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Nature of the disease
Avian Chlamydiosis (AC), also know as Psittacosis or Ornithosis, is caused by the bacterium Chlamydophila psittaci. It is a zoonosis that can have severe consequences.
OIE, List B disease
Susceptible species
Birds and many mammals including humans.
Worldwide, in the Pacific region is reported in many places.
Clinical signs 
The disease is most severe in young birds, pigeons, turkeys and migratory birds. Symptoms include:
  • Ruffled feathers,
  • Loss of condition,
  • Conjunctivitis,
  • Nasal and ocular discharge,
  • Pale, greenish faeces,
  • High mortality

In older birds and in ducks the disease is often Subclinical with reduced egg production.

Post-mortem findings 
Spleen and liver enlargement, fibrinous air-sacculitis, pericarditis and peritonitis
Differential diagnosis 
  • Salmonellosis,
  • Mycoplasmosis
Specimens required for diagnosis 
The bacteria can be identified from smears of affected tissues using immunochemistry, ELISA.  

Cloacal, choanal and conjunctival swabs from live birds and specimens of liver, spleen and serous membranes from dead birds can be submitted for chlamyda identification. Techniques include culture and identification by histo-chemical staining, antigen detection using immunochemistry or ELISA, and DNA detection.

The bacteria is shed in faeces and nasal discharges for months. Infection is transmitted by aerosols and contaminated dust. Risk of transmission increases with bird density. Oral transmission is possible.

Transmission to humans usually occurs when handling or slaughtering infected birds, especially ducks and turkeys.

Risk of introduction   
Chlamydiosis could be introduced by importation of live infected birds. Zoo or pet Psitacids are specially at risk as they are recognised as reservoir. Introduction via migratory birds is also possible.
Control / vaccines  
There are no commercial vaccines available for chlamydiosis control in poultry.
  • Avian Chlamydiosis, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p. 1907-1909
  • Office International des Epizooties, 2002
  • Office Vétérinaire Fédéral Suisse