Abstract:
AIMS : This study compared the bag-mediated filtration system (BMFS) and
standard WHO two-phase separation methods for poliovirus (PV)
environmental surveillance, examined factors impacting PV detection and
monitored Sabin-like (SL) PV type 2 presence with withdrawal of oral polio
vaccine type 2 (OPV2) in April 2016.
METHODS AND RESULTS : Environmental samples were collected in Nairobi,
Kenya (Sept 2015–Feb 2017), concentrated via BMFS and two-phase separation
methods, then assayed using the WHO PV isolation algorithm and intratypic
differentiation diagnostic screening kit. SL1, SL2 and SL3 were detected at
higher rates in BMFS than two-phase samples (P < 0 05). In BMFS samples,
SL PV detection did not significantly differ with volume filtered, filtration time
or filter shipment time (P > 0 05), while SL3 was detected less frequently with
higher shipment temperatures (P = 0 027). SL2 was detected more frequently
before OPV2 withdrawal in BMFS and two-phase samples (P < 1 9 10
5).
CONCLUSIONS : Poliovirus was detected at higher rates with the BMFS, a method
that includes a secondary concentration step, than using the standard WHO
two-phase method. SL2 disappearance from the environment was
commensurate with OPV2 withdrawal.
SIGNIFICANCE AND IMPACT OF THE STUDY : The BMFS offers comparable or
improved PV detection under the conditions in this study, relative to the twophase
method.
