Chlamydia psittaci

• Chlamydia psittaci are bacteria responsible for the sexually transmitted disease called psittacosis.
• Chlamydia psittaci often infects birds.
• Less commonly, these bacteria can infect people and cause a disease called psittacosis.
• Psittacosis can cause mild illness or pneumonia.

Chlamydophila psittaci FA stain

Chlamydia psittaci, an intracellular gram-negative bacterium that commonly infects birds, causes psittacosis in humans.

C. psittaci, along with C. pneumoniae and C. trachomatis, are members of the bacterial family Chlamydiaceae. The Chlamydiaceae family shares a unique developmental cycle that is different from all other bacteria. C. psittaci growth consists of two alternating forms:

• Elementary bodies
• Reticulate bodies

Elementary bodies are metabolically inactive. They infect the host when the cell ingests them (receptor-mediated endocytosis). Once inside the cell, the elementary bodies differentiate into reticulate bodies, which are metabolically active but noninfectious. The reticulate bodies, which rely on the host cell for adenosine triphosphate (ATP) synthesis, divide by binary fission and induce a host immune response. After 48 to 72 hours, the reticulate bodies reorganize themselves and condense to form new elementary bodies. The elementary bodies then leave the host cell and start a new infectious cycle.

Since C. psittaci growth takes place within host cells, laboratorians cannot grow the organism using typical bacterial culture media.

Transmission

Most commonly, C. psittaci infects humans who inhale dust containing dried droppings or respiratory secretions from infected birds. Less commonly, birds infect people through bites and beak-to-mouth contact. People rarely transmit C. psittaci to other people. There is no evidence that the bacteria spread by handling or eating poultry products.

Risk Factors

During the 1980s, public health surveillance indicated that exposure to caged pet birds accounted for 70% of the psittacosis cases for which the source of infection was known. Of these, owners of companion birds or bird fanciers were the largest group of affected persons (43%). Pet-shop employees accounted for an additional 10% of cases. Others at increased risk were persons whose occupation places them at risk of exposure, including:

Pet bird

• Employees in poultry-processing plants
• Veterinarians and veterinary technicians
• Laboratory workers
• Workers in avian quarantine stations
• Farmers
• Zoo workers

However, human infection can result from transient exposure to infected birds or their contaminated droppings. Therefore, persons with no identified avocational or occupational risk may become infected.

Risk factors

People of all ages can get psittacosis, but it is more commonly reported among adults. Those who have contact with pet birds and poultry, including people who work in bird-related occupations, are at increased risk:

• Bird owners
• Aviary and pet shop employees
• Poultry workers
• Veterinarians

Signs and symptoms

In general, psittacosis causes mild illness. The most common symptoms include:

• Fever and chills
• Headache
• Muscle aches
• Dry cough

Course

• Psittacosis can also cause pneumonia, a lung infection, which may require care in a hospital.
• Rarely, psittacosis can result in death.
• Most people begin developing signs and symptoms within 5 to 14 days after exposure to the bacteria (Chlamydia psittaci).
• Less commonly, people report symptoms starting after 14 days.

Diagnosis

• Symptoms of psittacosis are similar to many other respiratory illnesses.
• In addition, tests to detect the bacteria directly may not be readily available.
• For these reasons, clinicians may not suspect it, making psittacosis difficult to diagnose.

Tests

• Clinicians can use a number of tests to determine if someone has psittacosis.
• These tests include collecting sputum (phlegm), blood or swabs from the nose and/or throat to detect the bacteria.
• Laboratories typically perform tests on sputum specimens or swabs of the nasopharynx and oropharynx or serum, depending on the method used.
• In severe cases, other specimen types may be used. Clinicians should confirm the recommended specimen types with the laboratory receiving the specimen.

Treatment

• People diagnosed with psittacosis usually take antibiotics to treat the infection.

Chlamydia psittaci are sensitive to both macrolides and tetracyclines.

• However, tetracyclines are the drugs of choice, unless contraindicated due to reported macrolide failures.
• Tetracyclines are generally avoided in children aged <8 years, and macrolides are the drug of choice for children; however, tetracyclines could be considered when the benefits outweighs the risks, such as in life-threatening conditions or when macrolide failure is suspected.
• As psittacosis can be difficult to diagnose, clinicians should be aware that proper antibiotic treatment ensures quick recovery time.
• People with more severe presentation should be treated with doxycycline right away if psittacosis is suspected.

Complications

Most people treated properly for psittacosis make a full recovery. However, some people have serious complications and need care in a hospital. Complications include:

• Serious pneumonia (lung infection)
• Endocarditis (inflammation of the heart valves)
• Hepatitis (inflammation of the liver)
• Inflammation of the nerves or the brain, leading to neurologic problems

With appropriate antibiotic treatment, psittacosis rarely (less than 1 in 100 cases) results in death.

Prevention

While there is no vaccine to prevent psittacosis, there are things you can do to protect yourself and others. Buy pet birds only from a well-known pet store. If you own pet birds or poultry, follow good precautions when handling and cleaning birds and cages (see Safe Bird and Cage Care).

Previous Infections

Getting psittacosis will not prevent you from future illness. If you get psittacosis, you may still get sick from it again in the future.

Safe Bird and Cage Care

One important aspect of preventing psittacosis is to control infection among birds.

• Keep cages clean; clean cages and food and water bowls daily.
• Position cages so that food, feathers, and droppings cannot spread between them (i.e., do not stack cages, use solid-sided cases or barriers if cages are next to each other).
• Avoid over-crowding.
• Isolate and treat infected birds.

Use water or disinfectant to wet surfaces before cleaning bird cages or surfaces contaminated with bird droppings. Avoid dry sweeping or vacuuming to minimize circulation of feathers and dust. Also, remember to thoroughly wash your hands with running water and soap after contact with birds or their droppings. Use personal protective equipment (PPE), such as gloves and appropriate masks, when handling infected birds or cleaning their cages.

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