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Emerging Infectious Diseases of Poultry


In order to successfully combat an infectious disease, one must know the "chain of infection" of this disease. Hence, one must know about the agent involved, the reservoir where it can be found, how it can exit the reservoir and how it is successfully transmitted to a susceptible host. The objectives (1 to 4) listed below are aimed at increasing our understanding of some or all the links of this chain (depending on the disease), so that prevention and/or control strategies may be successful (objective 5).

<OL> <LI> Identify and characterize infectious agents associated with emerging infectious diseases of poultry. <LI> Develop and/or assess diagnostic tests designed to detect these agents. <LI>Determine the pathogenesis of, and the host response to, emerging infectious diseases of poultry. <LI>Identify risk factors associated with these diseases. <LI>Develop effective control strategies to contain such diseases

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NON-TECHNICAL SUMMARY: Infectious agents in poultry reduce productivity, increase production costs, and some have the potential to serve as trade barriers. Several infectious agents are food safety concerns and may impede consumer acceptance and marketing of poultry products; and are important causes of human food-borne illness. Once the agent(s) responsible for PEMS are identified, research efforts will focus on the development of efficient diagnostic tools. These diseases are being studied because of their economic importance to the poultry industry.


APPROACH: <BR> 1: Poult Enteritis Mortality Syndrome: Specific immunohistochemical procedures and polymerase chain reaction procedures will be developed for viruses identified as potential causal agents. <BR> Mycoplasmas: MG isolates from non-commercial avian sources will be DNA fingerprinted by the RAPD method and compared to isolates from commercial poultry and vaccine strains. <BR> Marek's disease virus: Research will be conducted to determine if other gallinaceous species of birds are susceptible to infection and tumor development induced by recent MDV isolates. Ovarian adenocarcinoma (OAC) in layer chickens: Will utilize immunohistochemical, polymerase chain reaction, and conventional virus isolation procedures to evaluate the role of viruses in this disease. <BR> <BR> 2. Poult Enteritis Mortality Syndrome: Monoclonal antibodies specific for turkey coronavirus (TCV) will be produced. Will be utilized for development of enzyme-linked immunosorbent assays for serological diagnosis of TCV and detection of the virus in feces. <BR> Mycoplasmas: Studies conducted to optimize random amplification of polymorphic DNA (RAPD) tests for strain identification of MG, MS, and MM. <BR> Transmissible viral proventriculitis (TVP): Monoclonal and polyclonal antibodies specific for TVP virus will be produced. Will be utilized for development of specific immunohistochemical (immunoperoxidase) procedures for detection of the virus in diseased chickens. <BR> Enteropathogenic E. coli: Diagnostic tests will be evaluated in cases of enteritis in young turkeys to determine sensitivity and specificity for detecting enteropathogenic E. coli. <BR> <BR> 3. Poult Enteritis Mortality Syndrome: A series of controlled experiments and field trials will be conducted. <BR> Mycoplasmas: Experimental infections using field isolates will be used to characterize virulence for chickens and/or turkeys, and to assess the performance of various diagnostic tests available or under development. <BR> Bordetella avium: B. avium mutant strains that each lack one of five virulence associated activities will be constructed. <BR> Escherichia coli: Procedures and methods for examining macrophage/bacterial interactions involve straightforward in vitro killing assays. <BR> <BR> 4. Poult Enteritis Mortality Syndrome: Prospective observational studies will be conducted. <BR> Food Safety: Studies will be conducted to assess the relative importance of different potential sources of transmission of Campylobacter, Listeria and Salmonella including arthropods, rodents, and feed. <BR> <BR> 5. Poult Enteritis Mortality Syndrome: The currently available PEMS turkey experimental model using seeder exposure to PEMS will be used with various treatment and prevention regimens. <BR> Mycoplasmas: We will continue to investigate outbreaks when they occur by isolating the involved mycoplasma field strains, fingerprinting them, and using this information to conduct `molecular epidemiology' providing feedback to the NCDA and poultry companies. <BR> Avian Influenza: A DNA vaccination strategy, shown to be efficacious in mice, will be tested in chickens. Food Safety: Studies will be conducted to determine the impact of biosecurity programs (including sanitation) on foodborne pathogens at the farm level.


PROGRESS: 2007/01 TO 2007/12<BR>
Objective 1: Identify and characterize infectious agents - AdLV R11/3 was determined to be a novel chicken birnavirus. Collaborations initiated on complete genome sequencing of M. gallisepticum (MG). Increased mortality and pneumonia associated with Mycoplasma synoviae (MS) infection of turkey breeder hens. Mycoplasma iowae (MI) was found associated with vertebral chondrodystrophy in turkeys. Enterococcus cecorum identified as cause of lameness and mortality in broiler breeder flocks. <BR> <BR> Objective 2: Develop and assess diagnostic - A method to diagnosis Marek's disease virus (MDV) from samples collected on FTA cards was developed. Methods to monitor MDV vaccine efficacy developed. <BR> <BR> Objective 3: Determine pathogenesis - Chicken birnavirus, R11/3, was shown to be the etiologic agent of transmissible viral proventriculitis. Differences in cytokine patterns in spleen and lung (i.e. IL6 and NOs) between high protective and low protective MDV vaccines identified. IFNã plays a major role in activation of immune response in spleen and lung. Eye-lesions induced by MDV are immune-mediated, not neoplastic. MDV vaccines shown to differ in ability to protect against early and late lesion development..Developed system to experimentally reproduce beneficial effects of double MDV vaccination. B. avium mutants were constructed to better understand pathogenesis of avian bordetellosis and to devise better control methods. Mortality in broiler breeder hens indicated involvement of primarily non-infectious factors, primarily vent picking. Myopathy - hypocalcemia syndrome identified as cause of mortality in early-lay broiler breeder hens. Pectoral muscle myopathy in broilers results in increased condemnations. Studies suggest exertional (transport) myopathy, possibility of underlying muscular dystrophy not excluded. Studies continue on epizootic of MG in free-ranging house finches; involvement of Mycoplasma sturni was not substantiated by experimental infection. <BR> <BR> Objective 4: Identify risk factors - Domestic house flies shown to be unlikely vectors of NDV. Oral exposure of house finches to MG can initiate infection suggesting that contaminated food/water may be route of transmission. Improved performance observed in turkeys placed day-of-hatch, compared with placement day-after-hatch.
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IMPACT: 2007/01 TO 2007/12<BR>
Identification of chicken birnavirus R11/3 as etiological agent responsible for transmissible viral proventriculitis provides impetus for further study leading to development of control procedures. Development of method to diagnosis MDV from FTA cards will facilitate collection and transport of samples. Samples collected on FTA cards can be submitted to USA from other countries. Understanding role of pulmonary immunity induced by MDV vaccine will allow development of better control methods. Understanding role of MDV in development of eye lesions will aid elucidation of pathogenesis of acute necrotic retinitis in humans Optimization of MDV vaccines might improve vaccine performance using currently available vaccines. MG sequencing will enable evaluation of molecular variability, development of improved strain identification methods, studies of molecular evolution and molecular correlates with pathogenicity. B. avium control requires basic understanding of organism. Genetic tools will examine B. avium pathogenesis. Studies on the epidemiology/pathogenesis of MG in house finches indicate a highly tractable model system for experimentally studying microbial diseases. MS should be considered in the differential diagnosis of pneumonia in turkeys. MI should be considered in the differential diagnosis of vertebral chondrodystrophy in turkeys.

Guy, Jim
North Carolina State University
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