Abstract: | We evaluated the in vitro efficacy of weak acid hypochlorous solution
(WAHS) against murine norovirus (MNV) by plaque assay and compared the efficacy with
diluted NaOCl (Purelox) and 70% ethanol. WAHS was as effective as 70% ethanol and diluted
Purelox for 0.5-min reactions. For 0.5-min reactions in the presence of mouse feces
emulsion, the efficacy of WHAS and 1:600 diluted Purelox was decreased, reducing the virus
titers by 2.3 and 2.6 log10, respectively, while 70% ethanol reduced the titer
by more than 5 log10. However, WAHS showed more than 5 log10
reductions for the 5-min reaction even in the presence of feces emulsion. Since WAHS
showed enough efficacy in inactivating MNV in vitro, we tried to
eliminate MNV from MNV-infected mice by substituting WAHS for their drinking water.
However, MNV was found to be positive in feces of mice drinking WAHS by an RT-nested PCR
and plaque assay. To investigate whether hypochlorite-based disinfectants could prevent
infection of a mouse with MNV, WAHS or 1:6,000 diluted Purelox was substituted for the
drinking water of mice for 2 or 4 weeks, and then the mice were placed in a cage with an
MNV-infected mouse. The supply of disinfectants was continued after cohabitation, but MNV
was detected in the feces of all the mice at 1 week after cohabitation. In this study, we
tried to eliminate and prevent MNV infection from mice by supplying hypochlorite-based
disinfectants as an easy and low-cost method. Unfortunately, drinking disinfectants was
ineffective, so it is important to keep the facility environment clean by use of effective
disinfectants. Also, animals introduced into facilities should be tested as MNV free by
quarantine and periodically confirmed as MNV free by microbiological monitoring. |