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Effects of different us isolates of porcine reproductive and respiratory syndrome virus (PRRSV) on blood and bone marrow parameters of experimentally infected pigs
  1. P.G. Halbur, DVM, PhD1,
  2. R. Evans, PhD1,
  3. W. A. Hagemoser, DVM, PhD1,
  4. F. J. Pallares, DVM, PhD2,
  5. J. A. Rathje, DVM3,
  6. P. S. Paul, DVM, PhD4 and
  7. X. J. Meng, MD, PhD5
  1. 1 Iowa State University, College of Veterinary Medicine, Ames, Iowa 5001 1, USA
  2. 2 Facultad de Veterinaria, Universidad de Murcia, 30071 Murcia, Spain
  3. 3 Kettle Moraine Veterinary Center, Plymouth, Wisconsin 53073, USA
  4. 4 University of Nebraska, Lincoln, Nebraska 68588, USA
  5. 5 Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA


Seventy five-week-old, crossbred, caesarean-derived, colostrum-deprived pigs were randomly divided into five groups of 14 pigs and assigned one of five treatments: the intranasal inoculation of 105.7 TCID5O of one of four plaque-purified isolates of porcine reproductive and respiratory syndrome virus (PRRSV) (VR2385, VR2431, ISU-984 and ISU-22), or uninfected cell culture and media. Haematological variables were measured for 21 days and bone marrow was analysed when the pigs were killed three, seven, 10, 21 or 28 days after the inoculation. The PRRsv-infected pigs had non-regenerative anaemia and markedly increased myeloid:erythroid ratios from three to 21 days after inoculation. There was a significant (P<0.05) difference in the severity of the anaemia induced by the four PRRSV isolates; the most highly pneumovirulent strains (VR2385, ISU-984 and ISU-22) induced more severe anaemia than the least virulent isolate (VR2431). The anaemia induced by PRRSV was probably due to a direct or indirect effect on erythroid precursor cells in the bone marrow.

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