Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Pathology


The purpose of this research was to investigate in sheep the pathogenesis of pseudorabies infection caused by an Iowa isolate of pseudorabies virus. The objectives of the study were (1) to trace the route and time sequence of pseudorabies virus spread from the lungs and respiratory tract to the brain by virus localization and lesion development, (2) to correlate neural lesions with clinical signs, (3) to identify the location of virus within the affected tissues, and (4) to evaluate nasal mucus for the potential horizontal spread of pseudorabies virus among sheep;Thirty-two sheep were randomly assigned to 8 groups composed of 4 animals per group. One group at a time was inoculated intratracheally with pseudorabies virus or Earle's balanced salt solution. Animals were killed at 24, 48, 72, and , if they survived that long, 86-96 hours post inoculation. This procedure permitted 2 control and 6 principal replicates at each postinoculation sacrifice period;Clinical signs of pyrexia, depression, frequent swallowing, facial fasciculations, chorea, excessive salivation, mild tympanites, labored breathing, and focal pruritus were followed by death. Macroscopic lesions were severe focal facial trauma, petechiae in cervicothoracic ganglia, and dilated esophaguses. The trigeminal, cranial cervical, cervicothoracic, and parabronchial ganglia and medulla oblongata contained pseudorabies virus and pronounced nonsuppurative inflammatory changes. The lesions and virus were limited to the solitary tract and solitary nucleus and spinal tract nucleus of the trigeminal nerve in the medulla oblongata. The nasal mucus contained virus from 2 animals killed between 86-96 hours post inoculation;The virus and lesion distribution within the central and sympathetic nervous systems could be correlated with the clinical signs. The neural distribution of lesions and virus suggests that the virus traveled from the respiratory mucosa to the central and sympathetic nervous system by two routes: (1) in the vagus and glossopharyngeal nerves to the medulla oblongata and (2) in the post ganglionic fibers to the sympathetic ganglia. The presence of virus in the nasal mucus indicated that horizontal transmission of pseudorabies virus may occur among sheep during an outbreak.



Digital Repository @ Iowa State University,

Copyright Owner

Stephen Peter Schmidt



Proquest ID


File Format


File Size

150 pages