Effective surveillance of human enteric viruses is critical to estimate disease prevalence within a community and can be a vital supplement to clinical surveillance. This study sought to evaluate simple, effective, and inexpensive secondary concentration methods for use with ViroCap™ filter eluate for environmental surveillance of poliovirus. Wastewater was primary concentrated using cartridge ViroCap filters, seeded with poliovirus type 1 (PV1), and then concentrated using five secondary concentration methods (beef extract-Celite, ViroCap flat disc filter, InnovaPrep® Concentrating Pipette, polyethylene glycol [PEG]/sodium chloride [NaCl] precipitation, and skimmed-milk flocculation). PV1 was enumerated in secondary concentrates by plaque assay on BGMK cells. Of the five tested methods, PEG/NaCl precipitation and skimmed-milk flocculation resulted in the highest PV1 recoveries. Optimization of the skimmed-milk flocculation method resulted in a greater PV1 recovery (106 ± 24.8%) when compared to PEG/NaCl precipitation (59.5 ± 19.4%) ( p = 0.004, t-test). The high PV1 recovery, short processing time, low reagent cost, no required refrigeration, and requirement for only standard laboratory equipment suggest that the skimmed-milk flocculation method would be a good candidate to be field-validated for secondary concentration of environmental ViroCap filter samples containing poliovirus. Electronic supplementary material The online version of this article (10.1007/s12560-018-09364-y) contains supplementary material, which is available to authorized users.

Environmental surveillance of poliovirus (PV) plays an important role in the global program for eradication of wild PV. The bag-mediated filtration system (BMFS) was first developed in 2014 and enhances PV surveillance when compared to the two-phase grab method currently recommended by the World Health Organization (WHO). In this study, the BMFS design was improved and tested for its usability in wastewater and wastewater-impacted surface waters in Nairobi, Kenya. Modifications made to the BMFS included the size, color, and shape of the collection bags, the filter housing used, and the device used to elute the samples from the filters. The modified BMFS concentrated 3–10 L down to 10 mL, which resulted in an effective volume assayed (900–3000 mL) that was 6–20 times greater than the effective volume assayed for samples processed by the WHO algorithm (150 mL). The system developed allows for sampling and in-field virus concentration, followed by transportation of the filter for further analysis with simpler logistics than the current methods. This may ultimately reduce the likelihood of false-negative samples by increasing the effective volume assayed compared to samples processed by the WHO algorithm, making the BMFS a valuable sampling system for wastewater and wastewater-impacted surface waters.

Environmental surveillance of poliovirus (PV) and other non-enveloped viruses can help identify silent circulation and is necessary to certify eradication. The bag-mediated filtration system is an efficient method to filter large volumes of environmental waters at field sites for monitoring the presence of viruses. As filters may require long transit times to off-site laboratories for processing, viral inactivation or overgrowth of bacteria and fungi can interfere with virus detection and quantification (Miki and Jacquet in Aquatic Microb Ecol 51(2):195–208, 2008). To evaluate virus survival over time on ViroCap™ filters, the filters were seeded with PV type 1 (PV1) and/or MS2 and then dosed with preservatives or antibiotics prior to storage and elution. These filters were stored at various temperatures and time periods, and then eluted for PV1 and MS2 recovery quantification. Filters dosed with the preservative combination of 2% sodium benzoate and 0.2% calcium propionate had increased virus survival over time when stored at 25 °C, compared to samples stored at 25 °C with no preservatives. While elution within 24 h of filtration is recommended, if storage or shipping is required then this preservative mixture can help preserve sample integrity. Addition of an antibiotic cocktail containing cephapirin, gentamicin, and Proclin™ 300 increased recovery after storage at 4 and 25 °C, when compared to storage with no antibiotics. The antibiotic cocktail can aid sample preservation if access to appropriate antibiotics storage is available and sample cold chain is unreliable. This study demonstrated that the use of preservatives or antibiotics is a simple, cost-effective method to improve virus detection from ViroCap cartridge filters over time.