Epidemiology of Salmonellosis in Garden Birds in England and Wales, 1993 to 2003

Salmonellosis has been reported as an important cause of mortality of garden birds in several countries, including Norway and Scotland. We investigated the frequency of the disease in garden birds submitted for postmortem examination by members of the public in England and Wales between 1993 and 2003, inclusive. We found salmonellosis to be the most frequent cause of death due to infectious disease in the garden birds submitted. This disease was confirmed in 7 of the 45 bird species that were examined postmortem, with the greenfinch (Carduelis chloris) and the house sparrow (Passer domesticus) most frequently affected. Salmonella Typhimurium definitive phage type (DT) 40, DT56 variant(v), and DT160 accounted for the majority of isolates. Salmonellosis incidents chiefly occurred in the English Midlands, the English/Welsh border region, and southern England. Variation in the temporal and spatial distribution of the phage types occurred over the study period. While birds were examined throughout the year, there was a marked winter seasonality in salmonellosis. A significant sex bias was observed in affected greenfinches, with males more frequently diagnosed with salmonellosis than females. No sex bias was observed for other affected species. Further research is required to determine if salmonellosis is an important constraint to the populations of affected species and if disease outbreaks are driven by human factors, such as provisioning.