Diagnostics in a Search for an Etiology to Feather Picking / Mutilation
Presenting Author: Karen L. Rosenthal, DVM, MS, Dipl ACVP(Avian)
Department of Clinical Studies, Philadelphia, University of Pennsylvania
Interpretive Review and comments by Dr. Nemetz:
Dr. Rosenthal's lecture approached feather picking, feather damaging behavior, and skin mutilation in a different way. The premise she presented was: "All diagnostic testing we have today will help rule out systemic disease (infectious and non-infectious), but will it answer why a particular bird is feather picking?"
As demonstrated in The BIRD C News handout "Feather "Picking" - What Really Causes it?" (Click here) and often explained by Dr. Nemetz, feather/skin pathology is a rule-out situation with NO presentation specific to a unique etiology. This is why the search for a known etiology can be lengthy and expensive. Dr. Rosenthal brought up another philosophical question: "If we find a systemic disease process, treat it and the feather/skin condition resolves, was that the true etiology that caused the feather picking?" This was brought to our awareness because many avian veterinarians have seen conditions in birds some with accompanying feather picking and others without feather picking. Could there be species differences? Could there be different environmental factors? Could there be something else?
The following goal of Dr. Rosenthal was to go through the various diagnostics avian veterinarians have at their disposal and address which ones, if any, give us a specific cause to feather picking.
The Complete Blood Count (CBC)
Because this is a measurement of general overall health, whether using this to determine a cause of feather picking or gauging the bird's health status, this test is essential in affected birds. Patterns that can be seen: A predominant lymphocytosis seen in lovebirds with disease. Often elevated eosinophils might indicate a parasite infestation and elevated basophils in conures and spectacled amazons often indicate an inflammatory process. A CBC is also used to monitor progression of healing in a disease process.
The Plasma Biochemistry Profile (general blood panel)
This is also a measurement of general overall health of the bird. Blood panels look at enzymes related to various organs in the body. Elevated plasma AST levels are found in liver and muscle conditions. Creatine phosphokinase (CPK) is ONLY released from muscle and therefore should be included on all avian profiles. An elevated AST without elevated CPK levels may be significant because it is known in people that liver disease can lead to pruritis because of bile acid salts that are deposited under the skin. Elevated uric acid (UA) levels indicate systemic disease and may indicate kidney pathology when a bird is picking or mutilating directly over the kidneys located over the back in the area of the hips. Plasma biochemistry analytes are also important to decrease risk before any surgery or anesthesia procedure is performed.
Plasma Protein Electrophoresis (EPH)
This test is like the CBC but looks at the various immunoglobulins in the body. It approaches general health through a look at the immune system. This should be used in conjunction with the CBC. An increase in the beta or gamma sections of this immune test would indicate acute or chronic conditions, respectively. There are many more complexities to the EPH test but are beyond the scope of this summary
Once these minimum tests are done, further testing is specific to each case based on the bird species involved, the history, and presentation.
One can diagnose yeast ( Candida albicans) and intestinal parasites such as Giardia species, Trichomonas species, or nematodes. These are important to treat but its correlation to feather picking has only been shown in cockatiels with Giardia infections and immunosuppression.
Most pet birds are raised and kept in such fashion that they are not exposed to many intestinal parasites and as such, unless history dictates to the contrary, fecal floatation is rarely indicated and rarely performed at The BIRD Clinic.
Heavy Metal Assays
The two heavy metals of most concern in pet birds are lead and zinc. At the BIRD Clinic, copper toxicosis has been diagnosed after the ingestion of strands of copper from electrical cords. Other heavy metals such as arsenic and magnesium have been demonstrated to elicit clinical signs.
Lead is a well-known toxin, but Dr. Rosenthal states pruritis and feather picking have not been documented to date. However, as mentioned in Dr. Garner's article "Histological Description of Avian Noninfectious Skin Disorders" , Dr. Nemetz believes if a bird mounted a primary hypersensitivity immune response to the foreign material, a perivascular dermatitis could ensue with a subsequent feather picking event. This scenario has not been proven, but has been seen in a few cases at The BIRD Clinic.
Zinc toxicosis is even more controversial. The lack of proper zinc concentration in the diet can lead to skin abnormalities, but zinc toxicosis is associated primarily with gastrointestinal disease and blood disorders and according to Dr. Rosenthal has not been shown to have a direct correlation with feather picking.
Dr. Nemetz has seen numerous cases of heavy metal toxicosis, some associated with feather picking. After proper treatment and resolution of the toxicosis some feather pickers have ceased this destructive process. This does not support a direct cause and effect relationship, but only to support Dr. Nemetz's belief that "feather destructive behavior" is ONLY a symptom of pain and not correlated to any one specific etiology. Some species and individuals under circumstances of pain have a greater tendency to represent this through destructive feather behavior. If a resolved toxicosis case continues to damage his feathers then further history and diagnostics are indicated.
Chlamydophila psittaci Assays
This disease has not been associated with feather picking or mutilation. This disease in its carrier state does affect the bird's immune system and should be ruled out.
There are antibody titers, antigen titers, and cultures available for this fungal organism. It has not been associated with feather picking or mutilation. It is the opinion of Dr. Rosenthal and Dr. Nemetz that titers are of very little diagnostic use and positive cultures are only helpful in conditions where the organism is found in the affected area of the body. Fungal disease is mostly a secondary condition and not a primary pathogen.
DNA or Endoscopic Sex Determination
If it is determined that feather picking is of behavioral origin, it may be important for treatment considerations to know whether the bird is a female or a male.
Psittacine beak and feather disease (PBFD) testing is warranted as part of a thorough evaluation. Species most of concern are cockatoos, African grey parrots and lovebirds. This disease causes dystrophic feathers (Click here) for Dr. Garners paper " Histological Description of Avian Noninfectious Skin Disorders" or (Click here) for Dr. Reavill's paper "Etiologies (causes) of Avian Inflammatory Skin Disease") and is sometimes mistaken for feather picking. Because this disease is terminal and highly infectious it is important to test any of the mentioned species presenting with abnormal feathers.
Testing is available for two other viruses: Pacheco's virus (herpesvirus) and polyoma virus. Neither is directly associated with feather picking, but are contagious and part of a complete systemic evaluation.
Whole Body Radiographs
This is part of a thorough evaluation of an ill patient, but only in certain circumstances will it elucidate the cause of feather picking. Radiographs demonstrate mass lesions and changes in size of organs away from the norm. This is helpful where an enlarged organ or foreign body may illicit direct or referred pain and then subsequently causes the bird to pick intensely at one area of the body. Dr. Nemetz has seen several cases where ventricular (gizzard) foreign bodies with subsequent ventricular distension have led to intense feather damage or mutilation in the referred local area of the body. A barium series is often necessary in diagnosing fabric non-radiopaque foreign bodies and where an enlarged proventriculus or ventriculus may lead to the diagnosis of Proventricular Dilatation Disease (PDD). PDD has been associated in some cases of feather picking due to an inflammatory neuropathy (nerve damage).
(Side note: Even though it has not been proven as of this writing, many researchers and clinical avian veterinarians believe PDD is of a viral origin. It is also the belief of Dr. Nemetz from research done at Purdue University, when he was a student in the late 1980's, and other current researchers that the most likely viral agent is a paramyxovirus type 3 (PMV-3). It is further believed that the organism resides in the host in low levels with low-level intermittent shedding and positively affected birds are permanently infected with or without clinical signs.)
As a diagnostic tool to diagnose feather picking, endoscopic examination is unlikely to be satisfying. If one is to further explore systemic disease processes this is a well-documented approach that is justified. Dr. Nemetz does not recommend endoscopic evaluation until less invasive diagnostics (i.e. radiograph, barium series) justify this useful tool.
Skin Diagnostic Testing
There are a number of assays available. The most useful is the skin biopsy.
Skin Biopsy : (Click here) for Dr. Garner's in-depth evaluation and interpretation from a skin biopsy
Skin testing (intradermal testing): It has been long been suspected that environmental allergens, as in mammals, could elucidate the cause of picking and mutilation. Unfortunately, it is NOT possible to use intradermal skin testing methods in birds and NO allergens have been found to cause feather picking in birds.
Skin scrapings : This is mainly used to find ectoparasites. Skin parasites are very uncommon in pet psittacine birds. The most common skin parasite found is Knemidocoptes and is primarily found in budgerigars. Interestingly enough these mites are not associated with feather picking or mutilation in this species.
Skin cultures and Gram stains : Cultures are useful to determine the cause of the secondary bacterial or fungal dermatitis. It is unlikely the primary etiology. Gram stains of the diseased skin area are useful tools that are often overlooked. It can give preliminary information on the type of bacterial and fungal organism that may be present pending the culture results.
Feather pulp culture and pulp Gram stain : Again these will unlikely lead to the cause of the picking.