Calves are born agammaglobulinemic and rely on colostrum consumption for the transfer of maternal passive immunity. Calves that fail to absorb adequate amounts of maternal antibodies from colostrum are commonly referred to as having failed transfer of passive immunity (FTPI). The overall aim of this dissertation was to explore the usefulness of FTPI testing in neonatal beef calves to predict their risk for subsequent illness or death. The objectives were to evaluate the impact of FTPI on pre-weaning disease in beef and dairy calves, quantify and compare the variance in IgG concentrations measured by radial immunodiffusion and serum total protein (STP) values measured by optical refractometry, and evaluate the correlation between herd-level prevalence of FTPI and herd-level prevalence of pre-weaning disease in beef calves. Evaluation of literature relevant to FTPI was compiled and assessed to quantify the impact of FTPI on pre-weaning disease in beef and dairy calves. A series of randomized trials were used to evaluate the variance in IgG concentrations and STP values from banked serum. Health records from multiple farms and IgG results were used to evaluate the relationship between FTPI and disease at the individual and herd-level. Failed transfer of passive immunity had a variable association with pre-weaning disease in beef and dairy calves. IgG concentrations were less precise than STP values especially when dilution was required. IgG concentrations and STP values were associated with an increased risk of disease in pre-weaned beef calves, but FTPI cut-off values poorly classified the risk for subsequent disease. The proportion of calves with FTPI was not correlated with the proportion of calves that developed pre-weaning disease. Using a single immunological factor, such as IgG concentration or STP, to predict disease results in the misclassification of disease risk and does not consider additional component causes of disease.

Lyme disease (LD) is the most prevalent vector borne disease is North America with 300,000-600,000 human cases each year. Preventative strategies for LD in humans are poorly developed and largely inadequate. While preventive vaccines for LD are widely used in veterinary medicine, there are no vaccines available for use in humans. The goal of this study was to develop a human vaccine that can elicit antibody responses that kill spirochetes in both the tick and mammalian environments. The approach applied in this study centered on the development of chimeric epitope proteins, referred to as chimeritopes. Chimeritopes consist of a series of epitopes derived from one or more proteins or protein variants. Three chimeritope proteins designated as Chv1, Chv2 and Chv3 were designed. These proteins harbor the same set of 18 linear epitopes derived from 9 different OspC type proteins. They differ in epitope arrangement or by the presence or absence of linkers between specific protein segments. The immunogenicity of each protein was assessed in multiple animal models including mice, rats, and purpose bred beagles. Immunoblot, ELISA, and IFA analyses using sera from immunized animals demonstrated that the Chv proteins elicit IgG responses that recognize a diverse array of OspC type proteins. Anti-Chv and anti-OspA antisera displayed complement dependent bactericidal activity. To assess protective efficacy, purpose bred beagles were immunized with each vaccine formulation and then challenged by infestation with infected ticks. Efficacy was assessed by monitoring seroconversion, cultivation of tissue biopsies, clinical presentation and histopathological analysis of joints and tissues. All dogs vaccinated with the Chv2-OspA combination were fully protected. All dogs in this group were seronegative for LD, biopsy culture negative and did not develop LD associated symptoms including lameness or lesions in tissues or joints. In light of market concerns centered on the use of full length OspA in a human vaccine, epitope mapping was performed to identify a linear epitope that could be employed in development of a possible OspC-OspA chimeritope. A linear epitope, designated as OspA221-240was identified. Antisera to KLH-OspA221-240displayed potent and broad bactericidal activity. Interestingly, the OspA221-240epitope has homology to residues 244 to 263 of OspB suggesting that OspB may also be a potential candidate for inclusion in a human vaccine. This study establishes proof of principle for the use of OspC chimeritopes in LD subunit vaccines and highlights the need to employ a multi-valent, multi-antigen vaccine approach in development of a human LD vaccine.

Malignant catarrhal fever (MCF) is a lymphoproliferative and inflammatory syndrome affecting primarily ruminant species. The disease, which is often fatal, is most often described as affecting bovids and cervids. No vaccines are available for prevention of MCFV infection. The primary method to control spread of disease is to prevent contact between carriers and clinically susceptible species. There is no known method to control infection of malignant catarrhal fever virus-white-tailed deer variant (MCFV-WTD), as the carrier animal of this virus is unknown. To determine the prevalence of malignant catarrhal fever viruses in Tennessee ruminant populations, blood and/or lymph node samples were collected from farms, animal processing and disposal facilities, and hunter check-in stations from 2006-2008 from several species of animals including cervids, cattle, and goats. Strain-specific real time PCR was developed to detect ovine herpesvirus-2 (OvHV-2), caprine herpesvirus-2 (CpHV-2), and MCFV-WTD DNA. MCFV DNA was detected in all species of ruminants sampled. Although disease related to infection with MCFV-WTD and CpHV-2 has not been reported in Tennessee cattle or cervid populations, MCFV-WTD DNA was detected in 3 percent of cervid samples, and MCFV-WTD and CpHV-2 DNA was detected in 27 and 3 percent respectively of cattle samples from animal disposal facilities that process dead or debilitated animals. One hunter harvested deer (n=781) and 25 cattle (n=165) tested from animal disposal facilities were positive for OvHV-2 DNA. This study demonstrated that healthy cattle and cervids can be infected with OvHV-2 and MCFV-WTD without apparent disease, and dead or debilitated cattle were infected with OvHV-2, MCFV-WTD and CpHV-2 at a higher percentage than healthy herd animals. Prevalence of CpHV-2 in Tennessee goat populations (7%) was significantly lower than reported in other goat populations (73%). Low prevalence of CpHV-2 in Tennessee goat populations likely explains why no evidence of infection was found in cervids tested, and the low prevalence of CpHV-2 infection in dead or debilitated cattle compared to prevalence of infection with OvHV-2 and MCFV-WTD. The discovery of infection in cattle with CpHV-2 and MCFV-WTD opens a new avenue of investigation into the pathology and virulence of MCFV’s in domestic cattle.

Enterovirus D68 (EV-D68) virus has become more prevalent over the last 15 to 20 years. EV-D68 attacks the respiratory system and can cause severe disease in individuals who have underlying respiratory problems. There have also been reports of individuals with EV-D68 showing signs of neurological system problems and acute flaccid paralysis. Because of the increase in patients with EV-D68 and also the potential for neurological disease, an animal model is needed to study the disease and to evaluate experimental therapies for EV-D68 infection. To develop the animal model, 4-week old AG129 mice that lack alpha and beta interferon receptors, making them immunosuppressed, were used. The mice were infected with EV-D68 by the intranasal route to allow infection of the lungs. On day-3 post-infection the mice were euthanized and lungs were removed and homogenized for collection of virus. The newly collected virus was then used to infect another set of mice. This procedure was repeated 30 times. As passage number increased so did the amount of virus that was collected from the lungs of mice. The virus titer increased 320-fold between mouse passage 0 to 30. At the end of the thirtieth passage, multiple tissues (lungs, liver, kidney, spleen, blood, brain, spinal cord and leg muscle) were collected from infected mice over several days and titered to demonstrate how quickly the virus spread to various tissues within the mouse. The virus replicated most rapidly in the lungs and remained in the lungs longer than the other tissues evaluated. However, large quantities of virus were found in all tissues evaluated. Finally, several experimental antiviral compounds were evaluated: rupintrivir, pleconaril, ribavirin, enviroxime and guanidine, all of which showed therapeutic potential in cell culture. In the animal model rupintrivir, pleconaril, ribavirin and enviroxime did not show any therapeutic effect. Only guanidine reduced the amount of virus that was found in the lungs as well as in whole blood.

No description available.

Lawsonia intracellularis and the disease it causes in horses, equine proliferative enteropathy (EPE), is an emerging pathogen of increasing importance to the horse industry from both an economic and welfare standpoint. Long recognized as an economically important disease of swine, the hallmark of EPE is a protein-losing enteropathy, where affected horses suffer weight loss and some ultimately succumb to the disease despite aggressive treatment. There are currently no known EPE preventative measures and the epidemiology of the disease remains poorly defined. While EPE is a sporadic disease affecting less than 25% of exposed horses, some farms experience clinical cases year after year. Further, weanlings are uniquely susceptible to this disease, although no conclusive reason for this predisposition has been identified. The overall hypothesis is that the host immune response plays a significant role in the susceptibility of weanlings to L. intracellularis infection and the occurrence of clinical equine proliferative enteropathy. To test this hypothesis, four individual hypotheses were proposed: (H1) previous farm history of EPE does not have an effect on weanling seroprevalence, (H2) passively-acquired antibodies do not have an effect on susceptibility to L. intracellularis and the occurrence of EPE, (H3) the serological status of mares can be used to determine the role they play in the epidemiology of EPE on endemic farms, and (H4) L. intracellularis-specific IFN-g expression is not associated with increased resistance to EPE.

Despite advances in mosquito management, mosquito-borne disease in the United States is still of relevant public health concern and vector control is a top priority in preventing transmission of pathogens. Insecticide barrier sprays have become a common tool for suppression of mosquitoes in single-homeowner backyards. The application of the synthetic pyrethroid, lambda-cyhalothrin to perimeter vegetation with a backpack sprayer has been shown to significantly suppress mosquito levels for around 6 weeks. In an attempt to lengthen the effective duration of treatment, the IGR, pyriproxyfen, was added to a backpack mist blower with lambda-cyhalothrin, as adult mosquitoes exposed to pyriproxyfen have been shown to disseminate it to oviposition sites and to experience lowered fecundity. This treatment was compared to lambda-cyhalothrin alone and to a water control. Mosquito populations were sampled using CO2-baited CDC light traps, CDC gravid traps, human landing rates, and ovitraps. Leaf bioassays were performed. The following summer, the same treatments were applied with a truck-mounted mist blower to tree lines in Central Kentucky, to test the efficacy of an application method that could be used on large properties. Finally, bioassays were performed with water sampled from pyriproxyfen-treated containers, exposed to field conditions to test for residual efficacy.

Staphylococcus pseudintermedius affecting dogs is analogous to S. aureus on humans, acting as both normal flora and opportunistic pathogen. Methicillin resistance in S. pseudintermedius is recent, with the first documented occurrence of an isolate bearing the methicillin resistance gene, mecA, in 1999. This gene encodes penicillin binding protein 2a, which renders all beta-lactam drugs ineffective and functions as a “gateway” antibiotic resistance determinant. In the presence of ineffective antibiotics, opportunities for mutational events and acquisition of mobile genetic elements increase as microbial densities increase, often leading to multi-drug resistance. Methicillin-resistant S. pseudintermedius (MRSP) infections have become increasingly common. For example, approximately 30% of the S. pseudintermedius isolates tested by the University of Tennessee College of Veterinary Medicine Clinical Bacteriology Laboratory are resistant to methicillin. An increasing number of MRSP isolates are also resistant to most clinically useful antibiotics available to veterinarians except for chloramphenicol, and resistance to this antibiotic is common among European MRSP isolates. Chloramphenicol resistance has begun to appear in the US and if this trend continues there may soon be few viable antibiotic treatment options. Compared with the arrival of methicillin-resistant S. aureus in the 1960s, the opportunity currently exists to apply advanced molecular methods early in this recognized emergence of MRSP. To that end I have pursued projects utilizing multilocus sequence typing, pulsed-field electrophoresis, and SCCmec characterization of both susceptible and resistant S. pseudintermedius. The initial result was the detection of a clonal population of MRSP in the southeastern United States. Further characterization of this and other clonal lineages using genomic sequencing and real-time RT-PCR expression analysis of antibiotic resistance and quorum sensing genes revealed a marked difference in the regulation of antibiotic resistance between regional clones. These discoveries have interesting epidemiological implications and provide a foundation for the development of novel therapeutics to circumvent the expanding antibiotic resistance repertoire of MRSP. Potential targets identified by this work include membrane-bound beta-lactamase receptors responsible for the regulation of mecA, non-cognate auto-inducing peptides, and synthetic antisense oligonucleotides.

The objectives of this thesis were: (1) to evaluate the downregulation of the stallion hypothalamic-pituitary-gonadal (HPG) axis by a GnRH antagonist (acyline) based upon endocrine, seminal, testicular and behavioral effects, and (2) to assess recovery after treatment. Stallions were treated for 50 days (n=4; 330µg/kg acyline q 5d) and controls (n=4) received vehicle alone. Stallions were assessed pre-treatment and for 72 days after last treatment. Treatment induced declines (p<0.05) in FSH, LH, testosterone (to castrate levels) and estrone sulfate. Gonadotropins and testosterone returned to control values within nine days and estrone sulfate by 14 days after treatment discontinuation. Acyline-treated stallions failed to respond with FSH, LH and testosterone increase after exogenous GnRH stimulation (25µg gonadorelin, IV) compared to pre-treatment and control stimulation. Total sperm numbers and motility were reduced in acyline-treated stallions, as well as total seminal plasma protein and testicular volume (p<0.05). Time to ejaculation was increased in acyline group (p<0.5). Testicular, sexual behavior and most seminal parameters regained normal levels within 72 days after treatment ceased. Sperm output of acyline-treated stallions was regained within seven months after ending treatment. Acyline reversibly suppressed the stallion HPG axis, thus has potential for treating the androgen-dependent Equine-Arteritis-Virus carrier state and as behavior modulator.

Cattle health and production records (CHPR) are data collected by cattle producers and veterinarians in the form of measurements, observations, counts of events over time, and physiologic attributes that describe individual and group-level health and production. These data are useful to both veterinarians and cattle producers for making evidence-based decisions on cow-calf operations. Currently, there are no uniform, industry-wide methods of capturing and recording CHPR in the U.S. cow-calf industry. Although many cow-calf producers in the U.S. are thought to collect some form of CHPR, it is believed that relatively few are doing so in an electronic manner that facilitates optimal use and analysis of those records. Technology offers many opportunities to collect, record, and analyze CHPR for decision-making on cow-calf operations, with smartphones having great potential as a point-of-care CHPR collection device. Little is known regarding 1) barriers faced by producers to collecting and using CHPR, 2) interest of U.S. cow-calf producers in using technology such as smartphones for collecting and recording CHPR, and 3) the role of veterinarians in the collection and use of CHPR on U.S. cow-calf operations. The first study included in this dissertation was a survey of the cattle health and production record-keeping methods of cow-calf producers in Mississippi. The second study in this dissertation was a survey of cow-calf producers across the U.S. regarding their methods and opinions of cattle health and production record-keeping, their access to technology for record-keeping purposes, current types of data being collected on cow-calf operations, and the role of veterinarians in record-keeping on those cow-calf operations. The third study in this dissertation was a demonstration of common epidemiologic and biostatistical skills needed by veterinary practitioners to analyze CHPR and provide quality, evidence-based management recommendations to their cow-calf clients.