An outbreak of Pullorum disease in a young layer parent flock in Austria presented with central nervous system signs

SummaryThe present report describes an outbreak of Pullorum disease in a young layer parent stock in Austria. The flock, which comprised 14,220 Lohmann brown layer chickens, experienced high mortality from the first week of life reaching a total of 1,905 chickens in the fifth week, when the flock was depopulated. Clinical signs included uneven size of the chicks, pasty vents, apathy, diminished water and feed intake, with some birds presenting central nervous system signs such as tremors and torticollis. The post-mortem investigation of 43 birds, ages one to four weeks, revealed retained yolk sacs filled with caseous exudate, purulent airsacculitis, hepatitis with whitish pinpoint coalescing necrotic foci, splenitis with splenomegaly, hemorrhagic-mucoid enteritis in the small intestine, fibrinous typhlitis, nephromegaly and urate deposits in the ureters and cloaca. Inflammation and/or necrosis were identified in liver, spleen, kidney, small intestine and heart by histopathology. However, no histopathological lesions were observed in the brain. Salmonella spp. were isolated from heart, liver, spleen and brain in pure culture. Group specific serotyping determined the presence of group D, with serovar S. Gallinarum being confirmed based on the Kauffmann-White Scheme. A duplex PCR further identified S. Pullorum as the responsible agent for the outbreak. Subsequently, the grandparent flocks, from which the affected flock originated, were tested and found to be negative for S. Pullorum, with no other progenies from the same GPs developing disease. Although the source of the pathogen could not be identified, such findings highlight the importance of “old” pathogens such as S. Pullorum causing sudden high mortality in chicks, even in a highly controlled environment.