NORD gratefully acknowledges Charlotte A. Gaydos, M.S., M.P.H, Dr. P.H., Professor of Medicine, Johns Hopkins University, Division of Infectious Diseases, International STD and Biothreat Research Laboratory, for assistance in the preparation of this report.
Psittacosis is an uncommon infectious disease that is most often transmitted to humans through exposure to infected birds, especially parrots, cockatiels, parakeets and similar pet birds. Psittacosis can affect the lungs and may cause inflammatory illness of the lungs (pneumonia). Additional common symptoms include fever, muscle pain (myalgia), headaches, and a dry cough.
Psittacosis is caused by infection with the bacterium, Chlamydia psittaci, and may also be known as ornithosis. It is rare among humans. People who own birds as pets are most likely to be affected by psittacosis. In addition, psittacosis may affect people who work in environments with birds that may be carriers of the infection such as pet store workers, farmers, veterinarians and ranchers.
The symptoms and severity of psittacosis can vary greatly. Some individuals may not develop any symptoms (asymptomatic) or only have a very mild infection; others can develop serious widespread infection that affects several organ systems of the body. The incubation period, which is the time between exposure to the bacterium to symptom development, is anywhere from five to 15 days. The onset of symptoms may be abrupt or gradual (insidious). The associated symptoms tend to be nonspecific and common to many different conditions.
Affected individuals may develop fever, chills, muscle pain (myalgia), headaches, and a general feeling of poor health (malaise). Pneumonia commonly occurs and, in some cases, can be severe. Breathing (respiratory) abnormalities may develop including a dry, nonproductive cough, difficulty breathing (dyspnea), a sore throat, and, in rare cases, chest pain. Frequent nosebleeds (epistaxis) and abnormal enlargement of the liver and spleen (hepatomegaly) are also common findings.
Although the lungs is the organ most often affected by psittacosis, the disease can potentially affect many organ systems in the body including the gastrointestinal tract, heart, liver, skin and central nervous system. Associated symptoms may include nausea and vomiting, abdominal pain, an abnormally slow heart rate (bradycardia), inflammation of the thin membrane (pericardium) that surrounds the heart (pericarditis), inflammation of the thin membrane (endocardium) lining the inside of the heart (endocarditis), inflammation of the liver (hepatitis) causing yellowing of the skin and eyes (jaundice), a rash on the face, severe headaches and a sensitivity to light (photophobia).
Psittacosis is caused in humans by exposure to the bacterium, Chlamydia psittaci, which is most often transmitted to humans from infected birds, especially parrots and poultry, especially turkeys.
Most infections occur from handling of infected birds themselves or by working in areas where such birds are kept or butchered (occupational exposure). Anyone in contact with an infected bird is at risk of psittacosis. However, cases have occurred in pet store workers, veterinarians, ranchers, and breeders of parrots, parakeets, love-birds, and macaws. Poultry workers handling the insides (viscera) of butchered turkeys also run a high risk of contracting the disease from blood and tissue. Another source of infection is the dried feces of birds and poultry and the dust from feathers and cages. Protective gloves and masks can often prevent transmission of the disease to these workers.
The respiratory system is the most likely manner through which individuals are affected. Individuals inhale airborne organisms either from dried droppings or respiratory secretions from infected birds.
The infected birds may be outwardly ill, or may show no signs of illness. Other animals such as cows, goats and sheep can be infected by the bacterium and can potentially transmit infection to humans. Human-to-human transmission is extremely rare, but has occurred and is usually associated with more severe symptoms than bird (avian)-to-human transmission.
Psittacosis affects males and females in equal numbers. Anyone who handles an infected bird is at risk of developing psittacosis. Since the disease can become epidemic in animals, discovery of a single case of the disease should be reported to local public health authorities. The number of report cases of psittacosis in the United States has varied, ranging from 50 to 200 per year. Many researchers believe the disorder is under-diagnosed and the true number of cases that occur per year is unknown.
The disease was first was first described in the medical literature in 1879. The term, psittacosis, which is derived from the Greek word for parrot, was first used to describe this disease in 1892. Many physicians prefer the term ornithosis, which indicates that the disease can spread by more than just birds of the parrot family.
The diagnosis of psittacosis is made based upon a thorough clinical evaluation, a detailed patient history, identification of characteristic findings and a variety of specialized tests such as specialized blood tests that reveal characteristic antibodies, produced by the body in response to psittacosis infection. Antibodies are specialized proteins produced by the body to fight off foreign material such as bacteria.
Antibiotic therapy is the primary treatment for individuals with psittacosis. Tetracycline and doxycycline are usually the first medications used. Most individuals respond within 24 to 72 hours. Erythromycin may be recommended for children or pregnant women. In rare cases, individuals have been treated with chloramphenicol.
Since the disease can become epidemic in animals, discovery of a single case of the disease should be reported to local public health authorities. The treatment of psittacosis in birds is important to avoid further transmission.
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For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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FROM THE INTERNET
Lessnau KL. Arjomand F. Psittacosis. Emedicine Journal, May 2 2006. Available at: http://www.emedicine.com/med/topic1951.htm Accessed on: February 6, 2008.
Centers for Disease Control and Prevention. Psittacosis. February 7, 2006. Available at: http://www.cdc.gov/ncidod/EID/vol11no03/pdfs/04-0601.pdf Accessed On: February 6, 2008.
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