Characterization of Porcine Epidemic Diarrhea Virus Isolate US/Iowa/18984/2013 Infection in 1-Day-Old Cesarean-Derived Colostrum-Deprived Piglets.

Porcine epidemic diarrhea virus (PEDV) was first recognized in North America in April 2013 and has since caused devastating disease. The objective of this study was to characterize disease and viral detection associated with an original North American PEDV isolate inoculated in neonatal piglets. Thirty-six 1-day-old cesarean-derived and colostrum-deprived piglets were randomly assigned to the control (n = 16) or challenged group (n = 20); the latter were orogastrically inoculated with 1 ml of US/Iowa/18984/2013 PEDV isolate titered at 1 × 10(3) plaque-forming units per milliliter. Rectal swabs were collected from all piglets prior to inoculation and every 12 hours postinoculation (hpi) thereafter, with 4 control and 5 challenged piglets euthanized at 12, 24, 48, and 72 hpi. One piglet had a positive real-time quantitative polymerase chain reaction test on rectal swab at 12 hpi, and all remaining piglets were positive thereafter, with highest viral quantities detected at 24 and 36 hpi. Diarrhea was evident in 30% and 100% of challenged piglets at 18 and 24 hpi, respectively. Viral antigen was detected in enterocytes by immunohistochemistry in the duodenum and ileum of piglets euthanized at 12 hpi and was apparent throughout the small intestine of all piglets thereafter, with villus height:crypt depth ratios consistently below 4:1. Viremia was confirmed in 18 of 20 pigs at euthanasia. Clinical disease was severe and developed rapidly following infection with an original North American PEDV isolate, with lesions, viremia, and antigen detection possible by 12 hpi.

Detection of a novel sapelovirus in central nervous tissue of pigs with polioencephalomyelitis in the USA.

An approximately 3,000 finishing swine operation in the United States experienced an outbreak of an atypical neurologic disease in 11-weeks-old pigs with an overall morbidity of 20% and case fatality rate of 30%. The clinical onset and progression of signs in affected pigs varied but included inappetence, compromised ambulation, ataxia, incoordination, mental dullness, paresis, paralysis and decreased response to environmental stimuli. Tissues from affected pigs were submitted for diagnostic investigation. Histopathologic examination of the cerebrum, cerebellum and spinal cord revealed severe lymphoplasmacytic and necrotizing polioencephalomyelitis with multifocal areas of gliosis and neuron satellitosis, suggestive of a neurotropic viral infection. Bacterial pathogens were not isolated by culture of neurologic tissue from affected pigs. Samples tested by polymerase chain reaction (PCR) were negative for pseudorabies virus and atypical porcine pestivirus. Immunohistochemistry for porcine reproductive and respiratory syndrome virus, porcine circovirus and Listeria was negative. Porcine sapelovirus (PSV) was identified in spinal cord by a nested PCR used to detect porcine enterovirus, porcine teschovirus and PSV. Next-generation sequencing of brainstem and spinal cord samples identified PSV and the absence of other or novel pathogens. In addition, Sapelovirus A mRNA was detected in neurons and nerve roots of the spinal cord by in situ hybridization. The PSV is genetically novel with an overall 94% amino acid identity and 86% nucleotide identity to a recently reported sapelovirus from Korea. This is the first case report in the United States associating sapelovirus with severe polioencephalomyelitis in pigs.

Pathogenesis of porcine epidemic diarrhea virus isolate (US/Iowa/18984/2013) in 3-week-old weaned pigs.

Porcine epidemic diarrhea virus (PEDV) is associated with clinical diarrhea in naïve swine of all ages. This report describes timing of antibody generation and disease progression following infection with a US PEDV isolate by assessing fecal viral shedding, morphometric analysis of intestinal lesions, and magnitude of immunohistochemical staining. Sixty-three, 3-week-old pigs were randomly allocated into control (n=27) and challenged (n=36) groups. Challenged pigs were administered 1 mL of 1 × 10(3) PFU/mL of US/Iowa/18984/2013 PEDV isolate by oro-gastric gavage. Three control and four challenged pigs were necropsied on days post-inoculation (dpi) 1, 2, 3, 4, 7, and weekly thereafter, until study termination on dpi 35. Clinical disease, fecal shedding, body weight, and temperature were monitored during the study period. Diarrhea was observed in challenged pigs beginning for some on dpi 2, affecting a majority of pigs by dpi 6 and subsiding by dpi 10. Average daily gain was significantly lower (P<0.001) for one week post-infection in challenged pigs. PEDV was detected in feces by PCR on dpi 1 and continued in a subset of pigs until dpi 24. PEDV-specific antigen was detected in villous enterocytes of challenged pigs by immunohistochemistry (IHC) on dpi 1, 2, 3, 4, 7, and 14. Microscopic lesions included severe diffuse atrophic enteritis with significantly reduced (P<0.001) villous length observed on dpi 3, 4, and 7. Under the conditions of this study, fecal shedding of PEDV and IHC staining can precede and continue beyond the observation of clinical signs, thus increasing the risk of viral transmission.