WHERE DO WE STAND?
Since July, we have tested 60 sentinel mice and found 13 seropositive
for MPV. All of these mice were derived from the same vendor and
11 were received on the same date from the same site. In no case
have we found MPV DNA in any of these mice when assessed by PCR.
The detection of positive sentinels has, however, resulted in
the imposition of quarantine isolation on five colony rooms. Encouragingly,
testing 354 mice from our colonies, with another 20 pending, has
shown no evidence of MPV. These findings suggest, but do not prove,
that we may have acquired seropositive mice from the vendor or
that the mice may have become infected with MPV either during
or shortly after shipment. Transportation of rodents, particularly
via air, where they may be mixed with other cargo and potentially
exposed to other rodents in cargo holding areas during layovers,
carries with it an estimated risk of infection of 1.25% (Lab Anim
Sci 48(5): 438-47, 1998). The vendor has been informed of our
suspicions and asked to redouble efforts to assess for MPV.
WHAT DOES THE IMMEDIATE FUTURE HOLD?
As mentioned in my last update, the sentinel program has been
beefed-up by quadrupling the number of sentinels per rack so as
to provide indirect exposure to more mice quickly. This increase
in surveillance should provide valuable information relevant to
MPV during the September and October sentinel assessments and
will permit us to discontinue the more expensive practice of testing
large numbers of mice selected from each room. It should also
enable us to determine whether we must continue to quarantine
colonies that have been isolated since the first positive sentinels
were reported. This situation has also afforded DAR the opportunity
to review our current quarantine and sentinel program practices
with our faculty advisory committee and to refine our practices
to better and more safely and effectively serve all rodent users.
While our findings are encouraging, this is no time to let up.
Renewed vigilance and continued adherence to preventive medicine
practices as described in the main "Mouse Parvovirus Outbreak"
posting remain paramount.
