Feather Defects in a Juvenile Common Swift (Apus apus) Associated with a Circovirus Infection

The common swift is the most observed swift species in Germany. During the summer months in urban areas, juvenile swifts in need of help are frequently cared for in wild bird rescue centers. Providing adequate housing and veterinary treatment for hundreds of juvenile swifts can be very challenging for non-specialized organizations and contact with other bird species is often unavoidable. The knowledge about the transmission of infectious diseases between individuals of this bird species specialized in an airborne life and of other bird species is limited. In this presented case a wild juvenile common swift was hand-reared for about 17 days and was noticed to have increasing feather abnormalities in a wildlife rescue center with close proximity to other wild birds. At the time of the investigation, the swift was of an age of about 35 days, and in good physical condition. The affected body, wing, and tail feathers showed retentions of feather sheaths, malformation of the feather vane, and circumferential constrictions with feather loss. The virological examination of the dystrophic feathers revealed a positive result for the circovirus and a negative result for the polyoma-consensus-nested PCR. The detected sequence of the circovirus showed the highest identity in 300 base pairs of 83.11% to a Canary circovirus isolate in NCBI Blast analysis. In addition to a transmission between common swifts during the nestling phase, other wild bird species can be discussed as a possible source of the infection.