Background
Lymphocytic choriomeningitis virus (LCMV) is a single-stranded RNA virus that belongs to the family Arenaviridae (so named because of its appearance on electron microscopy, which resembles grains of sand). Other members of this family include Lassa virus and the Tacaribe group. Infection with LCMV results in a febrile, self-limited, biphasic disease called lymphocytic choriomeningitis (LCM), which is often complicated by aseptic meningitis. Infected but asymptomatic (carrier state) rodents, most commonly house mice, domestic mice, and hamsters, serve as reservoirs for LCMV. [1, 2] LCMV is most commonly transmitted via inhalation of infected excreta. Contamination of skin scratches is an important route of LCMV infection in pet handlers and laboratory technicians. [2, 3]
Pathophysiology
The initial viremia of LCMV infection (phase 1) extensively seeds extra-CNS tissue. The secondary viremia (phase 2) infects the meninges and, less commonly, the cortical tissue. The leptomeninges are infiltrated mainly by lymphocytes and histiocytes, with few neutrophils. In LCMV encephalitis, the same type of inflammatory cells is observed in the perivascular Virchow-Robin spaces. LCMV is not cytotoxic. It appears that the host's immune response to the infected cells produces the various manifestations of this disease. Natural killer (NK) cells are first to respond, followed by the production of interferon by cytotoxic T cells. In addition, LCMV can suppress the production of acetylcholine neuronal cells in cell culture. [4, 5, 6, 7, 8]
LCM may affect the autonomic nervous system, various sensory modalities, and cranial nerves. Some cases of LCM become chronic, potentially resulting in hydrocephalus. Other organs, especially the testes, heart, and joints, may be involved. Orchitis is usually unilateral. Cardiac involvement is typical of viral myocarditis. The metacarpal phalangeal joint and the proximal interphalangeal joint are the most common sites of arthritis caused by LCM. The objective swelling, redness, and pain resolve within a few weeks. [6, 7, 9]
Epidemiology
Frequency
United States
The exact incidence of LCMV infection is unknown, although the seroprevalence is approximately 5%. Local variations in the frequency of LCMV infection depend on the rodent populations. LCMV infection in humans is most common in autumn. [7]
International
North America, South America, and Europe are the only continents where LCM has been definitively proven to occur. [7]
Mortality/Morbidity
LCMV infection carries a mortality rate of less than 1%. Death may be attributable to complications of encephalitis or to a massive hemorrhagic syndrome. As with other arenaviruses, immunosuppression may predispose to a fatal hemorrhagic fever syndrome. [10]
Race
LCMV infection has no racial predilection.
Sex
LCMV infection has no sexual predilection.
Age
LCMV infection is more common in young adults, although illness may occur in any age group. [7]
Tables
| Diagnosis | Season | Usual Source | Relative Bradycardia | Pharyngitis | Diarrhea | Parotitis | Orchitis | CSF Glucose level |
| LCM | Fall/winter | Mouse, hamster | + | +/- | - | +/- | +/- | Normal or decreased |
| Typhoid fever | Year-round | Food, water | + | + | + (late) | - | - | Normal |
| Enteroviral illness | Summer | Water | - | + | + | - | - | Normal |
| Arboviral illness | Summer | Mosquito | - | - | - | - | - | Normal |
| Leptospirosis | Summer/fall | Dogs, rats | - | - | - | - | - | Normal |
| Influenza | Winter | Person | - | + | - | - | - | Normal |
| Mumps | Winter/spring | Person | - | - | - | + | +/- | Normal or decreased |
