Browsing by Author "Elvinger, Francois C."

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    Adaptation of Three Different Apoptotic Methods in Equine Bronchoalveolar Cells and Comparison of Bronchoalveolar Lavage Cell Apoptosis in Normal and COPD Affected Horses Before and After Dexamethasone Administration
    Leichner, Teri Lynn (Virginia Tech, 2001-06-21)
    Recent studies suggest that lymphocyte apoptosis serves to regulate pulmonary inflammation. Equine COPD, an allergic disease of the lower airway, is likely due to dysregulation of the pulmonary immune response. In this study, the hypothesis tested was COPD affected horses would have less apoptotic airway lymphocytes than control horses during clinical disease. To achieve this, 3 methods of measuring apoptosis, Vindelov's propidium iodide with Triton-X (PI/Triton-X), 7-aminoactinomycin D (7-AAD), and Annexin V with propidium iodide (Annexin/PI) were evaluated in equine airway lymphocytes. A significant linear relationship was found for equine bronchoalveolar lavage (BAL) lymphocytes stained with 7-AAD and Annexin/PI . No relationship was identified with cells stained with PI/Triton-X and Annexin/PI, and 7-AAD and PI/Triton-X indicating that methods which preserve cell membrane characteristics are more comparable when measuring BAL lymphocytes apoptosis in a heterogeneous population of cells. Additionally, all stains appear to perform the same in COPD and normal horses in remission and disease. Comparison of predominately BAL lymphocyte apoptosis using the above methods were performed at baseline, after natural challenge, and after dexamethasone administration in nine horses, five of which were affected with COPD. No differences in bronchoalveolar lavage lymphocyte apoptosis between COPD and control horses were detected either before or after dexamethasone administration, although numerical trends in COPD horses identified less apoptosis after natural challenge indicating that defective apoptosis may play a role in equine COPD pathogenesis. Dexamethasone administration was associated with trends of improvement in the pulmonary gas exchange and increased apoptosis toward baseline in the COPD horses.
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    The Applicability and Use of Waterless Hand Sanitizer in Veterinary and Animal Agricultural Settings
    McMillan, Naya Subira (Virginia Tech, 2004-05-06)
    An increase in outbreaks caused by zoonotic agents has brought about intensified efforts to address the transmission of infectious organisms in animal settings. In October 2002, the CDC released recommendations for the use of waterless hand sanitizer (WHS) in human healthcare settings. The question arises whether WHS may be as effective in veterinary and animal agricultural settings given some of the dissimilarities in conditions. To address this question, three studies were conducted. The first was a retrospective analysis of a Samonella agona outbreak which occurred in 2001 at the Large Animal Teaching Hospital of the Virginia-Maryland Regional College of Veterinary Medicine (VMRCVM). The second evaluated the pattern of use and efficacy of hand hygiene products in the VMRCVM Large Animal Hospital. The third study assessed the efficacy of WHS among visitors to a children's petting zoo at the 2002 Virginia State Fair. Regarding the Salmonella outbreak, it is thought that a calf from the university owned dairy herd was the index case. A total of 16 equine patients acquired S. agona while hospitalized. The nosocomial disease incidence risk for in-house patients was estimated to be 33% (16/49). The LAH was closed for 7 months for cleaning, disinfection and renovation. The total cost of the outbreak was estimated to be at least $755,000. Waterless hand sanitizer proved useful in the veterinary hospital setting. When measured immediately after use, WHS reduced bacterial loads on the hands of 20 LAH personnel (P < 0.001). Before WHS use, HBC ranged from less than to 20 to 48,800 CFU/ml with a geometric mean of 6,926 CFU/ml. Counts after WHS use ranged from less than 20 to 23,400 with a geometric mean of 1,152 CFU/ml. Differences in before and after ranged from -4,000 to 48,200 CFU/ml with a median of 9,700 CFU/ml. The logarithmic reduction in bacterial load before and after WHS use was 0.78 (79.7%). In the petting zoo study, bacterial counts on the fingers of the children sampled before use of WHS ranged from 40 to 75,200 CFU/ml with a geometric mean of 8,653 CFU/ml. After WHS use, bacterial growth ranged from 19 to 58,400 CFU/ml with a geometric mean of 1,727 CFU/ml. Differences in before and after ranged from -35,600 to 59,400 CFU/ml with a median of 8,190 CFU/ml. The logarithmic reduction in bacterial load before and after WHS use was 0.70 (82.2%; P< 0.001). These data suggest that WHS may be of benefit in veterinary medicine and animal agriculture as a means to reduce nosocomial and zoonotic infections.
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    Bovine Coccidiosis: Dynamics of infection in grazing cattle and the potential role of stress and immunity
    Lucas, Aaron Scott (Virginia Tech, 2011-08-02)
    Eimerian parasites infect cattle worldwide. Information on the infection dynamics of these parasites is lacking in the central Appalachian region of the United States. Studies aimed at characterizing the seasonal dynamics of eimerian parasites in this region were carried out in order to assess the impact of these organisms in grazing systems. In these studies the prevalence of Eimeria spp. infection was highest in calves less than one year of age and subsequently decreased to stable levels in older animals. Although E. bovis was the most common species identified in calves, heifers and cows, mixed species infections dominated. Additional studies were carried out to investigate the effect of stress on Eimeria spp. infection in beef calves. Lower stress, two-stage, weaning methods had no effect on Eimeria spp. infection dynamics in beef calves. These findings must be interpreted in light of the fact that calves used in this study were not managed in a way typical of many calves in the U.S.A. The fact that they were only transported short distances, never commingled, or exposed to a livestock market may explain why a rise in post weaning FOC was not observed. A model of stress- induced coccidiosis was developed using dexamethasone and E. bovis challenge. In this model, an oral challenge of at least 500,000 sporulated E. bovis oocysts in addition to dexamethasone injection at 7 days post challenge increased subsequent FOC. Further investigation of the immune response to E. bovis challenge during times of stress indicates that stress-induced suppression of cell mediated immunity and E. bovis challenge are required to increase subsequent oocyst shedding. These findings may represent the mechanism associated with stress-induced outbreaks of coccidiosis reported to occur in beef cattle in the United States.
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    Characterization of Clinical and Commensal Escherichia coli Isolates from an Integrated Turkey Operation
    Altekruse, Sean Fitzgerald (Virginia Tech, 2001-10-26)
    Pathogenic E. coli infections cause approximately one quarter of disease losses in commercial turkey flocks. A small subgroup of E. coli causes most infections. Epidemiologic studies of this disease have been hindered by a lack of reliable markers to discriminate between pathogenic and fecal E. coli and by the diversity of poultry strains. Reliance on antimicrobials to control E. coli infections has caused widespread antimicrobial resistance. One hundred five clinical E. coli were obtained, and 1104 isolates were collected from fecal specimens of 20 flocks in an integrated turkey operation. Biochemical fingerprinting and antimicrobial susceptibility tests were performed on all isolates, and somatic antigen serologic testing and PCR for potential virulence genes were conducted on 299 strains including all clinical isolates and fecal isolates that had similar traits to clinical isolates. Most avian E. coli infections were caused by a few clonal strains that were uncommon in normal fecal flora. The potential virulence genes iss, K1 and tsh were detected more frequently among clinical than fecal isolates; however, the pattern of occurrence did not suggest that these genes were useful markers for identifying pathogenic strains. Syndromes consistent with colibacillosis were the most commonly reported illness and principal rationale for antimicrobial therapy in sampled flocks. Most clinical E. coli isolates were resistant to gentamicin, sulfamethoxazole and tetracycline. Although resistance to fluoroquinolones and β-lactam antibiotics occurred less frequently, the potential for resistance to emerge to these antimicrobials was evident. A Bayesian model to estimate sample size confirmed the diversity of avian fecal E. coli strains. Studies are needed to define risk factors for infection with and identify markers for avian pathogenic E. coli strains. These research priorities are complementary and may lead to the identification of new interventions to prevent this important infectious disease of poultry.
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    Curli Production and ERIC-PCR Fingerprinting of Escherichia coli from Clinical Cases of Bovine Mastitis
    Dyer, John Gilbert (Virginia Tech, 2005-02-04)
    Mastitis caused by Escherichia coli is among the most common and severe forms of environmental mastitis. Currently, the severity of E. coli mastitis is thought to be more related to cow factors than bacterial virulence. Some strains of E. coli, however, may be adapted to colonizing mammary tissue, increasing clinical severity, and impairing recovery. Curli are adhesive surface structures produced by some E. coli and Salmonella strains that bind a number of host proteins and have recently been found to play a role in the pathogenesis of bacterial sepsis. Sixty-one E. coli isolates from 36 clinical cases of bovine mastitis were characterized using ERIC-PCR and screened for their ability to produce curli by binding Congo-red dye. The effect of curli production on case recovery, based on a return to milk production, was investigated for a subset of 43 isolates from 20 quarters of 19 cows. Fifty-eight of the 61 isolates were clustered into two clonal groups at 52% genetic similarity. Thirty-five of all 61 isolates (57%) were curli-positive. Twenty-three isolates from 13 cows clustered in clonal group I, of which 5 cases (38%) were curli-positive; 35 isolates from 22 cows were clustered in clonal group II, 15 of which were curli-positive cases (68%). No association was found between genetic similarity and phenotypic curli expression of isolates from cows with clinical E. coli mastitis cases (p=0.16). Phenotypic curli expression in isolates did not affect the recovery of cows' milk yield to pre-mastitis production levels (p=0.18).
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    Data Standardization and Machine Learning Models for Histopathology
    Awaysheh, Abdullah Mamdouh (Virginia Tech, 2017-03-27)
    Machine learning can provide insight and support for a variety of decisions. In some areas of medicine, decision-support models are capable of assisting healthcare practitioners in making accurate diagnoses. In this work we explored the application of these techniques to distinguish between two diseases in veterinary medicine; inflammatory bowel disease (IBD) and alimentary lymphoma (ALA). Both disorders are common gastrointestinal (GI) diseases in humans and animals that share very similar clinical and pathological outcomes. Because of these similarities, distinguishing between these two diseases can sometimes be challenging. In order to identify patterns that may help with this differentiation, we retrospectively mined medical records from dogs and cats with histopathologically diagnosed GI diseases. Since the pathology report is the key conveyer of this information in the medical records, our first study focused on its information structure. Other groups have had a similar interest. In 2008, to help insure consistent reporting, the World Small Animal Veterinary Association (WSAVA) GI International Standardization Group proposed standards for recording histopathological findings (HF) from GI biopsy samples. In our work, we extend WSAVA efforts and propose an information model (composed of information structure and terminology mapped to the Systematized Nomenclature of Medicine - Clinical Terms) to be used when recording histopathological diagnoses (HDX, one or more HF from one or more tissues). Next, our aim was to identify free-text HF not currently expressed in the WSAVA format that may provide evidence for distinguishing between IBD and ALA in cats. As part of this work, we hypothesized that WSAVA-based structured reports would have higher classification accuracy of GI disorders in comparison to use of unstructured free-text format. We trained machine learning models in 60 structured, and independently, 60 unstructured reports. Results show that unstructured information-based models using two machine learning algorithms achieved higher accuracy in predicting the diagnosis when compared to the structured information-based models, and some novel free-text features were identified for possible inclusion in the WSAVA-reports. In our third study, we tested the use of machine learning algorithms to differentiate between IBD and ALA using complete blood count and serum chemistry data. Three models (using naïve Bayes, neural networks, and C4.5 decision trees) were trained and tested on laboratory results for 40 Normal, 40 IBD, and 40 ALA cats. Diagnostic models achieved classification sensitivity ranging between 63% and 71% with naïve Bayes and neural networks being superior. These models can provide another non-invasive diagnostic tool to assist with differentiating between IBD and ALA, and between diseased and non-diseased cats. We believe that relying on our information model for histopathological reporting can lead to a more complete, consistent, and computable knowledgebase in which machine learning algorithms can more efficiently identify these and other disease patterns.
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    Detecting Giardia: Clinical and Molecular Identification
    Saleh, Meriam Naim (Virginia Tech, 2017-11-13)
    The protozoan parasite Giardia duodenalis (syn. G. lamblia, G. intestinalis) can cause diarrhea in humans, cats, dogs and other animals. Giardia duodenalis consists of eight assemblages (A-H) that are morphologically identical but genetically distinct. Assemblages C-H are generally species-specific, while A and B infect people and animals and are considered potentially zoonotic. Most canine and feline isolates belong to their respective species-specific assemblages, but isolates of assemblages A and B (predominantly found in humans) have also been recovered from dogs and cats. Diagnosis of infection has historically been by morphologic techniques (observing trophozoites on direct fecal smears or cysts on centrifugal zinc sulfate fecal flotations), and it is currently recommended to use morphologic techniques in conjunction with a sensitive and specific antigen test. Diagnosis is important for management of clinical giardiasis in cats and dogs and also to identify the assemblage present to determine its zoonotic potential. In my dissertation research I evaluated diagnostic techniques in use for companion animals, including centrifugal zinc sulfate fecal flotation, antigen tests optimized for use in dogs and cats, direct immunofluorescent assay (IFA), and Polymerase Chain Reaction (PCR). I showed that when compared to the reference IFA the veterinary optimized antigen tests performed similarly and had no statistically significant differences in sensitivity or specificity when combined with a centrifugal zinc sulfate fecal flotation test. Sensitivity and specificity by comparison to IFA was ≥ 82% and ≥ 90%, respectively, for all diagnostic tests evaluated in dogs and cats. When analyzed via Bayesian analysis sensitivity and specificity for all diagnostic tests was ≥83% and ≥95%, respectively. The Bayesian analysis also showed that using the direct immunofluorescent assay (IFA) as the reference test was supported. I also evaluated PCR as a molecular diagnostic technique to detect Giardia infections in dogs with soft stool or diarrhea (mimicking clinical signs of infection). I utilized both conventional and real time PCR assays and compared the results to the recommended method of diagnosis, the zinc sulfate fecal flotation combined with an immunoassay test. I found that agreement between PCR and microscopy combined with an immunoassay was poor to fair and varied depending on the molecular parameters and size of the DNA target underscoring the complexity of test evaluation and molecular diagnostics for Giardia. I also evaluated cats from a varied population (owned, shelter, feral) in Virginia to determine to what extent (if any) they were infected with potentially zoonotic assemblages of Giardia. The species-specific assemblage F was detected in 57% of the samples and assemblage A, which is considered potentially zoonotic, was recovered from 32% of the sampleI. In 11% both assemblages F and A were detected. We showed for the first time that cats in Virginia are infected with potentially zoonotic assemblages of Giardia.
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    Escherichia coli Mastitis in the Dairy Bovine
    Leininger, Dagny Jayne (Virginia Tech, 2001-05-09)
    Diagnosis techniques and treatments for Escherichia coli mastitis in the dairy bovine were evaluated in two experiments. The first experiment evaluated eosin methylene blue agar as a method of distinguishing E.coli from other gram-negative mastitis pathogens. Escherichia coli will usually produce a green metallic sheen on eosin methylene blue agar. One hundred and twenty-nine milk samples or gram-negative isolates from milk samples were used to compare eosin methylene blue agar to a commercial biochemical test strip (the accepted standard). There was an intermethod agreement of 96.9% and a k-value of 93.7% indicating excellent agreement beyond chance between test methods. Eosin methylene blue agar is a reliable method for differentiation of E. coli from other gram-negative mastitis pathogens. The second experiment evaluated the efficacy of frequent milk-out as a treatment for E. coli mastitis. Sixteen Holstein dairy cows were divided into 2 blocks and randomly assigned to 1 of 4 treatment groups: 1) non-infected, not frequently milked-out, i.e. not treated (NI-NT), 2) experimentally infected with E. coli, not treated (EC-NT), 3) non-infected, frequently milked-out (NI-FMO), and 4) experimentally infected with E. coli, frequently milked-out (EC-FMO). Hours to bacterial, clinical and systemic cure were not different between the EC-NT and EC-FMO treatment groups. Serum a-lactalbumin concentrations were evaluated between treatment groups as a measure of udder health. Serum a-lactalbumin concentrations were higher in cows in the EC-NT treatment group than cows in the NI-NT, NI-FMO and EC-FMO treatment groups at 12 hours post-experimental challenge. Serum a-lactalbumin concentrations were higher in cows in the NI-FMO treatment group than in cows in the NI-NT, EC-NT and EC-FMO treatment groups at 36 hours post-experimental challenge. Results from this study do not support frequent milk-out as a treatment for E. coli mastitis.
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    Estrogen Regulates Interferon-gamma (IFN-g) and IFN-g-Inducible iNOS Gene Expression: Implications to Immunity and Autoimmunity
    Sahin, Ebru Karpuzoglu (Virginia Tech, 2005-04-07)
    It is now clear that estrogen not only modulates the differentiation and function of reproductive systems, but it also profoundly regulates the immune system of normal and autoimmune individuals. An important mechanism by which estrogen regulates the immune system is by altering the secretion and/or response to cytokines. We hypothesized that estrogen may alter the levels and/or response to IFN-g, a prototype Th1 cytokine, that plays a pivotal role in immunity against intracellular infections and in many autoimmune and inflammatory disorders. We found that estrogen treatment tended to upregulate the secretion of IFN-g protein and mRNA expression from Concanavalin-A (Con-A)-activated splenic lymphocytes. Impressively, we found that splenocytes from estrogen-treated mice when activated with Con-A also resulted in increased release of nitric oxide compared to placebo-treated mice. Furthermore, Con-A-activated splenocytes from estrogen-treated mice also had upregulated iNOS mRNA, iNOS protein, and nitric oxide-regulated COX-2 protein when compared to control mice. Blocking co-stimulatory signals mediated through interactions of CD28 and B7 molecules by using CTLA-4Ig markedly decreased not only IFN-g, but also nitric oxide, thereby implying an important role for CD28/B7 interactions in IFN-g/nitric oxide. Estrogen-induced upregulation of iNOS/nitric oxide is mediated through IFN-g since: (i) Estrogen alone did not upregulate iNOS/nitric oxide in IFN-g knockout mice; (ii) addition of rIFN-g to activated splenocytes from estrogen-treated mice further upregulated nitric oxide levels. We next investigated whether estrogen also upregulated IFN-g-inducing cytokines and select IFN-g-inducing transcription factors. Estrogen treatment resulted in increased mRNA and/or protein expression of IFN-g inducing cytokines and their receptors, including: IL-18, IL-15, IL-27, IL-12Rb2, and IL-18Rb. We also found that T-bet, a critical Th1 transcription factor, and STAT-4 phosphorylation, a key molecule in IL-12 signaling were both increased, while IRF-4, an important player in Th2 differentiation, was diminished in Con-A-activated splenocytes from mice treated with estrogen. Altogether, these studies are the first to demonstrate that estrogen regulates IFN-g-dependent iNOS and describes the potential mechanisms of how estrogen alters IFN-g-inducible genes, IFN-g inducing cytokines, and transcription factors in normal C57BL/6 mice. These studies may have profound implications to many autoimmune and inflammatory disorders, where estrogen is known to regulate the course of these diseases. Since estrogen may promote inflammatory disorders by upregulating pro-inflammatory biomolecules including IFN-g, nitric oxide, and COX-2, these studies may help in the design of therapeutic agents that regulate or block secretion and/or response to these inflammatory molecules.
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    Extracorporeal Circulation: Effect of Long-Term (24-Hour) Circulation on Blood Components
    Solberg, Robert Glen (Virginia Tech, 2010-04-20)
    Extracorporeal circulation damages blood and causes harmful side effects such as stroke and/or systemic inflammatory response in patients. Reactions of blood components to extracorporeal circulation include complement and inflammatory reactions, coagulation and thrombogenesis, frank hemolysis, and platelet activation and adhesion to the extracorporeal circuit. Non-physiologic pressure and flow produced by blood pumps contribute to blood injury. Two pump types, roller and centrifugal, are used for maintaining flow, with various models available from different manufacturers. This study compared the effects of these two pumps in identical, isolated, artificial circuits to a non-pumped control for a period of 24 hours on heparinized porcine blood. Hematology parameters were used to evaluate blood damage. Mean corpuscular volume, mean corpuscular hemoglobin, white blood cell count, platelet count, and mean platelet volume were affected by time of circulation. Mean corpuscular hemoglobin, platelet count, and red cell distribution width were different between circulated and non-circulated blood, however no differences were found between the pumping systems in any parameter. Red blood cell count, total hemoglobin, and hematocrit were not affected by time or treatment. The changes observed in this study have implications for the use of extracorporeal circulation in the clinical setting and in future use of blood as a potential organ perfusion medium.
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    Factors Influencing the Reproductive Efficiency of Dairy Herds in the Dominican Republic
    Billings, Angela Renea (Virginia Tech, 2002-02-04)
    Despite an increase in domestic milk production, the dairy industry in the Dominican Republic (D. R.) has not been able to adequately meet the demand of the ever-growing Dominican population, prompting the government and milk processing plants to sponsor programs which will increase the national production of milk and eventually lead to milk self-sufficiency. One obstacle to this goal is a very low reproductive rate in cows and heifers due in part to the tropical setting. Year-round heat stress may result in abnormal follicular dynamics and decreased oocyte and sperm quality causing reproductive efficiency to decline drastically. The specific purpose of this project was to examine and characterize the reproductive practices and outcomes of the Dominican dairy industry by region and to attempt to identify factors that influence dairy reproductive efficiency. During the course of the study, 43 farms were visited over a 10-week period and evaluated. Farms were chosen throughout 4 of the 5 regions of the country and were selected based on their size (preferably 40 adult cows or more), availability of data, and demonstrated motivation by the owner in improving the herd. Individual herd evaluation was broken into four major components: owner interview, farm evaluation, collection of individual cow reproductive data, and adult cow evaluation. Once observations had been made and catalogued, all data were summarized on the herd level and analyzed descriptively. In addition to descriptive analysis, multiple regression techniques were used to select independent variables which explain most of the variance for each of four reproductive outcomes: days to first service, services per pregnancy, projected calving interval, and service rate. In general, reproductive management practices varied depending on region and farm size. Average lameness within the herd was the most important factor in explaining the variability within services per pregnancy and projected calving interval. As average herd lameness increases by 1 point (based on a 1 to 4 scale), services per pregnancy and projected calving interval increase by 0.65 services per pregnancy and 61.1 days respectively according to the model formulated. Increase in the number of employees involved in estrus detection resulted in higher days to first service. The Santo Domingo region had lower days to first service possibly due to widespread reproductive hormone use within the region. The percentage of Holsteins within the herd was associated with increased services per pregnancy and projected calving interval. Increases in service rate were most closely associated with the type of record category used, indicating that a larger sample population with thorough insemination records may be needed to adequately assess this outcome. In part, reproductive efficiency in the Dominican Republic can be potentially improved by enhancing methods for estrus detection. Mechanical aids to estrus detection (tailhead chalk, K-mar® patches, etc.) may help increase estrus detection efficiency in herds currently only relying on visual observation. Assigning 1-2 people primarily to estrus detection and increasing the frequency of hormone usage may also improve estrus detection efficiency. The main emphasis for Dominican dairy producers, however, should be on preventing new lameness and culling chronically lame cows once it is economically feasible to do so. Reducing the incidence of lameness could, in itself, dramatically improve reproductive efficiency in the Dominican Republic.
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    Forest disturbance, mosquito vector ecology and La Crosse virus dynamics in southwestern Virginia
    Harris, Maria-Richetta Camille (Virginia Tech, 2014-09-22)
    The influence of forest canopy disturbance (FCD) on La Crosse virus (LACV), leading cause of US pediatric arboviral encephalitis, is critical to understand in landscapes where forests are periodically harvested. Southwestern Virginia is part of an emerging focus of this interior forest bunyavirus. I investigated how the temperate forest mosquito community, LACV vectors, and the LACV amplifying vertebrate host (chipmunks) were impacted by logging. This research was conducted across an experimental FCD gradient (from least to most disturbed: contiguous control, fragmented control, clearcut, and high-leave shelterwood (SW)). Using gravid traps, I found that the mosquito community was resilient to logging with no significant difference in diversity or community composition across treatments. Mean number of female mosquitoes caught per trap-night declined with disturbance. FCD significantly affected the abundance of vector species in different ways. The primary LACV vector, Aedes triseriatus, and the recent invasive Ae. japonicus declined with logging. Other vectors (Ae. albopictus, Ae. canadensis, and Ae. vexans) thrived with logging. Culex pipiens/restuans was affected by disturbance but had no treatment preference. A mark-recapture study revealed that chipmunk abundance and LACV seroprevalence were greatest on the SW. In sync with Ae. triseriatus abundance but in contrast to the chipmunk results, mosquito LACV detection was significantly greater on unlogged sites. Surprisingly, LACV was detected in Ae. japonicus and Cx. pipiens/restuans. In a follow-up study, I isolated LACV from field-collected Ae. japonicus. Although LACV was previously isolated from Cx. pipiens, the vector competence was unknown. Therefore, I examined the vector competence of Cx. pipiens and Cx. restuans. Although poor vectors, I did detect LACV in the saliva of both species. An additional experiment found that nutritionally-stressed Cx. restuans were better vectors than those in the control group, indicating that environmental stressors (e.g., FCD) may alter the ability of accessory vectors to spread LACV. The influence of FCD on LACV is complex. Because logging decreases Ae. triseriatus abundance, human LACV risk is likely lowered by decreased transovarial vertical transmission. However, high chipmunk seroprevalence on disturbed sites suggest horizontal transmission with accessory vectors plays a larger role in LACV risk on recently logged sites.
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    Implications of the ability of Enterococcus spp. to survive the ensiling process and bovine gastrointestinal tract on the risk of bovine mastitis
    Masiello, Stephanie Noelle (Virginia Tech, 2010-01-25)
    Three studies were conducted to assess if the ability of Enterococcus spp. surviving the ensiling process and bovine gastrointestinal tract could impact risk of bovine mastitis. The first study determined ability of enterococci to survive 3 wk ensiling. Grass and corn crops were divided into 3 treatments: 2 commercial silage inoculants, 1 negative control. After wk 1, 2, and 3 of ensiling, dry matter and bacterial enumeration were performed. Addition of silage inoculant led to greater levels of enterococci in grass silage compared with negative control levels, but showed less difference in inoculated corn silage. The second study quantified enterococci shedding rates in lactating dairy cows. Using a 4 x 4 Latin Square design, lactating, ruminally fistulated Holsteins were inoculated with enterococcal isolates from silage inoculants, ensiled forages, or clinical mastitis cases. Over the 4-period study, each period consisted of rumen and fecal sampling (2 wk) followed by a wash period (10 d). There were no significant differences in rumen or fecal enterococci levels between the 4 treatments. Both rumen and fecal enterococci levels showed significant differences between baseline and treatment periods (period 3, 4). The third study analyzed similarity in enterococcal isolates of silage and bovine origin using pulsed-field gel electrophoresis patterns from SmaI restrictions. Dendogram analysis showed none of the isolates met or were greater than a 75% genetic similarity and produced a genetically diverse population. Results suggest Enterococcus spp. from silage inoculants are not likely to contribute to an increased risk of enterococcal bovine mastitis.
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    Investigation of Community Annoyance as Invoked by a High School Stadium and a Train Horn Proximal to Residentially Zoned Homes
    Baker, Aubrey Anne (Virginia Tech, 2015-07-17)
    The effects of two different noise sources upon their surrounding communities were investigated with both quantitative and qualitative measures. A high school football game, which presents continuous noise over a relatively short duration on a predictable schedule was found to have a slight annoyance on its surrounding community. In contrast, a train horn blow at a residential intersection was investigated. This sound was unpredictable and could occur at any time. Residents in this community were found to have a moderate level of annoyance. It was found that each of the noises studied violated suggested noise levels for common household activities, in addition to many local, state, and federal noise regulations. It is recommended that both of the sounds studied herein be reduced or eliminated altogether. Limiting the level of sound produced by the PA system at the football game and using a noise reducing barrier would help in the case of the football game. Converting the railroad intersection into one with sufficient safety features, especially a crossing quad-gate that no longer requires trains to blow their horns would be the optimal solution, with the added benefit of precluding vehicles from entering the crossing when a train is present.
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    Pharmacokinetic Studies and Tissue Residue Analysis of Oxytetracycline in Summer Flounder (Paralichthys dentatus) Maintained at Different Production Salinities and States of Health
    Hughes, Kathleen Powers (Virginia Tech, 2003-04-10)
    Summer flounder, Paralichthys dentatus, culture is becoming increasingly popular in the United States because of high market prices and consumer demand. In addition, flounder is a marine fish species that can tolerate a wide range of salinities, allowing for inland intensive fish culture. Oxytetracycline (OTC) is one of two available FDA-approved antibiotics for use in foodfish in the United States. Oxytetracycline was chosen for these studies because it is excreted primarily unchanged through the urine and the absorption, distribution and elimination of this drug may be influenced by environmental and physiological conditions. Four experiments were conducted to investigate: 1) pharmacokinetic parameters of oxytetracycline (50 mg/kg) following intravascular (IV), intraperitoneal (IP), intramuscular (IM) and per os (PO) administration in summer flounder maintained at 28 ppt salinity and 20°C; 2) pharmacokinetic parameters of OTC (50 mg/kg) following IM and PO administration in summer flounder maintained at three different salinity levels of 0 ppt, 15 ppt and 32 ppt and the physiological adjustments summer flounder make to acclimate to environmental salinity; 3) OTC retention times in muscle tissue from summer flounder maintained at three different salinity levels (0 ppt, 15 ppt, 32 ppt) and treated with a single 50 mg/kg OTC dose via IM and PO administration; and 4) pharmacokinetic parameters of OTC (50 mg/kg) following IM and PO administration in clinically healthy and clinically diseased summer flounder maintained at 28 ppt and 20°C. Oxytetracycline plasma concentrations were determined using high performance liquid chromatography (HPLC) and analyzed using a non-compartmental pharmacokinetic model for all routes of drug administration. Statistical comparisons were not made between the different routes of OTC exposure, but results from experiment one indicated that IV administration of OTC resulted in the largest area under the curve (AUC) value (8147.9 µg·h/ml) and the highest maximum plasma concentration (Cmax) of 1173.2 µg/ml OTC at 5 min post-injection. Intramuscular injections of OTC resulted in prolonged total body elimination half-life (T ½) of 301.3 h and high fish-to-fish variability (0.6). Per os administration resulted in low Cmax (0.2 µg/ml OTC) and poor systemic bioavailability (0.2 %). Results from experiment two demonstrated that when OTC is administered IM AUC estimates are significantly (p<0.05) lower in summer flounder held at 0 ppt (1684.8 µg·h/ml) than fish maintained at 15 ppt or 32 ppt salinity (2067.8 µg·h/ml and 2241.3 µg·h/ml, respectively). Although not significantly different from other salinity treatments, time to maximum plasma concentration (Tmax) was longer in fish held at 15 ppt and 32 ppt (312 h and 168 h, respectively) compared to cohorts in freshwater (0.5 h) and Cmax values were higher in animals held at 15 ppt and 32 ppt (8.4 µg/ml OTC and 9.2 µg/ml OTC, respectively) than freshwater fish (4.9 µg/ml OTC) when OTC was administered via IM injection. No significant differences were detected in any of the pharmacokinetic parameters following PO dosing of OTC, however, the AUC estimates were lower in the 32 ppt acclimated fish (127.7 µg·h/ml) than in the 0 ppt or 15 ppt acclimated fish (190.2 µg·h/ml and 180.7 µg·h/ml, respectively). In addition, the T ½ was longer in the higher salinity groups (278.1 h and 266.0 h, respectively) than in the freshwater fish group (256.9 h). Physiological adjustments made by summer flounder including plasma and urine osmolality, urine flow rate and urine character, gill chloride cell size and density, and Na+ - K+ ATPase activity demonstrated trends that suggested physiological differences among the salinity groups. Plasma and urine osmolalities were typically significantly (p<0.05) higher in fish maintained at 32 ppt salinity than at the lower salinity treatments. In addition, urine flow rates were generally significantly (p<0.05) greater in freshwater adapted fish (0.13 - 0.21 ml of urine/kg/hour) in comparison to fish in the salinity treatments of 15 ppt and 32 ppt (0.06 - 0.12 ml of urine/kg/hour and 0.09 – 0.11 ml of urine/kg/hour, respectively). Changes in gill chloride cell size and density and enzyme activity of Na+ - K+ ATPase revealed no significant differences between the salinity treatments but summer flounder in saltwater had numerically larger and more chloride cells than summer flounder in freshwater, but enzyme activity was greater in freshwater acclimated summer flounder compared to fish in seawater. Experiment three results revealed similar OTC muscle tissue pharmacokinetic parameters in summer flounder following IM injection. However, there were significant differences (p<0.05) in the AUC parameters of the plasma and muscle OTC concentrations between fish maintained at different salinities following IM OTC treatment. These effects may be the result of a "depot" effect in the muscle tissue or may be related to the reduced solubility of OTC in the muscle tissue of marine fish. A single PO dose administration of OTC at 50 mg/kg did not result in plasma or tissue concentrations higher than the FDA tissue tolerance limit of 2 ppm. Results of the fourth experiment demonstrated that following IM OTC administration healthy fish had significantly (p<0.05) higher AUC (4700.6 µg·h/ml) values than diseased cohorts (2576.2 µg·h/ml). Maximum plasma concentrations were also higher in the healthy fish than in the diseased fish, although values were not significantly different (23.4 µg OTC/ml and 20.2 µg OTC/ml, respectively for healthy and diseased fish). Additionally, in diseased fish, the mean resident time (MRT) (293.7 h) and T ½ (203.5 h) parameters were longer compared to parameters in healthy fish (253.2 h and 175.4 h, respectively), although values were not significantly different. No significant differences were detected in any of the pharmacokinetic parameters following PO OTC administration, however, healthy fish achieved higher maximum plasma OTC concentrations (1.0 µg OTC/ml) than diseased fish (0.7 µg OTC/ml). Fish-to-fish variation was greater in diseased animals than in healthy regardless of route of drug administration. The results of these experiments indicated that OTC pharmacokinetic parameters are influenced by route of drug administration, environmental salinity and fish health status. These factors must be considered by veterinarians and governmental regulators when developing treatment regimens for summer flounder.
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    Prevalence of Cardiomyopathy in Apparently Healthy Cats
    Paige, Christopher Francis (Virginia Tech, 2007-06-29)
    Subclinical cardiomyopathy (CM) sometimes is identified after abnormalities are detected during auscultation of apparently healthy cats. Little is known regarding the prevalence of CM in this population. Furthermore, the clinical importance of auscultatory abnormalities in apparently healthy cats is unclear. In order to estimate the prevalence of murmurs and CM, we prospectively evaluated a sample of apparently healthy cats. Cats with systemic hypertension or hyperthyroidism were excluded. 103 cats were subject to physical and echocardiographic examinations which were performed by two different investigators; the echocardiographer was unaware of the physical findings. Left ventricular wall thickness was determined by two-dimensional echocardiography in short- and long-axis planes. Left ventricular hypertrophy (LVH) was defined as an end-diastolic wall thickness greater than or equal to 6 mm. Cats with LVH but without left ventricular dilation were considered to have hypertrophic CM (HCM). Cardiomyopathy was identified in 16 cats (15.5%; 95% CI: [9.2, 24.0]); 15 had HCM and one had arrythmogenic right ventricular cardiomyopathy. Murmurs were detected in 16 cats (15.5%; 95% CI: [9.2; 24.0]); of these cats, 5 had CM. Of 15 cats with HCM, 11 had segmental LVH, three cats had diffuse LVH, and one cat had borderline LVH and marked systolic anterior motion of the mitral valve. The sensitivity and specificity of murmurs for detection of a CM was 31% and 87%, respectively. The prevalence of feline subclinical CM in Southwest Virginia is near 16%; approximately a third of these cats had murmurs. In apparently healthy cats, a cardiac murmur is an insensitive marker of the presence of CM.
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    Shiga Toxin-Producing Escherichia coli: a Public Health Challenge in the Pre-Harvest Stage of the Farm-to-Table Continuum
    Baltasar, Patricia Pereira (Virginia Tech, 2016-06-06)
    Escherichia coli is part of the normal gastrointestinal microbiota of many animals, especially cattle. While most strains are commensal, Shiga toxin-producing E. coli (STEC) can cause severe human illness. Pathogenicity of STEC is associated with genes such as those encoding Shiga toxins, enterohemolysin, and intimin. By targeting these genes, highly sensitive molecular-based techniques help detect potentially harmful STEC. Persistent carriers and environmental contamination may be responsible for maintenance of STEC in cattle farms. Prevalence may be further influenced by diet, distance to contaminated water-sources, wildlife contact, slurry application to pasture, and population density. Relevance in environmental contamination is expected proportional to the amount of STEC shed in feces, but there is no consensus as to which production stage/age is most important. Distribution and transmission of STEC O157 are widely studied, but risk factors for non-O157 STEC are not as well defined. Understanding what contributes for contamination of animals prior to concentration in high-density feedlots may reveal opportunities for upstream control of shedding and transmission. Our purpose was to: (a) determine prevalence of STEC in fecal samples from animals in a cow-calf pasture-based production system; (b) describe effects of age class (dam, calf), spatial distribution of cattle, and time-point of sampling on distribution of strains positive for virulence genes stx1, stx2, eaeA, and hlyA; (c) isolate and identify serotypes present in stx-positive samples; and (d) assess genetic similarity of isolates. Understanding factors that influence distribution of STEC strains may help support on-farm management strategies with potential to yield safer beef products.
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    Veterinary Therapeutic and Biologic Agents in Virginia Sheep Production
    Rorrer, Rebecca Kathleen (Virginia Tech, 2002-07-16)
    Biological and therapeutic agents are used in food animal production to maintain animal health and well being, prevent and treat disease, and to maintain or enhance production. Concerns about the use of pharmaceutical agents in food animal production have been raised, especially in relation to food quality and safety. This study addressed the scarcity of information concerning the quantity of pharmaceuticals being used and the reasons for their use in sheep production. Additional goals included determining the sources of information used by shepherds in making treatment decisions and evaluating the economic impact that pharmaceutical usage has on sheep production. Thirty-nine Virginia sheep producers participated in this study of four months duration from March through September. After completing an initial questionnaire to determine flock and management characteristics, participants were asked to record all treatments with biological and therapeutic agents that occurred within their sheep flocks. A total of 14,310 treatments were recorded for a median of 1.5 treatments per sheep per month. Parasite control and vaccination were the most frequent reasons for treatment (64.9% and 15.2%, respectively) with vitamin/mineral supplementation being the next most common (8.8%). Price information was collected for 13,912 treatment events. An estimated total of $7,523.78 was spent on pharmaceutical treatment over the course of the study. This amounts to a cost of $0.63 per sheep per month of observation. Results of this study will enhance the ability of producers to evaluate treatment decisions, allow comparisons to be made between operations and provide a base of information for future research.