Prevalence and Pathologic Characterization of Mouse Kidney Parvovirus in Sentinel CD1 Mice

Mouse kidney parvovirus (MKPV) infection can cause significant morbidity and mortality by inducing moderate to severe inclusion body nephropathy and kidney fibrosis in aged immunodeficient mice. However, MKPV infection in immunocompetent mice is associated with histopathologic findings ranging from absent to minimal or moderate lymphoplasmacytic interstitial nephritis without inclusion body in most cases. We surveyed the prevalence of MKPV via PCR from August 2019 through January 2021, using feces, kidneys, and livers collected and pooled from 2 sentinel mice [Crl:CD1(ICR)] (CD1) per surveillance cage (a total of 212 cages). CD1 mice used as dirty-bedding sentinels were housed for 6 mo in a separate cage on the same rack as colony mice used in research at the Massachusetts Institute of Technology and at the Whitehead Institute for Biomedical Research. MKPV quantitative PCR positivity was 16.04%, 14.62%, and 10.02% for feces, kidney, and liver, respectively. The aggregate prevalence of MKPV was 22.64% (48 of 212 samples). Thirty-three of 103 rooms (32.04%) were MKPV positive. MKPV-positive kidneys had more severe chronic lymphoplasmacytic interstitial nephritis (CLIN) than MKPV-negative kidneys; however, there was no significant difference in hepatic lesions between MKPV-positive and -negative livers. Although no overt intranuclear inclusion body nephropathy was noted in MKPV-positive CD1 kidneys, MKPV RNA was sporadically detected within tubular epithelial cells in MKPV-positive kidneys but not in MKPV-positive livers. Our study indicates that MKPV can be easily transmitted through soiled bedding. It highlights that CD1 mice can be used as sentinels to detect MKPV, emphasizing the importance of monitoring MKPV distribution using quantitative PCR in sentinel mice if MKPV needs to be excluded from a colony. Importantly, as MKPV infection is associated with mild to moderate CLIN, MKPV can potentially confound the interpretation of in vivo biomedical data.