Saturday, February 9, 2008


Infection with Chlamydophila psittaci is common in pet birds. Clinical signs vary from none to a mild respiratory disease to a severe multisystemic, often fatal, disease. Psittacosis is particularly important in avian medicine because it can spread widely before it is recognized and because it is a zoonotic and reportable disease. Clinical signs and traditional diagnostic assays such as hematology, clinical pathology and radiology, while helpful, are generally insufficient to specifically diagnose this disease.

No test is 100% sensitive. Therefore, if the greatest degree of sensitivity is sought, the PCR and the EBA (Elementary Body Agglutination Assay) and egg inoculation culture or tissue culture could both be performed when screening parrots. PCR can be combined with the CF when screening doves and pigeons.

Chlamydophila psittaci infections can occur in almost any species of caged bird. The author recommends testing for this organism in most birds presented for new bird purchase examinations. The author especially recommends testing cockatiels (Nymphicus hollandicus) as they can carry this bacterium and not demonstrate clinical signs of disease. The few cases of human infections the author has observed have been acquired from an otherwise healthy pet cockatiel. Pigeons and doves are commonly infected with C. psittaci and should be routinely tested.

Chlamydophila psittaci is a zoonotic intracellular bacterial organism that causes the diseases psittacosis in humans and avian chlamydiosis in avian species. Clinical signs often associated witha psittacosis (human) infection include generalized "flu-like" symptoms to more severe pneumonia and complicating health issues. Avian chlamydiosis will present as non-specific clinical signs in a companion bird patient. These non-specific signs can include ocular, nasal or conjunctival irritation and discharge, anorexia, depression, dehydration, bright green urates and diarrhea. Many avian species have been diagnosed with C. psittaci, but it is the companion bird species where this disease is the greatest public health concern.

It is often difficult to confirm a diagnosis of avian chlamydiosis because of the intracellular life cycle of the organism, prophylactic treatment of patients with appropriate antibiotics but using inappropriate doses and treatment periods, and the periodic shedding of elementary bodies (the infectious form of the disease). The difficulty to confirm avian chlamydiosis cases encourages the veterinarian to use multiple testing methodologies. Testing methods that can be used either individually or preferably in combination include pathology, antibody testing (direct complement fixation and elementary-body agglutination) and antigen testing (enzyme-linked immunosorbent assay, immunofluorescent antibody tests, polymerase chain reaction (PCR) amplification technology on choanal/cloacal swabs and blood). Prior to sample submission, the diagnostic laboratory should be contacted for recommendations on proper sample collection, labeling, packaging, and shipment of the sample material. A breakdown in sample handling or shipment delay can adversely affect the reliability of C. psittaci test results.

There are several treatment options available to treat suspected or confirmed avian chlamydiosis cases. The treatment options are based on doxycycline as the drug of choice and being administered in the most appropriate way for the patient(s) to receive a therapeutically effective dose for the duration of the 45-day treatment regimen. There have been recent advances in using doxycycline hyclate powder from opened capsules a a seed coating for budgerigars or mixing the powder in water for larger birds. Oral doxycycline (monohydrate or calcium) or intramuscular injections of specific formulations can be effective treating the individual bird or group of birds that will tolerate the stress of capture and drug administration on a regular basis.

Chlamydiosis psittaci is a public health concern and can be a deadly, expensive disease within an aviary or to the individual companion bird. Although difficult to diagnose, avian chlamydiosis can be diagnosed and treated if there is an understanding of the available tests, and the proper tests are used to confirm the presence of the disease. Early communication to a client about the ability of this organism to resist improper treatment and the consequences of discontinuing treatment will often lead to owner compliance with antibiotic administration. In hopes of protecting birds and bird owners in the future, research is currently being conducted to improve C. psittaci diagnostic testing and to develop a vaccine to protect birds from infection if exposed to the infectious elementary bodies.

Reference: "Clinical Avian Medicine - Vol I and II" by Harrison and Lightfoot