Salmonella in small garden birds (passerines)
Cause: Usually Salmonella Typhimurium
Species: Finches, other passerines
Transmission: Ingestion of contaminated feed or faeces from infected birds
Geographic distribution: All of Scandinavia
Seasonal occurrence: Typically during winter (late winter/spring)
Cases of salmonellosis with deaths among birds are mainly seen in finches, such as bullfinch, green- and grey siskin, or greenfinch. The disease appears during late winter/spring and is often associated with garden bird feeding. The birds become infected from sick birds that excrete bacteria in faeces. Undoubtedly, bird feeders is a place where infection can spread since many birds gather in a small area. Therefore, it is important that the bird feeder/table is designed to prevent the birds from walking in the feed and contaminate it with their faeces. Also, birds should not be able to feed from spilled, soiled seeds on the ground below feeders, either by a net or other type of cover, or that the area is swept clean on a regular basis.
Birds that die from salmonella infection usually have a generalized infection with dissemination of the bacteria to different internal organs. Inflammatory foci might be found in the liver, spleen, pharynx, and oesophagus. Sick birds are often seen sitting with ruffled feathers in an apathic state below bird feeders, a typical appearance for seriously ill bird. In this state, they are an easy prey for predators. If the sick bird is caught by a cat, salmonella infection can be transmitted to the cat.
It is important to remember that salmonella also infects humans, and therefore it is important to keep strict hygienic routines whenever cleaning and refilling bird tables or handling sick or dead birds. Careful hand cleaning, i.e. washing with soap and water, is important to avoid infection after handling bird feeders or cleaning up after birds.