title: Experimental infection of SPF pigs with Actinobacillus pleuropneumoniae serotype 9 alone or in association with Mycoplasma hyopneumoniae.
abstract: The purpose of this study was to compare in SPF pigs, the pathogenicity of an Actinobacillus pleuropneumoniae serotype 9 strain 21 (isolated from the palatine tonsils of a healthy gilt on a French nucleus pig farm, with no clinical signs or lung lesions but a highly positive reaction to A. pleuropneumoniae serotype 9 antibodies) with a pathogenic A. pleuropneumoniae strain 4915 serotype 9 (isolated in France from an outbreak of porcine pleuropneumonia). The pathogenicity of one Mycoplasma hyopneumoniae strain alone or associated with A. pleuropneumoniae strain 21 was also compared. Eight groups of 7 pigs were infected (at 6 or 10 weeks of age) and a control group was kept non-infected. Results showed that sensitivity to A. pleuropneumoniae was related to the age of the pig (6 weeks vs 10 weeks) whatever the strain. Surviving pigs infected at 6 weeks of age developed severe clinical signs, lung lesions typical of A. pleuropneumoniae and they seroconverted. In contrast, symptoms and lung lesions were almost non-existent in pigs infected with strain 21 at 10 weeks of age, but a seroconversion was observed with very high ELISA titres. These results were in accordance with those observed in the nucleus pig farm. Infection with M. hyopneumoniae alone induced typical mycoplasmal symptoms, pneumonia and seroconversion. Symptoms and lung lesions were the most noticeable in pigs infected with M. hyopneumoniae at 6 weeks of age and with A. pleuropneumoniae 4 weeks later. Our results show that the presence of A. pleuropneumoniae serotype 9 in a pig herd may be clinically unnoticed and that M. hyopneumoniae may potentiate A. pleuropneumoniae infection.
authors.affiliation: Agence Française de Sécurité Sanitaire des Aliments (AFSSA), Unité de Mycoplasmologie-Bactériologie, BP53, 22440 Ploufragan, France. c.marois@ploufragan.afssa.fr
authors.forename: Corinne
authors.initials: C
authors.lastname: Marois
authors.forename: Marcelo
authors.initials: M
authors.lastname: Gottschalk
authors.forename: Hervé
authors.initials: H
authors.lastname: Morvan
authors.forename: Christelle
authors.initials: C
authors.lastname: Fablet
authors.forename: François
authors.initials: F
authors.lastname: Madec
authors.forename: Marylène
authors.initials: M
authors.lastname: Kobisch
mesh_terms: D000189:Actinobacillus Infections / Q000150:complications / Q000401:mortality / Q000662:veterinary*; D016977:Actinobacillus pleuropneumoniae / Q000302:isolation & purification / Q000472:pathogenicity*; D000818:Animals; D008168:Lung / Q000382:microbiology / Q000473:pathology; D045705:Mycoplasma hyopneumoniae / Q000302:isolation & purification; D045729:Pneumonia of Swine, Mycoplasmal / Q000175:diagnosis / Q000401:mortality / Q000503:physiopathology*; D013047:Specific Pathogen-Free Organisms; D016019:Survival Analysis; D013552:Swine; D013553:Swine Diseases / Q000382:microbiology*