Psittaci

Psittaci, most commonly referred to as Chlamydia psittaci, is a bacterial species in the family Chlamydiaceae. It is an obligate intracellular, Gram-negative organism with a biphasic developmental cycle that alternates between infectious elementary bodies and replicating reticulate bodies.

Its host range is broad among birds, including parrots (psittacines), pigeons, turkeys, ducks, and other poultry. Birds may be asymptomatic carriers or show signs such as conjunctivitis, nasal discharge, ruffled feathers, or systemic illness. Humans acquire infection chiefly through inhalation of dried secretions, aerosols, or feather dust from infected birds, with occasional direct contact.

In humans, the disease is psittacosis (ornithosis). It commonly presents with fever, headache, myalgia, and dry cough, and may progress to atypical pneumonia. Incubation is usually 5 to 14 days. Diagnosis relies on PCR testing of respiratory samples, serologic tests, or culture in cell culture under appropriate biosafety conditions. Treatment is typically doxycycline; alternatives include macrolides or tetracyclines. Most patients recover with timely therapy.

Epidemiology and control. Psittacosis is found worldwide, with outbreaks associated with pet birds, aviaries, and poultry operations. Prevention emphasizes reducing exposure during handling and cleaning of birds and contaminated materials, and implementing quarantine and hygiene measures. There is no widely used human vaccine; vaccination of birds is limited and region-specific.

Genomics and taxonomy. The name psittaci derives from its association with psittacine birds. The organism remains genetically diverse; its genome is roughly 1.0 to 1.2 megabases and encodes about 900 to 1100 genes. As an obligate intracellular organism, it cannot be easily cultured on standard media.