A Case of Cryptococcal Infection in a Patient with an Abnormal Immune System and a Pet Cockatoo

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The summary below is from the full report titled "Evidence of Zoonotic Transmission of Cryptococcus neoformans from a Pet Cockatoo to an Immunocompromised Patient." It is in the 1 February 1999 issue of Annals of Internal Medicine (volume 132, pages 205-208). The authors are J.D. Nosanchuk, S. Shoham, B.C. Fries, D.S. Shapiro, S.M. Levitz, and A. Casadevall.

What is the problem and what is known about it so far?

Cryptococcus neoformans is a fungus that causes infection in people with abnormal immune systems. Among other things, the immune system helps the body fight off infection. Experts believe that people can become infected with cryptococcus when they breathe in spores of the fungus. Spores can be found in soil and in bird droppings, but nobody had yet described a case where infection was shown to spread directly from a bird to a person.

Why did the researchers do this particular study?

The researchers encountered a case of cryptococcal infection in a woman who was living in the same house as a pet cockatoo. They realized this was an important opportunity to find out whether the patient had acquired her infection from direct exposure to the bird.

Who was studied?

A 72-year-old woman whose immune system was suppressed by medications she was taking after a kidney transplant.

How was the study done?

The researchers collected information about the patient. They isolated cryptococcus from both the patient's body fluids and from the cockatoo's droppings. They then used special laboratory tests to compare the type of cryptococcus from the patient with that from the cockatoo.

What did the researchers find?

The type of cryptococcus in samples from the patient was found to be identical to that in samples from the cockatoo.

What were the limitations of the study?

This is a single case, and the situation described in this case may be unusual. In addition, the presence of the same form of cryptococcus in the patient and the bird suggests but does not absolutely prove that the patient got the infection from the bird. It is possible that both got it from another source or, much less likely, that the bird got it from the patient.

What are the implications of the study?

This case strongly suggests that patients with weakened immune systems can get cryptococcal infection directly from bird droppings by inhaling cryptococcus spores that spread into the air from the droppings. Although this type of situation may be rare, it seems wise to advise persons with abnormal immune systems to avoid pet birds and situations where they might be exposed to large amounts of bird droppings.