Feasibility of the Bag-Mediated Filtration System for Environmental Surveillance of Poliovirus in Kenya

Abstract

The bag-mediated filtration system (BMFS) was developed to facilitate poliovirus (PV) environmental surveillance, a supplement to acute flaccid paralysis surveillance in PV eradication efforts. From April to September 2015, environmental samples were collected from four sites in Nairobi, Kenya, and processed using two collection/concentration methodologies: BMFS (> 3 L filtered) and grab sample (1 L collected; 0.5 L concentrated) with two-phase separation. BMFS and two-phase samples were analyzed for PV by the standard World Health Organization poliovirus isolation algorithm followed by intratypic differentiation. BMFS samples were also analyzed by a cell culture independent real-time reverse transcription polymerase chain reaction (rRT-PCR) and an alternative cell culture method (integrated cell culture-rRT-PCR with PLC/PRF/5, L20B, and BGM cell lines). Sabin polioviruses were detected in a majority of samples using BMFS (37/42) and two-phase separation (32/42). There was statistically more frequent detection of Sabin-like PV type 3 in samples concentrated with BMFS (22/42) than by two-phase separation (14/42, p = 0.035), possibly due to greater effective volume assayed (870 mL vs. 150 mL). Despite this effective volume assayed, there was no statistical difference in Sabin-like PV type 1 and Sabin-like PV type 2 detection between these methods (9/42 vs. 8/42, p = 0.80 and 27/42 vs. 32/42, p = 0.18, respectively). This study demonstrated that BMFS can be used for PV environmental surveillance and established a feasible study design for future research.

Keywords: BMFS; Environmental monitoring; Environmental surveillance; Poliovirus; Two-phase separation; Wastewater.

Fig. 1

Workflow of collected environmental samples. Bag-mediated filtration system (BMFS) samples were collected concurrently with 1 L grab samples for two-phase concentration according to World Health Organization protocols. KEMRI Kenya Medical Research Institute, UP University of Pretoria, CDC US Centers for Disease Control and Prevention, ITD intratypic differentiation

Fig. 2

Detection of Sabin-like polioviruses during April–September 2015 in bag-mediated filtration system (BMFS) and two-phase samples from four study sites in Nairobi, Kenya. BMFS bag-mediated filtration system, PV poliovirus, NPEV non-polio enterovirus, SL1 Sabin-like poliovirus type 1, SL2 Sabin-like poliovirus type 2, SL3 Sabin-like poliovirus type 3