Swine oral fluid and sampling has been recently recognized as a sample matrix and a cost effective tool for surveillance of numerous pathogens, notably PRRSV and SIV. The project was to determine if oral fluids can be a convenient sample matrix to detect PEDV and/or virus-specific antibody and to assess the utility of oral fluid and testing for PEDV monitoring on farm. The study was conducted in both experimental and field conditions in which paired individual pig fecal swab and pen-based oral fluid samples were collected from a group of pigs for viral testing. Serum samples were also collected from experimentally infected pig to assess diagnostic utility of oral fluid for antibody detection. PCR results on both fecal swab and oral fluid samples from the experimentally challenged groups showed good correlation, both in the duration of viral shedding as well as relative quantitation of viral shedding over time. Thus, oral fluids were shown to be a sample type to accurately detect the presence and circulation of PEDV in pig herds. Although the level of antibody in oral fluids was lower than sera, both samples showed a similar antibody response pattern after infection as measured by ELISA, indicating that oral fluid samples can also be used for antibody detection in lieu of traditional serology.
It was surprising to discover viral shedding in feces continued for nearly 30 days after clinical symptoms of PEDV infection ceased after experimental challenge. Such a longer fecal shedding was also observed in the field after PED outbreak on a farm. This information is vitally important for producers who are moving clinically normal animals among herds that have previously tested positive for PEDV. While fecal swab and oral fluid samples collected from experimental pig showed an excellent correlation on the duration of viral shedding, PED viral nucleic acid continued to be detected long (4 to 8 weeks) after fecal shedding was no longer detectable, suggesting that source of PEDV in oral fluid would be external (i.e., feces or environment) rather than secretion into the oral cavity. Hence, environmental contamination of PEDV should be a risk to mitigate for better control of PED on farms after outbreak. Since ‘time to normal’ in the field commonly ranges 10 to 16 weeks after initial PED outbreak, field observation further support the utility of swine oral fluid and sampling for surveillance of PEDV in populations.