Chlamydophila psittaci

Chlamydophila not Chlamydia, It’s Still Psittacosis

I came across the name for the organism that causes psittacosis recently and thought there was a misspelling.  Turns out that’s not the case.  Prior to 1999 the family chlamydiae had only one genus chlamydiae.   to form two genus groups under the chlamydiae family.  In 1999 the chlamydophila organisms were split from the chlamydia organisms based on technical criterion, but they are still closely related and in the same phylogenic family.

My hobby is bird watching, though we call ourselves birders.  Most of us have little interest in birds kept as pets, but psittacosis as a disease still fascinates me, probably in part because of my birding interest.  Psittacosis is an infection fairly common in cages birds, caused by the organism Chlamydophila psittaci.   This organism is in the same family as chlamydia trachomatis that causes the chlamydial STD in humans as well as trachomatis, a common cause of blindness in the third world.

As a chlamydia-like organism it should not be surprising to physicians that the common symptoms in birds of psittacosis are eye discharge and respiratory difficulty, although the eye discharge can be a late symptom, and the diagnosis can be obscure and difficult to make in caged birds.  Many of the symptoms of psittacosis in caged birds are nonspecific, like diarrhea, weakness, and weight loss.  Psittacosis is most common in some particular species of parrots, particularly It is most common in parrots and parakeets, and is sometimes called the parrot disease.  It occurs much less commonly in finches and canaries.  This organism can cause disease in humans, and as such is a zoonosis.

In medical school we were always taught to ask our patients admitted to the hospital with pneumonia of any respiratory disease.  When the uncommon patient who had a caged bird at home was admitted we’d get excited thinking maybe we could make a diagnosis of psittacosis and feel like a great diagnostician.  I’ve never had a case of psittacosis in my practice, and probably never will, but I’ll keep asking about caged birds in anticipation of my first case.

If I had a caged bird my question would be how can I tell if my bird has psittacosis?  The first thing to do before purchasing a pet bird is to think of this ahead of time.  Birds kept in close quarters with lots of other birds are more at risk, so look for a pet store with well-ventilated spacious aviaries or cages.  In addition avoid any bird which looks underweight or has an eye discharge.

Humans can present with symptoms of mild disease, but often become very ill.  The typical presentation is with an atypical pneumonia, with the triad of fever, nosebleeds and splenomegaly classic.  Diagnosis can be difficult, but hinges on obtaining the history of contact with birds, especially a sick bird.  Once the diagnosis is suspected there are specific tests to confirm the diagnosis, including serologic testing, looking for specific inclusion bodies in bronchoalveolar washings called Levanthal-Cole-Lillie bodies, and culture of sputum or washings.  Suspicion from history is the key.

So if you have caged birds, or are considering keeping a caged bird, and you develop a severe respiratory illness, be sure to tell you doctor about the pet so they will think to consider psittacosis in their differential diagnosis.

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