Psittacosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Omodamola Aje B.Sc, M.D. [2]

Psittacosis is a zoonotic infectious disease caused by a bacterium called Chlamydophila psittaci (formerly Chlamydia psittaci). The disease is contracted not only from parrots, such as macaws, cockatiels, and budgerigars, but also from pigeons, sparrows, ducks, hens, seagulls, and many other species of birds. The incidence of infection in canaries and finches is believed to be lower than in psittacine birds. As a systemic zoonotic infection with protean clinical features, the major risk factor is exposure to birds. Hence, bird owners, veterinarians, those involved with breeding and selling birds, and commercial poultry processors are most at risk. Patients typically present with 1 week of fevers, headache, myalgias, and a nonproductive cough. Although pneumonia is the most common manifestation, all organ systems can be involved. Serology remains the mainstay of diagnosis; however, polymerase chain reaction techniques offer a rapid and specific alternative. Doxycycline is the treatment of choice.

The word psittacosis is derived from the Greek work “psittakos,” which means parrot. Psittacosis infects psittacines (parrots, parakeets, cockatoos). “Ornithosis” is the term used if it infects other types of birds. It is assumed that the origin of psittacosis is in South America, where the rain forests are populated with many species of psittacine birds. Aboriginal tribes were fond of these birds and used their feathers as parts of their ceremonial clothing. Other psittacine birds were kept as pets in aboriginal villages.

There is no established classification system for psittacosis.

The major risk factor for acquiring psittacosis is exposure to birds. Transmission can occur either by inhalation of aerosolized organisms in form of dried feces or respiratory secretions or by direct contact with birds. The exact molecular details of bacterial uptake are not well understood. It is speculated that chlamydial cell contact is a two-step process: reversible binding followed by irreversible attachment. The key to understanding the pathogenesis of C. psittaci is that frequent and repeated episodes of reinfection are needed for the development of severe disease. Several studies also highlighted the critical importance of host microfilaments, microtubules, and microtubule motor proteins (kinesin and dynein) for uptake and intracellular development of C. psittaci and other Chlamydia spp. As with other intracellular zoonoses such as Q fever and brucellosis, the clinical conditions associated with psittacosis have been seen in many organ systems such as the pulmonary, hepatic, and central nervous systems.

Psittacosis is caused by the organism Chlamydia psittaci. Chlamydia is understood to be a Gram-negative bacterium belonging to the genus Chlamydia or Chlamydophila in the family Chlamydiaceae. Parachlamydiaceae, Waddliaceae, and Simkaniaceae also belong to the order Chlamydiales, class and phylum Chlamydiae. Chlamydiales are obligate intracellular infectious agents in eukaryotic cells characterized by a unique developmental replication cycle.

Psittacosis must be differentiated from other diseases that cause atypical pneumonia and febrile illness without localizing signs and extrapulmonary manifestations such as gastroenteritis, hepatitis, meningitis, or encephalitis. The three main diseases to differentiate psittacosis from are Chlamydia pneumoniae pneumonia, Mycoplasma pneumoniae pneumonia, and Legionella infection, as they tend to have similar clinical manifestations that can only be differentiated by taking appropriate histories and laboratory investigations. There are other conditions to watch out for which may also present similarly to psittacosis.

Since 1996, fewer than 50 confirmed cases of psittacosis have been reported in the United States each year. Many more cases may occur that are not correctly diagnosed or reported. In the United States, the incidence of psittacosis is 0.01 per 100,000 persons. The prevalence and incidence of psittacosis does not vary by gender. There is no racial predilection for psittacosis, as it has been identified in all parts of the world including Africa, China, Europe, and the United States.

Bird owners, pet shop employees, persons who work in poultry processing plants, and veterinarians are at increased risk for contracting psittacosis. Typical birds involved are parrots, parakeets, and budgerigars. Other animals documented with C. psittaci infection include horses, cattle, and koalas, but they have not been documented to transmit the infection to humans.

According to the USPSTF, there is insufficient evidence to recommend routine screening for psittacosis.

If left untreated, psittacosis usually presents as flu-like symptoms or an atypical pneumonia. In the first week of psittacosis, the symptoms mimic typhoid fever, including prostrating high fevers, arthralgias, diarrhea, conjunctivitis, epistaxis, and leukopenia. Headache can be so severe that it suggests meningitis and some nuchal rigidity. Towards the end of the first week, stupor or even coma can result in severe cases. The second week is more akin to acute bacteremic pneumococcal pneumonia with continuous high fevers, cough, and dyspnea. Some complications include respiratory failure, acute tubular necrosis, hemolytic anemia, endocarditis, hepatitis, encephalitis and, in some cases, death.

The hallmark of psittacosis is a flu-like reaction with a history of exposure to birds. However, a history of exposure to birds may not always be present. Psittacosis is characterized by a wide range in both disease severity and spectrum of clinical features, but it typically presents with fever, prominent headache, myalgia, and a nonproductive cough. The mainstay of diagnostic testing is serology, although molecular techniques are being increasingly utilized.

Physical examination findings in a patient with psittacosis include rose spot rashes on the skin called Horder’s spots and splenomegaly, which is frequent toward the end of first week. Diagnosis can be suspected in the case of respiratory infection associated with splenomegaly and/or epistaxis.

Exposure history is critical to diagnosis. Complete blood count shows leukopenia, thrombocytopenia, and moderately elevated liver enzymes. Culture of C. psittaci is demanding and requires a level 3 laboratory isolation facility because of the risk of laboratory transmission, so it is rarely performed. Serology is the most widely available method for laboratory diagnosis of C. psittaci infection. Complement fixation, microimmunofluorescence, and EIA are the most commonly used techniques.

There are no electrocardiogram findings associated with psittacosis. However, bradycardia may be noticed on electrocardiogram.

Chest X-rays show lobar consolidation, patchy infiltrates, a diffuse whiteout of the lung field, or pleural effusions.

On high resolution CT, infiltrates may be nodular and surrounded by ground glass opacity.

There are no MRI findings associated with psittacosis.

There are no echocardiography or ultrasound findings associated with psittacosis.

There are no other imaging findings associated with psittacosis.

Biopsy, culture, and serology have been found useful in the diagnosis of psittacosis.

Psittacosis is treated with tetracyclines. Remission of symptoms usually is evident within 48-72 hours. However, relapse can occur, and treatment must continue for at least 10-14 days after fever abates. For pregnant patients or infants, the preferred treatment is azithromycin because tetracyclines are contraindicated.

Surgical intervention is not recommended for the management of psittacosis.

Avoid exposure to birds that may carry this bacteria, such as imported parakeets. Medical problems that lead to a weak immune system increase the risk for this disease and should be treated appropriately.

The primary and secondary prevention strategies for psittacosis are the same.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Mohammed A. Sbeih, M.D. [2]Omodamola Aje B.Sc, M.D. [3]

Psittacosis is an infection caused by Chlamydia psittaci, a type of bacteria found in the droppings of birds. Birds spread the infection to humans.

• Blood-tinged sputum
• Dry cough
• Fatigue
• Fever and chills
• Headache
• Joint aches
• Muscle aches
• Shortness of breath

Psittacosis is a rare disease: 100 – 200 cases are reported each year in the United States.

Bird owners, pet shop employees, persons who work in poultry processing plants, and veterinarians are at increased risk for this infection. Typical birds involved are parrots, parakeets, and budgerigars, although other birds have also caused the disease.

Antibiotics are needed to treat this infection. If you develop symptoms of psittacosis, call your health care provider.

The health care provider will hear abnormal lung sounds such as crackles and decreased breath sounds when listening to the chest with a stethoscope.

Tests include:

• Antibody titer (rising titer over time is a sign of infection).
• Blood culture (grows chlamydia).
• Blood gases.
• CT scan of the chest.
• Sputum culture.
• X-ray of the chest.

The infection is treated with antibiotics. Doxycycline is the first line treatment. Other antibiotics that may be prescribed include:

• Azithromycin.
• Erythromycin.
• Moxiflacin.
• Rifampin.
• Tetracycline.

Note: Tetracycline and doxycycline by mouth is usually not prescribed for children until after all their permanent teeth have started to grow in or to pregnant women. The medicine can permanently discolor teeth that are still forming.

Directions to Hospitals Treating Psittacosis

Full recovery is expected.

• Brain involvement.
• Decreased lung function as a result of the pneumonia.
• Heart valve infection.
• Inflammation of the liver (hepatitis).

Avoid exposure to birds that may carry this bacteria, such as imported parakeets. Medical problems that lead to a weak immune system increase your risk for this disease and should be treated appropriately.

http://www.nlm.nih.gov/medlineplus/ency/article/000088.htm

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2], Omodamola Aje B.Sc, M.D. [3]

There is no established classification system for psittacosis.

There is no established classification system for psittacosis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]

The word psittacosis is derived from the Greek work “psittakos,” which means parrot. Psittacosis infects psittacines (parrots, parakeets, cockatoos). “Ornithosis” is the term used if it infects other types of birds. It is assumed that the origin of psittacosis is in South America, where the rain forests are populated with many species of psittacine birds. Aboriginal tribes were fond of these birds and used their feathers as parts of their ceremonial clothing. Other psittacine birds were kept as pets in aboriginal villages.

• In 1879, J. Ritter published the first case description of psittacosis, describing a mini-epidemic in which three out of seven patients died. He found the source of the infection and determined the incubation period and the non-transmissibility of the disease from human to human.^[1]
• In 1895, the term “psittacosis” was first applied.
• Between 1890 and 1930, several severe outbreaks of human psittacosis occurred in Europe and North and South America, all of which can be attributed to handling, sale, and purchase of parrots and other exotic birds.
• In 1962, J.W. Moulder conducted the first characterization of chlamydiae by analyzing the structure and chemical composition of C. psittaci “particles.”
• In 1970, A. Matsumoto and G.P. Manire obtained the first high-resolution images of chlamydial bodies using electron microscopy.
• In 1975, T.P. Hatch demonstrated the requirement of C. psittaci for energy intermediates from the host cell.
• In 1978, Wyrick and colleagues first described the structural features of chlamydial compartments and showed the capability of C. psittaci to infect immune cells.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2], Omodamola Aje B.Sc, M.D. [3]

The major risk factor for acquiring psittacosis is exposure to birds. Transmission can occur either by inhalation of aerosolized organisms in form of dried feces or respiratory secretions or by direct contact with birds. The exact molecular details of bacterial uptake are not well understood. It is speculated that chlamydial cell contact is a two-step process: reversible binding followed by irreversible attachment. The key to understanding the pathogenesis of C. psittaci is that frequent and repeated episodes of reinfection are needed for the development of severe disease. Several studies also highlighted the critical importance of host microfilaments, microtubules, and microtubule motor proteins (kinesin and dynein) for uptake and intracellular development of C. psittaci and other Chlamydia spp. As with other intracellular zoonoses such as Q fever and brucellosis, the clinical conditions associated with psittacosis have been seen in many organ systems such as the pulmonary, hepatic, and central nervous systems.

The exact molecular details of bacterial uptake are not well understood. Elementary bodies (EBs) of C. psittaci are thought to infect their target cells in the lung by attachment to the base of cell surface microvilli, where they are actively engulfed by endocytosis or phagocytosis. Further studies on the C. psittaci-related species of C. caviae showed that initial attachment is mediated by electrostatic interactions, most likely with glycosaminoglycan (GAG) moieties on the host cell surface. However, the observation that cellular binding of C. psittaci and related chlamydial strains is only partially or not inhibited by heparin strongly suggests that further adherence mechanisms contribute to chlamydial attachment. It was speculated that chlamydial cell contact is a two-step process:

1. Reversible binding
2. Irreversible attachment

Although chlamydial entry is extremely efficient, the exact molecular details of bacterial uptake are not well understood. The host protein disulfide isomerase (PDI) has been identified as being essential for both C. psittaci attachment and entry into cells. PDI is highly enriched in the endoplasmic reticulum, but is also found on the cell surface where it catalyzes reduction, oxidation, and isomerization of disulfide bonds.

The key to understanding the pathogenesis of C. psittaci is that frequent and repeated episodes of reinfection are needed for the development of severe disease.^[1] Repeated episodes of infection induce a marked and sustained inflammatory response that, with time, leads to scarring and structural damage. A one time exposure to birds is not enough to develop psittacosis; consequently, those at greatest risk are individuals with leisure or occupational exposure to birds, including pet bird owners, veterinarians, pet shop employees, and poultry-processing plant employees. As a result, cases of psittacosis can range from a sporadic case in a pet bird owner to an outbreak affecting several hundred birds in a commercial flock and multiple infected workers.^[2]

Several studies also highlighted the critical importance of host microfilaments, microtubules, and microtubule motor proteins (kinesin and dynein) for uptake and intracellular development of C. psittaci and other Chlamydia spp. In all cell types tested, participation of actin and tubulin seems to be necessary for optimal bacterial proliferation. It was also noted that the shutdown of prokaryotic protein synthesis seemed to have no effect on C. psittaci uptake, thus demonstrating that the internalization process does not require protein synthesis on the bacterial side. Once internalized in the early inclusion, the infecting EB transforms into a larger and more conventional bacterial form, the reticulate body (RB). Subsequently, the RB-containing inclusions translocate through a cytoskeleton-dependent mechanism to the perinuclear region, and RBs replicate by binary fission. The mechanisms by which C. psittaci manages its intracellular survival are still under intensive investigation.

As with other intracellular zoonoses such as Q fever and brucellosis, the clinical conditions associated with psittacosis have been seen in the following organ systems:

• Pulmonary
• Hepatic
• Central nervous system
• Cardiac
• Renal
• Rheumatic
• Hematologic and respiratory symptoms are frequently mild or absent on presentation

Disease severity can range from subclinical infection to fulminant sepsis with multiorgan failure in previously healthy individuals, which may occasionally be fatal despite appropriate treatment.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Mohammed A. Sbeih, M.D. [2]Omodamola Aje B.Sc, M.D. [3]

Psittacosis is caused by the organism Chlamydia psittaci. Chlamydia is understood to be a Gram-negative bacterium belonging to the genus Chlamydia or Chlamydophila in the family of Chlamydiaceae together with Parachlamydiaceae, Waddliaceae and Simkaniaceae in the order Chlamydiales, class and phylum Chlamydiae. Chlamydiales are obligate intracellular infectious agents in eukaryotic cells characterized by a unique developmental replication cycle.^[1]

• Birds are the major zoonotic reservoir. Despite its name, C. psittaci infection has been documented in 467 species from 30 bird orders, from psittaformes to ostriches to penguins have all been found to be associated with the development of psittacosis.^[2]
• Bird handlers and those who keep birds as pets have a higher prevalence of the disease.
• C. psittaci may be classified into eight serovars according to variation in the major outer membrane protein (MOMP): serovar A to F, WC and M56.^[3]

Table 1: Classification of Chlamydophila psittaci into 8 serovars^[4]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]; Omodamola Aje B.Sc, M.D. [3]

Psittacosis must be differentiated from other diseases that cause atypical pneumonia and febrile illness without localizing signs and extrapulmonary manifestations such as gastroenteritis, hepatitis, meningitis, or encephalitis. The three main diseases to differentiate psittacosis from are Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella infection, as they tend to have similar clinical manifestations that can only be differentiated by taking appropriate histories and laboratory investigations. There are other conditions to watch out for which may also present similarly to psittacosis.

The following diseases must be differentiated from psittacosis based on the presentation of cough, fever, myalgia, and shortness of breath.^[1][2]

Key;

+: Occurs in some cases

++: Occurs in many cases

+++: Occurs frequently

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]Omodamola Aje B.Sc, M.D. [3]

Since 1996, fewer than 50 confirmed cases of psittacosis have been reported in the United States each year. Many more cases may occur that are not correctly diagnosed or reported.^[1] In the United States, the incidence of psittacosis is 0.01 per 100,000 persons. The prevalence and incidence of psittacosis do not vary by gender. There is no racial predilection for psittacosis; it has been identified in all parts of the world including Africa, China, Europe, and the United States.

The prevalence of psittacosis has not been documented.

In the United States, the incidence of psittacosis is 0.01 per 100,000 persons.

The case fatality rate of psittacosis has not been documented.

Psittacosis commonly affects the middle aged between the ages of 35 and 55.^[2]

Both men and women are affected equally by psittacosis.

There is no racial predilection of psittacosis.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]Omodamola Aje B.Sc, M.D. [3]

Bird owners, pet shop employees, persons who work in poultry processing plants, and veterinarians are at increased risk for contracting psittacosis. Typical birds involved are parrots, parakeets, and budgerigars. Other animals documented with C. psittaci infection include horses, cattle, and koalas.

Psittacosis is acquired from birds, so people working with poultry are at a higher risk of contracting the disease. Other risk factors include:^[1][2][3]

• Being a pet shop owner
• Handling of sick birds
• Getting a bird bite
• Visiting a bird park
• Contact of beak to mouth

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Govindavarjhulla, M.B.B.S. [2]Omodamola Aje B.Sc, M.D. [3]

If left untreated, psittacosis usually presents as flu-like symptoms or an atypical pneumonia. In the first week of psittacosis, the symptoms mimic typhoid fever, including prostrating high fevers, arthralgias, diarrhea, conjunctivitis, epistaxis, and leukopenia. Headache can be so severe that it suggests meningitis and some nuchal rigidity. Towards the end of the first week, stupor or even coma can result in severe cases. The second week is more akin to acute bacteremic pneumococcal pneumonia with continuous high fevers, cough, and dyspnea. Some complications include respiratory failure, acute tubular necrosis, hemolytic anemia, endocarditis, hepatitis, encephalitis and, in some cases, death.

Psittacosis presents chiefly as an atypical pneumonia. In the first week of psittacosis, the symptoms mimic typhoid fever, including prostrating high fevers, arthralgias, diarrhea, conjunctivitis, epistaxis, and leukopenia. Severe headache and the presence of nuchal rigidity may suggest meningitis. Towards the end of the first week, stupor and coma result in severe cases. The second week is more akin to acute bacteremic pneumococcal pneumonia with continuous high fevers, cough, and dyspnea. If untreated, psittacosis progresses as following:

• Stage of flu-like syndrome
• Moderate pneumonia with X-ray findings
• Severe pneumonia
• Respiratory failure and sepsis

Complications that can develop as a result of psittacosis include:^{[1][2][3][4][4][5][6][7]}

• Respiratory failure
• Acute tubular necrosis
• Hemolytic anemia
• Endocarditis
• Hepatitis
• Endocarditis
• Reactive arthritis
• Chronic follicular conjunctivitis
• Lymphoma
• Gestational psittacosis
• Encephalitis, which is rare but fatal.

Psittacosis is a treatable infectious disease. With appropriate antibiotic therapy, the prognosis is good. If the disease is complicated by renal failure or respiratory failure, the prognosis is poor.