John A. Shadduck

ANIMAL INFECTIVITY OF ENCEPHALITOZOON CUNICULI

Rabbits, mice, rats and Rhesus monkeys were infected experimentally with a rabbit isolate of the mammalian microsporidan Encephalitozoon cuniculi. The lesions produced were typical of those occurring in spontaneous encephalitozoonosis in rabbits, mice, and rats, respectively. Viable E. cuniculi were recovered from tissues of injected animals with and without lesions. Titration of rabbit, mouse, and hamster isolates of E. cuniculi in mice and in rabbit choroid plexus cell cultures showed that the rabbit isolate was equally infectious for mice and cell cultures. Mouse and hamster isolates were less infectious for cell cultures than for mice. The results provide further evidence that the mouse, hamster, and rabbit isolates of E. cuniculi are identical.

The lesions of porcine adenoviral infection in germfree and pathogen-free pigs.

A porcine adenovirus isolated from the brain of a pig with encephalitis was shown to be pathogenic for germfree and pathogen-free pigs. Lesions were produced by 5 different routes of inoculation, of which the intranasal was the most effective. The animals inoculated intranasally developed an interstitial pneumonia which involved entire lobules and was especially prominent near the hilus. Distinct intranuclear inclusion bodies were seen. Lesions and inclusion bodies were also found in the kidneys, thyroids, and lymph nodes. Viral antigen was demonstrated in the lesions by immunofluorescence. Intracerebral inoculation resulted in polioencephalitis involving only the cerebral cortex. Many features of this disease were similar to adenoviral diseases of man and other animal species.

Effects of a Pathogenic Canine Herpesvirus on Established Thyroid Adenocarcinoma Cell Cultures

The effects of a pathogenic canine herpesvirus were studied sequentially in established canine thyroid adenocarcinoma tissue culture cells. The lesions were defined as early, middle, and late manifestations of viral effects based on the time a lesion first appeared. The early phase (3 to 10 hours) consisted of nucleolar swelling followed by disruption. The nucleolar changes were characterized by loss of RNA as determined with acridine orange and segregation of the nucleolar components as demonstrated by electron microscopy. The middle phase (10 to 34 hours) was characterized by the appearance of three types of eosinophilic intranuclear inclusions. One type of inclusion appeared to transform progressively into another. The appearance of viral antigen in the nucleus as demonstrated by immunofluorescence, correlated with ultrastructural evidence of viral replication. The late phase (34 to 72 hours) was manifested by cellular degeneration and viral release into the cytoplasm.

Future directions in veterinary pathology.

Roles for veterinary pathologists are changing ra~id1y.l~ Our historical dominance in the diagnosis of spontaneous animal diseases and interpretation of experimentally induced lesions in laboratory animals may be at risk. Indeed, the development of new investigative tools and the changing roles of our sister biological and medical disciplines will, we believe, result in major changes in the practice of veterinary pathology in the next century. In the following paragraphs we identify some issues we believe are especially significant and suggest some responses to these challenges.