The reliability of CrAssphage in human fecal pollution detection: A cross-regional MST marker assessment

Microbial Source Tracking (MST) markers play a key role in identifying sources of fecal contamination, particularly human-associated pollution, which is critical for public health. This study investigates the distribution and reliability of three MST markers (crAssphage, HMBif, and HF183) across various environmental contexts in Europe, Asia, and Africa. Samples were obtained from wastewater treatment plants (WWTPs) and rivers across different catchment areas, including sampling during extreme weather conditions such as heavy rainfall and drought. The concentrations of these MST markers were measured and compared with traditional fecal indicators. The obtained results indicate that crAssphage showed consistently the highest prevalence and concentrations in all regions and sample types, demonstrating its robustness as a marker of human fecal contamination. Population density and climatic conditions significantly influenced marker levels, with the highest concentrations found in highly populated areas with moderate climates. The impact of extreme weather events was different for each condition: heavy rainfall resulted in elevated MST marker concentrations, likely due to sediment resuspension, while drought led to more inconsistent results. Strong correlations were observed among the three MST markers and between these markers and conventional fecal indicators. This study underscores the value of crAssphage as a reliable and effective tool for tracking human fecal pollution and highlights the influence of environmental and climatic factors on MST marker behavior.