However, if a mouse is infected after the neonatal period, when the immune system is responsive, the immune response is active. This immunological conflict can result in one of three ways; immunological paralysis, significant or complete suppression of virus with immunity to reinfection, or death. Mice that are infected after the neonatal period often pass through a "runt" stage, which may last for several weeks. Clinical symptoms include excitability, weight loss, and severe retardation of growth and hair development. In general, as the period of time between birth and inoculation decreases, less disease and mortality occurs.Post mortem lesions in mice show signs of hepatomegaly, splenomegaly, lymphadenopathy, and swollen or shrunken and pitted kidneys due to glomerulonephritis. Histological findings in persistently infected mice often show chronic glomerulonephritis. In these mice, and some hamsters, vasculitis and lymphocytic infiltrates in many organs and tissues including the liver, spleen, lung, kidneys, pancreas, blood vessels, meninges and brain are present. Hamsters
Pathogenesis occurs in the same manner in hamsters as in mice. Symptoms in hamsters are highly variable, and typically indicate that the pet has been infected and shedding the virus for several months. Early signs may include inactivity, loss of appetite, and a rough coat. As the disease progresses, the animal may experience weight loss, hunched posture, inflammation around the eyes, and eventually death. Alternatively, some infected hamsters may be asymptomatic. Rats
Experimental intracerebral infection of suckling rats results in microcephaly, retinitis and the destruction of several brain regions, leading to permanent abnormalities of movement, coordination, vision and behavior.
The effectiveness of infection quickly declines below pH 5.5 and above pH 8.5. In addition, LCMV can also be inactivated by heat, ultraviolet light or gamma irradiation.Studies have indicated that human infection of the virus occurs primarily during the fall and winter months, presumably due to the movement of mice indoors. Several measures can be taken to prevent exposure to LCM from wild rodents in the home. A checklist of precautions is provided by the Centers for Disease Control and Prevention, providing tips for sealing the home to keep rodents out, using traps to eliminate existing rodents, and maintaining a clean, healthy home. New technology reflects a growing trend for more humane means of eliminating rodents. Products include devices that emit ultrasonic sound that allegedly irritates mice and drives them away, and more swift, painless means of death such as mini electrocution or gas chambers. However, the traditional snap trap remains an economic and popular option. Treatment
Treatment is symptomatic and supportive. Children with hydrocephalus often need a ventriculoperitoneal shunt. Nucleoside analog ribavirin is used in some cases due to the inhibitory effect the agent has in vitro on arenaviruses. However, there is not sufficient evidence for efficacy in humans to support routine use. The only survivor of a transplant-associated LCMV infection was treated with ribavirin and simultaneous tapering of the immunosuppressive medications. Early and intravenous ribavirin treatment is required for maximal efficacy, and it can produce considerable side effects.