title: Induction of dual infections in newborn and three-week-old pigs by use of two plaque size variants of porcine reproductive and respiratory syndrome virus.
abstract: OBJECTIVE
  To determine whether pigs can be dually infected with different plaque variants of porcine reproductive and respiratory syndrome virus (PRRSV).
  
  
  METHODS
  2 pregnant sows, 20 newborn pigs, and 20 three-week-old pigs.
  
  
  METHODS
  The 2 late-term pregnant sows were inoculated with the PRRSV small-plaque variant MN-Hs, and their pigs were challenge exposed at 7 days of age with the PRRSV large-plaque variant MN-HI. In addition, twelve 3-week-old pigs were inoculated with MN-Hs virus. Two groups of the pigs were challenge exposed with MN-HI virus at 14 and 42 days after initial inoculation. Virus was isolated from the pigs at various intervals, plaque sizes were examined, and serologic testing was performed.
  
  
  RESULTS
  From the 2 groups of ten 7-day-old pigs, small-plaque PRRSV was isolated form 8 and 10 pigs. After subsequent challenge exposure, dual infections were diagnosed in 3 of 10 inoculated and 4 of 10 contact control pigs. In 3-week-old pigs infected with MN-Hs virus, dual infections were documented in 2 of 6 pigs when challenge exposed 14 days after initial infection. Virus was not isolated from sera of another 6 pigs challenge exposed 42 days after initial infection. Serum neutralization antibody was detected in all 6 pigs at challenge exposure.
  
  
  CONCLUSIONS
  Dual infections were documented in viremic newborn pigs and 3-week-old pigs, using 2 plaque variants of PRRSV.
authors.affiliation: Department of Clinical and Population Sciences, College of Veterinary Medicine, University of Minnesota, St Paul 55108, USA.
authors.forename: B K
authors.initials: BK
authors.lastname: Park
authors.forename: H S
authors.initials: HS
authors.lastname: Joo
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000914:Antibodies, Viral / Q000097:blood*; D000917:Antibody Formation; D005260:Female; D009500:Neutralization Tests; D019318:Porcine Reproductive and Respiratory Syndrome / Q000276:immunology / Q000503:physiopathology*; D019316:Porcine respiratory and reproductive syndrome virus / Q000235:genetics / Q000472:pathogenicity* / Q000502:physiology; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000662:veterinary* / Q000821:virology; D013552:Swine; D013553:Swine Diseases; D010948:Viral Plaque Assay; D014766:Viremia / Q000276:immunology / Q000503:physiopathology / Q000662:veterinary
chemical_list: D000914:Antibodies, Viral