MOUSE PARVOVIRUSES Division of Animal Resources University of Illinois, Urbana

Background: There are two important parvoviruses chemical tumorigenesis. In immunological studies, of mice: minute virus of mice (MVM) and mouse they can interfere with the modulation of lymphocyte parvovirus type-1 (MPV-1). mitogenic responses, interfere with ascites Minute virus of mice (MVM) is an important production, result in cryptic infection of lymphocytes, infectious agent in laboratory mice. It is a ssDNA and interfere with the humoral antibody spectrum. virus of the family Parvoviridae. Multiple strains have They can interfere with infectious disease studies and been described. cell biology studies by modifying interviral interaction Mouse parvovirus type 1 (MPV-1) is a recently and causing immunosuppression of the host. They recognized and important infectious agent in can also result in altered patterns of rejection of skin laboratory mice. It is a ssDNA virus of the family allografts. A newly identified rat parvovirus (RPV-1) Parvoviridae and was formerly known as orphan may suppress lymphoid tumor development. parvovirus. Three isolates of one serotype have been identified. Prevention: To prevent this disease, obtain replacement stocks from sources that are known to Transmission: The parvoviruses require rapidly be free of disease. Tumor lines should be assessed dividing cells (such as GI, skin, and lymphoid organs) for infection using MAP tests or other appropriate to survive. They are shed in urine and feces and may tests. Personnel working with infected animals should be transmitted via respiratory routes. They are highly not enter rooms that contain naïve animals. contagious and shed virus for an undetermined time after infection. Direct contact with affected animals is Eradication: The most effective way to eradicate probably required, but transmission has not been well parvovirus infections is to cull the colony and obtain characterized. clean replacement stock. However, this is not always It is important to realize that it is not known if a feasible option when working with valuable mice. intermittent shedding of the virus occurs when mice Caesarian rederivation or embryo transfer can harboring virus in the intestines are exposed to be used to produce offspring that have not been environmental or experimental stressors. exposed to the virus. Repeated serological MVM has been reported as a common evaluations should be performed prior to contaminant of transplantable tumors and mouse reintroduction of the mice into a naïve population. leukemia virus stocks. A breeding moratorium of at least 8 weeks can also be used to prevent the spread of the virus from Clinical Signs: Mouse strains vary in their young weanling animals to younger naïve animals. sysceptibility to MVM. Natural parvovirus infections of The animals should be housed in microisolator immunocompetent and immunocompromised mice caging and handled with standard microisolator generally result in no overt clinical disease or techniques. This method requires repeated serologic pathology. Viral replication occurs in the pancreas, testing and strict adherence to a zero-tolerance for small intestine, lymphoid organs, and liver that breeding policy. It is important to note that transgenic persists for several weeks after infection. MVM also and knockout mice often have altered immune replicates in the kidneys. systems that may allow them to sustain the infection Experimental infection with MVM will result in for longer periods of time or to develop a carrier state. severe damage to multiple organs in the developing In these cases, the breeding moratorium would not fetus and in neonates. be the appropriate means of eradication.

Diagnosis: Diagnosis is usually based on serology, References: via ELISA or IFA or both. MVM and MPV-1 may Baker, DO. 1998. “Natural Pathogens of Laboratory Mice, Rats, cross-react during the IFA test due to similar non- and Rabbits and Their Effects on Research.” Clinical Microbiology Reviews. 11:231-266. structural proteins in the viruses. Shek. WR at al. 1998. “Characterization of mouse parvovirus Effects on Research: The parvoviruses have similar infection amoung BALB/c mice from an enzootically infected effects on research. They can reduce the rate of colony.” Laboratory Animal Science. 48: 294-297. transplantable tumor take by direct oncolysis or Tattersait, P and Cotmore SF. 1986. “The rodent parvoviruses.” In modulation of immune response to tumor cells, Viral and Mycoplasinal Infections of Laboratory Rodents. ed. Bhatt, interfere with the selection of new transplantable PN at el. Academic Press Inc. pp 305-348. tumor phenotypes, and cause a reduction in viral or