Riemerella anatipestifer outbreaks in commercial goose flocks and identification of isolates by MALDI-TOF mass spectrometry

Several outbreaks of Riemerella anatipestifer in commercial geese occurred within a short time period. A serious disease was recognized in the affected birds, mainly characterized by depression and severe neurologic disturbances. The morbidity ranged from 20 to 30% and the mortality from 5 to 20%. Generally, the clinical signs started at the age of 8 to 10 days. Post-mortem examination revealed fibrinous pericarditis, perihepatitis and airsacculitis in all birds. Some of the birds also had synovitis of the tibio-tarsal joints and oedematous swelling of the subcutaneous tissues around these joints and metatarsus. Histology revealed a characteristic severe inflammation with heterophilic granulocytes in different organs. Bacteriological investigation was made from several organs and R. anatipestifer could be isolated from all birds investigated. The identification of these clinical isolates, done for the first time by matrix-assisted laser desorption ionization–time-of-flight mass spectrometry, confirmed the aetiology. Sequence analysis showed 100% similarity between the clinical isolates, indicating a common source of infection.