In pet birds, diseases of the respiratory tract are very common. They can be caused by bacteria, viruses, fungi, or parasites. It is critical to recognize and treat these diseases in the early stages, when it is much more likely that treatment will be effective.
Aspergillosis
Aspergillosis is the most common fungal infection in birds. It occurs in 2 forms. The first form primarily occurs in young birds and newly imported birds and is the result of exposure to a large number of spores of the Aspergillus fungus. The second, more chronic form is more likely to occur in older birds that have been in captivity. Contaminated food, water, and nesting material with poor ventilation are sources of concentrated spores. Aspergillus spores are also widespread in the environment. Birds that inhale the spores may carry them into their lungs and air sacs. When the bird becomes weakened or stressed, and its immune function is decreased, the disease is triggered. Aspergillosis has been diagnosed in many species of birds. Longterm malnutrition, especially vitamin A deficiency, is the most common cause of a weakened respiratory system defense that predisposes birds to the chronic form of aspergillosis.
Aspergillosis usually affects the lower respiratory tract. Although the lungs and air sacs are usually involved, the trachea, syrinx (voice organ), and bronchi may be affected as well. Infection can spread from the respiratory tract to other organs (bone, liver, kidneys, or brain). Eye and skin infections can also occur.
Signs of infection in the severe, short-term form that affects young and newly imported birds include loss of appetite and labored breathing. Sudden death may occur. White mucous congestion of the lungs and air sacs, and nodules in the lungs may be noted during examination of the bird. The air sacs may become inflamed, leading to a condition sometimes called airsacculitis.
In the chronic form, labored breathing, voice change, lack of energy, depression, and emaciation may occur. Infection of the respiratory tract can be severe before signs are noted. Extensive or chronic fungal infection may lead to bone changes and permanent malformation of the upper respiratory architecture. If the central nervous system is affected, the bird may have a lack of coordination and paralysis.
The symptoms caused by aspergillosis are similar to those seen with other respiratory infections. Treatment with antifungal drugs is often successful if the infection is caught in its early stages. It is important to check with your veterinarian whenever your bird has signs of a respiratory illness.
To help prevent aspergillosis, good hygiene, including proper ventilation of the cage or aviary area and proper nutrition, should be maintained at all times.
Avian Influenza (Bird Flu)
Avian influenza is caused by a group of viruses that originated in wild birds.
One genetic clade of the severe form called high-pathogenicity avian influenza (HPAI)—the 2.3.4.4b clade of the goose/Guangdong (Gs/GD) Eurasian lineage—has become a great concern not only because it can infect domestic poultry and captive and wild birds but because it has the potential to infect people and other mammals.
The Gs/GD virus could become a more important health threat in birds and humans because, compared with other avian influenza strains, it has a broader geographical distribution and the risk of encounters with infected wild birds is higher.
Anyone purchasing a new bird should find out where it came from and have it checked by a veterinarian for any infectious diseases. The US has imposed restrictions on bringing pet birds into the country from places affected by avian influenza.
Spread of Avian Influenza
Avian influenza is transmitted by direct contact with respiratory secretions and feces from an infected wild, domesticated, or pet bird. Dogs and cats can become infected when they prey on carcasses of wild birds.
In early 2024, the specific genotype B3.13 of the 2.3.4.4b clade in the Gs/GD lineage of the H5N1 virus was found to have infected dairy cattle in the US, and its spread from farm to farm was associated with the movement of infected cows.
Signs of Avian Influenza in Birds
In birds, clinical signs of avian influenza infection and severity of the disease vary depending on the virus strain and the species infected. Some strains lead to mild disease; others cause severe disease with mortality rates of up to 100%. Some infected birds can have no clinical signs and recover; others may die suddenly with no signs of disease.
Birds that show clinical signs of respiratory illness should be promptly separated from other birds and examined by a veterinarian, who can diagnose avian influenza by submitting samples for molecular detection of the virus to a National Animal Health Laboratory Network (NAHLN) veterinary diagnostic laboratory.
Vaccines for Avian Influenza
Although vaccines have been developed for some types of avian influenza in domestic poultry, vaccination of poultry against HPAI requires emergency approval by USDA. In mid-2023, USDA began vaccinating the endangered California condor (Gymnogyps californianus); however, vaccination of poultry and pet birds is not allowed. An important way of preventing exposure to the virus is to prevent contact between domestic birds and wild birds that might carry the virus.
Avian Influenza in Cats
In late 2022 through mid-2023, several cases of fatal infection by the Gs/GD HPAI strain were reported in domestic cats (in the US, South Korea, France, and Poland) and in a dog (in Canada). Most of these affected animals had outdoor access and likely became infected through direct contact with or consumption of infected wild bird carcasses. Some of the infected cats in Poland were restricted to indoor access only, raising the possibility of exposure through feeding of infected raw chicken. Because the virus is shed from the respiratory tract and in feces, cat-to-cat transmission is possible but extremely rare.
Clinical signs of avian influenza in cats include listlessness, loss of appetite, fever, dyspnea, neurological signs, intestinal signs, jaundice, and death.
In early 2024, deaths of barn cats were reported on farms with infected dairy cattle. The cats were infected as a result of consuming raw (unpasteurized) infected milk from the cows.
Precautions for Avian Influenza
Any animals suspected of being infected should be isolated from other pets, and anyone handling them should wear appropriate personal protective equipment (PPE), such as gloves and masks. After contact with a suspected case, handlers should wash their hands with soap and water.
To minimize exposure when HPAI is present in wild birds within a given area, owners should keep pets indoors, if possible, or supervise outdoor access to minimize wild bird exposure.
Hypersensitivity Pneumonitis (Macaw Asthma)
A respiratory condition similar to chronic obstructive pulmonary disease (COPD) affecting macaws (primarily Blue and Gold macaws) has been recognized for several decades. These birds often have a history of being housed in poorly ventilated environments with birds (such as cockatoos and African grey parrots) that have a large number of powder down feathers that release a powdery substance when preened that can irritate susceptible birds’ respiratory tracts. This does not mean that all macaws must be kept in separate areas from cockatoos or African Greys, but good air circulation and environmental hygiene is needed.
Birds that develop this hypersensitivity may also have secondary bacterial or fungal infections. Your veterinarian may need to do several procedures to determine whether your macaw’s respiratory condition is due to this hypersensitivity or to other causes. A blood cell count and x-rays are often performed. A tracheal wash may be necessary to determine if a combination of these diseases is present, and to select the appropriate treatment. A lung biopsy is the only way to confirm the diagnosis.
Initially, the best treatment for a bird that is in respiratory distress from this condition is oxygen. Your veterinarian may also consider the use of glucocorticoids or other anti-inflammatory drugs. Longterm management requires optimal air quality and ventilation. A good air filter (such as a HEPA filter) located near the cage is invaluable. Repeat crises may occur and necessitate rehospitalization and treatment, but a change of environment and increased ventilation will reduce the likelihood of severe relapse. Some permanent lung damage is usually present, and exercise intolerance often persists due to interstitial fibrosis (scarring) of the lungs. Affected birds may have a shorter lifespan.
Polycythemia, an increase in the percentage of red blood cells, is a very common finding on the blood work and may be the best method to screen for this disease before it becomes a noticeable problem.
Newcastle Disease
Newcastle disease, caused by a paramyxovirus virus, is a significant threat to the poultry industry but can also infect pet birds. Transmission is by respiratory aerosols, fecal contamination of food or water, direct contact with infected birds, and contact with inanimate objects that harbor the virus. It is rarely seen in pet birds in the United States.
Signs of infection include depression, loss of appetite and weight, sneezing, discharge from the eyes or nostrils, difficulty breathing, bright yellow-green diarrhea, lack of coordination, head bobbing, and spasms. In later stages, paralysis of the wings or legs, involuntary or jerky movements, twisting of the neck and unnatural position of the head, and dilated pupils may also be seen. Birds may die suddenly without any signs.
There is no cure, and treatment is not recommended. If suspected, Newcastle disease must be reported to state and federal animal health authorities due to its potentially devastating effects on domestic poultry. Vaccination is prohibited in birds entering the United States because it does not eliminate the carrier state and makes it difficult to detect the virus during quarantine.
Respiratory Parasites
Air sac mites are parasites that can be found in the entire respiratory tract of affected birds, most frequently in canaries and Gouldian finches. All stages of the mite are found within the respiratory tissues. In mild infections, birds do not usually have any signs; in heavy infections, difficult breathing with high-pitched noises and clicking, sneezing, tail bobbing, and open-mouthed breathing are noted. Excessive salivation may also be present. Signs are made worse by handling, exercise, and other stresses. Mortality can be high in heavy infections. The veterinarian will most likely prescribe an antiparasitic medication that is given by mouth or by injection.
Gapeworms are parasites that live in the wall of the trachea, usually in finches and canaries. Infected birds often have difficulty breathing and will “gape” for air—hence the name. Gapeworms are rare in caged birds, but when present, they can cause death due to lack of oxygen or pneumonia. Effective treatment is possible when it is begun early.
Sarcocystosis is caused by a protozoan parasite that invades the body’s soft tissues and forms cysts in the respiratory tract, kidneys, nervous tissues, and eventually in the muscles. It is a major cause of death in parrots housed outdoors in the southern United States. In severely affected areas, even indoor birds can be infected by contaminated food. The infection occurs when birds are exposed to infected opossum feces, usually carried by insects such as cockroaches, or by rats that get into the bird’s feed. The feces of these transport hosts are then consumed by birds, and a rapidly fatal disease can develop. A high death rate is observed in untreated birds such as cockatoos, African Grey parrots, Eclectus parrots, and other Old World species that have not been exposed to this parasite. Signs of infection may include a lack of energy, passive regurgitation of water, and anemia. Treatment includes supportive care with injectable fluids, supplemental feeding if needed, treatment for anemia, and longterm antiprotozoal medications.
