TUCSON, ARIZ. — Although only 49 cases of lymphocytic choriomeningitis virus have been reported in the medical literature worldwide, Dr. Marilyn Baird Mets has a hunch that the prevalence could be much higher.
Since 1997, she has seen seven children with the condition present to Children's Memorial Hospital, Chicago, where she is head of ophthalmology.
Subsequently, three other clinicians have called her with reports of positive cases: one from the western suburbs of Chicago, one from Los Angeles, and one from Fort Collins, Colo.
“This virus is out there,” Dr. Mets said at the annual meeting of the Teratology Society. “Obstetricians should be telling their patients not to work around rats in medical labs during their pregnancy [and] not to get a hamster for their 4-year-old if they're going to have other children. It's a preventable disease, but people need to know about it.”
Discovered in 1933 and classified in the 1960s as a prototype for the arena virus, lymphocytic choriomeningitis virus (LCMV) is harbored in mice and transferred vertically by uterine infection. “There is documented infection to humans from wild mice, lab mice, rats, and hamsters,” said Dr. Mets, also professor of ophthalmology and surgery at Northwestern University, Chicago. “Transmission is thought to be airborne or contamination of food by infected mouse urine. There has also been experimental transmission demonstrated by ticks, fleas, mosquitos, and bedbugs.”
About one-third of adults who acquire LCMV are asymptomatic. Of the remaining two-thirds, about half have central nervous system disease. Illness occurs in a biphasic pattern. “First there's an acute febrile illness with myalgias and headache,” she said. “Later on, meningeal signs may develop, and rarely encephalitis, myocarditis, parotitis, orchitis, and pneumonia. Very rarely, fatal systemic disease is reported.”
It's the causative agent in about 10% of aseptic meningitis cases.
LCMV was first described as a fetal pathogen in Great Britain in 1955. The first case of congenital LCMV in the United States was reported in 1993. The baby was born with a birth weight of 2,898 grams. During pregnancy the mother lived in a well-maintained inner-city apartment. At 5 months' gestation, she had a febrile illness that lasted a week. The child was born with hydrocephalus and microphthalmos of the right eye. The right eye had leukocoria, a cloudy vitreous, and exudative retinitis.
A review of 26 infants with LCMV published in 1997 revealed that 88% had chorioretinopathy, 45% had hydrocephalus, and 13% had microcephaly. Diagnosis is made by IgG indirect fluorescent antibody, which is commercially available. “Or you can get an IgG ELISA at the [Centers for Disease Control and Prevention],” Dr. Mets said. “Complement fixation testing lacks the sensitivity” of the other two tests.
The differential diagnosis includes toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, enteroviruses, syphilis, parvovirus B19, and West Nile virus.
'Obstetricians should be telling their patients not to work around rats in a medical lab during their pregnancy.' DR. METS
An optical scan shows the eye of a 22-month-old with congenital LCMV who was referred for visual delay. Courtesy Dr. Marilyn Baird Mets