The viability of infective larvae of Dictyocaulus viviparus stored at 4°C decreased to 38.3% at 1 month of storage and 0.2% at 13 months of storage. No larvae were detected 1 month later. When administered orally with infective larvae, all 14 calves discharged first-stage larvae in feces. When administered with infective larvae stored for 4-6 months, calves excreted fairly large numbers of first-stage larvae for more than 2 months. When infected with larvae stored for less than 4 months, calves showed obvious pneumonic symptoms. It appeared that when stored at 4°C, infective larvae of D. viviparus might decrese in viability and infectivity with the lapse of time, although they remained viable and infective for a considerably long period of time.
Infectious bovine rhinotracheitis (IBR) virus was allowed to propagate in ST cell culture at 30°C and subjected to passage repeatedly. The virus thus obtained for the preparation of vaccine had no ability to induce the production of neutralizing antibody in rabbits when inoculated by the intravenous, subcutaneous, or intracutaneous route. It propagated much better in ST cell culture at 30°C than highly virulent virus. There was a difference of 103.0 TCID50, at the largest, between the two viruses. When challenged with highly virulent virus, vaccinated cattle were prevented completely from clinical infection, though reinfection was noticed. No pathogenicity recurred when the vaccine had been subjected to five consecutive passages in cattle. Safety and efficacy of the vaccine were demonstrated in a field trial with about 2, 000 animals. Contact infection was negative. Milk yields were not affected with vaccination. There was no reduction in the infective titer of the vaccine even at 14 months of storage at4°C.
Chick embryo fibroblast cell cultures infected with herpesvirus of turkey (FC-126) and containing approximately 5, 000 PFU were inoculated in to the yolk sac of 34 three-day-old chick embryos. Pocks appeared on the chorioallantoic membrane (CAM) 8 days after inoculation. Several grayish lesions were observed in the liver and heart of the embryos 13 days after inoculation. Microscopically, there were intranuclear inclusion bodies in the ectodermal and mesodermal layer of the CAM and hepatic and Kupffer's cells 8 days after inoculation. Ther inclusions were found in the heart muscle and the epithelium of the uriniferous tubule. Acidophilic inclusions were surrounded by a clear halo and basophilic ones often occupied the whole nucleus, with an incomplete or no halo. As the infection progressed, degenerative cells containing inclusions became necrotic. There were infiltration of variable mononuclear cells and eosinophilic granular cells, and mild propagation of reticular cells. The fluorescent antibody test of herpesvirus of turkey was performed in the liver and heart of infected embryos. It revealed that fluorescent foci coincided with microscopical lesions detected in frozen sections.