Spontaneous Wing Tip Edema in Captive Birds of Prey: Review of 41 Cases in the United Kingdom (2004-2022).

Abstract

There is limited literature regarding wing tip edema (WTE) in raptors, and much of our current understanding of the condition is based on anecdotal reports. The aims of this retrospective study were to describe the clinical features of WTE in birds of prey, to identify prognostic factors for return to flight and patient survival following diagnosis, and to develop and assess the clinical significance of a novel WTE grading system. Between 2004 and 2022, 41 cases of WTE were identified in 39 captive birds. No cases were found in wild birds. Harris's hawks (Parabuteo unicinctus), lanner falcons (Falco biarmicus), and peregrine falcons (Falco peregrinus) had the highest frequencies of WTE, and all cases presented between October and May. Increasing days of air frost per month and colder median monthly temperatures were significant risk factors for the development of WTE. Of the cases where patient outcomes were known, 23/31 (74.2%) cases returned to normal flight and 29/34 (85.3%) cases survived. End-stage disease, represented by primary flight feather loss and metacarpal ischemic (dry) gangrene, and enalapril use were associated with poor patient outcomes. Presentation within 24 hours of disease onset, isoxsuprine use, and physiotherapy were associated with improved patient outcomes. This study showed that WTE is an infrequently encountered but clinically significant condition in captive raptors and is associated with an overall high morbidity and moderate mortality risk.