Diagnosing SIV and the Strain of SIV in a Swine Herd

By Robyn Fleck, DVM, Technical Services Veterinarian, Schering-Plough Animal Health - In this Technical Service Update, Dr Fleck looks at methods of sample collection for diagnosing swine influenza virus (SIV) in a herd.
calendar icon 27 February 2006
clock icon 4 minute read
Schering-Plough Animal Health

Following are methods of sample collection for diagnosing swine influenza virus (SIV) in a herd and identifying the SIV strain.

To Confirm The Diagnosis of SIV

  1. Select three acutely affected, feverish pigs in good flesh with clear nasal discharge. Choose from a barn or room where animals have just started coughing or sneezing.

  2. Humanely euthanize pigs and remove lungs.

  3. Collect fixed lung tissue for histopathological detection of SIV lesions. Using scissors, cut two or three sections about 1 cm (0.4 inch) by 1 cm, including junction of healthy and diseased lung in area where small airways are found. Collect samples from different areas of the lung. Place samples in buffered formalin.

  4. Send fresh and fixed lung specimens and swabs on ice in an insulated cooler using next-day delivery. Request virus isolation, histopathology and genetic analysis. Turnaround for isolation may be 1 week; for sequencing, 1 to 2 weeks, depending on the lab.

To Identify The SIV Strain

  1. Collect fresh diseased lung tissue the size of a golf ball or larger. Include bronchi. Place in a sterile transport bag. Chill on ice, but do not freeze.

  2. To increase the odds of finding virus, select 10 pigs in good flesh with a high fever and clear nasal discharge. Pigs should be from a group that has just started to cough or sneeze.

  3. Restrain pigs by holding or snaring. Before swabbing, wipe feed and manure off nostril with dry cotton ball or gauze. Do not use alcohol or a disinfectant.

  4. Swab each pig’s nose with a non-cotton-tipped swab. Be sure to contact turbinates. Excessive blood may make virus isolation difficult, but a little red tinge is okay.

  5. Place each nasal and lung swab into a tube with sterile transport medium or use a swab system that already contains transport media. Swabs can be pooled if there are no more than two or three per tube.

  6. Places samples in cool place and if stored more than one week, use a -70ºF freezer. Do not use a frost-free freezer.

  7. Send swabs to diagnostic laboratory on ice in an insulated cooler, preferably using next-day delivery.

  8. Request virus isolation and sequencing of the hemaglutinin (HA) gene. Genetic analysis will reveal similarities between the SIV isolate and reference strains. Turnaround for isolation may be 1 week and, for sequencing, 1 to 2 weeks, depending on the laboratory.

For Serology

  1. Select 10 pigs, preferably unvaccinated pigs with no maternal antibody. Tag and bleed animals during acute SIV outbreak.

  2. Return two weeks later to re-bleed the same animals. Freeze serum from the acute bleed and submit to lab with convalescent serum. Request H1N1 and H3N2 hemagglutination inhibition and H1N1 ELISA.

Note: Iowa State University and University of Minnesota both have laboratories that perform SIV genetic analysis.

Source: Schering-Plough Animal Health
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