CaFÉ: A Sensitive, Low-Cost Filtration Method for Detecting Polioviruses and Other Enteroviruses in Residual Waters

Abstract

Acute flaccid paralysis (AFP) surveillance has been used to identify polio cases and target vaccination campaigns since the inception of the Global Poliovirus Eradication Initiative (GPEI) in 1988. To date, only Afghanistan and Pakistan have failed to interrupt wild poliovirus transmission. Circulation of vaccine-derived polioviruses (VDPV) continues to be a problem in high-risk areas of the Eastern Mediterranean, African, and Southeast Asian regions. Environmental surveillance (ES) is an important adjunct to AFP surveillance, helping to identify circulating polioviruses in problematic areas. Stools from AFP cases and contacts (>200,000 specimens/year) and ES samples (>642 sites) are referred to 146 laboratories in the Global Polio Laboratory Network (GPLN) for testing. Although most World Health Organization supported laboratories use the two-phase separation method due to its simplicity and effectiveness, alternative simple, widely available, and cost-effective methods are needed. The CAFÉ (Concentration and Filtration Elution) method was developed from existing filtration methods to handle any type of sewage or residual waters. At $10–20 US per sample for consumable materials, CAFÉ is cost effective, and all equipment and reagents are readily available from markets and suppliers globally. The report describes the results from a parallel study of CAFÉ method with the standard two-phase separation method. The study was performed with samples collected from five countries (Guatemala, Haïti, Thailand, Papua New Guinea, and the Philippines), run in three laboratories–(United States, Thailand and in the Philippines) to account for regional and sample-to-sample variability. Samples from each site were divided into two 500 ml aliquots and processed by both methods, with no other additional concentration or manipulation. The results of 338 parallel-tested samples show that the CAFÉ method is more sensitive than the two-phase separation method for detection of non-polio enteroviruses (p-value < 0.0001) and performed as well as the two-phase separation method for polioviruses detection with no significant difference (p-value > 0.05). The CAFÉ method is a robust, sensitive, and cost-effective method for isolating enteroviruses from residual waters.

Response to Vaccine-Derived Polioviruses Detected through Environmental Surveillance, Guatemala, 2019

“…During November 2018–July 2021, trained MoH staff monthly collected a 1 L wastewater sample from each site and transported them in cold chain (2°C–8°C) the same day to the National Health Laboratory. Samples were stored at −80°C, then shipped at −20°C to the US Centers for Disease Control and Prevention (CDC) reference laboratory for polioviruses to be processed and tested for the presence of poliovirus ( 16 – 18 ). All poliovirus isolates underwent genomic sequencing and analysis of the region coding the viral protein 1 surface protein for nucleotide substitutions compared with the parent Sabin strains.…”

Nearly Complete Genome Sequences of Type 2 Sabin-Like Polioviruses from Northern Nigerian Poliovirus Surveillance, 2016 to 2018

“…Polioviruses, the causative agent of polio, belong to the Enterovirus C species, in the family Picornaviridae . Viruses were isolated using the recommended WHO isolation protocol described previously ( 5 – 7 ). A stool suspension was inoculated in cell culture with two cell lines that contain the poliovirus receptor.…”

Genome Sequences of 16 Enterovirus Isolates from Environmental Sewage in Guatemala, 2019 to 2021

“…Sewage samples were processed using the concentration and filter elution (CaFÉ) method, as described previously ( 3 , 4 ). Resulting concentrates were inoculated into cells for enterovirus isolation according to the World Health Organization protocol ( 5 ).…”