Theses and Dissertations

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Open Access
A holistic approach to veterinary public health in animal shelters and other sites
(Colorado State University. Libraries, 2009) Steneroden, Kay K., author; Salman, M. D., advisor; Hill, Ashley E., advisor
Animal health and human health are intimately linked. Directly, through contact with or exposure to animals and their environments, and indirectly by way of food production, food safety and antimicrobial drug residues, humans are dependent upon and vulnerable to the health of animals. Veterinary public health is concerned with the interface of human and animal health and addressing problems at that interface. The potential impact of such exploration is greater human and animal health. Epidemiological needs assessment, problem investigation and subsequent outreach programs are essential tools of veterinary public health practice. These tools are used to explore infection control, infectious and zoonotic disease awareness, environmental contamination with infectious/zoonotic agents and monitoring the consequences of treatment of infectious and zoonotic diseases with antimicrobial drugs (i.e. antimicrobial drug resistance). The specific venues for these explorations for this dissertation include animal shelters, a veterinary teaching hospital, a former Soviet country and a United States governmental program. A holistic approach is used with animal shelters to assess infection control and zoonotic disease awareness needs, investigate environmental contamination with a zoonotic disease, develop training tools and train animal shelter workers and volunteers. The needs assessment provided valuable information on characteristics of animal shelters, provided impetus for the problem investigation and the basis for outreach training. The problem investigation tool provided the first available information on the prevalence and extent of salmonella contamination in Colorado animal shelters. The outreach components provided a tool and reference for training; the training itself indicated gaps in knowledge in various aspects of infection control and zoonotic disease awareness that could be addressed with training. Further, problem investigation is explored through the success of active surveillance in discovery and control of a zoonotic disease outbreak in a veterinary teaching hospital. Results of a needs assessment survey in the Republic of Armenia provide the basis for development of outreach materials for veterinarians, farmers and school-age children on their national animal health program. And a system of antimicrobial drug resistance monitoring is examined and challenged for completeness. Taken together, these studies further the examination of veterinary public health issues and highlight a holistic approach to their exploration.
Open Access
A study of factors associated with Giardia and Cryptosporidium infections in humans, dogs and cats in the USA
(Colorado State University. Libraries, 2016) Thigeel, Hanaa, author; Lappin, Michael, advisor; Olea-Popelka, Francisco, advisor; Twedt, David, committee member; Hyatt, Doreene, committee member
Giardia spp. and Cryptosporidium spp. are two of the leading causal agents of parasitic diarrhea in humans, dogs and cats. The two pathogens contain both host-adapted and zoonotic strains and dogs and cats can harbor both strains. There is critical need to understand factors potentially associated with the risk and prevalence of infection due to Giardia spp. and Cryptosporidium spp. in dogs, cats and humans. This will ultimately aid in disease management and control. Furthermore, molecular characterization of the human, dog or cat isolates may identify zoonotic genotypes and may provide further information concerning the transmission routes between humans, dogs and cats. In Chapter 1, a review of literature regarding Giardia duodenalis and Cryptosporidium spp. in humans and companion animals (dogs and cats) was conducted. The review involves a brief description of the two pathogens’ current taxonomy, epidemiology, and diagnostic methods. Chapter 2 presents a retrospective study designed to analyze results from dog and cat polymerase chain reaction (PCR) panels from the commercial laboratory, ANTECH Diagnostics. The main purpose of this study was to evaluate associations between the probability of testing positive to Giardia spp. and Cryptosporidium spp. and risk factors such as animal’s age, sex, region, and season. The results of this study showed that age (younger animals) was significantly associated with the risk of PCR positive results for Giardia spp. and Cryptosporidium spp. in both dogs and cats. Region was significantly associated with Cryptosporidium spp. in both dogs and cats, whereas season was only associated with Giardia spp. in dogs. Chapter 3 describes the validation and optimization a previously published 60 kDa glycoprotein (gp60) gene-based PCR assay. The objective of this study was to use the assay to subtype C. parvum and C. hominis isolated from human fecal samples. The analytical sensitivity of this PCR assay was determined by assaying serial dilutions of C. parvum oocysts and C. hominis DNA. The analytic specificity was determined by assaying Cryptosporidium and non-Cryptosporidium spp. DNA. The gp60 PCR assay consistently detected DNA of C. parvum if oocysts were present at 104/mL. The assay was detected the DNA of C. hominis in the lowest concentration. In Chapter 4, a prospective study was conducted to assess the risk of factors potentially associated with Giardia duodenalis and Cryptosporidium spp. infections and estimate the prevalence of these two pathogens in senior veterinary students and their pet dogs and cats. A structured questionnaire was developed to assess a baseline exposure of the students to large and small animals. In addition, a single voluntary sample was requested from students and their dogs or cats that live within the household. Giardia duodenalis and Cryptosporidium spp. were detected by the PCR and immunofluorescence (IFA) assays in students and their dogs and cats. As a result of the recruitment, 51 surveys, 42 human fecal samples, 31 dog fecal samples, and 17 cat fecal samples were collected. Clinical rotation, track preference, gender, pet ownership and farm exposure were factors selected to be evaluated for the risk of both pathogens in senior veterinary students. As a result of this evaluation, none of these factors selected was statistically associated with the risk of infection due to G. duodenalis or Cryptosporidium spp. All Giardia isolated from dogs were host-adapted assemblages. However, a zoonotic Cryptosporidium genotype (C. parvum subtype family IIa) was identified in one human sample. The analysis conducted in this dissertation provided an evaluation of potential risk factors associated with giardiasis and cryptosporidiosis in pet dogs and cats. The results of this research enhanced the understanding of the disease prevalence of Giardia spp. and Cryptosporidium spp. among senior veterinary students and their dogs and cats. The survey collected valuable and novel information on the students’ characteristics, student health status, their pets’ health status and activities that may have led to an increased risk of infection during their clinical rotations or intense handling of small or large animals. The analysis of the survey provided an evaluation of potential risk factors associated with the risk of infection in senior veterinary students. Molecular analysis of isolates of human, dog and cat origin helped in differentiating between G. duodenalis assemblages and Cryptosporidium spp. genotypes. Future directions may include an evaluation for associations of positive test results with clinical findings and further studies determining the likelihood dogs or cats are carrying zoonotic Giardia spp. or Cryptosporidium spp.. National research is recommended to be conducted to identify risk factors in veterinary students from different states in the United States. Additionally, a larger study should be performed to determine the baseline exposure of veterinary school faculty, specifically, those who work on large animal rotations and collect fecal samples from their pet dogs and cats to for genotyping to detail whether zoonotic infections with these two protozoans occur.
Open Access
A study of small-scale farms in the United States: characteristics and practices relevant to animal disease prevention and control
(Colorado State University. Libraries, 2013) Beam, Andrea, author; Olea-Popelka, Francisco, advisor; Van Metre, David, committee member; Thilmany, Dawn, committee member; Garber, Lindsey, committee member
To view the abstract, please see the full text of the document.
Open Access
A systemic review of brucellosis in the Kakheti region of the country of Georgia: an evaluation of the disease ecology, risk factors and suggestions for disease control
(Colorado State University. Libraries, 2011) Havas, Karyn Alicia, author; Salman, Mo D., advisor; Hill, Ashley E., committee member; Magennis, Ann L., committee member; Callan, Robert J., committee member; Gillette, Shana C., committee member
To view the abstract, please see the full text of the document.
Open Access
Accounting for productive time lost in dairy cattle: disease adjusted lactation
(Colorado State University. Libraries, 2016) McNeil, Ashleigh Ann, author; McConnel, Craig S., advisor; Garry, Franklyn B., committee member; Hadrich, Joleen C., committee member; Lombard, Jason E., committee member
Dairy cow mortality, morbidity, and poor welfare have been of increased concern over the past several decades. Traditionally, dairy farm management has focused on singular costs associated with pathologies without thoroughly quantifying losses tied to disease and consequent death or culling. Within human epidemiology, the economic burden of time lost due to ill-health or early death is measured through the World Health Organization's disability adjusted life years (DALY). This project utilized the DALY concept to estimate time lost during a lactation due to disease and subsequent early removal of dairy cows. This was accomplished through the development of the disease adjusted lactation (DALact) metric. The DALact is calculated by combining days lost due to illness or injury (DLI) and days lost due to early death or removal (DLRD). The DLI reflects the number of cases during a certain period, multiplied by a disability weight and specific disease duration. The DLRD is comprised of two components: days lost due to death, and days lost due to culling from a given disease. Disability weights for 13 common dairy cow diseases were derived from an international expert opinion survey of dairy producers, managers and veterinarians. The selected disease states included: calving trauma, diarrhea, ketosis, lameness, left displaced abomasum, mastitis, metritis, milk fever, musculoskeletal injury, pneumonia, right displaced abomasum, and retained placenta. Survey participants were asked to estimate the impact of each disease on overall health and milk production. Diseases were classified from 0 (no adverse effects) to 10 (terminal). Validity and scope of participants' responses were assessed using a modified beta-Pert distribution and median points were used to provide disability weights for the DALact calculation. To support development of the DALact, collection of disease and removal data from three Kansas dairy farms representing 9,000 Holstein cows began January 1, 2014 and ended on May 26, 2015. A total of 7,233 cows were enrolled in the study across the three dairies. DALact measures were calculated using disease, culling and death data for each disease state while combining the disability weights, duration, and average days in milk at time of removal. Mastitis accounted for the largest category on all three dairies representing 29,779, 23,917, and 36,183 days lost for Dairies 1, 2, and 3, respectively. Conversely, prevalence of mastitis was largest on only Dairy 1 (33%). Lameness was the second largest DALact category for Dairies 2 (9,934) and 3 (29,912) but not for Dairy 1 (pneumonia, 13,571). Prevalence for lameness was largest (35%) for Dairies 2 and 3. The DALact method confirmed that mastitis and lameness are areas of focus, but also highlighted that pneumonia is a primary concern on Dairy 1. The DALact aims to provide an assessment of the complete impact of mortality and morbidity on time lost in dairy cattle. The end result will be to validate the effectiveness of dairy health oversight and to determine where to focus management to reduce the number and economic impact of preventable removals and diseases while increasing animal welfare.
Open Access
Acurracy assessment of four diagnostic tests for the detection of Giardia and Cryptosporidium in the absence of gold standard: a Bayesian approach
(Colorado State University. Libraries, 2014) Palomares Velosa, Jairo Enrique, author; Salman, Mo D., advisor; Ballweber, Lora, committee member; Lappin, Michael, committee member
Giardia and Cryptosporidium are important parasites that cause gastrointestinal disease in numerous animal species including dogs and cats. The accurate diagnostic of this diseases is cucial for the aplication of preventive measures and precise treatment. Estimation of test accuraccy is not difficult when a reference test (gold standard) is available. However, when a gold standard test is not available the Bayesian Latent Class (BLC) Analysis is an effective analytical tool for the estimation of diagnostic accuracy. The aim of this study was to estimate the sensitivity (Se) and specificity (Sp) of four commercial diagnostic kits using BLC. The four diagnostic tests were (1) Merifluor®Direct Fluorecence Antigen (DFA; Giardia/Cryptosporidium; Meridian Diagnostics, Inc., Cincinnati, Ohio), (2) IVD®DFA (Giardia/Cryptosporidium; IDV Research Inc., Carlsbad, CA), (3) IVD Microwell ELISA® (Giardia ; IDV Research Inc., Carlsbad, CA), (4) and IDEXX SNAP® (Giardia ; IDEXX Laboratories Inc., Westbrook, ME). The results from 201 laboratory analysed samples, the prior distributions elicited from three experts, and the consistency of samples as splitting covariate were used as inputs for the BCL models. The estimated Se and Sp of the tests were 87.7% and 97.3% (Merifluor-Cryptosporidium), 68.0% and 99.1% (IVD-Cryptosporidium), 93.6% and 97.9% (Merifluor-Giardia), 96.1% and 97.9% (IVD-Giardia), 86.0% and 98.2% (ELISA-Giardia), and 84.8% and 98.0% (SNAP-Giardia) respectively. The prevalence for non-diarrheic versus diarrheic samples were 2.3% and 4.8% (Cryptosporidium), and 6.9% and 13.5% (Giardia) respectively. We were able to use BLC to assess the sensitivity and specificity of the four commercial diagnostic tests. We ran 36 models and used objective indicators of the performances of the models to choose the best model for estimation of parameters. The results of the study indicated that Merifluor, IVD, and ELISA are equally suitable as diagnostic tests for detection of Giardia. For detection of Cryptosporidium, Merifluor was more accurate than the IVD test.
Open Access
An evaluation of estrus suppression in the mare through the use of an altrenogest delivering intravaginal device
(Colorado State University. Libraries, 2022) Lederman, Jessica Danielle Ruth, author; Hatzel, Jennifer, advisor; Easley, Jeremiah, committee member; Hollinshead, Fiona, committee member; Bouma, Jerry, committee member
The ability to avoid adverse behavior in mares through manipulation of their reproductive cyclicity has been a desired technique for many years. The mare's sour reputation when in heat, is known by competitive professionals and hobby riders alike. As the breeding season approaches during long daylight days in the northern hemisphere, the mare will begin to transition into her regular twenty-one day interovulatory cycle. The estrus or "standing heat" phase of a mare's cycle occurs for approximately 5-7 days within a given estrous cycle. During this phase, the mare is primarily under the influence of estrogen, produced by the dominant follicle, driving signs of the sexual receptivity. Outward signs of estrus for the mare include: overt interest in other horses (especially stallions), leaning their hind end toward another horse (teasing), lifting their tail, posturing and urinating frequently. Dangerous behaviors associated with estrus such as biting, kicking, irritability, and distraction commonly persuade owners to look into estrus suppression options. Following ovulation, a corpus luteum (CL) is formed and the luteal cells begin to produce progesterone. Progesterone levels increase once again, overcoming the effects of decreasing estrogen levels for twelve to fourteen days, and often alleviating the undesirable behavior. Altrenogest, an oral and injectable synthetic progestin, is the most effective supplement for providing estrus suppression in the mare. The equine industry is in need of a reliable pharmaceutical device to suppress adverse behavior commonly associated with the estrus phase of the mare's cycle, yet allow the mare to resume normal cyclicity upon removal of the device for pursuant of reproductive procedures. A custom intravaginal ring specifically designed for the unique anatomy of the mare will provide a novel and effective method for sustained release of altrenogest administration while being safer to handle and administer. The first experiment focuses on the unique anatomy of the mare's caudal reproductive tract compared to intravaginal ring sizes in order to obtain a pilot device for experimentation. An unmedicated toroidal silicone intravaginal ring measuring 14.2 cm in diameter was selected during experiment one. The second experiment was to evaluate the vaginal ring delivering altrenogest in a trial along with a placebo intravaginal ring and control group to evaluate several parameters associated with estrus behavior suppression. Both oil-based and solid suspension-based intravaginal rings for drug administration was evaluated during experiment two. Finally, the third experiment examined the in vivo evaluation of solid suspension altrenogest IVR as well as the marketability of this product and what the future holds for novel medical devices in equine reproduction. Twelve total mares were used over the course of this study to determine the pharmacokinetics (PKs) and pharmacodynamics (PDs) of intravaginally administered altrenogest. Variables such as: teasing behavior when presented with a stallion, ultrasonographic examination of reproductive changes throughout several cycles, uterine and vaginal cultures, and blood collections for drug hormone bioanalysis were collected and monitored to evaluate the PK and PD of this novel drug delivery device. Throughout experiment three, each mare went through three cycles in a crossover design. An oral form of the drug was administered to serve as a control group, a placebo vaginal ring control group, and therapeutic vaginal ring treatment group were used for this study. This study aims to provide horse owners and trainers an alternative method for delivering behavior modulating hormones, through an effective, therapeutic, steady-state release from a vaginal ring, and importantly enable normal reproductive cyclicity to resume upon removal.
Open Access
Antimicrobial resistance surveillance in feedlot cattle
(Colorado State University. Libraries, 2011) Benedict, Katharine M., author; Morley, Paul S., advisor; Booker, Calvin W., committee member; Van Metre, David C., committee member; Basaraba, Randall J., committee member
Objectives: To develop and validate methodological components of a model for surveillance of antimicrobial use and resistance in feedlot cattle. Methods: A web-based survey of participants knowledgeable and interested in antimicrobial use in beef feedlots was used to solicit responses regarding appropriate metrics for quantifying, analyzing, and reporting antimicrobial exposures. The accuracies of two susceptibility tests commonly recommended for surveillance programs were determined using stochastic latent class analysis. Multivariable logistic and linear regression was used to investigate associations between exposures to antimicrobial drugs and antimicrobial resistance. Results: When reporting antimicrobial use in the context of antimicrobial resistance, survey participants believed that the Animal Defined Daily Dose metric was the most accurate. The two susceptibility tests investigated had comparable accuracies for the antimicrobial drugs tested. Exposure to parenteral tetracycline in the study feedlots was associated with resistance to tetracycline; however, exposures to all other classes of antimicrobials were not associated with antimicrobial resistance. Conclusions: Appropriate metrics for reporting and analyzing antimicrobial resistance are necessary to accurately investigate associations between use and resistance, though clarity of what the metric represents may be lost. Testing of susceptibility in surveillance programs is equally valid by way of disk diffusion testing. Multivariable logistic regression was an appropriate and useful method to investigate associations between use and resistance. Parenteral exposures to antimicrobials did not drive antimicrobial resistance at mid-feeding period.
Open Access
Assessment of novel causes and investigation into the gut microbiome in cats with chronic kidney disease
(Colorado State University. Libraries, 2020) Summers, Stacie, author; Lappin, Michael, advisor; Quimby, Jessica, committee member; Dow, Steve, committee member; Prenni, Jessica, committee member
To view the abstract, please see the full text of the document.
Open Access
Assessment of novel strategies for the prevention and treatment of feline upper respiratory tract infections in shelters and feline herpesvirus-1 in laboratory settings
(Colorado State University. Libraries, 2019) Contreras, Elena T., author; Lappin, Michael R., advisor; Olea-Popelka, Francisco J., committee member; Dow, Steven W., committee member; Mayo, Christie E., committee member; Veir, Julia K., committee member
Feline upper respiratory tract infection (URI) and its pathogens are ubiquitous in the feline population. Most URI cases are due to viral infections with feline herpesvirus-1 (FHV-1) and/or feline calicivirus (FCV) with secondary bacterial infections. After acute exposure to FHV-1, most cats develop persistent, latent infections with reactivation particularly during times of stress and immune suppression. Clinical signs including ocular and nasal discharge, sneezing, conjunctivitis, anorexia, lethargy, and pyrexia can vary in severity from mild and transient to severe and life-threatening. Preventive measures such as vaccination, stress reduction, environmental modifications, and infection control have lessened illness, recurrence, and spread, and many successful therapies such as antibiotics for secondary bacterial components, systemic and ocular antivirals for FHV-1, supportive care, and non-specific immune stimulation have helped to reduce the severity of illness and decrease mortality in cats. Despite these advancements in management strategies, many cats and kittens continue to suffer from URI, and those in crowded environments continue to become severely ill and either die or are euthanized. Furthermore, many animal shelters still lack information and resources regarding successful implementation of URI prevention and treatment protocols, and thus URI remains one of the most common medical reasons for euthanasia in shelters. This syndrome results in poor quality of life, and extended lengths of stay in shelters can lead to high financial burdens. Further work is needed to better understand the pathogenesis of the syndrome as well as improved preventives and treatments. The goals of the work described in this dissertation were to evaluate novel preventive and treatment strategies to decrease the incidence and severity of URI in shelters and with an emphasis on FHV-1 in experimental studies. This body of work was conducted in both the controlled research environment as well as in the animal shelter environment. Chapter 1 provides an overview of URI with a specific focus on FHV-1 and FCV and Chapter 2 presents the brief research objectives for each of the studies in this body of work. Three of the studies (Chapters 4, 5, and 7) in this body of work evaluated novel immune stimulants and preventive measures for primary FHV-1 infection and recrudescent FHV-1 in purpose-bred, experimentally infected cats in a controlled research setting. Chapter 4 evaluated a plant-based nutraceutical, Carnivora™, with anti-inflammatory and immune modulating components and its effects on recrudescence of clinical signs and viral shedding in young adult cats upon repeat challenge of FHV-1. Our study found that cats that were administered Carnivora™ had significantly less clinical manifestations of FHV-1 disease when compared to the control group. Chapter 5 assessed a new mucosal formulation of a liposomal toll-like receptor immune stimulant (LTC) as both a preventive and treatment for FHV-1 in purpose-bred kittens. This study found that administration of LTC as a preventive 24 hours prior to FHV-1 challenge resulted in some positive clinical effects and decreased shedding of FHV-1 DNA, whereas administration of LTC as a treatment during illness with FHV-1 did not influence clinical course of FHV-1 illness. Chapter 7 explored the use of a pheromone product in these same purpose-bred kittens and its effects on stress reduction, relaxation, and recrudescence of FHV-1 clinical signs. Results indicated that the pheromone product decreased stress, increased relaxation, and decreased some of the clinical signs of FHV-1 recrudescence in the kittens. Two of the studies (Chapters 3 and 6) evaluated novel immune stimulants and preventives in open-admission shelter environments. Chapter 3 explored whether the addition of an inactivated, broader spectrum FCV vaccine to a standard vaccination protocol at a shelter, would result in decreased incidence, duration, and severity of URI and oral ulceration in cats. The study did not find evidence that the additional vaccine protected cats from developing URI, severe URI, or oral ulceration indicative of calicivirus. Chapter 6 evaluated administration of the LTC discussed in Chapter 5 to cats in an open-admission shelter. Cats were administered the LTC upon admission to determine whether it would result in decreased incidence and severity of URI. The study did not find significant evidence that the LTC protected cats from developing URI or severe URI in the shelter, nor did it significantly impact clinical course of illness. Although neither of the shelter experiments had significant findings regarding the preventive product being tested, results provided additional important information regarding immune compromise and potential for immunomodulatory therapeutics and stimulation in the shelter environment, risk factors contributing to URI onset, timing, prevalence, severity, and outcomes in shelter environments. The work described in this dissertation has increased our knowledge of FHV-1 preventive and treatment options and mitigating and risk factors that might contribute to URI occurrence, recrudescence, and resolution. We hope that the findings in this work will help to decrease prevalence and severity of URI and improve the outcome for cats and kittens with URI, especially in the shelter environment.
Open Access
Assessment of the introduction and spread of highly pathogenic avian influenza (H5N1) in Thailand: application of market chain analysis of poultry and the use of community-based disease prevention strategies
(Colorado State University. Libraries, 2013) Limhapirom, Patchara, author; Salman, Mo, advisor; Keefe, Thomas, committee member; Wongsathapornchai, Kachen, committee member
An analysis of the market chain and trade pathway for the small poultry production system was conducted in Ban Klang Subdistrict, Nakhon Phanom Mueang District, Nakhon Phanom Province, Thailand. The aim of the study was to determine the risk of highly pathogenic avian influenza (HPAI/H5N1) introduction and transmission along the poultry market chain, and then apply a community-based approach to prevent the introduction and spread of H5N1 along the identified chain. The focus was on the layer market chain because an outbreak of HPAI was reported 24 July 2006 at a layer farm in Banklang Subdistrict. Six human patients were suspected to be infected with Avian Influenza virus (AI), but no cases were reported after the surveillance was initiated (MOPH 2006). A cross-sectional analysis method was used to identify the poultry market chain and assess the risk of introduction and transmission of AI along that chain. For linking actors along the poultry market chain, the snowball sampling method was used. The data were collected by using a structured questionnaire and applying focus discussion group activity (FDG), which is part of the community-based approach, to the high-risk actors in the poultry market chain. Participants' level of knowledge, attitude and practice behaviors (KAP) regarding AI was assessed, as well as the risk of AI in the poultry market chain. From three layer product pathways—eggs, spent hens and disposal of layer manure—the findings demonstrated that the spent hens and disposal of layer manure are higher-risk pathways for the introduction and transmission of HPAI than the egg products pathway. The farmers (producers) have the highest risk of contracting the AI virus because of their constant proximity to poultry, while traders have the highest risk of transmitting the AI virus along the layer market chain as their business requires moving from farm to farm. A survey of KAP regarding AI showed that the majority of farmers had a high level of knowledge and positive practice behaviors. This was compared to traders where more than half had only moderate to low knowledge, and positive practice behaviors. The majority of farmers and traders, however, had a positive attitude toward policies of prevention and control of HPAI through a surveillance system in their community. The FDG demonstrated that other actors expected an efficient HPAI prevention system at the producer level. The results of this study showed that community involvement in an HPAI surveillance system should be considered for all related actors in the poultry market chain. In order to be effective, the policies should be followed and periodically monitored for compliance.
Open Access
Biomarkers of disease progression and chemotherapeutic resistance in canine osteosarcoma
(Colorado State University. Libraries, 2011) O'Donoghue, Liza E., author; Duval, Dawn L., advisor; Thamm, Douglas H., committee member; Bouma, Gerrit J., committee member; Weil, Michael, committee member
Osteosarcoma is the most common primary bone malignancy in both humans and dogs. Over 10,000 canine patients develop this highly aggressive cancer annually and many succumb to metastatic disease in less than a year. In recent years, canine osteosarcoma has been increasingly recognized as an excellent model for the disease in humans, especially with regard to the molecular biology of the disease. Thus, research targeted at canine osteosarcoma benefits not only dogs but the field of human oncology as well. Research into the genetic and molecular derangements of osteosarcoma in both species has identified a number of oncogenes and tumor suppressor genes that may contribute to tumorigenesis. Additionally, some mediators of invasion and metastasis have been recognized (e.g. Ezrin, matrix metallopeptidases). Despite this, only a limited number of studies have been performed that examine the molecular genetics of osteosarcoma in the context of patient outcome. Thus, with the aim of identifying new target genes and pathways that contribute to disease progression and chemoresistance in osteosarcoma, we first performed transcriptomic and genomic analyses of primary tumors from dogs that had experienced good or poor outcomes following definitive treatment for osteosarcoma. These broad survey experiments yielded a selection of targets for future investigation. To further focus in on the genes that were most deranged from "normal" expression patterns, we compared gene expression patterns from tumors to those of normal bone. This study provided valuable perspective on genes that were identified in the outcome-based experiments, allowing selection of four promising gene targets to pursue. We next set out to validate in vitro models of canine osteosarcoma so that mechanistic studies could be pursued. Assays to test species and short tandem repeat identity were adapted to cell lines in use in our facility and presumed osteosarcoma cell lines were verified to be bone-derived via PCR testing of a bone-specific marker. Additionally, four anti-human antibodies were validated for use in canine samples. Two genes whose expression progressively altered with increased tumor aggressiveness where chosen for further study: insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1) and n-Myc downstream regulated gene 2 (NDRG2). IGF2BP1 has been identified as an oncofetal protein and its mRNA was strongly overexpressed in patients with the worst outcome while it was virtually undetectable in normal bone. We identified one possible mechanism for dysregulation of this gene in OSA and we also discovered that knock down of this gene in a canine osteosarcoma cell line inhibited cell invasion. NDRG2 has been dubbed a tumor suppressor in a number of different tumor types yet had not been previously investigated in osteosarcoma. We found NDRG2 mRNA to be underexpressed in all tumors relative to normal bone; patients with poor outcomes had the lowest expression levels. Multiple isoforms of the gene were found to be expressed in canine samples: these were cloned and transfected into a low-NDRG2-expressing cell line. Exogenous expression of NDRG2 in this in vitro system enhanced sensitivity to doxorubicin, one of the drugs most commonly used to treat osteosarcoma. Additionally, three possible mechanisms of dysregulation of this gene were identified. The studies presented herein progress from fact-finding surveys to in-depth functional examination of two genes that likely contribute to osteosarcoma invasion and chemoresistance. Furthermore, additional genes identified in our survey experiments offer promise for future studies into molecular mechanisms of osteosarcoma metastases and chemotherapeutic resistance. Finally, these studies have laid the groundwork for the development of gene-expression-based prognostic screens for dogs with osteosarcoma.
Open Access
Bovine tuberculosis slaughter surveillance in the United States: assessment of its trace-back function 2001-2010
(Colorado State University. Libraries, 2012) Mann, Heather, author; Olea-Popelka, Francisco, advisor; Orloski, Kathleen, committee member; Salman, Mo, committee member; Basaraba, Randall, committee member
The detection of gross bovine tuberculosis (bovine TB) lesions in cattle at slaughter and the successful trace-back to the herd of origin is critical to the detection of infected herds and for the progress of the national bovine TB eradication program in the United States (U.S.). A national animal identification system to identify and trace individual animals is currently under development in the U.S.; however, it is not yet fully implemented. In order to quantify the impact slaughter surveillance and traceability of bovine TB infected cattle has on the eradication of bovine TB from the cattle population in the U.S., this study was conducted with the aim to determine the ability of the current bovine TB slaughter surveillance system to trace infected cattle back to the herd of origin. Data obtained for the period 2001-2010, in which 386 bovine lesions were confirmed as bovine TB in the U.S., were used for this study. The specific objectives for this study were 1) to review and document the available literature related to the history of bovine TB control in the U.S., focusing primarily on the current method of disease detection (slaughter surveillance) and the impediments to eradication in the U.S., 2) to quantify the number of successful trace-backs of bovine TB infected animals to their herd of origin during 2001-2010 3) to quantify the number of trace-backs that found at least one bovine TB infected ("affected") herd, and 4) determine if selected factors were associated with the probability of successfully tracing infected animals and finding infected herds. The results of this study indicates that the odds of successful trace-backs are 7.06 times greater for cattle with official identification than without official identification (OR 95% CI: 1.66, 29.93, p-value =0.008). Additionally, the odds of successful trace-back are 15.47 times greater for adult cattle compared to fed cattle (OR 95% CI: 4.47, 53.48, p-value<0.001). Thus, application of official ID on all classes of cattle would increase the probability of successfully tracing bovine TB cases back to a herd of origin; however, under the current system it will not ensure a complete success in tracing bovine TB infected cattle to the herd of origin. While adult cattle are currently more likely to be traced back than fed cattle, it is worth noting that the effort and time required to find the herd of origin for both adult and fed bovine TB cases can be substantial and is highly variable. The results of this study provide an important tool to aid U.S. officials in their decision making with respect to the evaluation and implementation of strategies for the national bovine TB control and eradication program.
Open Access
Bovine tuberculosis surveillance at cattle abattoirs in Ireland, 2008
(Colorado State University. Libraries, 2017) Gompo, Tulsi Ram, author; Olea-Popelka, Francisco, advisor; Rao, Sangeeta, committee member; Henao-Tamayo, Marcela, committee member
Bovine tuberculosis (TB) surveillance is an ongoing program among abattoirs (slaughterhouses) in Ireland. It is a key complementary tool in addition to the tuberculin skin test to detect infected herds. A retrospective cross-sectional study was conducted to assess the association between potential risk factors and the risk of detection, and the subsequent risk of confirmation of bovine TB lesions for cattle slaughtered in 2008 in Irish abattoirs. Consequently, the abattoirs were ranked based on their efficiencies of detecting suspected bovine TB lesions and their subsequent confirmation in laboratory. A database containing cattle records was obtained from the Center for Veterinary Epidemiology and Risk Analysis (CVERA) at University College Dublin, Ireland, that includes the results of animal movements, tuberculin test results, number of suspected bovine TB lesions detected during slaughter of animals and number of lesions confirmed as Mycobacterium bovis (M. bovis) in laboratory. The known potential risk factors impacting bovine TB lesions detection in Irish abattoirs were animal and herd level characteristics: age, sex, herd type, length of time a herd free from bovine TB after restriction, animal origin and District Electoral Division (DED) risk class. The data were analyzed to control for these potential risk factors when assessing the probability of detecting suspected bovine TB lesions among abattoirs in Ireland. Descriptive analysis was performed to assess the distribution of cattle slaughtered over the different abattoir. Univariable logistic regression was applied to evaluate an association between the risk factors and detection of bovine TB lesions in the abattoirs. Multivariable logistic regression analysis was performed to calculate the adjusted risk of bovine TB lesion detection and confirmation for each abattoir. During 2008, a total of 1,362,195 attested cattle were slaughtered in total thirty-five abattoirs in Ireland. Overall, 3,437 lesions (0.25%, or 25 per 10,000 slaughtered cattle) were detected, and from these, 2,187 (62.68%) bovine TB lesions were confirmed as caused by M. bovis in the laboratory. The crude detection risks varied from 0 to 56 lesions per 10,000 animals slaughtered. The average crude confirmation risks ranged from 0 to 100%. Ultimately, the abattoirs were ranked (1 being the best and 35 the worst) according to their effectiveness of bovine TB lesions detection and confirmation after adjusting the potential risk factors. There is a considerable variability in efficiencies of Irish abattoirs in detecting and confirming bovine TB lesions. It is thus recommended that Irish abattoirs should be monitored regularly with regards their bovine TB slaughter surveillance effectiveness. Also, the abattoirs with lower than expected effectiveness should be strengthened in order to meet the required standards of the Irish bovine TB slaughter surveillance program.
Open Access
Cannabidiol induces apoptosis and perturbs mitochondrial function in canine and human glioma cells
(Colorado State University. Libraries, 2020) Gross, Chase, author; Gustafson, Daniel, advisor; McGrath, Stephanie, advisor; Regan, Daniel, committee member
Cannabidiol (CBD), the major non-psychoactive compound found in cannabis, is frequently used both as a nutraceutical and therapeutic. Clinical studies suggest CBD may be beneficial for treating rare forms of epilepsy and inflammatory conditions but despite anecdotal evidence as an anticancer agent, little is known about the effect it has on cancer cells. Given the intractability and poor prognoses of brain cancers in both human and veterinary medicine, we characterized the in vitro cytotoxicity of CBD on human and canine gliomas. Glioma cells treated with CBD showed a range of cytotoxicity from 4.9-8.2 μg/mL; canine cells appeared to be more sensitive than human. Treatment with >5 μg/mL CBD invariably produced large cytosolic vesicles. Next, the mode of cell death was interrogated using pharmacologic inhibitors. Inhibition of apoptosis was sufficient to rescue CBD-mediated cytotoxicity. Inhibition of RIPK3, a classical necroptosis protein, rescued cells from death and prevented the formation of the large cytosolic vesicles. Analysis of cell death by resazurin reduction showed much higher sensitivity than other cytotoxicity methods and suggested disruption of the mitochondria. Cellular mitochondrial activity in the presence of CBD was assessed and within two hours of treatment CBD reduced oxygen consumption in a dose dependent manner with almost complete ablation of activity at 10 μg/mL CBD. Fluorescent imaging with a mitochondrial-specific dye revealed that the large cytosolic vesicles were, in fact, swollen mitochondria. Lastly, calcium channels were inhibited and the effect on cell death was measured. Inhibition of mitochondrial channel VDAC1, but not the TRPV1 channel, rescued cells from CBD-mediated cytotoxicity. These results demonstrate the cytotoxic nature of CBD in human and canine glioma cells and suggest a mechanism of action involving dysregulation of calcium homeostasis and mitochondrial activity.
Open Access
Cartilage repair using trypsin enzymatic pretreatment combined with growth-factor functionalized self-assembling peptide hydrogel
(Colorado State University. Libraries, 2019) Zanotto, Gustavo Miranda, author; Frisbie, David D., advisor; Grodzinsky, Alan, committee member; McIlwraith, C. Wayne, committee member; Barrett, Myra F., committee member; Puttlitz, Christian, committee member
Treatment of cartilage defects remains challenging in the orthopedic field. Several techniques are currently available to treat cartilage defects, with subchondral bone microfracture being the most commonly used marrow stimulation technique. However, despite satisfactory results in the short-term, clinical and functional outcomes of microfracture treated patients tend to decline over time. Improving microfracture technique using tissue engineering principles may be a more attractive way to treat cartilage defects compared to other more complex and expensive alternatives. Self-assembling peptide hydrogel has been extensively studied as a scaffold for cartilage repair. This hydrogel is biocompatible within the joint environment and has been shown to increase cartilage healing and improve clinical and functional outcomes in both rabbit and equine models of cartilage repair. Recently, a clinically applicable technique was described using trypsin enzymatic pretreatment of the surrounding cartilage combined with local delivery of heparin binding insulin growth factor-1 (HB-IGF-1). The results of this study demonstrated improved cartilage integration in vitro when this technique is utilized. Thus, in the present study we evaluated the combination of trypsin enzymatic pretreatment with a self-assembling peptide hydrogel functionalized with growth factors to improve cartilage repair. First, the effect of trypsin enzymatic pretreatment alone or combined with self-assembling peptide hydrogel functionalized with HB-IGF-1 and/or platelet-derived growth factor- BB (PDGF-BB) was tested using a rabbit model (48 rabbits). Subsequently, trypsin enzymatic pretreatment combined with self-assembling peptide hydrogel functionalized with HB-IGF-1 and PDGF-BB was used to augment microfracture augmentation in an equine model of cartilage defects (8 horses). In the small animal model, trypsin enzymatic pre-treatment resulted in an overall increase in defect filling, as well as improvements in subchondral bone reconstitution, surface regularity, cartilage firmness, reparative tissue color, cell morphology and chondrocyte clustering. The presence of PDGF-BB alone improved subchondral bone reconstitution and basal integration, while the combination of HB-IGF-1 and PDGF-BB resulted in an overall improvement in tissue and cell morphology. In the equine model, microfracture augmentation using trypsin enzymatic pretreatment combine with self-assembling peptide hydrogel functionalized with growth factors (HB-IGF-1 and PDGF-BB) resulted in better functional outcomes, better defect healing on second look arthroscopy at 12 months, as well as improved reparative tissue histology and increased biomechanical proprieties of the adjacent cartilage compared to defects treated with microfracture only. In conclusion, trypsin enzymatic pretreatment combined with self-assembling peptide hydrogel functionalized with growth factors (HB-IGF-1 and PDGF-BB) resulted in successful microfracture augmentation. These therapeutic approaches can result in a more cost effective way to improve cartilage healing in patients undergoing subchondral bone microfracture.
Open Access
Clinical, clinicopathologic, histopathologic and immunohistochemical features of dogs with chronic enteropathy with and without concurrent protein-losing enteropathy: focus on the intestinal lymphatic vasculature
(Colorado State University. Libraries, 2018) Wennogle, Sara Anne Jablonski, author; Webb, Craig, advisor; Ehrhart, EJ, committee member; Lappin, Michael, committee member; Twedt, David, committee member
Chronic enteropathy (CE) is a term used to describe a group of chronic intestinal conditions in the dog that may respond to a variety of therapies including food, antibiotics, glucocorticoids, and immunosuppressives. Idiopathic CE is diagnosed after exclusion of extra-intestinal, infectious, parasitic, neoplastic and mechanical causes of gastrointestinal signs. Chronic enteropathies are often associated with histologic evidence of inflammation in the small intestine. In up to 20% of cases of CE with histologic evidence of inflammation in the small intestine, intestinal protein-loss occurs, a condition termed protein-losing enteropathy (PLE). Although several previous studies have identified the development of protein loss as a negative prognostic indicator in dogs with CE, the exact reasons why some dogs with CE develop concurrent PLE while others do not is not well understood. The goal of this work was to examine clinical, clinicopathologic, histopathologic, and immunohistochemical features of dogs with CE with and without PLE, with a special focus on the role of the intestinal lymphatic vasculature in cases of CE. In the first part of this work, we retrospectively examined histologic findings in a group of dogs with CE, and compared those findings between hypoalbuminemic and normoalbuminemic dogs. We found that many histopathologic features of idiopathic CE differed between dogs that were hypoalbuminemic versus those that were normoalbuminemic. Specifically, villous stunting, epithelial injury, crypt distension, lacteal dilation, intraepithelial lymphocytes, and lamina propria neutrophils were more common in hypoalbuminemic dogs with CE when compared to normoalbuminemic dogs with CE. We concluded that histopathologic features differ between hypoalbuminemic and normoalbuminemic dogs with CE and suggested that additional work is necessary to elucidate the clinical relevance of these differences. In particular, we noted that the high prevalence of lacteal dilation in hypoalbuminemic dogs with a primary diagnosis of inflammatory CE may be important and warranted further investigation. Next, we set out to prospectively evaluate whether a novel dietary approach could result in clinical improvement in dogs with CE and PLE who were not responding well to traditional therapy with glucocorticoids. We found that 8/10 dogs in the study achieved a complete clinical remission following a novel therapeutic dietary approach, with 7/8 dogs remaining in remission up to 3.5 years following the initial dietary change. Because 7/8 dogs that achieved a complete remission had been switched to a more fat-restricted diet than what they had previously been fed, we hypothesized that dietary fat-restriction may have played a role in their improvement. Because most of these dogs had not been diagnosed with lymphangiectasia, we speculated that the presence or extent of lymphatic abnormalities could have been underappreciated on routine histopathologic exam in this group of dogs. Lymphatic endothelial cell (LEC) immunohistochemical markers have identified intestinal lymphatic vasculature abnormalities in humans with inflammatory bowel disease (IBD). In the next chapter of our work, we utilized LEC markers and immunohistochemistry to evaluate the intestinal lymphatic vasculature in a group of dogs with CE. We uncovered significant mucosal lymphatic distension in some dogs with CE, most striking of which was in the ileum of dogs with CE and concurrent PLE. Several of these dogs did not have significant villous lymphangiectasia, therefore we concluded that routine histopathologic examination likely underestimated their lymphatic abnormalities. We also found that various abnormalities of the lymphatic vasculature were correlated with serum albumin levels. Finally, we aimed to improve our understanding of the pathogenesis of low serum vitamin D in dogs with CE. We did this by evaluating a variety of variables we felt could be associated with the mechanisms of low serum vitamin D in dogs with CE. We found that higher canine chronic enteropathy clinical activity (CCECAI) scores and serum CRP concentrations, and lower serum Vitamin E, cholesterol, and albumin concentrations were more likely in dogs with CE and low serum 25- hydroxyvitamin D (25[OH]D) concentrations compared to dogs with CE and normal serum 25(OH)D concentrations. In addition, histopathologic morphologic scores as well as overall WSAVA scores were correlated with serum 25(OH)D levels. Of particular relevance to this body of work were the findings of lower serum cholesterol and Vitamin E concentrations in dogs with low serum 25(OH)D and CE compared to dogs with normal 25(OH)D levels and CE. We concluded that the mechanism of low serum 25(OH)D in dogs with CE is likely multifactorial but fat malabsorption due to a variety of causes, including lymphatic dysfunction, could play a major role in the development of low 25(OH)D in this population. The work described in this dissertation has increased our understanding of protein-losing enteropathy as a consequence of canine CE, and in particular has highlighted the role of the intestinal lymphatic vasculature in these cases. This work can help to improve the lives of dogs suffering from CE and PLE and provides a solid foundation for further research in this arena.
Open Access
Coagulation abnormalities in Ehrlichia canis-infected dogs and detection and dynamics of anti-platelet antibodies in thrombocytopenic dogs
(Colorado State University. Libraries, 2018) Shropshire, Sarah, author; Lappin, Michael, advisor; Dow, Steve, committee member; Olver, Christine, committee member; Webb, Craig, committee member; Ames, Marisa, committee member
Vector-borne diseases affect millions of people and domestic animals worldwide resulting in significant morbidity and mortality rates. In dogs, vector-borne diseases such as Ehrlichia canis can cause a myriad of clinical signs (lethargy, weight loss, and epistaxis) and hematological abnormalities (hyperglobulinemia, thrombocytopenia, and anemia). It has been previously reported that E. canis results in systemic inflammation and vasculitis as well as the formation of immunoglobulin associated platelets or anti-platelet antibodies. It has been theorized that anti-platelet antibodies can deleteriously affect platelet function and if concurrent significant thrombocytopenia is present, signs of bleeding may manifest. However, anti-platelet antibodies and thrombocytopenia can occur in a variety of disease processes in the dog including other vector-borne diseases, neoplasia, and idiopathic primary immune syndromes. Thrombocytopenia is also one of the most common acquired hemostatic abnormality observed in dogs. Consequently, determining the underlying cause and mechanism for thrombocytopenia in dogs can represent a frequent diagnostic challenge. Additionally, inflammation is often present in dogs with thrombocytopenia due to various causes. Inflammation and immune system processes directly affect hemostasis which can lead to derangements in the coagulation system resulting in clinical signs of bleeding or thrombosis. The goals of the research described in this dissertation were to investigate the dynamic changes of anti-platelet antibodies in thrombocytopenic dogs and the changes that occur in the coagulation system during a vector-borne infection such as E. canis in dogs.
Embargo
Comprehensive investigation of chronic enteropathy in dogs through a prospective clinical trial, immunoassays, and RNA-sequencing
(Colorado State University. Libraries, 2024) Manchester, Alison C., author; Dow, Steven, advisor; Lappin, Michael R., advisor; Avery, Anne, committee member; Webb, Craig, committee member
Chronic enteropathy is a common condition in dogs causing recurrent or persistent gastrointestinal clinical signs. Pathogenesis is thought to involve intestinal mucosal inflammatory infiltrates, but histopathological evaluation does not predict treatment response, inform prognosis, or correlate with clinical remission. Many dogs may improve clinically with dietary intervention, but between 15 to 40% of dogs are refractory to all therapies. This negatively impacts quality of life for dogs and their families and can lead to euthanasia. Better understanding of the cellular and molecular differences between CE and health is necessary to improve outcomes for these dogs, and to enable use of the dog as a translational model for study of inflammatory intestinal conditions across species. The goal of this work was to critically evaluate the pathogenesis of CE in dogs through use of in vitro assays, a prospective clinical trial, and next-generation sequencing based approaches. Preliminary studies have highlighted an important role for intestinal bile acids in the pathogenesis of canine and human chronic enteropathies. Fecal bile acid populations differ between healthy dogs and dogs with CE. However, there has been little work to evaluate potential consequences of these metabolic shifts in dogs. We therefore investigated potential immunomodulatory roles of primary and secondary bile acids through in vitro experiments with canine macrophages. Both the primary bile acid cholic acid (CA) and the secondary bile acid lithocholic acid (LCA) influenced LPS-induced cytokine production via canine monocyte-derived macrophages similarly, with suppression of TNF-α secretion and enhancement of IL-10 secretion. Neither BA altered the expression of the BA receptor TGR5. Transcriptomic analysis revealed that CA activated inflammatory signaling pathways in macrophages involving type II interferon signaling and the aryl hydrocarbon receptor, whereas LCA activated pathways related to nitric oxide signaling and cell cycle regulation. Thus, we concluded that both primary and secondary BAs are active modulators of macrophage responses in dogs, with differential and shared effects evident with sequencing analysis. Diet is the most effective management strategy for dogs with CE, enabling two-thirds of patients to achieve clinical remission from their disease. Various dietary strategies may be beneficial. Nutritional formulae sourcing protein from amino acids have been used for the induction of remission in human Crohn's disease patients for decades. We conducted a prospective clinical trial involving exclusive feeding of the first diet sourcing protein from individual amino acids to 23 client-owned dogs with CE to determine its ability to induce clinical remission and begin to tease apart mechanisms of action. After 2 weeks of EL, 68% of dogs consuming the diet were classified as responders. At the conclusion of the 8 week feeding trial, 16/23 dogs (70%) were considered clinical responders. Feeding EL caused shifts in fecal bacterial communities, which differed between responders and non-responders, suggesting that diet's ability to modulate gut bacterial populations may predict its efficacy. Serum biomarker concentrations were unchanged throughout the study apart from serum alkaline phosphatase activity. Results of this study indicate that an amino acid based diet is another option to treat dogs with CE and implicates the intestinal microbiota in achievement of remission in these patients. Most studies comparing healthy and CE dogs completed to date have been limited in scope, evaluating individual or a small collection of biomarkers or cell types. This has hampered advancement of the understanding of CE pathogenesis in dogs. Ultimately, this results in generic treatment strategies for dogs and leaves a substantial proportion unable to achieve clinical remission from their disease. To this end, we applied next-generation transcriptomic sequencing to mRNA from duodenal biopsies from CE dogs and healthy beagle dogs. Results of this analysis highlighted important roles for epithelial cell gene signatures in differentiating CE tissues from healthy ones. Commonly implicated cytokines like TNF-α, IL-12, or IL-10 were not differentially expressed, but pathway analysis highlighted a potential role for upregulation of anti-viral pathways in CE dogs. This preliminary study underscores the power of RNA sequencing to provide a broad overview of cellular activities in tissues of interest, and question widely accepted theories regarding dysfunction present in the gut of dogs with CE. Single-cell RNA sequencing offers a high-resolution molecular technique enabling characterization of gene expression on an individual cell basis. This approach overcomes traditional barriers to disease investigation (e.g., species-specific reagents) and allows for definition of cell subtypes within heterogeneous samples. We thus employed single-cell RNA sequencing to catalog and compare the diversity of cells present in duodenal mucosal endoscopic biopsies from 3 healthy dogs and 4 dogs with CE. We identified populations of epithelial cells, T cells, myeloid cells, and plasma cells, with contributions from both the healthy and CIE samples. Neutrophils from CE samples exhibited a more inflammatory transcriptional program. T cells were broadly divided into non-resident and tissue resident subtypes, though minimal transcriptomic differences were appreciated within this class of cells. One subset of epithelial cells from CE dogs showed differential expression of a gene encoding a 2-pore potassium channel (KCNK16). Our results reveal a previously unappreciated cellular heterogeneity in canine duodenal mucosa and provides insights into molecular mechanisms underlying CE in dogs. The cell type gene signatures determined through this work will enable better understand the subtleties of canine intestinal physiology to allow more accessible interrogation of cellular activities in health and disease. The results of the studies described add further nuance and detail to understanding of the pathogenesis and management of canine CE. We have documented the power of transcriptomic analysis for differentiation of intestinal mucosal molecular programs in health and CE. Further investigation into intestinal bile acids, duodenal mucosal T cell subtypes and neutrophils, and intestinal epithelial cell activities are indicated.
Open Access
Construction and evaluation of epidemiologic simulation models for the within- and among-unit spread and control of infectious diseases of livestock and poultry
(Colorado State University. Libraries, 2012) Reeves, Aaron, author; Salman, M. D., advisor; Hill, Ashley E., advisor; Keefe, Thomas J., committee member; Wagner, Bruce A., committee member
Epidemiologic modeling is an increasingly common method of estimating the potential impact of outbreaks of highly contagious diseases, such as foot-and-mouth disease (FMD) and highly pathogenic avian influenza (HPAI), in populations of domesticated animals. Disease models are also used to inform policy decisions regarding disease control methods and outbreak response plans, to estimate the possible magnitude of an outbreak, and to estimate the resources needed for outbreak response. Although disease models are computationally sophisticated, the quality of the results of modeling studies depends on the quality and accuracy of the data on which they are based, and on the conceptual soundness and validity of the models themselves. For such models to be credibly applied, they should realistically represent the systems they are intended to reflect, should be based to as great an extent as possible on valid data, and should be subjected to careful and ongoing scrutiny. Two key steps in the evaluation of epidemiologic models are model verification and model validation. Verification is the demonstration that a computer-driven model is operating correctly, and conforms to its intended design. Validation refers to the process of determining how well a model corresponds to the system that it intended to represent. For a veterinary epidemiologic model, validation would address issues such as how well the model represents the dynamics of the disease in question in a population to which the model is applied, and how well the model represents the application of different measures for disease control. Among the steps that can be taken by epidemiologic modelers to facilitate the processes of model verification and validation are to clearly state the purpose, assumptions, and limitations of a model; to provide a detailed description of the conceptual model for use by everyone who might be tasked with evaluation of a model; document steps already taken to test the model; and thoroughly describe the data sources and the process used to produce model input parameters from data. The realistic representation of the dynamics of spread of disease within individual herds or flocks can have important implications for disease detection and surveillance, as well as for disease transmission between herds or flocks. We have developed a simulation model of within-unit (within-herd or within-flock) disease spread that operates at the level of the individual animal, and fully incorporates sources of individual-level variation such as variability in the durations of incubating and infectious periods, the stochastic nature of disease spread among individuals, and the effects of vaccination. We describe this stochastic model, along with the processes employed for verification and validation. The incorporation of this approach to modeling of within-unit disease dynamics into models of between-unit disease spread should improve the utility of these models for emergency preparedness and response planning by making it possible to assess the value of different approaches to disease detection and surveillance, in populations with or without some existing level of vaccine immunity. Models rely not only on realistic representations of the systems of interest, but also on valid and realistic information. For spatially explicit models of the spread and control of disease in populations of livestock and poultry, this means a heavy reliance upon valid spatial representations of the populations of interest, including such characteristics as the geographic locations of farms and their proximity to others in the population. In the United States, limited information regarding the locations of actual farm premises is available, and modeling work often makes use of artificially generated population datasets. In order to evaluate the accuracy and validity of the use of such artificially generated datasets, we compared the outcomes of mechanistic epidemiologic simulation models that were run using an empirical population dataset to those of models that made use of several different synthetic population datasets. Although we found generally good qualitative agreement among models run using various population datasets, the quantitative differences in model outcomes could be substantial. When quantitative outcomes from epidemiologic models are desired or required, care should be taken to adequately capture or describe the uncertainty in model-based outcomes due to the use of synthetic population datasets.