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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #336367

Title: Senecavirus A: overview of experimental studies

item BUCKELY, A - Oak Ridge Institute For Science And Education (ORISE)
item KULSHRESHTHA, V - Oak Ridge Institute For Science And Education (ORISE)
item VAN GEELEN, A - Oak Ridge Institute For Science And Education (ORISE)
item GUO, B - Iowa State University
item YOON, K - Iowa State University
item Lager, Kelly

Submitted to: American Association of Swine Veterinarians Annual Meeting
Publication Type: Proceedings
Publication Acceptance Date: 9/9/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Introduction Senecavirus A (SVA) is a picornavirus in the same family as Foot and Mouth Disease virus (FMDV) and swine vesicular disease virus (SVDV). SVA has been associated with rare cases of idiopathic vesicular disease (IVD) in the past. A "mini-epidemic" of IVD in US finisher and sow farms began in late summer 2015, and cases have continued to be diagnosed. SVA has been routinely detected in these cases and considered the presumptive cause, which was confirmed following experimental infections of swine with the early SVA isolates. Understanding the pathogenesis and ecology of this virus is important since SVA induced disease clinical resembles FMDV infection, and SVA may be emerging as an important primary pathogen. This manuscript summarizes SVA animal studies completed at the National Animal Disease Center. Materials and methods All animals used in experimental studies were inoculated intranasally with SVA. Virus was isolated from a case involving finishing pigs in South Dakota and subsequent virus was isolated from vesicles of experimentally infected swine.1 Samples collected included serum, milk, rectal swabs, and oral swabs. Vesicle fluid aspirates as well as vesicle swabs were also collected. Real-time reverse transcriptase polymerase chain reaction (PCR) was performed on samples collected for detection of SVA. Virus neutralization was performed on serum samples for neutralizing antibody detection. Results and discussion Reports from a series of animal studies are summarized. Clinical signs in nursery-age pigs to sows Coronary band lesions began to develop around 3-5 days post inoculation (dpi) with SVA. Snout lesions were observed less commonly and typically appeared 2-3 days after the appearance of coronary band lesions. SVA was detected in the serum until 7-10 dpi. Fecal and oral swabs have continued to test positive out to 4 weeks with sporadic positive samples beyond that time period. Swabs of vesicular lesions have the lowest CT values and the most genomic copies. Clinical signs near the time of parturition Sows inoculated more than 10 days prior to farrowing replicated virus but their piglets were PCR negative for SVA in serum, fecal and oral swabs throughout the study. Piglets born from a sow inoculated 10 days before farrowing were PCR positive for SVA in the serum pre-suckle providing evidence for vertical transmission. There was also evidence of horizontal transmission from sows challenged within a week of farrowing to their piglets. Since virus was present in sow feces and milk samples, they may be sources of viral transmission. No signs of vesicular disease were observed in the sows challenged pre-partum or their piglets. Both sows and piglets challenged within a week after birth replicated virus in serum, fecal and oral swabs. One sow was observed with a snout vesicle, but no other signs of clinical disease were observed in the other sows and their piglets. Protective immunity In order to explore protective immunity, nursery pigs were given a homologous challenge of SVA 45 days after immunization and were protected with no replication of the virus or development of clinical signs. In addition, a group of gilts were immunized before breeding and challenged pre-partum. All gilts were protected and no gilt or piglet replicated virus in serum. Isolate Comparison To study differences between historic and contemporary strains, an isolate comparison study was performed. Interestingly, all isolates produced similar clinical signs and replicated in pigs. Transmission in sows Studies looking at SVA transmission have been performed with mature sows. Naïve contact sows placed with infected sows at 7 and 14 dpi have developed lesions and replicated virus. Those naïve sows in contact with principle sows at 21 and 28 dpi did not develop lesions. Diagnostic recommendations Determine the question to