Zoonotic diseases: Part 5

In this fifth part of our series on zoonosis, we take a look at psittacosis, also known as parrot fever.

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Psittacosis, also known as parrot fever and ornithosis, is an infectious disease in humans caused by a bacterium called Chlamydia psittaci. The bacteria is contracted when coming into contact with infected parrots, such as macaws, cockatiels and budgerigars, and from pigeons, sparrows, ducks, hens, gulls and many other species of birds.

IN ANIMALS

Arnaud van Wettere writes that turkeys and ducks are more susceptible to infection than chickens. The infection can present as subclinical, acute, subacute or chronic. It is characterised by respiratory, digestive, or systemic infection, says Van Wettere.

"Infections occur worldwide and have been identified in at least 465 avian species, particularly caged birds (primarily psittacines), colonial nesting birds (egrets, herons), ratites, raptors and poultry. Among domestic species, turkeys, ducks and pigeons are most often affected. The disease is a significant cause of economic loss and human exposure in many parts of the world."

Birds become infected via the faecaloral route or by inhalation. "Respiratory discharge or faeces from infected birds contain elementary bodies that are resistant to drying and can remain infective for several months when protected by organic debris, such as litter and faeces. Airborne particles and dust spread the organism," says Van Wettere.

Van Wettere explains that other possible sources of C. psittaci include:

• Contact with infected sick birds or asymptomatic carriers;
• Vertical transmission from infected birds;
• Infected mammals;
• Infected arthropods;
• Contaminated environments.

He adds that stressors, such as transport, crowding, breeding, cold or wet weather, dietary changes, or reduced food availability can initiate shedding in latently infected birds.