Abstract
Members of the Chlamydiaceae are obligate Gram-negative intracellular pathogens that cause a variety of infectious diseases. As a zoonotic pathogen, Chlamydia psittaci (C. psittaci) has been associated with a wide range of infections in both wild and domestic animals, particularly birds. In humans, C. psittaci causes influenza-like symptoms, pneumonia, endocarditis, fever, chills, myalgia and headache. Similar to other Chlamydia species, the virulence factors of C. psittaci mainly include type III secretion system, type IV system effectors (TARP), CopN, HctA and HctB, OmcA, OmcB, OmpA, major outer membrane protein (MOMP), PorB and Euo. In particular, C. psittaci may predispose patients to other respiratory pathogens. Direct contact and inhalation of contaminated air droplets from birds is a risk factor for transmission of infection. Other risk factors include pregnancy, overcrowding, bird litter, and close contact with cats and dogs. Therefore, greater care should be exercised in close contact with these pet animals. Fortunately, these infections have been treated more effectively thanks to the development of novel drug delivery systems in recent decades. There is no similar review study to assess zoonotic potential of these species. Considering the highly contagious potential of C. psittaci and C. felis, together with the wide host range and available risk factors, appropriate control strategies are essential to prevent their dissemination.