THE MERCK VETERINARY MANUAL
Print Topic

Sections

Chapters

Geriatric Diseases of Pet Birds

-
-

As the average life span of pet birds has increased, so has the incidence of geriatric-onset diseases, including cataracts, neoplasia, arthritis, and cardiovascular disease.

Cataracts

Cataracts occur in many species of psittacine birds as they age—notably macaws, Amazons, and cockatiels. These species may be prone to this disorder or may merely be over-represented in the older pet bird population. If the onset of cataracts is gradual, adaptation to decreased vision usually occurs.

The eyes should be examined at each annual visit to detect early changes in lens opacity. Due to the small size of the exposed cornea and pupil in pet psittacines, and the numerous acquired diseases that can occur, screening by an ophthalmologist of geriatric birds is recommended. Additional ophthalmic conditions that may be encountered in geriatric birds include keratoconjunctivitis sicca, corneal ulcerations, third eyelid abnormalities, hypopyon, anterior uveitis, conjunctival granulomas and infection of the conjunctiva (eg, Chlamydophila, Mycoplasma, poxvirus), Harderian gland adenoma, and lymphoma.

In larger psittacines, surgical removal of cataracts is successful in many cases. The bird's general health and the degree to which the cataracts affect its quality of life should be evaluated prior to surgery. Commonly used mydriatics are not useful in birds due to the skeletal (as opposed to smooth) muscle found in the iris. In any bird with decreased vision, minimal alteration of the home environment is critical.

Arthritis

Septic and traumatic arthritis may occur at any age. Septic arthritis is most commonly noted in the digits of birds. Geriatric-onset arthritis occurs in many species, and birds are no exception. Their small size makes radiographic diagnosis difficult. Radiographically, the stifles seem to be affected most often, although coxofemoral joint range-of-motion limitations are common in older birds. The weight of the bird, its general physical condition, previous injuries, and any concurrent medical conditions can all contribute to the onset and severity of arthritis. Concurrent pododermatitis is often present and may be both a cause and result of decreased activity. Malnutrition, which decreases the integrity of the plantar epithelium, and concurrent obesity are often noted in affected birds. The cage environment, especially the variety, diameter, and texture of perches, can be important in providing comfort and stability for arthritic birds, while preventing or minimizing pododermatitis. If possible, the nails should be left with sharp points to add strength and stability to the grip. Wings can be used to help with balance and should not be overclipped. Some medications such as meloxicam are being successfully used in birds, as well as glucosamine, acupuncture, and other holistic treatments, to decrease inflammation and discomfort.

Articular gout is also common in older birds (see Miscellaneous Diseases of Pet Birds). Differentiation between arthritis and articular gout is critical due to vast differences in progression, quality of life, and prognosis.

Cardiac Diseases

As birds live longer and diagnostic techniques improve, cardiac disease is being noted more frequently. It can be difficult to detect and may mimic other problems, such as respiratory disease. The bird may appear weak or lethargic, and may have an increased respiratory rate and effort. With right-sided heart disease, hepatomegaly and ascites are common. Disease also may be subclinical, then present acutely, with the bird expiring when diagnostic tests or treatment are attempted. Right-sided heart disease is more prevalent in birds than left-sided cardiac disease.

Working in conjunction with a cardiologist on any avian patient with suspected cardiac disease is advised. Diagnosis of the cardiovascular abnormality and formulation of a therapeutic plan requires both knowledge of avian anatomy and physiology and a cardiologist's diagnostic skills and pharmacologic recommendations. Although most avian therapeutic regimens are still extrapolated from mammals, numerous reports indicate that cardiac drug therapy can improve cardiac function, thereby increasing the quality and length of life.

The cardiovascular system of birds differs anatomically and physiologically from that of mammals. The right atrioventricular valve is a single, muscular valve with no chordae tendinae. The physiologic responses that maintain low pulmonary vascular resistance (both vascular distensibility and vasculature recruitment) are absent in birds, resulting in the inability of the pulmonary vasculature to accommodate increased cardiac output by either altering vascular diameter or changing the percentage of vascular channels being used. This is, at least in part, responsible for the high incidence of pulmonary hypertension syndrome (PHS) in the poultry industry as well as right-sided heart disease in psittacines. Studies on the impact of PHS in broiler hens have demonstrated that the response to pulmonary arterial hypertension in chickens involves an increase in 2 vasoactive substances: a vasodilator and a vasoconstrictor. The vasoconstrictor predominates over the vasodilator in broiler hens susceptible to PHS. For geriatric psittacine patients with pulmonary hypertension, vasodilator therapy should be explored. Macaw asthma may theoretically cause pulmonary hypertension, both from chronic capillary hypoxia and subsequent polycythemia.

Atherosclerosis is common in psittacine birds. It is generally a geriatric condition, with the exception of African Grey parrots, in which this disease has been noted in very young animals. Radiographically, the right aortic arch may be enlarged with increased density. Lipemia is often noted, and marked elevations in cholesterol and triglycerides may be seen. Unfortunately, definitive antemortem tests are lacking. At necropsy, grossly thickened arterial walls are noted.

The stress of handling can increase intracardiac blood flow velocity 300% in avian patients; therefore, inhalant anesthesia is preferred over manual restraint for performance of echocardiograms in all but the most docile birds. The equipment necessary for echocardiology in birds includes an ultrasound unit with Doppler function, 100 frames/sec minimum speed and microcurved or phased array probes with a minimum 7.5 MHz frequency. Anatomic constraints in birds also limit the echocardiograph windows available. Parameters for chamber sizes, blood flow velocities, functional contractility, and valvular insufficiency have been determined for several species, and studies are ongoing in this area.

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

Copyright     © 2009-2015 Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, N.J., U.S.A.    Privacy    Terms of Use    Permissions