Fate of human enteric viruses during dairy manure-based composting

Murine norovirus 1 (MNV-1), Aichi virus (AiV), and human adenovirus 41 (Ad41) were seeded in dairy manure and composted for 60 days, and both the stability of virus genomes and infectious viruses were evaluated. For compost started in late fall, pile temperature reached approximately 54.5 degrees C on day 1 and remained between 55 and 60 degrees C for 3 days. For viral genomes, AiV had an approximate 1.4-log loss of viral genome after 1 day and more than a 3.1-log loss after 2 days; while for MNV-1, there was a roughly 0.6-log reduction on day 1 and a more than 4-log reduction after 5 days. For compost started in late spring, the center temperature reached about 70 degrees C on day 1 and remained warmer than 65 degrees C for 3 days. The MNV-1 viral genome level was below the detection limit (ca. 3.4 log reverse transcriptase and quantitative PCR unit per g) after 1 day. Compared with RNA viruses, the Ad41 DNA genome was more stable in compost started in late spring; there was no reduction in DNA after 1 day, and ca. a 2.1-log loss at 5 and 7 days. For viral infectivity, the AiV infectious concentration was below the detection limit (about 2.8 log tissue culture infectious dose assay per g) after day 1 for both trials 1 and 2, and for Ad41, there was a greater than 4-log reduction of infectivity after 1 day for trial 2. Overall, temperature is a critical factor, which affects the survival of viruses in compost, and the fate of the viral genome in the generated heat is virus dependent as well. For U.S. Environmental Protection Agency Class A compost, current compost regulations require maintaining temperatures between 55 and 70 degrees C for at least for 3 days for a static aerated-pile system. This study indicated that these temperature conditions could effectively inactivate MNV-1, AiV, and Ad41.