Birds can suffer from a variety of diseases, some of which are common among pet birds while others are more prevalent in wild bird populations. Understanding the most common avian diseases, their causes, symptoms, and treatment options is an important part of providing proper care for pet birds and protecting wild bird species.
Bacterial Diseases
Many common bird diseases are caused by bacterial infections. Bacteria are microscopic organisms that can be transmitted between birds through direct contact, ingestion of contaminated materials, or exposure to infected surfaces. Some types of bacteria occur naturally in a bird’s environment while others are opportunistic pathogens that infect immunocompromised birds.
Psittacosis
One of the most well-known avian bacterial diseases is psittacosis, also known as parrot fever or ornithosis. This disease is caused by Chlamydia psittaci, a type of intracellular bacteria. Infected birds shed the bacteria through their droppings and nasal discharges which can then be transmitted to humans and other birds. The most common symptoms in birds include discharge from the eyes and nostrils, difficulty breathing, lethargy, and diarrhea. Without treatment, severe cases can lead to pneumonia, liver damage, or sudden death.
Mycoplasmosis
Mycoplasmosis is caused by Mycoplasma bacteria such as Mycoplasma gallisepticum. It is a chronic respiratory disease that often affects the sinuses, trachea, and air sacs. Infected birds will show symptoms like sneezing, coughing, nasal discharge, swelling around the eyes, difficulty breathing, and lethargy. The disease is highly contagious between birds and can result in irreparable damage to the respiratory tract.
Avian Cholera
Avian cholera is caused by the bacterium Pasteurella multocida. While it primarily affects wild waterfowl, avian cholera can also infect domestic poultry and pet birds. Infected birds experience severe diarrhea, respiratory distress, swelling around the eyes, and may die suddenly without showing any symptoms. Avian cholera spreads rapidly through migratory wild bird populations and can also be transmitted through contact with infected carpets, cages, and clothing.
Salmonellosis
Salmonella bacteria can infect a wide variety of bird species and cause the disease salmonellosis. Infected birds will show nonspecific signs like ruffled feathers, diarrhea, vomiting, and lack of appetite. Salmonella spreads through the fecal-oral route via contaminated food and water. Backyard poultry flocks are at high risk for exposure to salmonella. Proper sanitation and biosecurity measures are necessary to prevent outbreaks.
Viral Diseases
Some of the most serious avian diseases are caused by viral infections. Viruses invade host cells and replicate rapidly, often evading the immune response. Direct contact with infected birds or contaminated surfaces spreads viruses between bird populations. The following are examples of common viral diseases in birds:
Psittacine Beak and Feather Disease
Psittacine beak and feather disease (PBFD) is caused by a circovirus that affects parrots. The virus impairs the immune system and causes progressive feather loss, beak deformities, and eventual death. Young birds and cockatiels are particularly susceptible. PBFD is extremely persistent in the environment and direct bird-to-bird contact spreads the disease. There is no known cure.
Avian Polyomavirus
The avian polyomavirus infects a wide range of birds but is most problematic in psittacine species. Infected birds develop tumors in various body organs which interfere with normal function. Symptoms include weight loss, neurological signs, feather loss, and death. The virus is transmitted through direct contact with infected birds. Vaccination can help control polyomavirus infections in captive psittacine flocks.
Pacheco’s Disease
Pacheco’s disease is caused by a herpesvirus that affects parrots. Infected birds develop severe liver necrosis and intestinal inflammation which leads to acute death. The virus is easily spread through feather dust and droppings. Outbreaks often occur when birds are under stress. Supportive care and anti-viral medications may be used to treat infected birds.
Avian Influenza
Avian influenza viruses can adapt to cause infection in pet birds. Wild waterfowl are reservoirs for influenza viruses in nature. Domestic poultry are most severely impacted by the highly pathogenic form H5N1. Symptoms include respiratory distress, diarrhea, edema, and sudden death. Avian influenza is readily transmitted between birds via direct contact. Strict biosecurity and vaccination protocols must be followed to protect domestic and captive birds.
Parasitic Diseases
Parasites are organisms that live on or in a host organism and derive nutrients at the expense of the host. Several common parasites can infect birds and cause detrimental clinical disease. The following are examples of parasitic infections seen in pet birds and wild birds.
Malaria
Avian malaria is caused by Plasmodium parasites which are transmitted by infected mosquitoes. Parasitemia causes anemia, organ damage, and eventual death in affected birds. Wild birds that survive infection can become reservoirs for the parasite. Captive outdoor birds are at highest risk and should be monitored for mosquito exposure.
Intestinal Worms
Birds may host a variety of parasitic intestinal worms such as roundworms, tapeworms, and thorny-headed worms. Heavy burdens cause diarrhea, weight loss, and lethargy. Fecal samples should be evaluated for eggs. Anti-worm medications are used to treat infected birds. Proper sanitation of cages, food, and water prevents reinfection.
External Parasites
Mites, lice, and flies that live on the feathers and skin can irritate birds and cause feather damage. Scaly leg mites burrow under the scales on the feet and legs. Parasites are readily transmitted between birds through direct contact. Topical insecticides are used to kill the parasites. The environment must also be treated to prevent recurrence.
Trichomoniasis
The protozoal parasite Trichomonas gallinae causes trichomoniasis in doves, pigeons, and raptors. Infected birds have lesions in the mouth, throat, and upper digestive tract which interfere with eating. Birds appear fluffed up and emaciated. Direct transmission between birds occurs through contaminated food and water. Supportive care and anti-protozoal drugs may be used for treatment.
Fungal Diseases
Fungi are ubiquitous in the environment and some can cause infections in birds under opportune conditions. The following fungal diseases are most likely to affect pet and wild birds.
Aspergillosis
Aspergillus fungi can infect a bird’s respiratory tract and cause aspergillosis. Spores are often inhaled from contaminated litter, soil, or feed. Symptoms include labored breathing, discharge from the eyes and nares, loss of appetite, and eventual suffocation. Anti-fungal medications are used to treat infection while addressing underlying conditions that suppressed immune function.
Candidiasis
Candida albicans fungal infections, also known as thrush, often occur in the crop of birds. Infection causes thick plaques in the mouth, difficulty swallowing, and crop stasis. Candidiasis usually occurs secondary to other illnesses that have decreased immune function and altered the normal microflora. Anti-fungal medications must be used to treat the infection or it can spread and become fatal.
Dermatophytosis
Dermatophyte fungi can infect the skin of birds and cause dermatophytosis or ringworm. This causes circular areas of feather loss, scaling, and crusting. Dermatophytes are very contagious between birds and can spread rapidly in a flock. Infected birds require anti-fungal treatment as well as environmental disinfection.
Aspergillus in Wild Birds
Aspergillosis caused by Aspergillus fumigatus is a major fungal disease that impacts wild bird populations, especially raptors. Aspergillus grows on decaying organic matter in the environment. Birds feeding and nesting in contaminated areas easily inhale the spores which then colonize the air sacs and lungs. Treatment in rehabilitation centers has low success so prevention of exposure is critical.
Non-infectious Diseases
In addition to infectious diseases, birds can also suffer from non-infectious illnesses caused by genetics, toxins, nutritional deficiencies, allergies, and accidents. Being aware of these disorders can help bird owners identify and address issues early on.
Feather Destructive Behavior
Feather plucking and self-mutilation occurs in pet birds due to behavioral disorders. The exact cause is often unknown but contributing factors include stress, inadequate environment, poor diet, and lack of mental stimulation. Birds will pluck their own feathers or chew on body parts. Providing proper care, enrichment, and anti-anxiety medications may help stop the behavior.
Fatty Liver Disease
Obese, high fat diets can cause hepatic lipidosis or fatty liver disease in pet birds. The excess fat accumulates in the liver and causes dysfunction. Affected birds become lethargic and anorexic. The condition must be reversed through dietary change, increased exercise, and nutritional support. Prevention through proper diet is key.
Egg Binding
Egg binding occurs when a female bird is unable to pass an egg through the oviduct. Binding can be caused by obesity, poor nutrition, lack of nesting sites, or reproductive tract abnormalities. Birds will strain to defecate and appear ill. Binding can be life-threatening if the egg does not pass. Veterinary assistance is often needed.
Trauma
Birds can suffer various types of physical trauma such as fractures, wounds, and burns. Cage accidents, collisions with windows or vehicles, predator attacks, and heat sources result in injuries. Minor wounds can be treated at home while more severe trauma requires stabilization and veterinary care. Prevention through safe housing is ideal.
Toxicity
Birds are highly sensitive to toxins and often ingest poisonous materials in their environment. Heavy metals, pesticides, avicides, dietary toxins, and household poisons can all sicken or kill birds. Symptoms depend on the toxin. Identifying and removing the source while providing supportive care improves outcomes. Public education can help reduce wildlife poisonings.
Prevention
There are several important preventative measures bird owners and wildlife managers can implement to reduce the impact of common avian diseases:
- Quarantine and test new birds before introducing them into an existing flock
- Isolate sick birds immediately to prevent transmission
- Practice good sanitation of living areas, food, and water
- Avoid overcrowding and stress
- Vaccinate domestic flocks appropriately
- Limit contact between domestic and wild birds
- Remove sources of toxins, parasites, and entanglements
- Provide proper nutrition and regular health exams
- Improve wildlife habitat quality and biodiversity
Conclusion
There are a multitude of infectious and non-infectious diseases that can affect birds. Bacterial, viral, parasitic, and fungal organisms pose threats along with factors like toxins, trauma, and nutritional imbalances. Understanding the most prevalent avian diseases, modes of transmission, susceptible species, preventative measures, and available treatments allows for earlier intervention and better outcomes. With proper care, husbandry, and biosecurity practices, bird owners and wildlife managers can reduce disease-associated morbidity and mortality.
