Merck Manual

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Pet Owner Version

Disorders Affecting Multiple Body Systems of Pet Birds


Teresa L. Lightfoot

, DVM, DABVP (Avian), Avian and Exotics Department, Florida Veterinary Specialists

Reviewed/Revised Jan 2020 | Modified Oct 2022
Topic Resources

A number of diseases may involve multiple parts or organ systems of a bird’s body. Signs can be general (such as weakness or lack of interest in food or activities) or more specific. Sometimes no signs are noted. The more common of these disorders are discussed here.


Polyomavirus was first identified in budgerigars (budgies), then in other parrots and parakeets, and most recently has been shown to cause disease in finches. Polyomavirus can infect birds of all ages, but nestlings and juveniles are the most susceptible. Affected birds may have a lack of appetite, diarrhea, and generalized weakness, and the onset of these signs is usually rapid. Bruising of the skin and muscles may also occur, and the infection may target the heart, liver, and kidneys. Infection is usually fatal, and death may occur in 24 to 48 hours. If a bird survives, it may have abnormal feather growth, heart disease, and liver damage as an adult. Adult birds may be carriers of the virus and can spread infection. The prevalence of this virus in adult parrots and budgies is thought to be high.

Polyomavirus can be passed from the female to the egg, but most infections are spread by direct contact, feather dander, and exposure to feces. Exposed females may develop protective antibodies that are passed on to nestlings and may provide temporary immunity. Offspring from unexposed females are at higher risk of infection because they lack protective antibodies.

There is no treatment available for infected birds. Spread of the virus can be controlled through testing and isolation of all infected birds and by vaccination. Because infected adults shed the virus only under certain conditions, identifying infected adults can be difficult. Control during an outbreak can be maintained by disinfecting handfeeding utensils, incubators, and brooders and by vaccination. The chances of exposure to polyomavirus can be reduced by following standard hygiene procedures closely, preventing access to baby birds by visitors or any returned bird or outside bird, and using appropriate quarantine procedures for all new birds. Screening by a veterinarian should first be done to make sure that avian polyoma-virus is not already present.

A vaccine to prevent polyomavirus infection is available and is given in 2 doses. The first dose may be given by the veterinarian as early as 4 weeks of age to properly complete the vaccination series and allow full immunity to develop. Older birds receive 2 vaccines 2 to 4 weeks apart, then 1 booster annually. Both negative and positive adult and juvenile parrots can be vaccinated.

Pacheco’s Disease (Pacheco’s Herpesvirus)

Pacheco’s disease is a highly contagious, fast-developing disease of parrots (psittacines) caused by a herpesvirus. This disease is associated with stress, which can cause healthy-looking birds that carry the virus to pass the infection to susceptible birds. It is spread by direct contact between birds, airborne secretions, or contamination of food or water with feces. Macaws, Amazon parrots, Monk parakeets, and conures are often involved in outbreaks of the disease. Old World species are less likely to be either carriers or susceptible to infection.

Infected birds may not show any signs of disease until just before dying. The birds are usually in good condition and have a good appetite. Fluffing, loss of energy, and watery feces are signs that sometimes can be seen in infected birds. Most birds do not recover from the infection. Diagnosis of Pacheco’s disease must be made quickly in order to prevent further spread of the infection. See Pacheco's disease Pacheco's Disease/Papillomatosis (Psittacine herpesvirus) Birds have various digestive disorders, including infections and parasites, that can cause problems. The next section discusses some of the more commonly seen disorders in detail. Avian gastric... read more to learn more.

Other Herpesvirus Infections

Other important herpesviruses of pet birds include the strain responsible for wart-like foot growths (called papillomas) in Cacatua species and an abnormal loss of color noted on the feet of macaws. The internal papillomatous disease of macaws (most notably green-wing macaws, Ara chloroptera) and Amazon parrots is caused by a herpesvirus related to the one causing Pacheco’s disease. Amazon tracheitis (inflammation of the trachea), which is an uncommon infection, is also caused by a herpesvirus.

Poxvirus Infections

Because of import restrictions, the poxvirus that was historically common in imported blue-fronted Amazon parrots is rarely seen in pet birds. However, poxvirus infections may still occur in canaries and pigeons and in several species of wild birds. These viruses are not contagious to psittacines (parrots).

Pet birds may show one of 3 different types of clinical signs. The first type, skin infection, is the most common. These birds have individual growths, small abscesses, or crusty scabs on the skin of unfeathered areas, such as the face (especially around the eyes and the mouth) and the legs and feet. The diphtheritic or “wet” form is the second type, which may follow the skin form or occur on its own. Swelling and discharges from the eyes are followed by injuries on the mucous membranes of the throat, upper airways, and esophagus. The third and most severe form occurs with a rapid onset of generalized signs of illness, including depression, bluish discoloration of the skin, loss of appetite, and rapid death.

Veterinarians often recommend treatment with vitamin A and antibiotics, ointments for the eyes, heat, humidity, daily cleansing of the affected areas, and attention to diet. Poxvirus infections are transmitted by insect (usually mosquito) bites or through breaks in the skin. Therefore, mosquito control and indoor housing are vital to prevent outbreaks. Vaccines for canarypox and pigeonpox are available, but are protective only for their host species.

Mycobacteriosis (Avian Tuberculosis)

Mycobacteriosis is a bacterial infection that is sometimes called avian tuberculosis, although it differs from tuberculosis in mammals. A few species of Mycobacterium bacteria are linked with mycobacteriosis in pet birds.

Mycobacteriosis is seen most frequently in pet birds of the parrot family, in which it usually affects the intestinal tract. Most birds that are infected are adults. The disease is long-lasting and progressive and affects the liver and gastrointestinal tract. For many birds, infection is fatal.

Signs of infection may include loss of appetite, weight loss (in spite of having a good appetite), depression, and diarrhea. Birds with early infections may not show signs. Diagnosis can be challenging and is most reliably done with a biopsy and special staining for the organisms. The organisms are difficult to culture.

Treatment can be difficult and may take up to a year. In addition, the disease can potentially be transmitted from birds to humans, so great care must be taken to avoid infection by thoroughly washing hands with soap and water after contact with a sick bird, wearing gloves, and practicing other good hygiene. Although some evidence suggests that the risk of transmission from pet birds to people is low, people who are elderly, very young, or have weakened immune systems (such as individuals infected with the HIV virus) should avoid any contact with infected birds.

Psittacosis (Chlamydiosis, Parrot Fever)

Psittacosis or chlamydiosis is a serious infection that is caused by the bacteria Chlamydia psittaci. The bacteria are found in the nasal secretions and in the stool from infected birds, recovering birds, and carriers. Because the disease can be transmitted from birds to people, there are certain regulations in the United States regarding the reporting and quarantine of birds that are suspected of having psittacosis. Although still a disease of concern, chlamydial infection has decreased dramatically since the importation of South American birds has been curtailed.

Some birds, because of their genetic resistance, are less likely to become ill when infected and, consequently, are more likely to develop into carriers. These include pigeons, doves, budgies, cockatiels, cockatoos, and about 100 additional species. Other species, such as rosellas, lorikeets, mynahs, canaries, and some parrots have low natural resistance.

Depending on the species of bird affected, the signs of psittacosis will vary. Typical signs of infection include a bird that is ruffled, depressed, has labored breathing, discharge from the eyes and nose, and is neither eating nor vocalizing. The appearance of lime-green or yellow droppings, especially when the urine is also discolored, is often present with psittacosis. One form of psittacosis that occurs infrequently involves the central nervous system and includes signs such as tremors, shaking, head twisting, and convulsions. This form has most often been recognized in African Grey parrots and cockatoos. Additionally, cockatiels and Neophema species (turquoisines, scarlet-chested parakeets) may seem to have an eye disease resembling conjunctivitis or a stye. Various internal organs may be affected by psittacosis, including the liver and heart.

Once psittacosis is diagnosed, treatment usually involves giving antibiotics (often added to the food or water) for an extended period of time. Birds in chlamydial crisis need intense, supportive care (injectable antibiotics, fluids, heat, isolation, extremely clean conditions, absence of stress), as well as treatment for any other signs of illness.

The best way to control psittacosis is to keep susceptible birds away from the infectious agent. Because the bacteria can remain infective for many months in dried excrement, cleanliness and disinfection are essential. Eliminating drafts and spraying the area with appropriate disinfectants will help keep infectious feathers and dust to a minimum. Birds that have had the disease or are under treatment can be reinfected.

Because the bacteria can cause illness in people as well as birds, care should be taken to always practice good hygiene when caring for a sick bird. This includes wearing gloves when handling the bird, thorough hand washing with soap and water, and disinfecting cages, feeders, and other utensils daily. All new birds should be tested for psittacosis before being introduced into your household.

In most areas, physicians must report cases of psittacosis to local health authorities, and treatment may need to be coordinated with and approved by the governing agency.


Clostridial Diseases

Clostridial bacteria cause several disorders in birds depending on the species of the bacteria involved and the location of infection. Birds become infected by eating contaminated food or water, inhaling spores or bacteria from the air or other contaminated surfaces, or by infection of wounds. One common method of entry in birds occurs when the bacteria invade damaged cloacal tissue (the area where the urine, feces, and urates wait to be passed) in birds with cloacal prolapse or papillomatosis.

Signs vary depending on the type of clostridial infection. Disease-causing strains of the bacteria produce a toxin in the small intestines of birds, resulting in rapid loss of condition and weight loss, lethargic behavior, decreased appetite, and bloodstained or undigested food. The toxin and its effects may remain in the system for a long time even after the original bacterial infection has been treated.

For prevention, minimize stress and overcrowding, ensure proper ventilation, and provide a nutritionally sound diet. Make sure feed is properly stored and is free of bacterial growth. Spores may be present in corn and grain products as well as manufactured pellets or extruded food and may develop bacterial growth if they are not properly stored. The stool of household pets (dogs and cats) may also harbor these bacteria.

Other Bacterial Diseases

Several types of bacteria can cause disease in birds. Some are normally present in the bird’s body or environment, but do not cause disease except under certain circumstances, such as in birds that are very young, old, weak, stressed, or that have an impaired immune system. Escherichia coli, Pseudomonas, Aeromonas, Serratia marcescens, Salmonella, Klebsiella, -Enterobacter, Proteus, and Citrobacter species are bacteria that are frequently isolated in birds. Pasteurella species have been reported as possible agents causing infection in birds bitten by other animals, such as pet cats or rats.

Heavy Metal Poisoning

Heavy metals such as lead and zinc are common throughout the environment, so limiting your bird’s exposure to them is important. Birds should not be allowed to play outside their cages without supervision. The environment should be inspected for the presence of heavy metals, and the sources should be removed from the area if possible. Because cage and fencing materials are common sources of heavy metals, proper selection of nontoxic materials is important. Stainless steel and welded wire should be used. Cage clips should be made from alloys that do not contain lead or zinc.

Lead and zinc poisoning are the 2 most common poisonings in caged birds. Zinc poisoning is now more common than lead poisoning, due to the heightened awareness of the dangers of lead, and the increased use of galvanized materials. Galvanization is a process of coating other metals such as iron with a zinc-based surface to prevent rust. This galvanization is found on much of the manufactured wire and other hardware used in home-made cage construction.

Potential sources of lead include old paint, stained glass, lead curtain weights, lead fishing weights, and lead solder. Signs of heavy metal poisoning include regurgitation of water, excessive thirst, depression, lack of energy, and weakness. Trembling, lack of coordination, excitability, or seizures may occur in lead poisoning.

Your veterinarian will suspect heavy metal poisoning when signs of this toxicity are accompanied by the presence of metal in the gizzard on an x-ray. This diagnosis can be confirmed by determining levels of lead or zinc in the blood. The initial treatment, besides supportive care, is usually one of a class of drugs called chelating agents that is injected into the muscle until the bird no longer has signs. Once your bird is stable, you can give a chelating agent by mouth at home. If the toxicity is not severe, the bird’s response to treatment is usually rapid. As with all poisonings, prevention is the key.

Poisoning from Fumes and Aerosols

Many bird owners are aware of the hazard that occurs when surfaces coated with Teflon®, Silverstone®, Tefzel®, or other fluoropolymers are overheated. Nonstick cookware and bakeware, some heat lamp bulbs (those manufactured for use in the food industry), self-cleaning ovens, and irons are often coated with fluoropolymers. Fluoropolymers start releasing particles at temperatures as low as 396°F (202°C) and release vaporized fluoropolymer particles starting at 464°F (240°C). These temperatures are commonly reached during normal cooking. For example, when cooking meat, the normal frying temperature is between 400 to 450°F (204 to 232°C). When heated to 680°F (360°C) or higher, fluoropolymers give off acidic fumes that can be lethal for birds. This temperature may be reached when cooking meat in broilers or when using the cleaning feature on some self-cleaning ovens.

Fluoropolymer fumes are not the only potential home chemical hazard for birds. A number of aerosol products (including some carpet fresheners), plastics melted or burned in a microwave oven, or new heating duct systems may also be irritating or toxic to caged birds ( See also Household Hazards for Pet Birds Household Hazards for Pet Birds While time outside a cage can be a positive experience your bird, it can also be dangerous, especially for small birds that can be easily stepped on or injured in falls. Birds also do not understand... read more ).

Signs of poisoning include labored breathing, neurologic signs, and sudden death. Most exposures are deadly before action can be taken, but if you have time, get the bird into fresh air and then to the veterinarian as soon as possible. It is best to locate your bird’s cage in an area well away from any fumes that might be created as a result of cooking. Cages should always be well ventilated.

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