Abstract
In recent years, porcine epidemic diarrhea virus (PEDv) has caused major epidemics, which has been a burden to North America’s swine industry. Low infectious dose and high viability in the environment are major challenges in eradication of this virus. To further understand the viability of PEDv in the infected manure, we longitudinally monitored survivability and infectivity of PEDv in two open earthen manure storages (EMS; previously referred to as lagoon) from two different infected swine farms identified in the province of Manitoba, Canada. Our study revealed that PEDv could survive up to 9 months in the infected EMS after the initial outbreak in the farm. The viral load varied among different layers of the EMS with an average of 1.1 × 105 copies/ml of EMS, independent of EMS temperature and pH. In both studied EMS, the evidence of viral replication was observed through increased viral load in the later weeks of the samplings while there was no new influx of infected manure into the EMS, which was suggestive of presence of potential alternative hosts for PEDv within the EMS. Decreasing infectivity of virus over time irrespective of increased viral load suggested the possibility of PEDv evolution within the EMS and perhaps in the new host that negatively impacted virus infectivity. Viral load in the top layer of the EMS was low and mostly non-infective suggesting that environmental factors, such as UV and sunlight, could diminish the replicability and infectivity of the virus. Thus, frequent agitation of the EMS that could expose virus to UV and sunlight might be a potential strategy for reduction of PEDv load and infectivity in the infected EMS.
Highlights
Porcine epidemic diarrhea virus (PEDv), a highly contagious virus that causes severe diarrhea, vomiting, dehydration and high mortality in piglets, is an enveloped, single-stranded RNA virus under the Coronaviridae family (Pensaert and de Bouck, 1978; Debouck and Pensaert, 1980; Song and Park, 2012)
In farm-2, pigs were actively shedding porcine epidemic diarrhea virus (PEDv) and 100% of tested pit and fecal samples were positive to virulence PEDv strain with average viral loads of 2.4 × 106 copies/ml of manure mix in the pit and 3.2 × 106 copies/g of feces, respectively
Our current findings showed that PEDv could survive up to 9 months in the infected earthen manure storages (EMS) under fall winter, spring and summer temperatures in Manitoba
Summary
Porcine epidemic diarrhea virus (PEDv), a highly contagious virus that causes severe diarrhea, vomiting, dehydration and high mortality in piglets, is an enveloped, single-stranded RNA virus under the Coronaviridae family (Pensaert and de Bouck, 1978; Debouck and Pensaert, 1980; Song and Park, 2012). In late 1970, PEDv was first identified in the UK and Belgium (Wood, 1977; Pensaert and de Bouck, 1978). It has been reported in other European countries and Asia. Fecal-oral route presents the major transmission route for PEDv, airborne dissemination has been proposed as a potential additional transmission route because the virus can be aerosolized and transported over long distances (up to 10 miles downwind) by air (Alonso et al, 2014). Fecal shedding of PEDv in pigs appears prior to clinical presentations, and increases the risk of transmission (Madson et al, 2014)
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