Diagnostics, epidemiological observations and genomic subtyping in an outbreak of pullorum disease in non-commercial chickens

Salmonella Gallinarum biovar Pullorum (S. Pullorum) is a poultry pathogen able to cause significant economic losses and animal suffering. Strict eradication programmes have eliminated S. Pullorum from the commercial poultry sector in most regions. In 2012, pullorum disease was diagnosed in a non-commercial flock in Sweden. Epidemiological, pathological and bacteriological investigations identified three more infected flocks. To study the epidemiological relationships between the flocks and the merits of different typing methods for S. Pullorum, isolates representing the four infected flocks were investigated by high-throughput sequencing. Sequencing results suggested at least two different sources of infection or a common genetically mixed source in 2012.