title: Pathogenicity of three type 2 porcine reproductive and respiratory syndrome virus strains in experimentally inoculated pregnant gilts.
abstract: Mechanisms of reproductive failure resulting from infection with porcine reproductive and respiratory syndrome virus (PRRSV) are still poorly understood. Presented herein are the results of a side-by-side evaluation of the pathogenicity of three type 2 PRRSV strains in a reproductive model, from a pilot study used to develop experimental conditions and laboratory methods for a larger experiment. Pregnant gilts were experimentally infected with PRRSV at gestation day 85 or served as uninfected negative controls. After 21 days, all gilts and fetuses were necropsied. Clinical signs, litter outcome, viral load, cytokine levels, and pathology were compared from samples collected among pigs exposed to the three PRRSV strains. Based on differences in histologic lesions, and fetal weights, and numeric differences in gilt serum cytokine levels, litter outcome and virus replication in fetal tissues KS06-483 appeared less virulent than NVSL 97-7895 and KS06-72109 isolates. Levels of chemokine ligand 2 (CCL2), interferon alpha (IFNα), and interferon gamma (IFNγ) were increased in PPRRSV-infected compared to non-infected gilts (0.01 > P < 0.06). Inoculation with NVSL 97-7895 induced higher levels of all three cytokines. All three PRRSV isolates were able to induce high mean viral load in individual litters, which was closely related to the proportion of PRRSV positive fetuses in the litter. Viral load in fetal samples was also positively associated with viral load at the maternal-fetal interface. All but one dead fetus were positive for PRRSV RNA, and higher concentrations of PRRSV RNA in fetal thymus increased the odds of fetal death. Our results suggest that virus replication in fetal tissues and the maternal-fetal interface, but not in other gilt tissues, are important for the outcome of reproductive PRRS. Additionally, our data indicate that umbilical lesions decreased corresponding to the use of pentobarbital sedation prior to euthanasia of pregnant gilts by captive bolt.
authors: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada. Electronic address: andrea.ladinig@vetmeduni.ac.at.
authors: Andrea
authors: A
authors: Ladinig
authors: Department of Veterinary Pathology, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada. Electronic address: susan.detmer@usask.ca.
authors: Susan E
authors: SE
authors: Detmer
authors: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada. Electronic address: kyle.clarke@usask.ca.
authors: Kyle
authors: K
authors: Clarke
authors: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada. Electronic address: carolyn.ashley@usask.ca.
authors: Carolyn
authors: C
authors: Ashley
authors: Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, K-221 Mosier Hall, Manhattan, KS 66506-5802, USA. Electronic address: browland@vet.k-state.edu.
authors: Raymond R R
authors: RR
authors: Rowland
authors: Animal Parasitic Diseases Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, 10300 Baltimore Blvd., Building 003, Beltsville, MD 20705, USA. Electronic address: Joan.Lunney@ARS.USDA.GOV.
authors: Joan K
authors: JK
authors: Lunney
authors: Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK S7N5B4, Canada. Electronic address: john.harding@usask.ca.
authors: John C S
authors: JC
authors: Harding
mesh_terms: D032761:Animal Experimentation; D000825:Animal Structures / Q000473:pathology; D000818:Animals; D016207:Cytokines / Q000097:blood; D005260:Female; D006651:Histocytochemistry; D010865:Pilot Projects; D019318:Porcine Reproductive and Respiratory Syndrome / Q000473:pathology* / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000472:pathogenicity*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D013552:Swine; D019562:Viral Load; D014774:Virulence
chemical_list: D016207:Cytokines
keywords: Cytokine; Fetal preservation; PRRSV; Pathogenicity; Pregnant gilt; Viral load