THE MERCK VETERINARY MANUAL
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Miscellaneous Diseases of Pet Birds

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Diabetes mellitus in pet birds causes fairly typical signs of polyuria, polydipsia, and high glucose levels in blood and urine. Normal glucose levels in birds are significantly greater than those in mammals. Diabetes is often seen in conjunction with obesity or pancreatic or reproductive problems and may be transient in such cases. Depending on the species, a deficiency of insulin or a relative increase in glucagon may be present. The mechanism for persistent hyperglycemia in birds may not be the same as in mammals; therefore categorizing this as diabetes mellitus is controversial. The etiology of hyperglycemia in birds is still unknown. Blood glucose levels in birds seem much more responsive to glucagon levels than to insulin levels. Response to mammalian insulin is variable and it is generally less effective than in mammals. Oral hyperglycemics, such as glypizide and glucophage, are usually preferred and are often effective when administered via the water because the amount of water, and therefore drug, that is consumed decreases as the medication reaches therapeutic levels.

Gout is the abnormal deposition of uric acid in the body. Articular gout occurs in the joints of birds (most often the metatarsal and phalangeal joints) and tends to be severely painful. If effective pain control cannot be accomplished, euthanasia should be considered. Diagnosis of articular gout is by the identification of gout tophi—whitish yellow, subcutaneous and intra-articular deposits that demonstrate uric acid crystals upon staining. Surgical removal of these tophi is not practical in most cases because they are extremely vascular and the risk of fatal hemorrhage is high. Additionally, unless the underlying condition can be identified and corrected or controlled, new tophi will appear very rapidly. Allopurinol (10–30 mg/kg, PO, bid) and colchicine (0.04 mg/kg, PO, sid-bid) may be useful in the control of articular gout. Visceral gout is seldom diagnosed premortem. The serosal surface of various organs and the renal tubules are the locations of uric acid deposition. Acute death is often the only clinical sign noted. Serum uric acid levels are seldom elevated with visceral gout. The genetic, nutritional, or environmental factors that predispose a bird to gout are not fully understood. However, current treatment of birds with elevated uric acid levels includes a low-protein diet.

Feather cysts are ingrown feathers that result in a granulomatous mass. Recurrence is common unless the extensive dissection of the feather follicle is accomplished. In birds with multiple affected feathers, such as the genetically predisposed Norwich canary, this is not practical.

The phrase “feather plucking” is commonly used to describe behavior that ranges from mildly excessive preening to self-mutilation. Management of this condition is frequently challenging. Feather plucking seldom has a single etiology, and it is prudent to thoroughly explore all possible contributing factors, including underlying medical problems. Good communication concerning feather plucking in birds at the onset will help clients realize that the odds are not in favor of a simple (or indeed, any) cure. The goal should be to improve the health of the bird and to reduce or eliminate the plucking behavior if possible.

Possible medical etiologies for feather plucking include: 1) Endoparasites (especially giardiasis in cockatiels) and occasionally tapeworms or roundworms. 2) Ectoparasites (rarely). 3) Hepatic disease, with associated pruritus. 4) Coelomic cavity granuloma or mass. 5) Neoplasia, which typically causes localized plucking of the area associated with an underlying mass. 6) Folliculitis or dermatitis that is primary, or secondary to excessive plucking and/or mutilation. Bacteria, viruses, fungi, or yeasts may be involved. 7) Allergies. Although difficult to confirm, a change in environment or diet when allergens are suspected may lead to a decrease in plucking and a tentative diagnosis by elimination. 8) Endocrine abnormalities, the most likely being hypothyroidism. However, hypothyroidism is overdiagnosed due in part to the lack of established normal values for avian thyroid levels, the low range for baseline T4 noted in birds, and difficulty in obtaining a reliable thyroid stimulating hormone response test. Nevertheless, some obese birds that demonstrate a lack of weight loss following a rigid diet, accompanied by poor quality feathers and infrequent molts, may be thyroid deficient. The plucking exhibited by these birds is often an attempt to rid themselves of old, damaged feathers. 9) Heavy metal toxicity, notably zinc. Barbering and feather plucking from zinc ingestion have been hypothesized. Many of these cases lack radiographic evidence of heavy metal and require a blood zinc analysis for diagnosis.

Malnutrition is likely a more common contributing factor to feather plucking than the medical conditions listed above. Basic seed and table food diets often create multiple nutritional deficiencies. These deficiencies cause abnormal skin and feather development resulting in plucking behavior, as well as a myriad of other medical problems that may occur later in life. The dyes and preservatives added to seeds and most pelleted diets may be detrimental to birds. The relatively low humidity in most households also has a drying effect on the skin. Being deprived of natural sunlight, fresh air, humidity, and the normal light/dark cycle has negative physiologic and psychologic effects on birds.

Although treatment of medical and environmental factors may reduce the severity of feather plucking, a strong behavioral component is often involved. Treatment of some of the above-mentioned problems may lead to initial improvement, followed by a relapse. Psychological stressors can lead to feather plucking as a displacement behavior. Unfortunately, once the stress has been relieved, the habit may still remain. Feather plucking does not occur in the wild, where birds are occupied with finding food, maintaining their social status in the flock, seeking a mate, avoiding predators, and breeding and raising young. Therefore, often the best-kept birds, which have all their apparent needs met, will pluck feathers for behavioral reasons. Psychological conditions that may cause feather plucking in birds vary. Overstimulation may cause plucking in a nervous bird. Another bird that was plucking from boredom may feel both stimulated and slightly threatened by increased activity in the home and stop plucking in order to pay attention to the environment and guard itself against potential predators. Birds that reach sexual maturity may begin to pluck as an outlet for their increased energy and agitation. Owners of these birds often report that their birds show more cage territoriality, more aggression toward family members, and potentially, sexual behavior toward a perceived human mate or inanimate objects.

A thorough understanding of the bird's environment and the associated behavioral changes that have accompanied the onset of plucking is required in order to make appropriate suggestions for environmental manipulation. When the history suggests a social or sexual cause of plucking, the veterinarian and owner may elect to combine environmental manipulation with either hormonal or psychotropic medications (see Psychotropic Medications Used for Feather Plucking in Pet BirdsTables). Neither of these categories of drugs tends to produce longterm positive results, and side effects may be seen. As is true of most medications administered to pet birds, FDA approval has not been obtained. In addition to traditional medical therapies, acupuncture has been reported to be helpful in some cases. Dietary supplementation with omega fatty acids has been reported to be helpful. Whether this is due to the antiprostaglandin effect or a true fatty acid deficiency is not certain.

Table 5

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An ideal medical treatment is not likely to be found for feather plucking in captive birds. Environmental manipulation, ensuring quality nutrition, and psychological adaptations suited to the species and temperament of the bird offer the best hope for reducing this syndrome. Consultation with a board-certified behaviorist who is familiar with psittacines may be indicated.

Last full review/revision July 2011 by Teresa L. Lightfoot, DVM, DABVP (Avian)

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