Psittacosis
Psittacosis
Disease History, Characteristics, and Transmission
Introduction
Psittacosis is a bacterial zoonotic (from animals) infection caused by the bacterium Chlamydia psittaci. This bacterium is present in birds and passed on to humans when they inhale airborne infectious particles such as feather dust, or bird secretions. Psittacosis causes acute symptoms of fever, headache, body aches, and a dry cough. Respiratory distress such as pneumonia may also arise. Psittacosis is not usually fatal, with approximately a 1% mortality (death) rate in the United States. Treatment using tetracycline antibiotics usually leads to a full recovery.
Psittacosis is a worldwide disease but outbreaks are rare. Importation of birds helps to spread the disease from one location to several. People in close contact with birds such as veterinarians, pet store owners, pet owners, and poultry producers are most at risk of contracting psittacosis. Psittacosis can be prevented through avoiding contact with infected birds or wearing protective gear such as gloves and masks when handling infected birds.
Disease History, Characteristics, and Transmission
Psittacosis was first identified in 1879 as a bacterial disease that infected birds and was later confirmed to also infect humans and other animals. During 1929 and 1930, a worldwide outbreak of psittacosis occurred when a shipment of infected parrots from Argentina spread the disease to numerous regions of the world. There were approximately 1,000 cases of which 200– 300 were fatal. This resulted in a ban on importation in many major countries, including the United States, but this ban was lifted in 1973.
Psittacosis is a bacterial disease caused by the bacteria Chlamydia psittaci and is common in many bird species, both wild and tame. Humans become infected with C. psittaci if they inhale dried secretions from infected birds. This may include aerosolized (suspended in the air) feces, feather dust, and droplets from sneezing or coughing birds.
Psittacosis symptoms include fever, headache, body aches, and a dry cough. Pneumonia may also occur. Severe or untreated cases of psittacosis may develop complications such as a heart valve infection (endocarditis), liver inflammation (hepatitis), and neurologic complications. The mortality rate for psittacosis is approximately 1%.
Scope and Distribution
The organism that causes psittacosis occurs worldwide. Importation of birds exacerbates the chances of infection spreading from one region to another. Furthermore, the bird industry, including poultry farming and the pet trade, provide a route for the infection to spread.
In 2002, an outbreak in the Blue Mountains, Australia, involved 59 probable cases. The source of the infection was wild birds. The outbreak prompted the health department to raise public awareness about psittacosis. In Belgium in 1995, an outbreak occurred involving customs officers. The source of the infection was imported parakeets.
Most cases of psittacosis occur in people who have a close association with birds. This includes pet owners, pet store owners, bird fanciers, and poultry producers. In addition, young children, older adults, smokers, alcoholics, and immunocompromised people (people with a weakened immune system) tend to be more susceptible to infection.
Treatment and Prevention
Infection with Chlamydia psittaci is effectively treated using antibiotics. The most commonly prescribed anti-biotics are tetracycline, doxycycline, and erythromycin. Treatment is normally administered for two weeks, after which a full recovery is expected.
The best prevention method against infection with C. psittaci is to avoid contact with infected birds, and to ensure birds are kept free from infection. Investigating the cause of sickness in ill birds will help determine whether C. psittaci is present. Once an infected bird is found, measures can be taken to prevent the disease spreading to other birds or to humans. Avoidance measures such as facemasks, gloves, and handwashing can help reduce the chance of inhaling or ingesting contaminated particles. No vaccine is available to prevent contraction of psittacosis.
WORDS TO KNOW
AEROSOL: Particles of liquid or solid dispersed as a suspension in gas.
IMMUNOCOMPROMISED: A reduction of the ability of the immune system to recognize and respond to the presence of foreign material.
MORTALITY: Mortality is the condition of being susceptible to death. The term “mortality” comes from the Latin word mors, which means “death.” Mortality can also refer to the rate of deaths caused by an illness or injury, i.e., “Rabies has a high mortality.”
ZOONOSES: Zoonoses are diseases of microbiological origin that can be transmitted from animals to people. The causes of the diseases can be bacteria, viruses, parasites, and fungi.
Impacts and Issues
Some cases of psittacosis may go undiagnosed or be misdiagnosed as diagnosis can be difficult. The occurrence of pneumonia can mislead a practitioner to diagnose the illness as a case of pneumonia, rather than psittacosis. Therefore, the prevalence of psittacosis may currently be underestimated.
Another issue surrounding this disease is the difficulties associated with tracing the disease to its source. First, infected birds may be asymptomatic making it difficult to determine whether they are a source of infection. Secondly, the pet bird industry is not heavily regulated, making it difficult to track the exchange of birds. Therefore, tracing an infected bird back to its original origin may be impossible, making it difficult to prevent the spread of the disease. Wildlife trade, including exotic bird trade, also spreads the disease to new areas. This makes it problematic to effectively control psittacosis and prevent outbreaks.
IN CONTEXT: REAL-WORLD RISKS
Although psittacosis is a reportable condition in most states, psittacosis is a rare disease. Within the United States, the annual number of cases of psittacosis has been fewer than 50 since 1996. However, the CDC suggests that some cases of psittacosis may go undiagnosed or misdiagnosed.
SOURCE: Centers for Disease Control and Prevention (CDC), Coordinating Center for Infectious Diseases, Division of Bacterial and Mycotic Diseases.
See AlsoAnimal Importation; Bacterial Disease; Pneumonia; Zoonoses.
BIBLIOGRAPHY
Periodicals
Karesh, W.B., R.A. Cook, E.L. Bennett, and J. Newcomb. “Wildlife Trade and Global Disease Emergence.” Emerging Infectious Diseases. vol. 11, no. 7 (2005): 1000–1002.
Web Sites
American Museum of Natural History. “Some Facts about Psittacosis.” 2003 <http://research.amnh.org/users/nyneve/psittacosis.html#hist> (accessed Mar. 7, 2007).
Centers for Disease Control (CDC). “Psittacosis.” Oct. 13, 2005 <http://www.cdc.gov/ncidod/dbmd/diseaseinfo/psittacosis_t.htm> (accessed Mar. 7, 2007).
NSW Health Department. “Psittacosis: Questions and Answers.” 2002 <http://www.health.nsw.gov.au/public-health/pdf/PsittacosisQA.pdf> (accessed Mar. 7, 2007).