Epidemiology and Risk Factors. The natural reservoir for the lymphocytic choriomeningitis virus (LCMV) is the common house mouse. Hamsters and laboratory animals can also be infected with this virus. Most human infections result from contact with house mice. y , y Four clinical syndromes due to infection with LCMV have been described: (1) subclinical asymptomatic infection, (2) nonmeningeal influenza-like illness, (3) aseptic meningitis, and (4) meningoencephalomyelitis. y The
LCMV was the first specific etiological agent of the aseptic meningitis syndrome to be identified. y
Pathogenesis and Pathophysiology. The LCMV is a member of the arenavirus family and is maintained in nature primarily by vertical intrauterine infection in mice, hamsters, and rodents, producing a chronic asymptomatic infection in the offspring. These animals shed the virus in saliva, nasal secretions, semen, milk, urine, and feces.y The route of transmission to humans remains unknown but is presumed to occur through contamination of open cuts or aerosolized spread of virus. There is no evidence of person- to-person transmission of LCMV infection. y Local replication of LCMV is followed by dissemination to the reticuloendothelial system with a subsequent viremia.y The CNS is infected during the course of the viremia.
Clinical Features and Associated Findings. Clinical manifestations of acute LCMV infection in children and adults range from asymptomatic seroconversion to an in
fluenza-like illness to an aseptic meningitis, and rarely to a meningoencephalomyelitis. In patients with aseptic meningitis there is often a history of a biphasic illness. The first stage resembles an influenza-like illness. This is then followed by a symptom-free period of time varying from a few days to 3 weeks, which is followed in turn by the acute onset of high fever, headache, vomiting, and signs of meningeal irritation. y Although the clinical presentation of CNS infection with LCMV is most frequently an aseptic meningitis, it may also be a meningoencephalitis. Congenital LCMV infection can result in intrauterine or early neonatal death, hydrocephalus, chorioretinitis, and psychomotor retardation. y
Differential Diagnosis. The diagnosis of LCMV infection can be made by the appearance of IgM antibodies in a serum sample or by a fourfold or greater rise in antibody titer between the acute and convalescent serum samples. The classic cerebrospinal fluid abnormalities include the following: (1) a lymphocytic pleocytosis of 300 to 3000 cells/mm3 , and (2) hypoglycorrhachia.y LCMV is one of the few etiological agents of an aseptic meningitis with hypoglycorrhachia. LCMV can be isolated from the CSF. The diagnosis of congenital LCMV infection is based on the clinical presentation and laboratory evidence of persistently high IgG immunofluorescent antibody (IFA) titers.y
Management. Prevention of LCMV infection is the priority. Laboratory animals acquired from areas where arenaviruses are indigenous should be tested for LCMV infection. Pregnant women should avoid contact with laboratory and household mice and hamsters. LCMV aseptic meningitis in children and adults is self-limited and complete recovery is the rule.
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