Ocular herpes simplex and the establishment of latent infection

Latent infection of the trigeminal ganglion following ocular and labial herpes simplex in the mouse was investigated. Latent infection of the ophthalmic part of the trigeminal ganglion followed subclinical ocular infection. When primary infection resulted in severe eye disease, latent infection was subsequently demonstrated not only in ophthalmic parts of the ganglion but also in parts which did not serve the eye. Primary infection of the lip resulted in latent infection of the mandibular part of the trigeminal ganglion, but also of maxillary and ophthalmic parts. Previous infection by herpes simplex virus in a non-ocular site necessitated a hundred-fold increase in the amount of virus required to initiate keratitis which resulted in a much lower incidence of latent infection and only in the ophthalmic part of the ganglion. The results are interpreted to explain how latent infection of the ophthalmic part may precede and provide a source of virus for symptomatic eye disease. Such latent infection is most likely to arise from previous subclinical ocular infection or primary infection in a non-ocular site.