The humerus of a racing horse Thoroughbred is highly susceptible to stress fractures at a characteristic location as a result of cyclic loading. The propensity of a Thoroughbred to exhibit humeral fracture has made equines useful models in the epidemiology of stress fractures. In this study, a racing Thoroughbred humerus was simulated during training using a 3D finite element model in conjunction with a bone remodeling algorithm. Nine muscle forces and two contact forces were applied to the 3-dimensional finite element model, which contains four separate load cases representing fore-stance, mid-stance, aft-stance, and standing. Four different training programs were incorporated into the model, which represent Baseline Layup and Long Layup training programs along with two newly implemented programs for racing, which have an absence of a layup period, last a period of 24 weeks, and a race once every four weeks. Muscle and contact forces were rescaled for all load cases to simulate dirt, turf, and synthetic track surfaces. Bone porosity, damage, and BMU activation frequency were examined at the stress fracture site and compared with a control location called the caudal diaphysis. It was found that race programs exhibited similar remodeling patterns between each other. Damage at the stress fracture site and caudal diaphysis was reduced during all training programs for the turf and synthetic track surfaces with respect to the dirt track surface. Key findings also included changes in bone remodeling at the stress fracture site and caudal diaphysis as a result of turf and synthetic track surfaces. This model can serve as a framework for further studies in human or equine athletes who are susceptible to stress fractures.

As keeping backyard poultry rises, human contact with zoonotic pathogens will increase. One such pathogen that backyard enthusiasts have exposure risks to is Salmonella spp. which may cause a potential public health threat due to its increasing multidrug resistancy. Salmonella spp. were present in 33 of 50 samples collected from 29 sites with backyard poultry coops in San Luis Obispo County during March to May in 2014. Two different Hardy-CHROME™ Salmonella Selective Media plates were used to culture and isolate positive samples of Salmonella spp.. Each positive isolate was tested for antimicrobial sensitivity to 6 standard antibiotics: Ampicillin, Bacitracin, Erythromycin, Gentamicin, Penicillin, and Tetracycline, at the standard disk concentration levels. The Kirby-Bauer antimicrobial sensitivity test determined that 12 different profiles emerged from the Salmonella spp. isolates. All antimicrobial sensitivity profiles showed multidrug resistance in vitro with only high susceptibility to 2 major antibiotics, Gentamicin at 97% and Ampicillin at 51%. All profiles were resistant to 1 or more of the antimicrobials tested, plus the control. One Salmonella isolated was resistant to all 6 antimicrobials and another isolate to 5. The Salmonella spp. isolates proved multidrug resistance between 73%-100% to the other 4 antibiotics tested. The 24 Salmonella spp. positive sites displayed a lack of proper biosecurity and poultry husbandry practices. The criteria developed for accessing the poultry’s environment ranged from dedicated shoes for cleaning, egg handling, access to other animals and wildlife, number of birds and breeds or species in a coop, cleaning routine, over-all biosecurity and human interactions. Human exposure to Salmonella spp. pathogenic strains could increase due to environmental cross contamination and deficiencies in sanitation. The presence of Salmonella spp. with a diversity of antibiotic resistance serotypes is an important source of zoonotic pathogens for animal and human diseases that has public health risk implications.

Shelters often make euthanasia or adoption decisions based on the results of FeLV-FIV point-of-care tests but given the low estimated prevalence of these diseases and imperfect test performance, this might not be a good practice because of diagnostic error. The objectives of this study were to determine the true prevalence of FeLV and FIV in apparently healthy and sick shelter cats in Mississippi, estimate predictive value of the Zoetis Witness FeLV-FIV Rapid ImmunoMigration test results at the estimated true prevalences through Bayesian latent class modeling, and formulate testing recommendations for shelters. One chapter will review the literature on FeLV and FIV. The bulk of this thesis will focus on determining the true prevalence of retroviral infection in Mississippi shelter cat populations. The last chapter will use Bayesian modeling to estimate test performance and predictive value of test results in healthy and sick shelter cat populations.

Tick populations have been immigrating into northeast Tennessee from east Tennessee, Kentucky, Virginia, and North Carolina. Counties in states bordering northeast Tennessee harbor tick species associated with human illness. Human diseases transmitted by ticks include ehrlichiosis, spotted fever rickettsial group diseases, tularemia, anaplasmosis, babesiosis, Lyme disease, alpha-gal syndrome, Heartland virus, Powassan virus, and southern tick-associated rash illness (STARI). These diseases cause morbidity and mortality in human populations and may pose a high risk to individuals, wildlife, and livestock. The Cherokee National Forest covering the east Tennessee border provides a permissible environment for ticks to immigrate and thrive. Residents of northeast Tennessee frequently use the natural environment for a variety of purposes, creating exposure risk at the human-animal-environment interface. This study performed a scoping review and meta-analysis addressing topics informing epidemiological investigation of tick populations. The meta-analysis identified geography, climate, and Shannon-Wiener Diversity Index as the most significant variables associated with northeast Tennessee tick populations. Additionally, tick surveillance in northeast Tennessee counties was performed. These counties included Carter, Greene, Hancock, Hawkins, Johnson, Washington, and Unicoi. Primary tick species present in the summer included the American Dog tick (Dermacentor variabilis); the winter included the Blacklegged/Deer tick (Ixodes scapularis). Canonical correlation analysis was used to identify which environmental variables had the most influence, to what degree, and in a positive or negative direction. Altitude, total forest land, forest canopy, and fraction of surface water area were statistically significant. More altitude was correlated with more clinical cases; less total forest land, canopy, and fraction of surface water area was correlated with less clinical cases. Lastly, species distribution modeling of the invasive Asian longhorned tick was conducted. Study results indicate a low to moderate risk for tick-borne illness exposures among human populations, which is poised to increase. Species distribution modeling and clinical case data reports suggested an increasing exposure risk from improved habitat suitability. Increased risk is related to climate change and tick population growth in metropolitan areas. Finally, surveillance and control methods are summarized for integration into public health interventions.

To increase capacity for monitoring and surveillance of tick-borne diseases, publicly available tick distribution and climate change datasets are required to create accurate predictive distribution models. It is difficult, however, to assess model accuracy and utility when using incomplete datasets.  The more recent development of comprehensive tick databases for Europe and availability of climate change scenarios from multiple IPCC Assessment Reports allows for improved modeling efforts. Multiple tick datasets were combined and three climate change projections were compared by predicting current and future distributions of Ixodes ricinus ticks in Europe using the MaxEnt species distribution model. Overall, much of Europe contains suitable habitat for the Ixodes ricinus tick, both now and under future climate change projections.  Contraction of habitable areas is predicted to occur at lower latitudes and altitudes, while expansion is predicted to occur at higher altitudes in mountainous regions and the higher latitudes, primarily in northern Scandinavia.

Human body lice, Pediculus humanus humanus, and head lice, Pediculus humanus capitis, have been hematophagous ectoparasites of humans for thousands of years. Despite being ecotypes, only body lice are known to transmit bacterial diseases to humans, and it appears that lower humoral and cellular immune responses allow body lice to possess a higher vector competence. We previously observed that the transcription level of the defensin 1 gene was up-regulated only in head lice following oral challenge of Bartonella quintana, a causative agent of trench fever, and also that body lice excreted more viable B. quintana in their feces. In this study, we first investigated this differential immune response by performing RNAi to knockdown defensin 1 by dsRNA injection. B. quintana was orally infected 72 h after injection and proliferation was compared at 2 hours (day 0) and day 4 post-infection. At day 0, bacterial cell numbers increased 1.5-fold in defensin 1 (Def1(-)) knocked down head lice compared with non-knocked down, pQE30-dsRNA injected, head lice control. At day 4, Def1(-) knocked down head lice had 2.55-fold more bacterial cells than control head lice and 1.65-fold greater than body lice, indicating that defensin 1 was active in reducing B. quintana cell number in non-knocked down head lice. Second, the levels of cytotoxic reactive oxygen species (ROS) generated by the epithelial cells of the alimentary tract were measured using two general indictors of ROS in both body and head lice at day 1 and day 4 following B. quintana challenge. Challenged body lice showed a 42% and 34% increase in ROS, whereas head lice showed a 70% and 22% increase at day 1 using CM-H2DCFDA and HPF as general indicators, respectively. On day 4, all challenged lice showed similar ROS levels except for body lice which maintained their ROS levels (40% increase using CM-H2DCFDA). Head lice are likely to have multiple immune and/or non-immune factors that suppress B. quintana proliferation, and the production of sustained ROS levels and/or the single knockdown of Defensin 1 is not enough to increase B. quintana proliferation in head lice to that seen in body lice.