November 2016 – Swine in Minnesota

Confirmed detection of a new porcine circovirus: introducing PCV3

This past Friday, the Virology journal published a short report confirming the detection of a new porcine circovirus named PCV3. The virus was identified by a team of diagnosticians and researchers from the Veterinary Diagnostic Laboratory at the U of M in collaboration with the Blood Systems Research Institute and the Department of Laboratory Medicine in San Fransisco.

The pigs, gathered from three different cases, which expressed cardiac pathology and lesions of systemic inflammation tested negative for PCV2 by PCR. The article also reports the complete genetic sequences of the viruses and illustrates how different their proteins are from PCV2 and PCV1 ones in a phylogenetic tree.

pcv3-virology-nov-2016

Abstract
Background
Porcine circovirus 2 causes different clinical syndromes resulting in a significant economic loss in the pork industry. Three pigs with unexplained cardiac and multi-organ inflammation that tested negative for PCV2 and other known porcine pathogens were further analyzed.
Methods
Histology was used to identify microscopic lesions in multiple tissues. Metagenomics was used to detect viral sequences in tissue homogenates. In situ hybridization was used to detect viral RNA expression in cardiac tissue.
Results
In all three cases we characterized the genome of a new circovirus we called PCV3 with a replicase and capsid proteins showing 55 and 35 % identities to the genetically-closest proteins from a bat-feces associated circovirus and were even more distant to those of porcine circovirus 1 and 2. Common microscopic lesions included non-suppurative myocarditis and/or cardiac arteriolitis. Viral mRNA was detected intralesionally in cardiac cells. Deep sequencing in tissues also revealed the presence of porcine astrovirus 4 in all three animals as well as rotavirus A, porcine cytomegalovirus and porcine hemagglutinating encephalomyelitis virus in individual cases.
Conclusion
The pathogenicity and molecular epidemiology of this new circovirus, alone or in the context of co-infections, warrants further investigations.

Link to the full article

Which air sampler to detect swine airborne viruses?

This is the question that Drs. Carmen Alonso, Sagar Goyal, Peter Davies, and Montse Torremorell from the College of Veterinary Medicine studied in collaboration with Drs. Bernard Olson and Peter Raynor from the College of Science and Engineering and the School of Public Health respectively, in the following paper published in Aerosol Science and Technology this past month.

In this study, the team form the University of Minnesota compared the capacity of two different air samplers to detect PRRSv and SIV in an experimental setting. The challenge to detect viral aerosol is to find a technique capable of capturing small amount of virus in a large amount of air. This experiment found that the particle size, the media used for collection as well as the extraction technique (passive or active) all had a significant effect on the detection of the viruses.

alonso-comparison-two-air-samplers

Abstract: Detection and quantification of dilute viral aerosols, as encountered outside animal housing facilities, requires methods that are able to detect small numbers of viruses in large volumes of air. This study compared the performance of two size-differentiating cascade impactors; an Andersen 8-stage (ACI; 28.3 L/min) and a high volume Tisch (TCI; 1,133 L/min) to assess sampling efficiency for detecting porcine reproductive and respiratory syndrome virus (PRRSV) and influenza A virus (IAV). Samples of particles sorted by aerodynamic diameter were analyzed by quantitative polymerase chain reaction (qPCR) and collection efficiency was assessed by particle size. Collection media (minimum essential medium [MEM] and beef extract [BE]), elution technique (active versus passive), and sampling times (10, 20, and 30 min) were variables assessed for the TCI sampler. Extraction efficiency was 35% higher with BE as compared to that of MEM (p = 0.0007); active extraction technique was 19% more efficient than the passive technique (p = 0.03); time of sampling did not significantly affect the amount of virus recovered. The ACI sampler was more efficient in detecting both viruses from small and medium sized airborne particles (≤3 μm) as compared to the TCI sampler (p < 0.001). The latter sampler, however, was more efficient at IAV detection from large airborne particles (>3 μm) (p = 0.0025) indicating the potential of this sampler in detecting the presence of small amounts of viruses in aerosols under field conditions.

Link to the full article

Pregnancy diagnostic wet lab for veterinary students

This past week-end, a dozen of veterinary students chose to meet with Drs. Maria Pieters and Perle Boyer at the University of Minnesota Southern research and outreach center in Waseca, MN to practice their pregnancy diagnostic skills over enjoying the unusually warm weather.

For over 3 hours, the first to third-year veterinary students each got the chance to perform an ultrasound examination on sows at various stages of gestation as well as on a sow that was not pregnant to appreciate the difference. Various tools were presented to them to compare and to get familiar with.

By the end of the lab, we are glad to say that all students were able to successfully tell if a sow was pregnant or not!

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Investigation of Senecavirus A pathogenesis in finishing pigs

Dr. Fabio Vannucci, a University of Minnesota swine pathologist and his graduate student Dr. Talita Resende collaborated with a team from South Dakota State University to study the pathogenesis of Senecavirus A in finishing pigs. The results of their experiments were published online a few weeks ago in the Journal of General Virology and the printed version should be following shortly.

The importance of Senecavirus A in swine production resides in a striking resemblance in clinical signs with Food and Mouth Disease. Indeed, Senecavirus A causes vesicular lesions around the mouth and on the feet of pigs.

The collaborative work showed that Senecavirus A viremia occurred between 3 to 10 days post-inoculation (dpi), and that the neutralizing antibody response started 5 dpi. Clinical signs first observed 4dpi, lasted up to 10 days.
This study advances our understanding of Senecavirus A pathogenesis to hopefully be able to better manage it in the future.

vannucci-senecavirusa

Abstract: Senecavirus A (SVA) is an emerging picornavirus that has been recently associated with vesicular disease and neonatal mortality in swine. Many aspects of SVA infection biology and pathogenesis, however, remain unknown. Here the pathogenesis of SVA was investigated in finishing pigs. Animals were inoculated via the oronasal route with a contemporary SVA strain SD15-26 and monitored for clinical signs and lesions associated with SVA infection. Viremia was assessed in serum and virus shedding monitored in oral and nasal secretions and feces by real-time reverse transcriptase PCR (RT-qPCR) and/or virus isolation. Additionally, viral load and tissue distribution were assessed during acute infection and following convalescence from disease. Clinical signs characterized by lethargy and lameness were first observed on day 4 pi and persisted for ~2-10 days. Vesicular lesions were observed on the snout and feet, affecting the coronary bands, dewclaws, interdigital space and heel/sole of SVA-infected animals. A short-term viremia was detected between days 3-10 post-inoculation (pi), whereas virus shedding was detected between days 1-28 pi in oral and nasal secretions and feces. Notably, RT-qPCR and in situ hybridization (ISH) performed on tissues collected on day 38 pi revealed the presence of SVA RNA in the tonsil of all SVA infected animals. Serological responses to SVA were characterized by early neutralizing antibody responses (5 days pi), which coincided with a progressive decrease in the levels of viremia, virus shedding and viral load in tissues. This study provides significant insights on the pathogenesis and infectious dynamics of SVA in swine.