title: The emergence of a new strain of porcine circovirus-2 in Ontario and Quebec swine and its association with severe porcine circovirus associated disease--2004-2006.
abstract: In the late fall of 2004 more severe lesions of porcine circovirus-2 associated disease (PCVAD) than usual occurred during an outbreak of porcine circovirus-2 (PCV-2) infection in Ontario nursery and grower/finisher pigs. The lesions were of unprecedented severity and included diffuse bronchointerstitial pneumonia, granulomatous enteritis, vasculitis, interstitial nephritis, and new lesions of splenic infarction. Some affected herds had up to 50% mortality. The outbreak correlated with the sudden emergence of a variant PCV-2, with PCR restriction fragment length polymorphism (RFLP) type 321. Phylogenetic comparison of ORF2 sequences and full genome sequences showed the new variant to be different from the previously dominant RFLP type 422 viruses, and similar to viruses that had occurred in France and other European and Asian countries. A subsequent retrospective study showed a statistically significant increase in the frequency of histological lesions in lymph node, spleen, lung, small intestine, colon and kidney, for pigs spontaneously infected with RFLP type 321, compared with the older RFLP type 422 strain. Viral burden, based on IHC staining in lymph node, also showed a statistically significant increase in pigs infected with the newer variant RFLP type 321, compared with the older RFLP type 422 strain. This enhanced virulence in pigs infected with PCV-2 RFLP type 321 strain may be related to the genetic differences in this new strain of PCV-2. This virus is now the dominant strain of PCV-2 virus found in Ontario and Quebec swine.
authors.affiliation: Animal Health Laboratory, Laboratory Services Division, University of Guelph, Guelph, Ontario N1G 2W1. scarman@lsd.uoguelph.ca
authors.forename: Susy
authors.initials: S
authors.lastname: Carman
authors.forename: Hugh Y
authors.initials: HY
authors.lastname: Cai
authors.forename: Josepha
authors.initials: J
authors.lastname: DeLay
authors.forename: Sameh A
authors.initials: SA
authors.lastname: Youssef
authors.forename: Beverly J
authors.initials: BJ
authors.lastname: McEwen
authors.forename: Carl A
authors.initials: CA
authors.lastname: Gagnon
authors.forename: Donald
authors.initials: D
authors.lastname: Tremblay
authors.forename: Murray
authors.initials: M
authors.lastname: Hazlett
authors.forename: Peter
authors.initials: P
authors.lastname: Lusis
authors.forename: Jim
authors.initials: J
authors.lastname: Fairles
authors.forename: Hazel S
authors.initials: HS
authors.lastname: Alexander
authors.forename: Tony
authors.initials: T
authors.lastname: van Dreumel
mesh_terms: D000818:Animals; D018173:Circoviridae Infections / Q000453:epidemiology / Q000473:pathology / Q000662:veterinary* / Q000821:virology; D017925:Circovirus / Q000235:genetics / Q000472:pathogenicity*; D004196:Disease Outbreaks / Q000662:veterinary*; D005260:Female; D014644:Genetic Variation; D007150:Immunohistochemistry / Q000662:veterinary; D008297:Male; D008969:Molecular Sequence Data; D009864:Ontario / Q000453:epidemiology; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D011792:Quebec / Q000453:epidemiology; D017422:Sequence Analysis, DNA; D012720:Severity of Illness Index; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000473:pathology* / Q000821:virology; D019562:Viral Load / Q000662:veterinary; D014774:Virulence / Q000235:genetics