Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Veterinary Microbiology and Preventive Medicine


The work described in this dissertation falls into 3 main parts. Firstly, the effect was tested of pregnancy and parturition upon latent infection with Aujeszky's Disease virus. A pig was infected when 1 month old with strain S62/26 of the virus and eventually made a complete clinical recovery. When it farrowed 19 months later, it was observed to shed virus from its nostrils from the 3rd through the 8th day postpartum. This is the first time that a natural recrudescence of latent Aujeszky's Disease virus has been directly observed. On two subsequent parturitions, the pig was not observed to shed virus. The effect of hormonally simulated pregnancy and parturition as a recrudescing agent was also tested in another group of pigs without success. The pigs were infected when 5 weeks old with S62/26 strain of virus and the pseudopregnancies were initiated in one pig at 28 weeks of age and in the other 3 pigs at 40 weeks of age. Estrus and ovulation were induced with Pregnant Mare Serum and Human Chorionic Gonadotrophin. The corpora lutea were maintained with Estradiol Cypionate to simulate pregnancy, and Estradiol, Adrenocorticotropic Hormone and Prostaglandin F(,2(alpha)) were used to induce pseudofarrowing after a pseudopregnancy of 47 days. The pro forma of the schedule of hormone injections used to simulate pregnancy and parturition is given, and the relationship of cortisol, prostaglandin and oxytocin to the recrudescence of the Herpetoviridae is discussed;Secondly, the isolation of a strain of Aujeszky's Disease virus (IA80) of relatively low pathogenicity is described. The virus was isolated from the brain of a newborn pig which was presumed to have been infected transplacentally. It was of relatively low pathogenicity when compared with S62/26 strain, but was invasive and was shed after intramuscular inoculation, causing seroconversion of an incontact sentinel pig. The virus is of some importance in disease eradication programs, as it may cause silent seroconversion of herds without clinical disease;Thirdly, the establishment of a persistent infection of Aujeszky's Disease virus in porcine turbinate, salivary gland, and tonsilar fragments maintained in vitro, for up to 126, 56, and 51 days, respectively, is described. The addition of antiserum did not clear turbinate or salivary gland fragments of infection. On removal of antiserum, virus was shed and recovered for up to 189 and 182 days after initial infection, respectively.



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Edward Bryan Davies



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149 pages