Despite the strong link to bird exposure, it is not necessary for a diagnosis. This is especially true in areas with large numbers of wild birds. For example, there have been two outbreaks in Australia with towns surrounded by a large avian flora.[11][12] Regardless, a large part of the diagnosis relies on a thorough history with regards to the patient’s medical history, occupation, hobbies, travel history, as well as a high index of suspicion. Symptoms of psittacosis are mainly respiratory in humans, but clinical symptoms can vary tremendously. After replication in the respiratory system, the infection can spread hematogenous to affect multiple organ systems. It is often described initially as an influenza-like syndrome characterized by fevers, chills, headache, and a cough. Case studies have shown that despite this, the infection can range from an asymptomatic state to a fulminant invasive disease with an average incubation period of 5 to 14 days.[13]

Symptom onset is typically abrupt, with a headache cited as the most prominent complaint in addition to fever, myalgias, nausea, vomiting, diarrhea, and cough.[2] Studies have cited the presence of a severe headache as being a characteristic feature, with consideration of meningitis in the differential diagnosis given its severity.[1] Other signs of psittacosis that have been documented include altered mental status, mild neck stiffness, photophobia, hepatosplenomegaly, and pharyngitis.[1]

Psittacosis can affect multiple different organ systems and manifestations reported in the literature are listed below:

• Central nervous system manifestations including meningoencephalitis, cerebellar ataxia, cranial nerve palsies, transverse myelitis, Guillain-Barre syndrome, and status epileptics[1]
• Respiratory manifestations include pneumonia, acute respiratory distress syndrome, respiratory failure, and septic shock[1]
• Cardiac manifestations include myocarditis, pericarditis, culture-negative endocarditis, and aortitis[1]
• Renal and gastrointestinal manifestations include acute interstitial nephritis, acute renal failure, glomerulonephritis, hepatitis, pancreatitis, as well as acute abdomen prompting exploratory laparotomy[1]
• Hematological manifestations include disseminated intravascular coagulation (DIC), splenomegaly, and hemophagocytic syndrome[1]
• Rheumatological manifestations include reactive arthritis and polyarteritis[1]
• There have also been cases of gestational psittacosis with poor fetal and maternal outcomes, as well as an association with ocular lymphoma.[1]

In the appropriate clinical scenario with signs and symptoms consistent with psittacosis, the clinician should consider laboratory workup and imaging. Laboratory workup may show a normal to slightly lowered white blood cell count initially during the acute phase of the illness with noted leukopenia later in the disease course.[14] Anemia has also been observed, most commonly attributed to hemolysis.[14] Liver function testing, specifically aspartate and alanine aminotransferase, as well as gamma-glutamyl transpeptidase (AST, ALT, GGT) have also been shown to be variably elevated in psittacosis.[14] Additionally, C-reactive protein (CRP) is variable elevated as well in case studies.[14]

Regarding imaging, it has been noted that the chest x-ray is abnormal in up to 80% to 90% of hospitalized patients, showing a wide range of findings. These include unilateral consolidation to bilateral, miliary, interstitial and nodular infiltrates.[1][14] It should be noted that a normal chest x-ray does not rule out psittacosis.

The CDC has published guidelines for the diagnosis of psittacosis. In the appropriate clinical scenario, a diagnosis is made by meeting any one of the criteria listed below:

1. Isolation of the causative organism from respiratory secretions
2. A noted four-fold or greater increase in antibody titer between serum samples collected 2 weeks apart via the complement-fixation test (CFT) or micro-immunofluorescence (MIF)
3. A single IgM antibody titer detected by MIF of 1:16 or higher

It should be noted that isolation of C. psittaci culture during the acute infection is the most reliable diagnostic test, but it is not recommended as it requires a biosafety level three facility due to the risk of transmission, and thus, is rarely performed.

Treatment for this bacterial infection is based on intracellular activity, pharmacokinetics, and evidence from clinical trials that recommend tetracycline antibiotics, particularly doxycycline in the individual without contraindications. Case studies have shown that with treatment, most infected individuals will have an improvement in fever and clinical symptoms by 48 hours.[2] In cases where oral antibiotics cannot be used, intravenous doxycycline can still be used. The treatment with doxycycline uses 100 mg orally or intravenously every 12 hours for 10 to 14 days.

In pregnancy and in patients where doxycycline is contraindicated, the infection is best treated with macrolide antibiotics, such as azithromycin and erythromycin for a 7-day course.

Third line antibiotics active against C. psittaci include fluoroquinolones, which are less effective than tetracyclines and macrolides.

• Mycoplasma pneumonia
• Legionella pneumonia
• Q fever (Coxiella burnetii)
• Tularemia (Francisella tularensis)
• Influenza
• Typhoid fever
• Brucellosis
• Bacterial pneumonia
• Fungal pneumonia

The prognosis of psittacosis will depend on the patient’s clinical disease severity, co-morbid conditions, as well as the time of treatment and supportive care. Despite antibiotic treatment, it is estimated that the mortality rate is 1%.[15]

Patients infected with psittacosis can present with many different manifestations owing to its hematogenous spread after initial inoculation. Please refer to the “History and Physical” section above for a thorough outline of different complications. In short, complications of infection with C. psittaci include severe pulmonary complications including pneumonia, ARDS, respiratory failure, as well as endocarditis, myocarditis, sepsis, DIC, meningoencephalitis, hepatitis, and pancreatitis; rarely the patient may present with a fulminant disease course characterized by multi-organ failure.

Per the CDC, isolation precautions and contact prophylaxis are not indicated, as the rates of person-to-person transmission are exceedingly rare. However, in the United States, most states classify psittacosis as a reportable condition. A timely diagnosis aims to control the spread of this disease.

Patients and the public, in general, should be educated on the purchase, handling, and cleaning of birds and birdcages to control the acquisition and spread of disease better. Birds suspected of as a source of infection should be referred to veterinarians and health department personnel.

• Psittacosis is caused by the bacterium C. psittaci and is a zoonotic infection mostly attributed to contact with birds.
• Diagnosis hinges on the clinician performing a thorough patient interview, asking about occupational history, hobbies, travel history, as well as maintaining a high index of suspicion.
• Most infected individuals present with an influenza-like illness characterized by fevers, chills, myalgias, and a cough, but the presence of a severe headache and gastrointestinal symptoms in the appropriate clinical setting may clue the clinician into the diagnosis.
• Laboratory testing is largely non-specific but may reveal elevated liver function testing, anemia, and leukopenia, and the chest x-ray is noted to be abnormal in 80% to 90% of cases of hospitalized psittacosis.
• Diagnosis is clinical but can be confirmed with serological testing as outlined by the CDC.
• Treatment is with tetracyclines, such as doxycycline, with macrolides being utilized in those with contraindications to tetracyclines.

In 2017, the National Association of State Public Health Veterinarians compiled a compendium on measures to control C. psittaci infection with recommendations being assigned a level of evidence using the United States Preventive Services Task Force (USPSTF) framework. They note that secondary to the limitations of psittacosis surveillance, there should be a close relationship between healthcare personnel and public health authorities early in the differential diagnosis to discuss diagnostic options and care.[16] They recommend that those persons at risk, as well as healthcare providers, be educated on the signs, symptoms, and appropriate workup of the disease.[16] (Level B). This should include a public education component outlining proper bird handling, use of protective clothing, and use of a disposable particulate respirator when applicable.[16] (Level B). A combined public health department and healthcare personnel coordinated effort should be undertaken to educate the public and the industry on maintaining accurate records of all bird-related transactions to help with identifying sources of infection.[16] (Level B). The level A evidence-based recommendations noted include the quarantine of exposed birds and isolation of ill birds with signs of psittacosis as well as the use of appropriate disinfection measures on all exposed surfaces.[16] (Level A). These recommendations all stress that a coordinated effort that utilizes healthcare personnel, as well as public health officials, veterinarians, coupled with a public education initiative, is the best way to go about educating and controlling this disease.