Abstract #LB8

# LB8
Monitoring survivability and infectivity of porcine epidemic diarrhea virus within two different on-farm lagoons.
Hein M. Tun*1, John P. Carney2, Mark Fynn3, Lorne Grieger4, Ehsan Khafipour1,5, 1Department of Animal Science, University of Manitoba, Winnipeg, MB, Canada, 2Manitoba Livestock Manure Management Initiative Inc, Winnipeg, MB, Canada, 3Manitoba Pork Council, Winnipeg, MB, Canada, 4Prairie Agricultural Machinery Institute, Portage La Prairie, MB, Canada, 5Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, Canada.

Porcine epidemic diarrhea virus (PEDv) has emerged as a new threat to the North American swine industry since 2013. Despite best efforts, not much is known about its survivability and infectivity within open lagoons over time. Two positive farms in Manitoba, Canada were included in the study, the first being infected 20 wk before the study and the second being identified during the initial farm study. Lagoon samples were collected over a 7-wk period during fall 2014 where active viral shedding was (lagoon 2) or was not present (lagoon 1). Lagoon sampling was conducted using a grid layout of 12 sites at 3 depths in lagoon 1, and 16 sites at 2 depths in lagoon 2. For lagoon 2, spring sampling was conducted in mid-May as described above. Survivability of PEDv was tested using duplex qRT-PCR for virulent PEDv (subgroup 2a) and the 2014 variant. 99.5% of lagoon samples collected in the fall were positive for virulent PEDv, whereas all samples tested negative for the 2014 variant. The PEDv survival in the lagoons exceeded 27 wk within lagoon 1, and viral load significantly increased over time (P < 0.01). The viral load was high in the initial weeks within the top and middle layers, but the reverse trend was observed in subsequent weeks with the highest levels detected within the bottom layer (P = 0.076). The viral load within lagoon 2 was significantly higher due to active shedding during wk 1 of sampling but decreased in subsequent weeks (P < 0.01). The virus infectivity was based on viral replication in Vero cells, showing 15% of samples were infective. In both lagoons, the virus was infective at the last week of fall sampling with higher infectivity in the middle layer of lagoon 1 (P = 0.015), and in the bottom layer of lagoon 2 (P = 0.285). In total, 87.5% of lagoon 2 samples were still positive for PEDv in the spring, 9 mo after the outbreak, but only 28% were infective. The data show the presence and infectivity of PED virus exceeding 9 mo in infected lagoons.

Key Words: PEDv, lagoon, survivability