Chronic infections by herpes simplex viruses and by the horse and cat herpesviruses.

Rabbit eyes experimentally infected with either type 1 or type 2 herpes simplex viruses occasionally released virus spontaneously. Injection of adrenalin was not highly effective for stimulating virus release but did seem to have a slight and erratic activating capacity. No spontaneous virus release were detected from the eyes of six cats infected with cat herpesvirus, but, when adrenalin was administered, an episode of virus release did ensue in one animal. Rabbit spinal cords could be chronically infected with either herpes simplex virus type 2 or equine herpesvirus type 2. The viruses could be reisolated over subsequent months from about half the animals without prior stimulation; the interval between inoculation of trypsinized spinal tissue into tissue cultures and the development of cytopathic effect was often long—more than 4 weeks in some cases.