Abstract

Feather destructive behavior and self-mutilation of the skin are common problems in captive birds, particularly psittacines.^1,2,4,5 A number of causes have been identified or suggested, including mycotic, bacterial, viral and parasitic agents, hypersensitivity, hormonal derangements, hepatic or pancreatic disease, and psychogenic disorders.^1,2,4,5 This report summarizes findings of a retrospective study of paired biopsy results from birds with feather loss, feather-picking or self-mutilating behavior, or other alterations in the skin recognizable to clinicians.

From 1994 to 2005, 16162 avian biopsies or necropsies were accessioned at Northwest ZooPath. Dermatitis or skin trauma was diagnosed in 1183 of these cases for an incidence of 7.3%. Because skin conditions appear to be a common avian problem, a “paired” biopsy protocol was devised to aid in the understanding of the pathogenesis of dermatitis or other skin lesions,^1,2 and this study summarizes data collected with this protocol. Briefly, the protocol requested that clearly labeled full-thickness biopsies of skin and feather from affected and unaffected sites be obtained and fixed routinely in formalin for histologic examination. Affected sites were clinically abnormal and usually were areas easily reached by the bird’s beak such as the legs or chest. Unaffected sites were areas that appeared clinically normal or were not easily reached by the bird, such as the top of the head or neck. All biopsies were examined at three different levels in the paraffin block.^1,2

Criteria used for the diagnosis of inflammatory skin disease included the presence of perivascular to diffuse inflammation in the superficial or deep dermis of clinically affected and unaffected sites. Inflammatory cells typically were lymphocytes with fewer plasma cells, histiocytes, and eosinophilic granulocytes. Varying degrees of edema, epidermal and follicular hyperkeratosis, and perivascular pulpitis were also present in some cases. For most cases, it was necessary to examine all levels of the biopsies to confirm the presence of inflammation. Cases with scarring (suggestive of trauma) in the unaffected site generally were not included in the inflammatory skin disease subset, to avoid confusion regarding the pathogenesis of the inflammation; however, few cases were included in this subset if the scarring was disproportionately mild compared to the severity of the inflammatory process. The primary criterion for the noninflammatory skin disease subset was an absence of inflammation in unaffected sites. These cases sometimes had no inflammation or other lesions in affected sites as well, but usually had some degree of scarring and inflammation in affected sites, and sometimes also had some scarring in the unaffected sites. Any cases that had histologically recognizable infectious agents, neoplasia or follicular dysplasia were excluded from this study.

Results of this study are summarized in Table 1. Using the above criteria, the total study population was 412 birds. Inflammatory skin disease was diagnosed in 211 birds for a prevalence of 51%. Noninflammatory skin disease was diagnosed in 201 birds for a prevalence of 49%. Species trends were identified and included a preponderance of inflammatory skin disease in macaws and amazon parrots. A preponderance of noninflammatory skin disease or trauma was seen in the cockatoos and African grey parrots. The prevalence of each was about equal in several other species, including conures, Eclectus parrots, quaker parrots, cockatiels, parakeets, and caiques. Total submissions of remaining species were low, and trends were not interpreted from these data. Birds with inflammatory skin disease and noninflammatory skin disease had a broad distribution in the United States and also were seen in Sweden. Trends relative to the sex of the bird were not identified, and interpretation was hampered by the large number of birds in many species categories for which the sex was not known. A single large population of lorikeets had 100% prevalence of inflammatory skin disease, but skin disease was not seen in lorikeets from other regions or populations. This finding suggests that lorikeets may be susceptible to inflammatory skin disease, but that it may not be common in the general population for this species. No budgerigars met criteria for this study, suggesting that this common pet species may not be prone to inflammatory or traumatic skin disease. Very few non-psittacine cases fit criteria for inclusion in this study; this may be because fewer dermatopathies are recognized due to less human contact with these birds, or that a lower prevalence of inflammatory skin disease exists for nonpsittacine species.

Table 1. Prevalence and sex of birds with inflammatory and noninflammatory skin disease associated with clinical dermatopathy, feather picking or self-mutilation, based on paired biopsy technique

^aSex ratio is male.female.unknown.
^bRepresents a single population
^cSpecies not known
^dNon-psittacine species

The etiology for inflammatory skin disease in the study birds was not determined. Based on the large number of affected species, obvious species trends, and wide demographic distribution of affected birds, it is considered likely that more than one etiology may exist. The pattern of the inflammation is most suggestive of cutaneous hypersensitivity, or a cutaneous manifestation of systemic inflammation. In a detailed report of the normal histology of the avian integument, inflammation is not described.³ In the author’s opinion, the presence of inflammation in the skin of birds is not normal, may be a source of discomfort or pruritis for affected birds, and provides at least one plausible explanation for the feather picking or self-mutilation seen in some psittacine birds. Inflammation for which the cause cannot be identified probably should not be regarded as nonspecific, incidental, or insignificant. Our findings support previous reports that inflammatory skin disease may be prevalent in feather-picking birds based on examination of paired biopsy specimens.^1,2 Our findings are in contrast to those of a previously published report that did not associate inflammatory skin disease with feather-picking birds;⁴ however, sample size was much smaller in that study (eight birds total, one per species), and a paired sampling technique with multilevel histologic examination was not used.

Acknowledgments

Northwest ZooPath is grateful to the following institutions for submission of study cases: Avicultural Breeding and Research, Loxahatchee, FL; All Creatures Vet Hospital, Stuart, FL; All Creatures Animal Hospital, Bremerton, WA; Angell Animal Medical Center, Boston, MA; Animal Hospital of Centereach, Centereach, NY; Animal Health Clinic, Jupiter, FL; Barberton Vet Clinic, Norton, OH; Bethel Park Animal Hospital, Bethel Park, PA; Bird and Exotic Clinic of Seattle, Seattle, WA; Dallas Zoo, Dallas, TX; Des Moines Vet Hospital, Des Moines, WA; Djurkliniken Roslagstull, Stockholm, Sweden; Ellensburg Animal Hospital, Ellensburg, WA; Floridawild Vet Hospital, Deland, FL; Fort Worth Zoo, Fort Worth, TX; Guardian Animal Hospital, Ashland, KY; Hendricks County Animal Hospital, Danville, IN; Dr. Jackie Gai, Vacaville, CA; Kansas State University, Manhattan, KS; Karlskrona Distr. Vet Station, Lyckeby, Sweden; Kraft Mobile Vet Services, Snohomish, WA; Los Angeles Zoo, Los Angeles, CA; Latah Creek Animal Hospital, Camano Island, WA; Old County Animal Clinic, Plainview, NY; Dr. Susan Clubb, Loxahatchee, FL; Regiondjursjukhuset Helsingborg, Helsingborg, Sweden; Safari Animal Care Center, League City, TX; Sno-Wood Vet Hospital, Snohomish, WA; Summertree Animal and Bird Clinic, Dallas, TX; The Toledo Zoo, Toledo, OH; Valley Animal Hospital, Roanoke, VA; Village Vet Hospital, Bellingham, WA; West Valley Pet Clinic, Woodland Hills, CA; Windcrest Animal Hospital, Wilmington, DE; and Yukon Vet Hospital, Yukon, OK. The author also thanks Jamie Kinion for data retrieval.

Literature Cited

1.  Clubb, S.L., M.M. Garner, and C. Cray. 2001. Detection of inflammatory skin disease in psittacine birds using paired skin biopsies. Proc. Assoc. Av. Vet. Annu. Meet. Pp. 193–199.

2.  Clubb, S.L., M.M. Garner, C. Cray, K. Arheart, and M. Goodman. 2004. Diagnostic assessment of feather damaging behavior in African grey parrots (Psittacus erithacus) Proc. Assoc. Av. Vet. Annu. Meet. Pp. 313–320.

3.  Lucas, A.M. and P.R. Stettenheim. 1972. Avian Anatomy. Integument. Agricultural handbook 362, U.S. Department of Agriculture, Washington DC, Pp. 485–635.

4.  Rosenthal, K.L., D.O. Morris, E.A. Maudlin, E.S. Ivey, and H. Peikes. 2004. Cytologic, histologic and microbiologic characterization of the feather pulp and follicles of feather-picking psittacines birds: a preliminary study. J. Av. Med. Surg. 18: 137–143.

5.  Schmidt R.E., and T.L. Lightfoot. 2006. Integument. In: Harrison G.J. and Lightfoot T.L. Clinical Avian Medicine. Vol. 1. Spix Publishing, Palm Beach, FL. Pp. 395–410.