published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Some ill. mounted. Bibliography: leaves 109-129.

The objective of this study was to determine the effect of time, temperature and organic matter on disinfectant efficacy. Staphylococcus aureus (SA) and Salmonella Typhimurium (ST) were used as organisms to represent Gram positive and Gram negative bacteria, respectively, commonly found in poultry housing. Three independent experiments evaluated the effect of temperature, time, and organic matter on the efficacy of working concentrations of disinfectants against representative organisms found in commercial poultry housing. Quaternary ammonium, chlorhexidine, phenolic and binary ammonium based solutions represented disinfectants commonly used within the poultry industry. Results from these experiments indicated that long term storage of disinfectants will reduce their efficacy against SA. However, a reduction (p ≤ 0.05) in efficacy was observed with the phenolic compound against ST at elevated temperatures. Following the inclusion of organic matter (OM), reduced (p ≤ 0.05) efficacy of all disinfectants was observed in a dose dependent manner against both organisms, with the exception of the phenolic compound against SA. Fresh disinfectant performed better (p ≤ 0.05) in the presence of OM than 30 wk old disinfectant. These results emphasize the need to use fresh disinfectants and that OM should be removed prior to disinfection. We also evaluated the effect of bismuth citrate, lactose and citric acids on the development of necrotic enteritis in broilers. Clostridium perfringens’ associated necrotic enteritis in poultry causes significant loss and increased morbidity in the industry. Due to the reduced usage of antibiotic growth promoters, the incidence of necrotic enteritis has increased. These experiments evaluated different levels of bismuth citrate and bismuth citrate with lactose or citric acid added, on lesion development, bacterial intestinal colonization of C. perfringens and pH levels in the gut of broilers orally challenged with C.perfringens. Results from this investigation indicate that bismuth citrate at 100 ppm and 200 ppm caused a reduction (p ≤ 0.05) in C. perfringens colonization and intestinal lesion development. The addition of dietary lactose to bismuth citrate enhanced the effect of bismuth citrate on intestinal lesion development. These data suggest that bismuth citrate alone or in combination with dietary lactose will reduce intestinal lesion development in broilers with necrotic enteritis.

Necrotic enteritis (NE) is an economically important enteric disease of broiler chicken primarily caused by a-toxin (Cpa) secreted by C. perfringens type A. Mice immunized with recombinant C-terminal domain of Cpa (CpaCD) had transient and fewer localized lesions upon challenge with C. perfringens type A. These results demonstrate the usefulness of CpaCD as an immunogen for vaccine development against NE for chickens. Chicken CD40 (chCD40) is mainly expressed on the surface of chicken antigen-presenting cells (APCs), and the interaction of chCD40 and chCD40L (natural ligand for chCD40) provides crucial activation signals for chicken B-cells. A hypothesis was proposed that in ovo vaccination with an adenovirus-vectored CpaCD vaccine capable of targeting immunogen to APCs through the CD40 pathway will improve protection against NE in chickens. One agonistic monoclonal anti-chCD40 antibody (designated 2C5) was produced and characterized. 2C5 not only detected expression of chCD40 on chicken APCs, but also induced NO synthesis in chicken HD11 macrophages and enhanced proliferation of serum-starved chicken DT40 B-cells. This demonstrated substantial functional equivalence of 2C5 with chCD40L. The potential of 2C5 as an immunological adjuvant was further assessed by targeting a hapten to chicken APCs in hopes of enhancing an effective IgG response. Seven-week old chickens were immunized subcutaneously once with a complex consisting of 2C5 and peptide, and relative quantification of the peptide-specific IgG response showed that this complex was able to elicit a strong IgG response as early as four days post-immunization. This demonstrates that CD40-targeting antigen to chicken APCs can significantly enhance antibody responses and induce immunoglobulin isotype-switching. An agonistic anti-chCD40 single-chain variable fragment (designated DAG1) was combined with an adenoviral delivery system to create a vaccine, Ad-(DAG1-Cp aCD-FLAG), for in ovo administration. The efficacy of in ovo vaccination of broilers with Ad-(DAG1-Cp aCD-FLAG) in controlling NE was evaluated by C. perfringens type A challenge at 18 days post-hatch. Neither statistically significant IgA / IgG response nor protection against C. perfringens type A challenge was found in the vaccinated birds. These preliminary data suggest that a super-optimal dose of Ad-(DAG1-Cp aCD-FLAG) may be the main issue, because Cpa-specific B-cells may undergo apoptosis through the CD40 pathway.

Proefschrift Universiteit van Amsterdam. / Met lit. opg. - Met samenvatting in het Nederlands.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 6 uppsatser.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Proefschrift Universiteit Maastricht. / Met lit. opg. - Met samenvatting in het Nederlands.

Canine parvoviral enteritis is an economically important disease in South Africa and globally. Although treatment of dogs with parvoviral enteritis is often successful, many dogs die of complications related to septicaemia or are euthanized because of anticipated high costs. More effective prediction of the outcome of this disease will have an economic impact if a prognosis can be determined early in the course of the disease. Although leukocyte responses seldom are pathognomonic for a specific disease, they can provide clinical information to establish a fairly reliable prognosis. A prospective study was performed on 62 puppies presented to the OVAH with typical clinical signs of canine parvoviral enteritis that subsequently was confirmed on electron microscopy. Full haematology was performed at admission as well as every consecutive day until death or discharge. Of the 11 puppies that died (18%), nine died due to complications of the disease and two were euthanized due to financial restrictions and a poor prognosis. The puppies that died due to the disease died within the first three days of hospitalization. All the puppies that died were sent for a full post mortem examination and histopathological evaluation. Statistical analysis of the data showed that there was a definite difference between the puppies that died and those that survived in several of the leukocyte parameters. These parameters included the total leukocyte, lymphocyte, monocyte and eosinophil counts. In none of the puppies that died from the disease did the total leukocyte count rise above 2.0 × 10 9 /l (normal reference range: 6.0-15.0 × 10 9 /l). In the puppies that survived, the total leukocyte count started rising within 24 – 48 hours after admission and often resulted in a rebound leukocytosis. The puppies that died did not develop lymphocytosis to indicate an immune response, whereas the surviving puppies developed lymphocytosis within 24 – 48 hours after admission. The puppies that died also did not develop monocytosis and remained severely eosinopaenic during the course University of Pretoria etd – Goddard, A (2006) xii of the disease. Evidence of impaired leukocyte production was found on histopathology. Most of the puppies that died from the disease showed marked to severe thymic and lymphoid atrophy and marked to severe bone marrow hypocellularity. These results show that a reliable prognosis can be obtained at 24 and 48 hours after admission by evaluation of the leukocytes, specifically the total leukocyte, lymphocyte, monocyte and eosinophil counts. / Dissertation (Master in Veterinary Medicine(Clinical Laboratory Diagnostics))--University of Pretoria, 2006. / Companion Animal Clinical Studies / unrestricted

Intensified poultry production to meet global food demands has faced challenges associated with the removal of in-feed antibiotics due to concerns over antibiotics resistance. The reduction of low-dose antibiotics in feed has allowed for reemergence of intestinal diseases that diminish animal welfare and producer economics. Alternative mechanisms to preventing disease are therefore required. The objective of this dissertation was to examine factors that contribute to chicken development and health including intestinal structure and function, environment, and genetic selection. Chapter 2 investigated the host response to infection of the parasite Eimeria maxima that predisposes chickens to a bacterial infection Clostridium perfringens. Intestinal structure, function, inflammatory response, and epithelial composition was examined during a mild subclinical infection. Analysis of E. maxima and C. perfringens as individual infections revealed how each pathogen contributes to a co-infection. E. maxima caused a more severe inflammatory response, increasing pathology scores, shortening intestinal villi, and elongating crypts in the jejunum at peak infection. C. perfringens was shown to manipulate intestinal epithelial composition by influencing stem cells to differentiate into secretory goblet cells. The most deleterious effects were observed when the pathogens were introduced together, increasing pathology scores further, damaging intestinal villi, and increasing crypt depth. The introduction of C. perfringens and E. maxima also increased signaling for the production of reactive oxygen species, stimulation of tumor necrosis factor- that is involved in innate immunity, and decreased transcription of Hes1, which is involved in Notch signaling towards absorptive cell differentiation. Hes1 has previously been shown to be involved in the inflammatory response and could be an area of interest in determining new treatments to prevent or relieve the effects of E. maxima and C. perfringens. Chapter 3 applied an environmental perspective to disease prevention and examined the properties of C. perfringens that allow it to persist in the poultry house environment. Spores resist treatments used to sanitize poultry houses and litter has been shown to be a reservoir for disease, potentially increasing occurrence in certain houses. The metabolic and physiological properties of C. perfringens were utilized to separate the microbe from other poultry litter bacteria to enumerate spores within houses. A selective and differential medium combined with a heat treatment was developed to isolate C. perfringens spores from poultry litter samples. On average, houses that had histories of necrotic enteritis harbored a greater abundance of C. perfringens spores. Colonies that were isolated on the specialized medium were confirmed using PCR as C. perfringens. Lastly, Chapter 4 examined how genetic selection for multiple traits has influenced early intestinal development compared to divergently selected lines based on eight-week body weight. This study showed the morphological and gene expression differences between lines and revealed that most pathways involved in intestinal development are conserved through genetic selection. The major differences between lines were an increase in peptide transporter PepT1 on d5 and d7 in chicks selected for low eight-week body weight (LWS) compared to high weight selected (HWS) chicks and modern broiler Cobb500 chicks. In HWS chicks, the opposite mechanism was observed with an increase in expression of secretory goblet cell marker Muc2. The findings of these studies give multiple perspectives into poultry production and how major factors in management including nutrition, environment, and genetics can be used to increase efficiency while preventing disease. / Doctor of Philosophy / In poultry production, it is important to use management methods that help chickens grow efficiently while preventing illnesses. A few factors that contribute to the success of a producer include the use of nutrition to enhance intestine health and efficiency, a healthy environment in the poultry house, and using genetics to select for multiple traits to increase productivity. These factors have become even more significant after concerns of antibiotic resistance has eliminated the use of in-feed antimicrobials, allowing for reemergence of diseases that were suppressed. Therefore, the objective of this dissertation was to utilize each of these management strategies to determine how a common disease to the poultry industry affects the chicken intestine, how the environment influences the occurrence of this disease, and how genetic selection impacts the early development of chicks that may contribute to how they handle incidences of disease. Chapter 2 investigated how the bacteria Clostridium perfringens and parasite Eimeria maxima that are commonly seen together in the industry impact the intestinal function, structure, and how the chicken's immune systems respond to invasion by these pathogens. The major finds of this chapter included an increased inflammatory response after E. maxima infection that damaged intestinal structures. These pathogens also decreased the expression of a gene involved in absorptive cell formation that contributes to the inflammatory response. In Chapter 3, environment was investigated to determine if poultry houses that harbored more C. perfringens spores, which are resistant to sanitary treatments, predispose chickens to disease. On average, houses with more spores were correlated with increased disease occurrence. The method developed to determine isolate C. perfringens spores can also be used to monitor the abundance in poultry litter and used as a management tool to prevent or diagnose disease outbreaks. In Chapter 4, the influence of genetic selection on early intestinal development was studied using a modern line of broiler chicks compared to chicks selected for low or high body weights. This study gave insight into how intestinal development is mostly conserved after selecting for multiple genetic traits or a single trait (growth). The main differences were greater body weight in the modern line and high weight selected chicks compared to low weight selected chicks and an increase in gene expression of a peptide transporter in low weight chicks and a decrease in secretory cell expression in high weight chicks. These projects investigated multiple management strategies to address intestinal development and response to pathogens, disease occurrence, and genetic selection as tools to shape intestinal structure and composition.