Evaluation of tomato brown rugose fruit virus as a microbial source tracking marker for human sewage in Thailand.

Tomato brown rugose fruit virus (ToBRFV) has emerged as a major plant pathogen with the potential to spread through contaminated wastewater, posing risks to agriculture and public health. This study evaluated ToBRFV as a human-specific microbial source tracking (MST) marker in Thailand, comparing its performance to crAssphage. Using qPCR assays, ToBRFV was detected in 62.5 % of building sewage samples (n = 16) and 100.0 % of wastewater treatment plant (WWTP) influent samples (n = 16). Notably, ToBRFV showed minimal cross-detection in non-human fecal samples (35 pooled samples), collected from cows, pigs, chickens, ducks, and goats, with only one detection in a pig fecal-source sample, demonstrating high specificity to human sewage. Concentrations in WWTP influent were significantly higher (mean: 5.19 ± 5.05; range: 3.96-5.62 log₁₀ copies/100 mL) than in building sewage (mean: 4.36 ± 4.40; range: 2.33-4.85 log₁₀ copies/100 mL) (p < 0.001). ToBRFV concentrations were significantly lower than crAssphage in building sewage but higher in WWTP influents. Additionally, ToBRFV and crAssphage exhibited moderate correlations in both building sewage and WWTP influent samples. These results suggest that ToBRFV could serve as a valuable MST marker for identifying human contamination in water bodies, complementing established markers. While ToBRFV's broader utility across diverse geographic regions remains to be fully validated, this study highlights its potential as a reliable indicator of human sewage in environmental surveillance.