title: Experimental reproduction of postweaning multisystemic wasting syndrome in pigs by dual infection with Mycoplasma hyopneumoniae and porcine circovirus type 2.
abstract: The objectives of this study were to investigate the interactions between Mycoplasma hyopneumoniae and porcine circovirus type 2 (PCV2) and to establish a model for studying the pathogenesis of and testing intervention strategies for the control of PCV2-associated porcine respiratory disease complex (PRDC). Sixty-seven pigs were randomly assigned to four groups. Group 1 (n=17) pigs served as controls, group 2 (n=17) pigs were inoculated with M. hyopneumoniae, group 3 (n=17) pigs were dual infected with M. hyopneumoniae and PCV2, and group 4 (n=16) pigs were inoculated with PCV2. Pigs were inoculated intratracheally with M. hyopneumoniae at 4 weeks of age followed by intranasal inoculation with PCV2 at 6 weeks of age. Dual-infected pigs had moderate dyspnea, lethargy, and reduced weight gain. The overall severity of macroscopic lung lesions, PCV2-associated microscopic lesions in lung and lymphoid tissues, and the amount of PCV2-antigen associated with these lesions were significantly (P <0.05) higher in dual-infected pigs compared with all other groups. Four of 17 (23.5%) dual-infected pigs had decreased growth rate and severe lymphoid depletion and granulomatous lymphadenitis associated with high amounts of PCV2-antigen consistent with postweaning multisystemic wasting syndrome (PMWS). PCV2-antigen in lung tissue was most often associated with M. hyopneumoniae-induced peribronchial lymphoid hyperplasia, suggesting that this is an important site for PCV2 replication in the lung. This study indicates that M. hyopneumoniae potentiates the severity of PCV2-associated lung and lymphoid lesions, increases the amount and prolongs the presence of PCV2-antigen, and increases the incidence of PMWS in pigs.
authors.affiliation: Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, IA 50011-1250, USA.
authors.forename: T
authors.initials: T
authors.lastname: Opriessnig
authors.forename: E L
authors.initials: EL
authors.lastname: Thacker
authors.forename: S
authors.initials: S
authors.lastname: Yu
authors.forename: M
authors.initials: M
authors.lastname: Fenaux
authors.forename: X-J
authors.initials: XJ
authors.lastname: Meng
authors.forename: P G
authors.initials: PG
authors.lastname: Halbur
mesh_terms: D000818:Animals; D018173:Circoviridae Infections / Q000150:complications / Q000473:pathology / Q000662:veterinary*; D017925:Circovirus / Q000472:pathogenicity*; D008168:Lung / Q000473:pathology; D008198:Lymph Nodes / Q000473:pathology; D045729:Pneumonia of Swine, Mycoplasmal / Q000209:etiology* / Q000473:pathology; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology* / Q000473:pathology / Q000821:virology*; D014766:Viremia / Q000662:veterinary; D019282:Wasting Syndrome / Q000209:etiology / Q000662:veterinary*