Lecture 3 Garner

Histological Description of Avian Noninfectious Skin Disorders

Presenting Author: Michael M. Garner, DVM, Dipl ACVP

Pathologist for Northwest Zoopath, Snohomish, WA

Interpretive Review and comments by Dr. Nemetz:

The BIRD C News publication titled "Feather "Picking" - What Really Causes it?" (Click here) shows that skin/feather disorders have either an infectious or noninfectious cause. Noninfectious feather/skin disorders fall into THREE main categories when diagnosed through histopathology from properly selected multiple skin biopsies. Dr. Garner gave a concise presentation of these different findings.

Perivascular Dermatitis

This is a delayed reaction mechanism causing feather picking, reddened skin, and behavior suggestive of pruritis (itching). This condition has a generalized histological presentation with visually affected as well as non-affected areas demonstrating the identical microscopic reaction. The important differential here is this condition affects all surfaces of the skin.

This condition can present intermittently or seasonally. Finding an exact cause can be difficult, but diagnosing this generalized condition suggests a primary hypersensitivity immune response and greatly facilitates discovering the true etiology. Perivascular dermatitis is most often seen in macaws, particularly blue and gold macaws, amazons, and eclectus parrots and is rarely seen in African grey parrots and cockatoos.

Psychogenic Self-mutilation

This condition can present similarly to birds with perivascular dermatitis, however this is a localized histological reaction with the absence of inflammation in the non-affected areas. The important differential here is in this condition the inflammation is only in the affected areas. This is evident of a non-primary inflammatory skin condition. Psychogenic Self-mutilation is most often seen in African grey parrots, cockatoos, cockatiels, and golden conures. Dr. Nemetz has seen localized inflammatory conditions of non-psychogenic origin (internal foreign bodies, tumors, and localized disease processes) that have responded to correct therapy.

Follicular Dysplasia

This is an abnormality in the growth pattern of developing feathers. This is most common in psittacine birds infected with circovirus (Psittacine Beak and Feather Disease, PBFD). Some cases indicate a congenital etiology in young affected birds and thus may be inherited. Other cases spontaneously occur in older birds and may resolve with proper husbandry and subsequent molts. The feather dysplasia, if generalized, can lead to furunculosis (rupture of the feather shaft with pruritis) and present histologically as perivascular dermatitis.

 

Conclusion

Dr. Garner demonstrated the key to diagnosing avian patients with skin disorders, after known infectious/non-infectious etiologies are ruled out, is with multiple properly obtained skin biopsies from affected and non-affected areas. This will categorize the immune reaction thereby giving further direction to the immune response and possibly lead to a proper treatment program. Dr. Nemetz agrees this is an excellent diagnostic procedure but non-invasive diagnostic tests (blood analysis, radiographs) should be evaluated first since skin biopsies elucidate the skin's reaction to a cause, but does not identify that cause.