Exclusion of mouse hepatitis virus from a filtered, plastic rodent shipping container during an in transit field challenge.

Although leading suppliers of laboratory mice and rats continue to use filtered shipping boxes to protect their animals from contamination during transport to the end user, no information had been available in the literature to demonstrate that any of these boxes actually accomplish this task. To test this hypothesis, 12 plastic shipping boxes with filters and tight-fitting lids and six cardboard shipping boxes without filters (controls) were each stocked with adult, adventitious disease-free mice. All 18 shipping boxes were transported to a facility housing a breeding colony of mice enzootically infected with four murine viruses, including mouse hepatitis virus (MHV), and were placed inside the colony for 15 h. The boxes were then transported to a commercial testing laboratory, at which the animals were aseptically removed and were held in microisolation cages for 28 days, after which their sera tested for antibody to all four murine viruses. All serum samples from mice held in the control boxes were positive for antibody to MHV, whereas sera from all mice held in filtered boxes were negative for antibody to any of the four viruses. This study demonstrates that at least one type of filtered shipping container protects mice from a field challenge of MHV. To the best of our knowledge, this is the first documentation of any microbial efficacy testing conducted on filtered shipping containers for laboratory animals.