Clinical Features

In humans, fever, chills, headache, muscle aches, and a dry cough. Pneumonia is often evident on chest x-ray.

Etiologic Agent

Chlamydia psittaci, a bacterium

Incidence

Since 1996, fewer than 50 confirmed cases were reported in the United States each year. Many more cases may occur that are not correctly diagnosed or reported.

Sequelae

Endocarditis, hepatitis, and neurologic complications may occasionally occur. Severe pneumonia requiring intensive-care support may also occur. Fatal cases have been reported.

Transmission

Infection is acquired by inhaling dried secretions from infected birds. The incubation period is 5 to 19 days. Although all birds are susceptible, pet birds (parrots, parakeets, macaws, and cockatiels) and poultry (turkeys and ducks) are most frequently involved in transmission to humans.

Risk Groups

Bird owners, pet shop employees, and veterinarians. Outbreaks of psittacosis in poultry processing plants have been reported.

Surveillance

Psittacosis is a reportable condition in most states.

Trends

Annual incidence varies considerably because of periodic outbreaks. A decline in reported cases since 1988 may be the result of improved diagnostic tests that distinguish C.psittaci from more common C. pneumoniae infections.

Challenges

Diagnosis of psittacosis can be difficult. Antibiotic treatment may prevent an antibody response, thus limiting diagnosis by serologic methods. Infected birds are often asymptomatic. Tracebacks of infected birds to distributors and breeders often is not possible because of limited regulation of the pet bird industry.

Opportunities

Characterize new and rapid diagnostic tests for human and avian psittacosis, and determine value of screening flocks for avian psittacosis to prevent human infection.