ACVC 2001 - Avian Common Clinical Presentations: Neoplastic, Toxic, Viral and Miscellaneous

Avian Common Clinical Presentations: Neoplastic, Toxic, Viral and Miscellaneous

Teresa L. Lightfoot D.V.M., Diplomate ABVP - Avian

NEOPLASIA:

The age distribution of neoplasia in psittacines is similar to that of dogs and cats. The highest incidence is in older birds. A percentage of birds will develop tumors while still immature. Genetic predisposition accounts for most neoplasias that are seen in young to middle-aged birds. As the average age of our pet bird population increases, the incidence of neoplasia is also increasing.

This lecture will illustrate some of the more commonly diagnosed tumors in psittacines and also list differential diagnoses that are non-neoplasitic.

Skin and subcutis:

Fibrosarcomas are often seen as firm subcutaneous masses in older birds. Complete surgical resection can be difficult and recurrence is possible. Radiation therapy may be warranted. Metastasis has rarely been documented. Conversely, fibromas are rare in birds.

Hemangiomas are common in birds - often presented as raised, circular red masses. Hemangiosarcomas are reported with much less frequency.

Squamous cell carcinomas (s.c.c.) occur in many locations in birds, including the cere, beak, aural area, and digits. Facial s.c.c. must be differentiated from allergic hyperkeratotic-appearing dermatitis by histopathology.

Lipomas are common benign neoplasias seen most frequently in budgerigars.

Xanthomas are non-neoplastic masses of thickened, yellow skin and subcutaneous tissue composed of cholesterol and fat. Some xanthomas are so extensive that surgical resection/amputation may be necessary. Others may be treated with dietary correction.

Gastrointestinal Tract:

Papillomas of the cloaca are the most commonly diagnosed tumor of birds in the g.i. tract. Choanal papillomas and intestinal papillomas also occur. Macaws are over-represented with papillomas, but many other species can be affected. Although a viral etiology has not been determined, the epidemiology of this disease suggests a viral origin.

Carcinomas of the liver, pancreas, kidney, ovary and proventricular / ventricular isthmus have all been documented.

Lymphoma has many manifestations in birds. Recently, several reports of lymphoma that have presented as a retrobulbar mass have been seen in young Congo African Grays. (Michelle Curtis-Velasco, I.C.E. Proceedings, 2000). Lymphatic, hemopoetic, hepatic and subcutaneous lymphoma have also been documented with some frequency.

Bone

Osteosarcoma of the long bones is the most prevalent tumor in this category. Chondromas and chondrosarcomas have been reported.

Pituitary tumors:

The literature reports most cases of documented pituitary neoplasia in budgies. Although few reports have occurred in the literature of this neoplasia in other species, this author and others have seen cockatiels and other psittacines present with either neurologic signs (seizure, head tilt, ataxia) or clinical signs attributable to pituitary hormone alteration - with exhibition of signs such as polyuria/polydypsia. Some pituitary tumors may affect the eye, either causing blindness and/or exophthalmia. This presentation requires differentiation from retrobulbar lymphoma and Harderian gland neoplasia.

TOXIC

Toxic conditions in birds are always a concern in the captive environment. Numerous reports of toxic reactions to aerosolized substances in addition to the well-known over-heated non-stick cookware have been documented. African Gray sp. seem to be especially susceptible to some aerosols.

Zinc toxicity has become a prevalent problem in aviary medicine. Since most wire is galvanized, many cages are constructed with wire that has a coating with a high component of Zn. Ingestion of this galvanized wire coating may cause the more severe signs of heavy metal toxicity, which generally consist of depression, diarrhea, polydypsia and polyuria, regurgitation (often passive reflux of water from the crop upon handling). Rarely there will be CNS signs other than weakness. Low-grade zinc toxicity is thought to be responsible for conditions such as feather picking. Treatment initially is CaEDTA injectably. Once the bird is stable, dl-penicillamine can be used orally (see formulary). Lead poisoning still occurs, but the increase in awareness of the danger to humans has decreased the availability of Pb. Also, bird owners are more aware of sources of lead than they are of zinc. Lead toxicity can present with the same clinical signs as zinc, but there will be a more frequent occurrence of neurologic signs (seizures, hyper-excitability) and in some species such as Amazons, hemaglobinuria may be noted. Luckily, radiographic evidence of metal in the ventriculus and clinical signs of heavy metal toxicity are sufficient to warrant the initiation of therapy, and both Zn and Pb respond to Ca EDTA. Note that it is common to have an elevated WBC with heavy metal toxicity. Whether or not this is a true infection is questionable. Fluid therapy should be used to ensure that no renal damage occurs with the Ca EDTA treatment.

VIRAL/COMMUNICABLE DISEASES:

When you start talking about these diseases, it often alarms clients and breeders. Especially with these diseases, where tests on live birds have no absolute negatives, it is a precarious situation. When we tell owners that we have seven different tests for Chlamydia, but that even if we run them all, we cannot be certain that the bird is not harboring Psittacosis, it doesn't engender confidence.¹² The serum and cloacal swab Chlamydial tests that have recently become available have greatly improved out antemortum diagnosis of Chlamydiosis. Dr. Tom Tully and others are currently conducting research at Louisiana State into the development of a vaccine against Chlamydia. A valuable aid for Chlamydial testing, treatment, and legality issues is the CDC "Compendium of Measures To Control Chlamydia psittaci Infection Among Humans (Psittacosis) and Pet Birds (Avian Chlamydiosis), 2000" (see reference #12).

Proventricular Dilatation Disease (PDD) is even more difficult. It is often only definitively diagnosed on necropsy, and there is currently no innocuous in vivo test.⁵ The passage of whole seeds in the droppings of adult birds is not present in hand-feeding babies. One precaution on baby birds is not to even tentatively diagnose this disease on a one-time radiograph unless the bird is fasted. Weaning birds often regurgitate, loose weight, and on plain films, have dilated proventriculi with a variety of disease syndromes. Fast these birds overnight for 8-12 hours and re-radiograph them and you will "cure" many of them of PDD. The benefits & risks of proventricular, ventricular, and crop biopsies are beyond the time constraints of this talk. Be familiar with these options and their limits and risks.

Psittacine Beak and Feather Disease - due to available testing, we see fewer affected cockatoos than we did ten or twenty years ago. The disease does occur in African Grays, Eclectus, and lovebirds more commonly now. A PCR test is available and confirmatory in clinically affected birds, or on repeat positive testing

Polyoma virus has taken a great toll on the avicultural industry in the U. S. as well as causing much heartbreak and controversy between owners, breeders, and pet stores. The disease is predominately manifested as an acute death in well-fleshed fledgling birds, with classic signs of hemorrhage, pale breast musculature, petechiation and ecchymosis on the heart, pericardial effusion, and a swollen, pale liver. Recent research has indicated that adult birds may be as susceptible to Polyoma virus as are juveniles, however, they rarely develop clinical disease. This susceptibility of adults may act as a reservoir in an aviary or pet store population. Three different tests are currently available. Two of these are PCR (polymerase chain reaction - DNA testing). This test can be performed on a cloacal swab, where a positive result indicates that the bird is currently shedding the virus.⁶ The same test, when applied to serum, will show recent exposure to the virus, while portions of the viral DNA are still present in the circulation. In the absence of clinical disease, this test does not indicate whether the bird has overcome the infection and will survive. The third test is an antibody test, which demonstrates previous exposure to the virus. Whether a clinically normal adult bird can harbor this virus latently is not known. Extensive research at the University of Georgia has failed to locate any site of latency to date in non-budgerigar species of psittacines (Branson Ritchie, personal communication, January, 1998). A vaccine is available, and should be administered at 2-3 week intervals, starting at 4-5 weeks of age, and continuing until the bird is immune competent if it is to be exposed to other birds. This may necessitate two, three, or even four vaccinations with the current policy in the U.S. of selling young birds to pet stores while they are still hand feeding. The pet stores then house these birds in the same enclosures as birds from other sources and sell them while they are still not weaned, often to inexperienced owners. Besides the increased risk of Polyoma exposure with this sequence, the incidence of hand feeding accidents and aspiration pneumonia, or the inadvertent starvation of birds by first time owners are frequent occurrences. Unfortunately, the economics of aviculture make it unlikely that this will change in the near future, especially with the myth that a bird that is hand fed by its new owner will bond more effectively. Hopefully, the combination of education of the clients and the increased prevalence of vaccination against Polyoma will eventually decrease or eliminate its devastating effects.

MISCELLANEOUS PRESENTATIONS:

Preen gland (uropygial gland) - infection or neoplasia? (Note - Amazons do not possess a preen gland. The psittacine species most commonly affected with uropygial gland problems seem to be cockatiels and cockatoos.)

Pelican Hook and Line Disease - A common and readily reparable problem in most cases, with minimal expense, but maximum odor..• The lecture will addresss manual exptraction, a device for extraction through an ingulivotomy incision when needed, and surgical removal.

Cataracts - Acute vs. gradual onset. Gradual onset cataracts are common in older birds of all species, "older" being relative to the species (usually 40's in macaws, 30's in Amazons, etc.) Much like dogs, gradual onset allows adaptation and the owner may not be aware of the development of the cataracts. However, acute onset can mimic a CNS disease, seizure, sudden behavioral changes such as aggression, anorexia, and other clinical presentations. Some birds do not adapt to the rapid development of cataracts and will virtually starve to death, unwilling or unable to resume eating and drinking. Cataract surgery is performed successfully by many veterinary ophthalmologists who equipped with the proper medications for dilation of the striated musculature of the ciliary body in birds.

Other miscellaneous conditions:

In summary, using sound clinical judgment in determining when it is prudent to implement aggressive medical or surgical techniques is one of the major skills needed in avian medicine. The corollary is knowing when less is more and preventing disaster by evaluating the risk vs. benefit of each diagnostic and therapeutic procedure prior to its implementation.