Pathogenesis of Riemerella anatipestifer (RA) in turkeys after experimental mono-infection via respiratory routes or dual infection together with the Avian Metapneumovirus (aMPV)

Dennis Rubbenstroth (1) , Martin Ryll (1) , Klaus-Peter Behr (2) , Silke Rautenschlein (1)

1 TIHO - Clinic for Poultry
2 AniCon Labor GmbH

Riemerella anatipestifer (RA) is the causative agent of septicaemic and exudative diseases in a variety of bird species. Despite numerous outbreaks little is known about the pathogenicity of RA for turkeys. We investigated the development of RA-induced disease in commercial turkey poults following RA-inoculation via different respiratory routes. Inoculation by aerosol or injection into the abdominal air sac led to systemic infection and mild gross lesions, including pericarditis, epicarditis and airsacculitis, which were less pronounced compared to field outbreaks. It was speculated, that viral pathogens, such as the avian Metapneumovirus (aMPV), may exacerbate RA-pathogenesis under field conditions. We inoculated turkey poults with virulent aMPV. Subsequently, aMPV-infected and virus-free birds were exposed three to five days later to a high dose of RA by aerosol (>1010 colony forming units [CFU]/ml in 8 ml aerosol per 11-12 birds) or were four days later inoculated with a low RA dose (104.9 CFU per animal) via the intranasal route. Intranasal RA-inoculation with the low bacterial dose led to a respiratory and systemic RA infection in aMPV-infected birds, while virus-free birds remained RA-negative. Following exposure to a high RA-dose by aerosol, aMPV-infected groups showed slightly enhanced incidences of gross lesions and RA-reisolation. This study clearly confirms that RA is pathogenic for turkeys after experimental inoculation via respiratory routes, which are speculated to be the natural route of infection. However, experimental models in this study did not reproduce the severity of RA-related disease as observed under field conditions, which emphasizes the importance of other contributing factors. aMPV-induced respiratory lesions may serve as a predisposing factor for the establishment of RA infection, since they favour colonization of the bacterium.

Mots clés: Life Sciences

Dennis Rubbenstroth, Martin Ryll, Klaus-Peter Behr, Silke Rautenschlein. Pathogenesis of Riemerella anatipestifer (RA) in turkeys after experimental mono-infection via respiratory routes or dual infection together with the Avian Metapneumovirus (aMPV). Avian Pathology, 2009, 38 (06), pp.497-507. ⟨10.1080/03079450903349220⟩. ⟨hal-00540169⟩