Degree Type


Date of Award


Degree Name

Master of Science


Veterinary Microbiology and Preventive Medicine


Veterinary Microbiology


The objective of this thesis is to review the role of porcine tonsil in immunity and disease and to characterize the duration of the carrier state of porcine reproductive and respiratory syndrome (PRRS) virus infection. Two chapters are presented within this thesis. The first is a literature review of the role of the porcine tonsil in immunity and disease. The second describes an experiment to estimate the proportion of PRRS virus carriers over time and determine which combination of sample and diagnostic assay could most effectively identify persistently-infected animals. Chapter One reviews the role of the porcine tonsil in immunity and disease. The anatomical and functional features of the tonsils and the tonsillar crypts are discussed. Immunobiological properties of the tonsils and their contribution to the immune function in the pig are examined. The interaction of the tonsil with diseases that affect swine is detailed, particularly in regards to the tonsil as a portal of entry, location of primary replication, location of persistence after acute infection and as a reservoir for transmission. In Chapter Two, diagnostic test results from samples collected periodically over 105 day period post infection from sixty 3-week-old PRRS virus inoculated pigs and sixty age-matched uninoculated controls were tested for evidence of PRRS virus infection by virus isolation (VI), swine bioassay, and reverse trancriptase-nested polymerase chain reaction (RT-nPCR). Overall, infectious PRRS virus was found in 51 of 59 (84%) necropsied animals by VI or swine bioassay. RT-nPCR on oropharyngeal scrapings was the most effective combination of assay and sample for detecting carriers. Infectious PRRS virus was present in most pigs the first 105 days following infection, a fact that complicates control and / or elimination of PRRS virus within swine herds.


Copyright Owner

Dennis Carl Horter



OCLC Number


File Format


File Size

73 pages