ASK THE VET (Psittacosis)

Psittacosis:

Chlamydia psittaci is an obligate(1) intracellular parasite that has been found in over 130 avian species. Different strains exist; some able to cause severe disease, while other strains cause only mild disease. One strain may cause very mild illness in one type of bird but severe illness and death in another.

Clinical signs of Psittacosis can be very variable. Some birds may be asymptomatic carriers, which means they are infected by show no signs of illness. These birds can infect other birds. Other birds may die suddenly, while some birds may show signs of weight loss, anorexia (appetite loss), depression, frequent sneezing, and nasal and ocular discharges. Diarrhea with lime green feces and urates may be present. Chlamydia is shed in nasal and ocular secretions, feces, and feather dust. Birds become infected when they inhale or ingest the infectious particles.

Very young birds and birds suffering from malnutrition or other diseases are most susceptible. Some species of birds are more susceptible than other species; more resistant species include cockatoos and African Greys.

Diagnosis of Psittacosis can be very difficult. An elevated white blood cell count and a mild anemia may be present as well as elevated liver enzymes. Some infected birds, however, may not show any of the above. Tests are available that allow the detection of antibodies, which are proteins produced by the body to fight the organism. Other tests detect the presence of the antigen, or organism, itself. It is best to do a test for both antibody and antigen. Sometimes it is necessary to repeat these test in 3-4 weeks if the initial results were questionable. It is also possible to look for the organism in the feces. This last test requires collection of feces over 5-7 days, since birds may be intermittent shedders.

If a bird is diagnoses as having Psittacosis, it will be placed on tetracycline for 45 days. The bird's environment must be cleaned thoroughly since chlamydia can survive in dried feces and feather dust for several months. If the bird is re-exposed, it will be re-infected.

An important consideration to keep in mind is that people also may be infected with Chlamydia psittaci. The respiratory route is the usual means of infection - from either direct contact with an infected bird or from aerosolization(2) of avian feces and nasal discharges. Incubation in people can be from 1 to 2 weeks, and may resemble flu-like symptoms. Blood tests are available to diagnose the disease in humans; they are also placed on tetracycline.

(1) Ed note: Obligate: must gain entry to the host's cell in order to live and reproduce. This is a characteristic common to viruses, although this organism is not considered a virus.

(2) becoming airborne