The use of cross-foster rederivation to eliminate murine norovirus, Helicobacter spp., and murine hepatitis virus from a mouse colony.

Over 10 mo, 287 mouse litters were cross-fostered by using 1 of 2 paradigms to eliminate murine norovirus (MNV), Helicobacter spp., murine hepatitis virus (MHV), and Syphacia obvelata. Paradigm 1 involved cross-fostering litters at younger than 48 h with no attention to the changing of bedding material. Paradigm 2 involved cross-fostering litters at younger than 24 h from cages in which the bedding material was changed within 24 h before cross-fostering. After cross-foster rederivation, mice were tested for the presence of Helicobacter spp. by means of fecal PCR at 4, 8, and 12 wk. Surrogates also were tested for MNV by use of multiplex fluorometric assay serology at 4 wk and fecal PCR at 12 wk. Surrogate mice were tested for MHV by means of MFIA at 4 wk and for pinworms by perianal tape test and fecal flotation at 4 and 12 wk. Compared with those from paradigm 1, litters from paradigm 2 were less likely to be positive for MHV and Helicobacter spp. The use of cross-foster rederivation alone was unsuccessful for the elimination of Syphacia obvelata. For cross-foster rederivation, we recommend that litters be younger than 24 h and from cages in which the bedding material was changed within 24 h before cross-fostering. The presence of MNV, Helicobacter spp., and MHV can be predicted reliably at 12, 8, and 4 wk, respectively.