Occurrence of Human Norovirus and Hepatitis A Virus in Domestic Agricultural Waters

Assessing the prevalence of foodborne pathogens in the environment is an important step toward mitigating those risks. In this comprehensive two-year study, we assessed the occurrence of human norovirus (NoV) and hepatitis A virus (HAV) in agricultural water used for crop irrigation to better understand potential sources of contamination, which can contribute to outbreaks caused by these viruses. For the first series of experiments, samples of surface and ground water were collected monthly during the growing seasons from 36 sites, representing 21 farms in two regions in the US, namely Georgia (GA) and Ohio (OH). Two primary concentration methods were employed to capture naturally occurring viruses from 10L of water: either dead-end hollow fiber ultrafiltration (DEUF) or modified Moore swab (MMS). For secondary virus concentration, DEUF was coupled with polyethylene glycol (PEG) precipitation, while MMS was paired with ultracentrifugation. The detection rate using RT-qPCR was 8.4% for NoV genogroup II (NoV-GII) and 9.4% for HAV, found across 24 sampling sites on 15 farms. We then directly compared the performance of DEUF and MMS for virus recovery by concentrating 10 L of agricultural water spiked with NoV with each method. The DEUF consistently provided both higher detection rates and lower Ct values across various levels of virus spiking (p < 0.05 at the seeding level of 5.0E+05 genome copies/10L). There were no significant differences in virus recovery between the two secondary concentration methods (PEG or ultracentrifugation). Improving methods for obtaining surveillance information will provide greater insights into the prevalence of human enteric viruses in irrigation water and support the development of viral pathogen mitigation strategies in the prevention of foodborne outbreaks.