Degree Type

Dissertation

Date of Award

1981

Degree Name

Doctor of Philosophy

Department

Veterinary Pathology

Abstract

Effects of vaccination against pseudorabies virus (PRV) infection were studied in 93 pigs. Pigs were challenged with virulent PRV at 1, 3, 5, 8, 10, 12 and 14 months after vaccination (AV). Live and inactivated PRV vaccines were used as immunizing agents. The protection provided was evaluated by comparison of clinical signs, gross and microscopic lesions, levels of cellular and humoral immunity and presence of virus among vaccinated and non-vaccinated pigs after challenge;Both vaccines provided a similar degree of protection for a period of 8 months after vaccination. The type and distribution of microscopic lesions were the same in the vaccinated and non-vaccinated pigs after challenge; however, a significant decrease in lesion severity was noted in the vaccinated animals for a period of 8 months AV. Microscopic lesions in the central nervous system (CNS) were characterized by a lympho-histiocytic-eosinophilic meningoencephalitis with focal areas of edema, demyelination, malacia and microgliosis. Lesions were present throughout the CNS and were equally distributed in the white and gray matter. Intranuclear inclusion bodies were extremely rare. In other tissues, only the turbinates, tonsils, lungs, and mandibular and bronchial lymph nodes had gross and microscopic lesions. Microscopic lesions were diffuse areas of coagulative necrosis with suppurative inflammation and eosinophilic and basophilic intranuclear inclusion bodies. Virus was only demonstrated by electron microscopy in the eosinophilic inclusions in tonsilar epithelium;Both vaccines induced a detectable primary humoral response in a large percentage of pigs. The response lasted for several months. Vaccination however, failed to induce a detectable first type cell-mediated immune response when measured by the lymphocyte transformation assay 1 to 16 months AV. Vaccination induced a detectable secondary response after challenge at the humoral and cellular level for 14 months AV. The secondary levels of humoral immunity were lower at 8 months AV, while cellular immunity remained high for 16 months AV. The cell-mediated immune response is useful in predicting early response after challenge especially in non-vaccinated pigs. In vaccinated pigs humoral and cellular immunity were detected for the first time at 6 and 7 days after challenge. Challenge virus could frequently not be isolated from vaccinated swine after challenge, thus indicating that virus isolation alone is not a reliable test parameter to detect post-vaccination exposure to PRV.

DOI

https://doi.org/10.31274/rtd-180813-5959

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Roberto Alva-Valdés

Language

en

Proquest ID

AAI8215116

File Format

application/pdf

File Size

169 pages

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