Causes of Morbidity and Mortality in Free-Living Birds in an Urban Environment in Germany

Free-living birds are often presented to veterinarians at rehabilitation centers as well as in private practice. Information about disease processes and causes of death of indigenous free-living birds can aid the clinician in establishing proper treatment and in the assessment of potential zoonotic risks. For the present study, pathogens as causes of morbidity and mortality were determined by performing a complete necropsy on free-living birds presented to the Clinic for Birds and Reptiles of the University of Leipzig (Germany) that died shortly after admission or were euthanized due to an unfavorable prognosis. Over a 2-year period, 251 birds representing 13 families (Accipitridae, Apodidae, Columbidae, Corvidae, Falconidae, Fringillidae, Hirundinidae, Paridae, Passeridae, Picidae, Strigidae, Sturnidae and Turdidae) were examined. Trauma (62%), including several bite injuries inducing bacterial septicemia caused by Pasteurella multocida, was the most common cause of morbidity. Parasitic disease (18%) was mainly caused by Trichomonas gallinae, Eucoleus dispar and Syngamus trachea. Metabolic disease (13%), including fibrous osteodystrophy, was almost exclusively limited to juvenile specimens. Different Enterobacteriaceae including E. coli, Salmonella Typhimurium DT040 as well as Mycobacterium avium ssp. avium were identified as causal agents of primary bacterial disease (5%). Primary bacterial infection as cause of death or disease was of major importance in nestlings. Viral infections, mycoses and intoxication had minor significance as causes of morbidity.