presley, Steven; Nisbett, Richard; McIntyre, Nancy E.; Cox, Stephen B.; Anderson, ToddThe threat of emerging and resurgent vector-borne diseases associated with weather conditions, global climate change, and biologic attacks is of major concern. West Nile virus (WNV) first appeared in the United States in the summer of 1999. Since then it has spread rapidly across the nation and continues to be a threat to humans, domestic animals (particularly horses), and wildlife. The goal of this project was to model the factors involved in the WNV maintenance and transmission cycle. Mosquito surveillance to determine mosquito community dynamics and WNV infection in mosquito populations has been ongoing in Lubbock County, TX (33.65°N; 101.81°W; 975 m elevation), since the summer of 2002. West Nile virus was first detected in Lubbock County in late summer 2002 and has continued to appear each summer. The occurrence of WNV in mosquitoes collected over a three-year period was determined and related to very diverse annual weather conditions during those years in order to determine trends in WNV occurrence. Differences in weather conditions between study years was reflected in differences in mosquito collections and WNV maintenance and transmission. In the Lubbock area, 2003 was a drought year, and Culex tarsalis Coquillett dominated mosquito collections due to an abundance of stagnant pools that allowed for the proliferation of this species. Additionally, a large number of mosquito pools tested positive for WNV. The following year, however, was a wet year, and Aedes vexans Meigen, a floodwater species, dominated mosquito collections. During 2004, the number of WNV-positive mosquito pools was reduced by two-thirds, despite testing approximately the same number of pools. Modeling mosquito populations and WNV occurrence in relation to weather patterns revealed interesting trends. Both of these were predicted by weather conditions, typically rainfall and temperature, in the weeks prior to collection of WNV infected mosquitoes. By understanding the factors that drive mosquito populations and the occurrence of WNV, future patterns of disease occurrence can be predicted and efficient mosquito control operations can be initiated prior to a major disease outbreak. Models which explain when and why disease transmission occurred are important as related to effective surveillance and control activities as well as with respect to climate change and the potential for biologic attacks. Climate change is expected to increase the geographic distribution of many vector-borne diseases, and especially mosquito-borne diseases. Malaria, among other diseases, has already reappeared in regions in which it had previously been eradicated. Global warming that is projected to occur with climate change will allow for the geographic range of many mosquito species to be expanded, with the potential for these species to carry new diseases into naïve areas. Additionally, climate change is expected to increase the frequency of extreme events such as floods and droughts, which have previously been shown to facilitate the outbreak of various mosquito-borne diseases. Models of disease transmission will help public health officials initiate effective surveillance and proactive control strategies to prevent the further spread of disease. Acts of terrorism involving biologics is also of major concern. Models of disease transmission will aid in distinguishing between natural outbreaks of disease and a biologic attack. Understanding how a disease outbreak was initiated is also critical for effective surveillance and control operations, since biologic attacks could involve genetically altered pathogens, thus potentially requiring a different means of disease treatment or control.Item Environmental impact of disease vector control(2007-12) McNew, Rachel M.; Presley, Steven; Maul, Jonathan D.; Cañas, Jaclyn E.Control of arthropod vectors of disease encompasses a large realm of science, including the biology and mechanisms of diseases and the ability to control their spread. This combination of studies focuses on the arthropod-borne virus, West Nile virus (WNV), which is endemic in the United States and is maintained in the environment through a bird-mosquito-bird cycle. West Nile virus can incidentally infect humans and other mammals. One means of controlling the spread of this mosquito-borne disease is the systematic use of pesticides to reduce the mosquito population, which in turn has been proven to reduce the number of human and animal infections of the sometimes deadly disease. The first study was performed to understand environmental influence on transmission dynamics of a free-ranging alligator population in Louisiana, USA by surveying for active WNV infection in 93 blood samples from these alligators. Blood samples from alligators were negative for active WNV infection. The second study focused on developing a method to quantify the concentration of a commonly used pesticide in a sediment matrix. The target pesticide was permethrin and we also screened for the pyrethroid synergist piperonyl butoxide (PBO). The combination of these compounds are used in many areas to control the mosquito population that can spread WNV. The third study employed the methodology developed in the second study to quantify permethrin and PBO residues in sediments of playa lakes located in the Lubbock County vicinity. The objective was to assess the fate and transport of permethrin and to identify potential risks or environmental impacts resulting from the control of mosquito vectors.