Additional Records of Pinching-off Syndrome in White-tailed Eagles

Pathological changes involving the feathers of raptors include the pinching-off syndrome (POS). The disease is manifested by defective feather growth, wherein the young, vascularized remiges and rectrices are twisted and prematurely fall out. Upon examination, the feathers that are prematurely shed are found to have a marked constriction at the base of the shaft. Remiges and rectrices reach just 1/2 half to 2/3 thirds of their normal length, after which the blood supply is reduced and dystrophic feathers are dropped. Feather development deteriorates further, and new flight feathers are dystrophic and become progressively shorter with each new feather generation. Affected birds are unable to fly. The first survey of POS in white-tailed eagles (WTE; Haliaeetus albicilla) focused on 33 cases in Germany, Poland, the Czech Republic, the United Kingdom, and Russia from 1975 to 2006 (J Avian Med Surg. 2007;21:103-105). We revealed 43 new cases from 2007 to 2024, identifying these in Germany (n = 15), Poland (n = 9), the Czech Republic (n = 10), Russia (n = 8), and Kazakhstan (n = 1). In addition, 3 cases in Poland, 2 in the Czech Republic, and 1 in both Russia and Kazakhstan were identified from 1999 to 2006 but not published previously. In total, we report 50 new clinical cases of POS in WTE. The investigation thus far into the cause of POS has failed to determine an etiological agent. Based on the association of a higher prevalence of POS in an area occupied by a WTE population with a different genetic structure compared with other WTE populations and based on 6 family cases registered, we support a hypothesis for a genetic cause of POS.