Effect of murine norovirus infection on mouse parvovirus infection.

Enzootic infection with mouse parvovirus (MPV) remains a common problem in laboratory colonies, and diagnosis of MPV infection is complicated by viral and host factors. The effect of an underlying viral infection on MPV infection has not previously been investigated. We assessed the effect of murine norovirus (MNV) infection, the most prevalent infectious agent in laboratory mice, on MPV shedding, tissue distribution and transmission. Fecal MPV shedding persisted longer in BALB/c mice infected with MNV 1 wk prior to MPV infection than in mice infected with MPV only, but transmission of MPV to soiled-bedding sentinels was not prolonged in coinfected mice. MPV DNA levels in coinfected BALB/c mice were higher in mesenteric lymph nodes and spleens at 1 and 2 wk after inoculation and in small intestines at 1 wk after inoculation compared with levels in mice infected with MPV only. In C57BL/6 mice, fecal shedding was prolonged, but no difference in soiled bedding transmission or MPV DNA levels in tissues was detected between singly and coinfected mice. MPV DNA levels in singly and coinfected SW mice were similar. MPV DNA levels were highest in SW, intermediate in BALB/c and lowest in C57BL/6 mice. MPV DNA levels in mesenteric lymph nodes of BALB/c and SW mice exceeded those in small intestines and feces, whereas the inverse occurred in C57BL/6 mice. In conclusion, MNV infection increased the duration of MPV shedding and increased MPV DNA levels in tissues of BALB/c mice.