Zoonotic concern: Lymphocytic Choriomeningitis Virus in Rodents

Key Points

  • Lymphocytic choriomeningitis or LCM is a rodent-borne viral infectious disease.
  • Humans are infected with lymphocytic choriomeningitis virus or LCMV by direct contact with or inhalation of fresh urine, droppings, saliva, or contaminated nesting materials.
  • Clinical infection in humans can result in serious systemic infection including aseptic meningitis or meningoencephalitis.
  • Anyone who comes into contact with rodents is potentially at risk.
  • Always wash your hands with soap and water after handling rodents or their cages and bedding.

Introduction

The physical and psychological benefits of pet ownership have been well established (Friedman 2009), however close contact with pets is not without risks including the potential for transmission of zoonotic disease. Rodents can carry a number of potential pathogens including lymphocytic choriomeningitis virus (LCMV).

mouse Tiia Monto WC

Figure 1. Rodents can carry lymphocytic choriomeningitis virus. Photo credit: Tiia Monto [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons.

Rodent-borne disease

Lymphocytic choriomeningitis virus (LCMV), is a rodent-borne viral infectious disease caused by an arenavirus. Lymphocytic choriomeningitis virus is found throughout the world in wild rodents. Disease is especially common in the common house mouse (Mus musculus), which may be infected and shed virus without ever showing any signs of illness. Approximately five percent of mice in the United States carry LCMV.

Although not primary hosts, other rodents such as the hamster and guinea pig (Cavia porcellus) can also serve as disease reservoirs after they are exposed to wild mice infected with LCMV.

Infected rodents are typically asymptomatic, but clinical signs may include weight loss, sensitivity to light, and central neurologic signs such as tremors or seizure activity (Mitchell 2004). Lymphocytic choriomeningitis is also a potential cause of paresis or paralysis in guinea pigs.

Transmission

Humans are infected with LCMV by direct contact with or inhalation of fresh urine, droppings, saliva, or contaminated nesting materials. Transmission can also occur when LCMV is introduced into broken skin or mucous membranes as well as through rodent bites. Person-to-person transmission has only been reported from infected mother to the fetus.

 

Clinical picture

In immunocompetent individuals, disease is either asymptomatic or mild with self limiting flu-like signs such as lethargy, anorexia, muscle pain, headache, fever, nausea, and vomiting.

In pregnant women, the very young or the very old, individuals on radiation, chemotherapy, high doses of steroids, as well as the HIV-positive, clinical disease can include:

  • Neurologic signs, such as stiff neck, confusion, neurologic deficits, and paralysis, may predominate.
  • Death is possible but rare. Although in a recent report, four transplant recipients became ill after receiving organs from a common donor infected with LCMV by a pet hamster. Three patients died (Amman 2007).
  • Infection of pregnant women can cause birth defects such as congenital hydrocephalus, chorioretinitis, blindness, and mental retardation.
  • Lymphocytic choriomeningitis virus infection during pregnancy has also been associated with spontaneous abortion.

 

Who is at risk?

Although house mice are considered the most common source of infection, the Centers for Disease Control recommends that pregnant women and immunocompromised people should not own pet rodents. Veterinary staff, laboratory workers, and owners of pet rodents may also be at risk for infection if the animals originate from colonies contaminated with LCMV or if animals become infected after exposure to wild mice.

 

Prevention

To minimize the risk of LCMV infection in pet rodents, breeders, pet stores, and pet owners should take measures to prevent wild rodent infestations. Individuals should also wash hands with soap and water after handling rodents or their cages and bedding. When working closely with large numbers of rodents, wear protective clothing to reduce exposure.

References