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Archives - August
27, 1999 Update
Prepared by Dr. Huerkamp
What have we done? To date, we have tested 184 colony (non-sentinel)
mice by serologic means and found no evidence of MPV antibody other
than in 10 sentinels. Interestingly, 8 of the 10 seropositive sentinels
were from the same stock, source and batch of mice received in March
1999 and used for health surveillance in the Rollins Building.
The assessment of 184 mice should be sufficient to detect at least
one infected mouse with a 99% level of confidence if the prevalence
of MPV infection is 2.5% or more. Another 16 serology samples are
pending. That is the good news. The bad news is that it may take
up to 6 weeks for an individual mouse to seroconvert following MPV
infection. Thus, the negative serology results are only reflective
of the health status of the mice up to 2-6 weeks ago and it is possible
that we could be on the cusp of seroconversion of more mice. However,
we have also used PCR to assess for MPV in the mesenteric lymph
nodes of 38 mice and an additional 15 samples are pending. PCR enables
us to detect MPV DNA suggestive of infection and has also permitted
us to expand our breadth of testing to include immunosuppressed
mice incapable of mounting a diagnostic humoral response. The assessment
of 38 mice is sufficient to detect at least one infected mouse with
a 95% level of confidence if the prevalence of infection is at least
7.5%. The assessment to date of a total of 222 mice is sufficient
to detect at least one positive with a 99% level of confidence if
the prevalence of MPV is 2% or greater. It remains to be seen whether
we have a low prevalence of infection or early detection of acute
infection.
What are we doing? The accumulation and testing of the total of
253 mice has met our immediate objective and two weeks ahead of
schedule. Based upon our findings, a prime suspicion for infection
in the Rollins Building is that we may have purchased seropositive
sentinels or the sentinels may have become infected shortly after
acquisition. In pursuit of this possibility, all remaining mice
from the March sentinel shipment have been sent to necropsy for
MPV assessment by serology and lymph node PCR. In addition, the
DAR is concentrating diagnostic efforts on the five quarantined
rooms (Eye BT 414, Eye BT 419, Rollins G22, Rollins G23, Rollins
G24) in an attempt to identify pockets of infection. The sentinel
program has been beefed-up to provide more intensive monitoring
of all of our colonies through the use of more sentinels, more frequent
testing, changes in the sentinel exposure strategy, and retraining
of the DAR staff. As it may take considerable time to find infected
animals and manage them, we need and appreciate everyone's continued
cooperation with the wearing of garb and adherence to preventive
medicine procedures as described in the main "Mouse Parvovirus
Outbreak" posting.
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