Katy A. Parr, DVM

Viral diseases

Beak and Feather Disease

Beak and Feather Disease is caused by a virus which attacks the beaks and feathers of parrots.  There is no cure for this disease, and it is spread through the feather dust and bodily fluids via inhalation, ingestion, or contact with open wounds.  Infected birds may have abnormally formed feathers and beaks which get worse with each molt, or may have no symptoms at all.  Affected birds often have additional bacterial or fungal infections as a result of the beak and feather abnormalities. Birds infected as babies usually die, while birds infected as adults may die, or become carriers and develop disease later in life.  Beak and feather disease is diagnosed through samples of blood or damaged feathers. Birds are eventually euthanised due to the severity of the deformations produced by the disease.

Papillomavirus/Herpes Virus

Papillomas are wart-like growths which are usually found in the mouth and vent, but can also affect the face and internal organs. They can still be seen from time to time but are less common now that many birds are captive bred instead of wild caught.  Both Herpes virus and Papillomavirus have been implicated as the cause for this disease, which is lifelong, and can have varying effects on the bird. In some birds the growths become large enough to block the normal function of the mouth or vent, and require surgical trimming.  In some cases, papillomas can lead to cancers of the liver and pancreas, and eventually death.
PDD (Proventricular Dilatation Disorder)

The Bornavirus which causes PDD was only very recently identified.   The disease is latent, meaning that the virus may be present for many years before signs of disease develop.  The virus attacks nerves, especially those of the digestive system, so signs vary from vomiting and passing whole seed in the stools, to wobbling or seizures.  There is currently no cure for PDD, so it is eventually fatal, but some medications may help improve quality and length of life.

Polyomavirus is very contagious and is most commonly a problem in breeding colonies, especially in budgies.  Signs of this disease may include abnormal feathers, bruising, distended abdomen, or sudden death.  It is spread via feather dust and bodily fluids which are aerosolized, thus it is very difficult to decontaminate the environment.  There is no treatment, but a vaccine is available for prevention. This vaccine is usually recommended in baby birds, breeders, or those exposed frequently to other birds from outside the home (e.g. at bird fairs).

Bacterial Diseases


This disease is caused by the bacterium Chlamydophila psittaci which is contagious to people.   It can cause respiratory disease and liver disease, so sick birds may have a variety of signs of illness ranging from sneezing, runny nose, eye discharge, and conjunctivitis, to diarrhea, yellow urates, vomiting, and lethargy.  However, birds can be carriers of the disease and never show clinical signs. Psittacosis is spread through contact with body fluids from infected animals or people, but it is usually not fatal and is curable with antibiotics.

Gram Negative Bacteria

There are many steps to identify bacteria.  One step in identification is a procedure called Gram staining, which separates bacteria into two large groups called “gram-positive” bacteria and “gram negative” bacteria.  These are very broad groups, and do not tell us the exact species of the bacteria, but help the veterinarian to determine the general health of the bird’s respiratory or intestinal tract.  Birds should normally have mostly (90%-100%) gram positive bacteria, while cats, dogs, reptiles and people can normally have many gram negative bacteria.  If gram negative bacteria are detected in the nasal sinus, crop smear or fecal smear of your bird, your veterinarian may culture the area in question and prescribe antibiotics and/or pro-biotics as is appropriate.

Fungal Disease


Yeast infections in birds most commonly affect the digestive system, and may overgrow due to a variety of conditions.  Baby birds often get yeast infections of the crop or stool because they are fed warm, soft foods which are a perfect environment for yeast growth.  Adult birds that dunk their food in water, or have a diet high in sugar may also get yeast infections.  Birds who have yeast infections may or may not show signs of infections such as vomiting, scratching the beak, or diarrhea.  These infections are usually easily treated with anti-fungal medications.


Normal healthy birds are not usually prone to aspergillosis; however individuals with weakened immune systems, such as those with nutritional deficiencies, are more susceptible.  Aspergillosis is caused by the fungus Aspergillus sp. which is naturally found in the environment.  You may have seen Aspergillus sp. growing on rotten fruits and vegetables, stale bread, or as a component of mildew in your home.  It is so common in the environment that it is impossible to completely eradicate.  You can however reduce your bird’s exposure to it by promptly removing any uneaten soft, moist foods from your bird’s cage, and routine cleaning of the cage.

Aspergillosis most commonly causes respiratory disease, and is often not noticed until the pet is very sick.   Common signs include sneezing, nasal discharge, general
weakness, inability to tolerate exercise or handling, open mouth breathing, and increased breathing effort.  Severely affected birds often need to be hospitalized.  Blood tests can be done to confirm whether a bird has aspergillosis, but diagnosis is often difficult and may require endoscopy.  Treatment is usually with liquid medications and nebulizations (aerosol medication) for several months.  Some birds recover from aspergillosis, but many do not.


Giardia and other protozoa

Protozoa are microscopic parasites, which can cause diarrhea, malodorous stools, feather-picking, or even no signs at all.  It is usually spread by oral contact with infected feces. In birds, flagyllated protozoans can be very difficult to clear completely, and may go away for some time, then return in times of stress.  Although this can be a frustrating infection, it is still important to treat it to keep your bird as healthy as possible.


The most commonly diagnosed mites in birds are the “Scaly Leg Mites” or Knemidocoptes sp., which is most often found in budgies and canaries.  These mites burrow into and around the beak, and under the skin on legs, causing a spongy, scaly appearance.   Canaries may also have tracheal mites, or Sternostoma tracheacolum, which can cause respiratory disease. Treatment for both types of mites consists of a series of injections which kill the mites.


While not all diseases and treatments are included here, these are some of the most common ones.  Contact your Chicago Exotics veterinarian if you have more questions or notice any unusual signs in your pet bird.  Having your bird examined yearly by an avian veterinarian increases the likelihood of detecting any of these diseases early, before they become a severe condition for your bird.

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