title: Exposure to environmental stressors result in increased viral load and further reduction of production parameters in pigs experimentally infected with PCV2b.
abstract: Porcine circovirus type 2 (PCV2) has been identified as the essential, but not sole, underlying infectious component for PCV-associated diseases (PCVAD). Several co-factors have been suggested to convert an infection with PCV2 into the clinical signs of PCVAD, including co-infection with a secondary pathogen and the genetic background of the pig. In the present study, we investigated the role of environmental stressors in the form of changes in environmental temperature and increased stocking-density on viral load in serum and tissue, average daily weight gain (ADG) and food conversion rate (FCR) of pigs experimentally infected with a defined PCV2b strain over an eight week period. These stressors were identified recently as risk factors leading to the occurrence of severe PCVAD on a farm level. In the current study, PCV2-free pigs were housed in separate, environmentally controlled rooms, and the experiment was performed in a 2×2 factorial design. In general, PCV2b infection reduced ADG and increased FCR, and these were further impacted on by the environmental stressors. Furthermore, all stressors led to an increased viral load in serum and tissue as assessed by qPCR, although levels did not reach statistical significance. Our data suggest that there is no need for an additional pathogen to develop PCVAD in conventional status pigs, and growth retardation and clinical signs can be induced in PCV2 infected pigs that are exposed to environmental stressors alone.
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Robert
authors: R
authors: Patterson
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Amanda
authors: A
authors: Nevel
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Adriana V
authors: AV
authors: Diaz
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Henny M
authors: HM
authors: Martineau
authors: Royal Veterinary College, Department of Clinical Sciences, Hawkshead Lane, AL9 7TA, UK.
authors: Theo
authors: T
authors: Demmers
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Christopher
authors: C
authors: Browne
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK.
authors: Bettina
authors: B
authors: Mavrommatis
authors: Royal Veterinary College, Department of Pathology and Pathogen Biology, Hawkshead Lane, AL9 7TA, UK. Electronic address: dwerling@rvc.ac.uk.
authors: Dirk
authors: D
authors: Werling
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D018173:Circoviridae Infections / Q000503:physiopathology / Q000662:veterinary* / Q000821:virology; D017925:Circovirus / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D060085:Coinfection / Q000821:virology; D004279:DNA, Viral / Q000097:blood / Q000302:isolation & purification; D004435:Eating; D004777:Environment; D060888:Real-Time Polymerase Chain Reaction; D012307:Risk Factors; D013312:Stress, Physiological / Q000276:immunology; D013552:Swine; D013553:Swine Diseases / Q000503:physiopathology / Q000821:virology*; D019562:Viral Load; D015430:Weight Gain
chemical_list: D000914:Antibodies, Viral; D004279:DNA, Viral
keywords: ADG; Environment; FCR; Housing; PCV2; PCVAD; Temperature; qPCR