Lymphocytic Choriomeningitis Virus in Employees and Mice at Multipremises Feeder-Rodent Operation, United States, 2012

Barbara Knust

, Ute Ströher, Laura Edison, César G. Albariño, Jodi Lovejoy, Emilian Armeanu, Jennifer House, Denise Cory, Clayton Horton, Kathy L. Fowler, Jessica Austin, John Poe, Kraig E. Humbaugh, Lisa Guerrero, Shelley Campbell, Aridth Gibbons, Zachary Reed, Deborah Cannon, Craig Manning, Brett Petersen, Douglas Metcalf, Bret Marsh, Stuart T. Nichol, and Pierre E. Rollin

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (B. Knust, U. Ströher, L. Edison, C.G. Albarino, L. Guerrero, S. Campbell, A. Gibbons, Z. Reed, D. Cannon, C. Manning, B. Petersen, S.T. Nichol, P.E. Rollin); Georgia Department of Public Health, Atlanta (L. Edison); Indiana Board of Animal Health, Indianapolis, Indiana, USA (J. Lovejoy, D. Metcalf, B. Marsh); Deaconess Hospital, Evansville, Indiana, USA (E. Armeanu); Indiana State Department of Health, Indianapolis (J. House); Vanderburgh County Health Department, Evansville (D. Cory); Green River District Health Department, Owensboro, Kentucky, USA (C. Horton, J. Austin); Kentucky Department for Public Health, Frankfort, Kentucky, USA (K.L. Fowler, J. Poe, K.E. Humbaugh)

Abstract

We investigated the extent of lymphocytic choriomeningitis virus (LCMV) infection in employees and rodents at 3 commercial breeding facilities. Of 97 employees tested, 31 (32%) had IgM and/or IgG to LCMV, and aseptic meningitis was diagnosed in 4 employees. Of 1,820 rodents tested in 1 facility, 382 (21%) mice (Mus musculus) had detectable IgG, and 13 (0.7%) were positive by reverse transcription PCR; LCMV was isolated from 8. Rats (Rattus norvegicus) were not found to be infected. S-segment RNA sequence was similar to strains previously isolated in North America. Contact by wild mice with colony mice was the likely source for LCMV, and shipments of infected mice among facilities spread the infection. The breeding colonies were depopulated to prevent further human infections. Future outbreaks can be prevented with monitoring and management, and employees should be made aware of LCMV risks and prevention.

Lymphocytic choriomeningitis virus (LCMV), a rodent-borne arenavirus, is a rare, zoonotic cause of aseptic meningitis in Europe and North America. It is carried by the common house mouse (Mus musculus), but other rodent species, such as hamsters and guinea pigs, can become infected and transmit infection to humans (1). Infected rodents shed the virus in urine, saliva, and droppings. Transplacental infection in mice results in persistently infected offspring, that shed virus throughout life (2). Humans become infected through close contact with infected rodents, through transplantation of infected organs, or by vertical transmission. In immunocompetent adults, infections range from mild febrile illness to aseptic meningitis; in immunosuppressed organ recipients, infections are highly fatal, and congenitally infected infants can have a range of severe birth defects (3).

In late April 2012, an infectious disease physician contacted the Centers for Disease Control and Prevention (CDC, Atlanta, GA, USA) about a 27-year-old woman (patient 1) who sought hospital care for fever, severe headache, photophobia, and vomiting. Cerebrospinal fluid (CSF) had elevated leukocytes (> 1,000/mm3 [reference < 5]), elevated protein (153 mg/dL [reference 12–80 mg/dL]), and negative bacterial culture. Patient 1 reported working at an Indiana rodent breeding facility (facility A). In April 2012, aseptic meningitis had been diagnosed in patient 2, who was patient 1’s domestic partner and co-worker (E. Armeanu, unpub. data). LCMV infection was suspected, and specimens were submitted to CDC for diagnostic confirmation. Serum samples from patients 1 and 2 and CSF from patient 1 were positive for LCMV IgM by ELISA, indicating recent LCMV infection. Reverse transcription PCR (RT-PCR) for LCMV was negative, indicating that viremia was no longer present.

The Vanderburgh (Indiana) County Health Department, in conjunction with the Indiana State Department of Health, Indiana Board of Animal Health, and CDC, initiated an outbreak investigation to determine the extent of LCMV infection in the staff and rodents in facility A (4). Trace-back investigations also identified a distributor (facility B) where live rats (Rattus norvegicus) and mice (M. musculus) from facility A were handled and packaged for sale as live and frozen animal food in 21 states (5). An additional mouse breeding facility in Kentucky (facility C) had shipped live mice to facility B, which redistributed them to facility A shortly before the outbreak. We describe the diagnostic and epidemiologic aspects of this investigation and the response taken to control the outbreak at these facilities.