No latent infection or carrier state occurs. The disease is not fatal, and is generally subclinical. The rats may exhibit a porphyrin oculonasal discharge. The submaxillary salivary gland may be palpably enlarged due to sialoadenitis. Dacryoadenitis may cause exophthalmos, which can lead to keratitis and corneal ulcers.
Symptomatic rats are at a greater risk for inhalation anesthesia.
Cessation of all breeding activity in a production colony for 60 days and concomitant removal of all suckling and weanling animals or intentional exposure of these young rats by frequent mixing will eliminate the infection in the colony. The virus is highly contagious and is spread by aerosol, direct contact, and fomites. No latent infection or carrier state occurs. The incidence of infection is high. The disease is not fatal, and is generally subclinical.