Characterizing Environmental Surveillance Sites in Nigeria and Their Sensitivity to Detect Poliovirus and Other Enteroviruses

Abstract

Background Environmental surveillance (ES) for poliovirus is increasingly important for polio eradication, often detecting circulating virus before paralytic cases are reported. The sensitivity of ES depends on appropriate selection of sampling sites, which is difficult in low-income countries with informal sewage networks. Methods We measured ES site and sample characteristics in Nigeria during June 2018–May 2019, including sewage physicochemical properties, using a water-quality probe, flow volume, catchment population, and local facilities such as hospitals, schools, and transit hubs. We used mixed-effects logistic regression and machine learning (random forests) to investigate their association with enterovirus isolation (poliovirus and nonpolio enteroviruses) as an indicator of surveillance sensitivity. Results Four quarterly visits were made to 78 ES sites in 21 states of Nigeria, and ES site characteristic data were matched to 1345 samples with an average enterovirus prevalence among sites of 68% (range, 9%–100%). A larger estimated catchment population, high total dissolved solids, and higher pH were associated with enterovirus detection. A random forests model predicted “good” sites (enterovirus prevalence >70%) from measured site characteristics with out-of-sample sensitivity and specificity of 75%. Conclusions Simple measurement of sewage properties and catchment population estimation could improve ES site selection and increase surveillance sensitivity.

The challenges of informative wastewater sampling for SARS-CoV-2 must be met: lessons from polio eradication

“…Locations include the entrances of sewage treatment works, upstream pumping stations, or direct collection at rivers or latrines. Industry effluence, runoff from excess rain, and the pH of the sample 7 can all affect sample quality, which might influence the ability to detect and isolate virus. The method of sampling (eg, 24-h composite samples vs periodic grab samples), population demographics of the catchment area, and local epidemiological factors are important for planning environmental surveillance.…”

Defining the methodological approach for wastewater-based epidemiological studies—Surveillance​ of SARS-CoV-2

“…Wastewater sampling in cities requires sewer network maps to understand the population being represented. Outside of dense populations, there are fewer sewer networks that restricts the representative wastewater sampling ( Hamisu et al, 2020 ). Interpretation of positive wastewater samples along with clinical investigation will yield more information ( Asghar et al, 2014 , O’Reilly et al, 2020 ).…”

High Diversity of Human Non-Polio Enterovirus Serotypes Identified in Contaminated Water in Nigeria

“…Lastly, recent studies suggest there is little interference between the circulation of different EV serotypes in the same population with circulation of specific EV serotypes not having a major impact on the transmission of other EV serotypes [24]. Indeed, several other factors do seem to have an effect on the detection of EVs in environmental samples such as the nature of the sewage network, the appropriateness of the sampling site, the catchment population, and the physicochemical properties of sewage [25]. Samples used in this study were taken from water streams that are often contaminated with sewage, but levels of contamination and catchment population numbers are difficult to estimate making that comparisons between sites more difficult.…”