Etiology: Lactate dehydrogenase elevating virus (LDV) is an enveloped arterivirus composed of a single strand of RNA.
Incidence: Infection of research mice is rare outside of those used for tumor or tissue transplantation.
Transmission: Infected mice have a long-standing viremia which enhances transmission of virus through reuse of contaminated needles in experimental manipulations or transplantation of infected tumors or tissues.
Clinical Signs: Experimental infection of susceptible mouse strains (C58 or AKR) with neurotropic strains of LDV leads to a progressive paralysis when ecotropic mouse leukemia virus infection is concurrently present.
Pathology: Virus replicates in macrophages and within 24 hours of inoculation, serum levels of lactate dehydrogenase become elevated due to impairment of clearance of virus. Viremia develops and continues for extended period of time even though an antiviral antibody is produced. Antibody-antigen complexes occur but do not appear to prevent use of antibody for detection of infection. Lesions observed in experimentally inoculated mice are non-specific and transient and include a decrease in thymus weight and splenomegaly. In experimental infection with neurotropic strains, neuronal necrosis with accompanying lymphocyte infiltrates has been reported in the grey matter of the spinal cord.
Diagnosis: MFI or IFA can be used to diagnose infection. Blood or tumors from mice suspected of infection can be screened by PCR. Infection can also be determined by measuring levels of lactate dehydrogenase in plasma or serum. However, trauma to cardiac muscles during cardiocentesis, inflammation, or other stressors can falsely elevate LDH; therefore confirmation by PCR is recommended.