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Neospora caninum is a protozoan parasite reported as a leading cause of cattle abortions and reproductive failure worldwide. After ingestion of infected tissues, definitive hosts such as coyotes (Canis latrans) and dogs (Canis lupus familiaris) excrete oocysts into the environment and can contaminate food and water sources available to livestock. Ingestion of N. caninum oocysts results in infection of cattle and other intermediate hosts. The parasite can then be vertically transmitted, resulting in spontaneous abortions, fetal reabsorption, and decreased milk production, costing the cattle industry approximately $1.3 billion annually. With wild pig (Sus scrofa) populations nearing six million in the United States, contact between wild pigs and livestock is inevitable. This is a result of an already widespread geographic distribution combined with continuous, rapid range expansion. As a known reservoir for numerous fungal, bacterial, viral, and parasitic diseases, wild pigs are of particular importance for human and veterinary health relative to the prevention of infectious diseases. Seroprevalence of N. caninum in wild pig populations was documented in the United States in 2013 and 2016 at 15.8% and 15.0%, respectively, raising the question as to their frequency of exposure. In collaboration with the Noble Research Institute, 521 wild pigs were captured in southern Oklahoma during a three-year study. From this collection, blood and tissue samples were collected from 389 wild pigs and 89 serum samples were screened for N. caninum antibody presence using commercially available enzyme-linked immunosorbent assays (ELISAs). The first kit utilized was from MyBioSource and seroprevalence of this population was observed at 66.2% ((p ) ̂= 0.678). The same samples were re-tested using a competitive ELISA from Veterinary Medical Research and Development (VMRD) and the observed seroprevalence was 1.2%. These results address a lack of consistent methodology and availability of controls when assessing disease prevalence in wildlife. This data also signifies the importance of continued disease surveillance in wild pigs to better understand their exposure to N. caninum in the environment.

Mosquitoes are known as the deadliest animals on the planet, due in large part to their global distribution, pathogen vectoring capabilities, and blood-feeding habits. Vector control programs (VCPs) are established to monitor and control mosquito populations and reduce the threat of mosquito-borne disease outbreaks in local jurisdictions. Insecticides are an important tool in a VCPs abatement efforts. Unfortunately, the development of insecticide resistance is a common and increasing problem. It is also reported that most vector control jurisdictions lack the required resources required to properly accomplish their mosquito abatement activities. In an effort to strengthen VCP capabilities, I developed statistical models using weather factors as the independent variables to help predict the number of human West Nile virus (WNV) cases expected to occur locally, the probability of mosquito populations having a WNV infection during a given week, and the abundance of three medically important mosquito species. These statistical models, when implemented by the VCPs, will give them additional tools and insights into what weather variables may influence the threat of WNV. These models will also help direct abatement efforts to guide when and when not to apply insecticides and, as a result, reduce the potential of insecticide resistance from developing in local mosquito populations.

In Texas, white-tailed deer farming is an established and growing industry. Owners and managers struggle with animal health problems within the deer industry; as a result, veterinary drugs are used. The administration of antibiotics for treatment of infectious diseases may lead to residues in tissues. The quality and safety of food from animal origin is a growing concern for public health agencies. It is important in the deer industry as well as in other food producing animals such as cattle, to monitor the use of veterinary drugs to minimize residues in tissues after slaughter. Residue analysis are based on qualitative and quantitative methods. These methods are used to determine the amount of compound present in a sample. The choice of analytical method of residue testing is based on the assessment of the benefits and disadvantages of the technique. Qualitative methods include, confirmation of the identity of the compound present while quantitative is the determination of the amount of the compound present. It is important to develop quantitative methods that are highly selective, sensitive, and reliable to accurately determine veterinary drugs in complex matrices. Currently, for quantitative and qualitative analysis the most powerful technique to use is liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS). In this dissertation, a brief synopsis of the methodology, instrumentation, sample preparation methods and critical parameters for an analytical method validation will be discussed, as well as, the work flow of liquid chromatography tandem mass spectrometry (LC-MS/MS) method development. LC-MS/MS was exploited for qualitative and quantitative analysis of veterinary drugs (florfenicol, chlortetracycline, tulathromycin, chloramphenicol, and ractopamine). To facilitate qualitative and quantitative analytical method development of veterinary drugs, a sample preparation method was developed to extract individual and multiple veterinary drugs, and an LC-MS/MS method was developed and validated to quantify these drugs. The methodology was applied to white-tailed deer tissues. This research will aid the white-tailed deer breeder with regulation and safety compliance.

The decline of northern bobwhite quail (Colinus virginianus) populations across Texas over the last few decades is of significant ecological importance. Old World (Phasiandiae) and New World (Odontophoridae) quail and related galliformes have been historically important birds as livestock, game, agriculture, and scientific study. The high incidence of the eye worm, Oxyspirura petrowi, and its infestation within the ocular tissue of northern bobwhites is a biotic factor with influence on C. virginianus physiology and behavior that has not been completely elucidated. Conjunctivitis, intraorbital gland fibrosis, atrophy, and bilateral cataract are conditions resulting from oxyspiruriasis that have been observed in avian species. Helminthiasis of birds is also known to alter the oxidative status of the host’s systems, facilitating oxidative stress and damage to host tissues. Oxidative stress (OS) is linked to etiology of many diseases including severe vision debilitating ophthalmic disorders, and OS can occur through persistent helminth induced dysregulation of host inflammatory immune responses. Under these conditions, host system immunopathology and oxidative stress induced by O. petrowi infestation can lead to the clinical manifestation of eye disorders within the intraocular microenvironment compromising the host’s vision. We have utilized histopathology, enzymatic and non-enzymatic antioxidants, oxidative damage by-products, and gene expression studies to assess surrogate biomarkers associated with the formation of intraocular disease in O. petrowi infected bobwhite quail. We report O. petrowi infected northern bobwhite exhibited a consistent and higher degree of inflammation within the uveal tract, manifesting as choroiditis, as well as abnormalities of the lens relating to the formation posterior sub capsular cataract. Variation in oxidative status of intraocular tissue was observed between bobwhites infected and those uninfected by O. petrowi. Antioxidant concentration and activity was observed to be either significantly reduced (glutathione and glutathione peroxidase), or increased (catalase and superoxide dismutase) among infected quail as compared to uninfected subjects. Lipid peroxidation markers were significantly elevated within infected quail intraocular tissue compared to uninfected bobwhites. We observed increased gene expression of T-helper 2 (Th2) cell immune response cytokines, anti-inflammatory cytokines, and avian uncoupling protein, as well as lower expression of glutathione peroxidase among eye worm infected quail relative to uninfected quail. These studies indicate that O. petrowi infected quail are mounting a Th2 immune response by signaling the recruitment of leukocytes and initiating respiratory bursts of cytotoxic reactive intermediates, altering the oxidative status of the host’s system and increasing intraocular tissue inflammation that could affect the host’s vision. The surrogate biomarkers used in this study can act as indicators of clinical endpoints for ophthalmic disease or symptoms of impaired vision, and can be useful in the study of animal vision, behavior and ophthalmic disease detection in human health.

Mosquitoes pose risks to humans, both as nuisances and as vectors of disease. The control of mosquito populations typically involves the use of chemical pesticides targeting both the aquatic larvae (i.e, larvicides) and the terrestrial adults (i.e., adulticides). Both extrinsic (e.g., temperature) and intrinsic (e.g., species) factors influence the efficacy of these chemicals, and their effects on life history characteristics and population dynamics. In the field of mosquito control, primary goals are to assess mosquito populations in space, and to predict how they will respond to pesticide applications given conditions. However, because many factors interact to influence population dynamics, including pesticide exposure, this can be a challenging task. To assist in this effort, spatially-explicit mathematical population models are promising tools that can help mosquito control authorities by (1) providing insight into mosquito population dynamics; (2) predicting mosquito populations in space; and (3) potentially providing quantitative estimates of risks posed by mosquitoes. This research had two main goals, including (1) to investigate how some common environmental factors influence the effects that larvicides have on larval and adult life history characteristics of two medically important mosquitoes, and (2) to develop spatially-explicit mosquito population models with the potential of being utilized as operational tools. My research revealed that (1) larvicides can interact with age, temperature, and water quality to affect the life history characteristics of both larvae and adults; (2) these affects can potentially influence population dynamics; (3) real-world larvicide and adulticide applications have significant but local effects on population dynamics in the landscape; and 4) spatially explicit population models have the potential to be useful tools for mosquito control, with the recommended model structure depending upon the needs and capability of the mosquito control authority.

The Northern bobwhite (Colinus virginianus, bobwhite) has been in steep decline over its entire range for several decades, including the Rolling Plains. Researchers, hunters, and land owners have all been trying to find the cause of this decline. It is within this context that Operation Idiopathic Decline began in 2011, after a disastrous decline in 2010, a year which was predicted to exhibit a sharp population increase. Within the framework of OID, I set out to investigate whether bobwhites in the Rolling Plains have been undergoing stress in recent years, as demonstrated by corticosterone concentrations. I specifically wanted to accomplish three objectives. First, I wanted to measure corticosterone concentrations in bobwhites, using their feathers as the sampling matrix. Second, once the corticosterone data were obtained, I wanted to discern any differences in concentrations between years, sex, ecoregions, etc. Finally, I wanted to investigate potential correlations between these corticosterone concentrations and weather variables such as temperature, precipitation, or drought. I successfully extracted corticosterone from bobwhite wing feathers. Concentrations ranged from 0.12 pg/mm to 13.98 pg/mm with an average of 1.42 ± 0.6 pg/mm. These numbers are comparable to those found in the literature for other bird species. I determined that the corticosterone concentrations varied between years, sex, and ecoregions, though not necessarily significantly. In particular my results suggest that birds that underwent wing molt in 2010 and 2011 were subjected to more stress than those that underwent wing molt in 2012 and 2013, possibly due to weather conditions. My comparison of concentrations between male and females between years was inconclusive, with females having greater concentrations in some years but not in others. I believe that macronutrient availability may play a role in these results. Regarding ecoregions, I determined that yearly stress levels were consistently greater in the Central Great Plains (CGP) compared to the Southwestern Tablelands (SWT) except in 2011, for which the presence of several outliers may have affected the comparison. My results suggest that bobwhites living in CGP, where native grassland has since been overtaken by invasive species, are more susceptible to drought than bobwhites living in SWT, where native grassland and rangeland is prevalent. I developed generalized mixed linear models of corticosterone response for each of the two ecoregions for each year vs principal components of the weather data on one hand and other parameters such as the Vegetation Drought Index (VegDRI), sex, weight, or intensity of eyeworm (Oxyspirura petrowi) infestation on the other hand. Results from the models indicate that the first principal component, which was mostly reflective of drought, was the most consistent parameter found in the different best-fit models. VegDRI, a more holistic indicator of drought which I hoped would show strong correlation to the corticosterone response, was only part of 3 of the 6 best models. However, in 2 of those 3 instances, it was the parameter that had the most influence on the corticosterone response. This is an encouraging sign for future studies incorporating this indicator. I believe that the reason I did not get better results for VegDRI is due to the seasonal discrepancy between the weather data used in the models (spanning Aug-Oct of each year) and VegDRI (spanning June to Aug of each year). To my knowledge, no previous study has examined bobwhite corticosterone concentrations using feathers as the sample matrix, nor am I aware of any study of bobwhite corticosterone concentrations in the Rolling Plains. I hope that the conclusions reached from this innovative study will lend to a better understanding of bobwhite quail decline and inform management practices.

Mosquitoes are one of the most important insects worldwide because of their role in transmitting pathogens that cause human and animal diseases. Their public health importance has led to extensive global efforts to control both the larvae and adults and these efforts often implement the use of chemical and biological insecticides. The efficacy of these insecticides in controlling larval mosquitoes can be modified by a number of factors in the aquatic environment such as pH, temperature, resource conditions, competition, predation, and other chemicals. Understanding and predicting how each of these stressors modifies insecticide toxicity is important so that mosquito control tactics can be optimized. The goal of this research was to determine how mosquito control insecticides interact with two stressors in the developmental environment: a biotic stressor, larval crowding, and a chemical stressor, exposure to the neonicotinoid thiamethoxam. Results show that larval crowding during insecticide exposure can significantly influence toxicity to the pyrethroid insecticide, permethrin, and that this effect can occur with seemingly innocuous changes in larval density. Possible mechanisms for this effect were investigated. Induced detoxification enzymes do not appear to be a factor, but density-modified larval exposure is likely a mechanism. Results for thiamethoxam exposure showed that at higher sub-lethal concentrations, thiamethoxam interacts with Bti and temephos synergistically, but at certain lower sub-lethal concentrations thiamethoxam pre-exposure increases larval tolerance to both larvicides. When tested alone, thiamethoxam exposure significantly alters sex ratio by disproportionately killing female larvae, likely due to slower female development rate. This research provides important insights into how mosquitoes may respond to control efforts when various environmental stressors are present. Understanding the influence larval crowding and neonicotinoids have on mosquitoes and their control is vital in predicting disease transmission and ensuring the efficacy and longevity of mosquito control programs.

On March 12, 2006 two large-scale wildfires ignited the Borger and Interstate 40 Fires. Together these fires comprised the East Amarillo Complex and burned approximately 907,245 acres. These fires were extremely fast-moving with flame lengths > 11 feet. Destruction of woody and herbaceous vegetation was extensive, leaving livestock without forage and wildlife with little food or cover. This fire damage holds potentially severe consequences for wildlife in the area including northern bobwhite (Colinus virginianus); a bird of significant ecological and economic importance within the region. Ironically, fire can be used as a positive influence for quail populations. Low intensity, cool season prescribed fires are often used for northern bobwhite management, because of the beneficial changes for quail the fires may bring about in the plant community. Because of their January to February timing, these fires tend to increase the number of forb species, which increases supplies of seeds and insects for northern bobwhite. Effects of the more homogenous and intense wild fires on northern bobwhite populations are unknown. A late March or April burn favors grass species over forbs and can be sufficiently intense to severely set back shrubs, which form the foundation for quail habitat. We hypothesize that loss of shrub cover and reduced forb availability will negatively influence northern bobwhite populations within the burned areas. Hen survival for spring-summer 2008 was estimated at 43.7% from 52 radio-marked hens and nesting success at 65%. Spring-summer monitoring for 2009 estimated hen survival at 47.4% from 69 radio-marked hens and nesting success at 63%. These findings are not significantly different from a similar study on a non-burned region of western Oklahoma and may indicate a quick recovery in bobwhite populations and required habitat. Additional analysis of nest site characteristics, nutritional quality, and brood survival will provide better understanding of the net effects of wildfire on bobwhite populations.

Transmission of vector-borne diseases is associated with vector and host infection phenotype and dynamic. The threat of such diseases, both emerging and resurgent, is of major concern and interest. Ilheus virus (ILHV), a Flavivirus, was first isolated from mosquitoes (Aedes and Psorophora spp.) on the northeastern coast of Brazil near Ilheus City, state of Bahia in 1944. Though this virus has not been connected with epidemic disease, it has been isolated from intermittent patients presenting with symptoms that may result in clinical diagnosis of dengue, yellow fever, Saint Louis encephalitis, or influenza. Ilheus virus has not been reported in the United States; however, many states include eco-regions with conditions that favor the circulation of zoonotic arboviruses: large concentrations of hematophagous arthropods and diverse wildlife species. The overall goal of this study was to model infection phenotype and dynamic of ILHV. Adult female Aedes albopictus mosquitoes were infected and then allowed to incubate the virus for up to 12 days to allow the mosquito to become infective (i.e., for the virus to travel to the salivary glands). Virus titers calculated from FFU/mL were found to be highest overall at Day 12 post inoculation in the mosquito salivary glands. Midgut titers decreased significantly overall from Day 6 to Day 12 across all treatment groups, a high and low ILHV inoculation concentration (P

A marked decline in bobwhite and scaled quail in the Rolling Plains ecoregion of Texas and Oklahoma has spurred efforts to elucidate the cause. Organochlorine (OC) pesticides are persistent pollutants that have affected avian health for decades since their introduction in the late 1940s. Toxic effects of OCs can be direct or indirect. Direct toxicity, for example eggshell thinning caused by DDT/DDE, is a result of severe impairment of an organism’s normal physiology. Indirect toxicity, such as immunosuppression, is a toxic effect that can be elicited by small amounts of OCs and generally does not have an impact as intense or obvious as direct toxicity. Quail may be impacted in one manner or both, depending on the levels of OCs present, and therefore the potential for these contaminants to affect populations could not be overlooked. This study investigated the extent to which quail from the Rolling Plains ecoregion were contaminated with 20 OC pesticides. Thigh muscle (n=298), livers (composites, n=19), brains (composites, n=17) and skin and feather samples (composites, n=19) were analyzed for concentrations and frequency of detection of OCs. Some potential food items of quail, including mesquite pods (Prosopis glandulosa), cactus tunas (Opuntia sp.), insects, guayacan seeds (Guaiacum angustifolium), soil, and nightshade berries (Solanum elaeagnifolium) were also analyzed. Lipid percentages of thigh and livers were also ascertained for the purposes of residue normalization and characterization of fat storage. The OC concentrations were low in all samples tested (generally below 10 ppb) and almost all were below the detection limit. The exceptions were DDE (56 and 43 ng/g ww) and DDD (21, 21, and 27 ng/g ww) in a few liver composite samples, lindane in mesquite pods (18 ng/g ww), and gamma-chlordane in an insect composite (14 ng/g ww). Patterns of OC frequencies in each tissue were largely consistent with other studies of OCs in birds and animals. Some patterns suggested the usage of certain products, particularly lindane, which was used in the past for livestock ectoparasite control. Other patterns could be explained by metabolic factors. Significant differences were found for some pesticides in certain tissues that suggest that sex, age, species, and location can have effects on the number, type, and perhaps amount of OCs a quail accumulates. The low concentrations of pesticides, combined with the extensive presence of metabolites and degradation products, suggests that OC contamination in the Rolling Plains ecoregion occurred in the past and, at least through the exposure routes likely available to quail, presents a low risk of direct toxicity. The possibility still exists for indirect toxicity, especially if other factors, such as disease and parasite burden, are taken into account.

Feral swine populations from Texas and Oklahoma were examined for Coxiella burnetii and Brucella spp. exposure using enzyme linked immunosorbent assays (ELISA) and polymerase chain reaction assays (PCR). Whole blood and serum samples were collected from 502 feral swine during 2009 through 2012. Samples collected from feral swine were grouped into three geographic locations with 113 samples from Northwest Texas, 55 samples from Central Texas and 331 samples from Oklahoma. We also surveyed for the presence of C. burnetii DNA in 36 environmental samples associated with feral swine using a PCR assay. We found 1.6% (7/439) of feral swine surveyed were seropositive for exposure to C. burnetii phase I and 1.4% (5/351) were seropositive for exposure to Brucella spp. None of the environmental samples collected were positive for C. burnetii DNA. We did not find any statistically significant differences in serological results based on geographic location.

Wildlife in the Great Plains evolved with fire and grazing interacting spatially and temporally to create a shifting mosaic landscape comprised of severely disturbed habitats, undisturbed habitats, and patches that vary in time since the most recent disturbance. When given the choice, bison grazed on the most recently burned areas, much as they were suspected of doing prior to European settlement of the Great Plains. Currently, rangeland managers try to achieve uniform cattle distribution or uniform coverage by prescribed burning in an effort to utilize their resources as efficiently as possible. Additionally, these 2 types of disturbance are nearly always used apart from each other. This traditional rangeland management promotes homogeneity of vegetative communities and may have a critical impact on biodiversity and wildlife habitat. With the increased interest in using prescribed fire to manage Rolling Plains rangelands for wildlife and livestock we propose the effects of patch burning and grazing in sand sagebrush (Artemisia filifolia)-honey mesquite (Prosopis glandulosa) grassland will positively impact the diversity and abundance of grassland birds, particularly northern bobwhites (Colinus virginianus). This study was conducted within the Matador Wildlife Management Area (WMA), located in Cottle County, Texas approximately 10 km north of the town of Paducah, Texas in the Rolling Plains ecoregion from 2009-2011. My study site consisted of 619-ha of contiguous sand sagebrush-mesquite rangeland in the Entrance and Headquarters pastures of the Matador Wildlife Management Area (34.117721, -100.356536). The Entrance pasture was subjected to patch-burning with grazing as well as rotational grazing. The Headquarters pasture was subjected to patch-burning only. Vegetation and grassland birds were monitored throughout the entire study site, with northern bobwhites monitored for survival, home range, and nest success. Due to severe drought effects during the duration of the study, grass and forb cover was reduced from 2009 to 2011. Grassland bird species richness and abundance declined from 2009 to 2011. Northern bobwhite survival from 2009-2011 was 19%, 5%, and 36%, for respective years. Northern bobwhites did not use treatments proportionately more than what was available during any year. Mean home range size did not differ among years (P=0.0298). Pooled nest survival was calculated using ProgramMARK for the 24 day incubation period and was observed at 29%. The model with the covariates of percent residual cover at nest site, percent shrub cover at nest site, and proximity to edge resulted in the strongest model (AICc=0.0000). Patch burning-grazing did not positively benefit grassland birds or northern bobwhites. Consideration for drought conditions should be applied when trying to implement a patch burning-grazing system.

Feral swine are present in 215 of 254 Texas counties. They are also known to harbor diseases transmissible to other animal species and humans. The objective of this study was to determine the antibody prevalence of two pathogens in Texas feral swine populations. Overall prevalence of antibodies to Francisella tularensis and Brucella spp. were 27.8% and 4.1% respectively. Prevalence rates between males and females for either antibody were not significant (P = 0.6475 for tularemia, P = 1.0 for brucellosis). Conversely, prevalence rates for antibodies against tularemia between adults and juveniles, 81.5% and 18.5% respectively, were significant (P = 0.0012). Seropositive samples for either antibody were sent to Lubbock’s Bioterrorism laboratory for screening using real-time polymerase chain reaction (RT-PCR). Three samples from Crosby County were determined presumptive positive. These data indicate that Texas feral swine populations may be reservoirs of these two zoonotic diseases. Abstract: Antibiotic resistance in commensal bacteria of domestic livestock is well documented. A few studies have also examined resistance in bacteria isolated from wildlife interacting with domestic livestock. The aim of this study was to identify the presence of antibiotic resistance in Escherichia coli isolated from feral swine occurring in close proximity to domestic livestock. Feral swine were sampled over a five month period from a ranch in Crosby County, Texas. Rectal swabs (n = 20) were collected and cultured for Escherichia coli. Three isolates from each confirmed sample (n = 13) were pooled and examined for susceptibility to four antibiotics. Resistance to the antibiotics tested (ampicillin, erythromycin, gentamicin, or penicillin) was not detected in any isolate.

Larvae of Sarcophaga bullata (Diptera: Sarcophagidae), a necrophagous insect commonly utilized in the field of entomotoxicology, were reared on rabbit tissues of rabbits that were previously exposed to arsenic trioxide (As2O3) by different methods. We observed the effects of arsenic (As) and As metabolites in acute versus chronic exposure in rabbit tissues on growth rate (mean larval length), metamorphosis, mortality and reproductive output of S. bullata. The New Zealand white rabbit was utilized as a vehicle to create natural concentrations of As and As metabolites in liver tissue and to serve as food media for S. bullata. Acutely exposed rabbits (2 per group) received three different doses of As2O3 corresponding to the dosages of half the median lethal dose or 0.5 MLD (10.1 mg/kg body weight (BW)), median lethal dose or MLD (20.2 mg/kg BW) and twice the median lethal dose or 2 MLD (40.4 mg/kg BW) and one control rabbit received dosing vehicle only. Chronically exposed rabbits received a dosage of 1.5 mg/kg BW daily for 35 days and one rabbit received dosing vehicle only. Rabbits were subsequently euthanized either eight hours post-exposure (acute) or on day 36 (chronic). The liver of these rabbits were removed and half was used as food media for 100 S. bullata larvae per experimental rabbit liver. The remaining half of the rabbit liver was used as a food media for 100 offspring of the prior experimental fly generation. Ten of these larvae were sampled and measured every eight hours until the onset of larval migration, for both generations of flies. Larval and pupal mortality was recorded, as well as the number of offspring, per dose group. ANOVA revealed a significant increase in mean larval body length in MLD as compared to the chronic dose group. Metamorphic time of S. bullata was positively correlated to the concentration of total As in exposed rabbit liver and mortality was negatively correlated to the concentration of total As in exposed rabbit liver. The reproductive output of S. bullata was not correlated to the concentration of total As in rabbit liver tissue.

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.

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.

The 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.