Chlamydia psittaci: what is it, how does it spread, clinical signs

Early diagnosis of any disease is important so that specific treatment can be started as soon as possible, recovery is as smooth and quick as possible, and the chance of the disease spreading, either to in contact animals or people, is kept to a minimum. Most birds are well known to hide the signs of disease they may be suffering from. This is because, as prey species, in the wild they would be predated on as soon as they appeared to be weaker than the rest of their flock. The need for a quick diagnosis at the time a bird is presented in a veterinary clinic is of the utmost importance, as they have often been subclinically ill for a longer time than has been obvious to their owner.

Chlamydia psittaci is a bacterial infection that causes disease in many species of parrot. The disease may be referred to as psittacosis, chlamydiosis, chlamydophilosis, or ornithosis in other species of bird. It is especially common in budgies, cockatiels, macaws and lorikeets, although it can affect any parrot. Infection can be asymptomatic or symptomatic, with sudden death sometimes occurring. This disease is of zoonotic concern, especially in the elderly, very young or immunocompromised.

What is Chlamydia psittaci?

Chlamydia, or Chlamydophila psittaci, is an obligate intracellular bacteria, meaning that, similar to viruses and parasites, it has to live inside the hosts cells to survive, reproduce and cause disease. This makes eradicating the disease with treatment challenging. Latent infection is common, with infected birds not always exhibiting clinical signs of disease, and shedding of the bacteria seen intermittently. Transmission to humans can lead to a disease called psittacosis or ornithosis, which typically causes flu-like symptoms, but can lead to pneumonia or non-respiratory disease.

How is this disease spread?

Chlamydia is spread from bird to bird, or bird to human, by inhalation or ingestion of dust particles that contain the bacteria. These particles become airborne from dried faeces or respiratory secretions. Less commonly, beak to mouth contact and bite wounds can lead to bird to human transmission, and direct spread to offspring can be seen as a result of food regurgitation.

Common clinical signs associated with Chlamydia infection in birds.

Chlamydia can lead to a range of clinical signs in birds. Some animals will be asymptomatic, with others showing mild non-specific illness, for example lethargy, weight loss, a fluffed up appearance and anorexia, while others can be clinically normal before collapse and death. Respiratory tract signs are commonly seen, including nasal and ocular discharge, sneezing and respiratory distress. Chlamydia will also commonly lead to gastrointestinal signs, such as diarrhoea, vomiting and bright green urates and faeces, most often as a result of hepatic involvement.

Common clinical signs associated with Chlamydia infection in humans

Mild infection in humans will cause flu-like symptoms such as a fever, headache, myalgia, a dry cough and/or dyspnoea which may progress to pneumonia. In more severe cases other organs can be affected which can lead to encephalitis, conjunctivitis, hepatitis, arthritis and cardiac problems such as endocarditis and myocarditis. If any of these clinical signs occur after contact with a bird, whether they are showing symptoms or not, you should visit your doctor as soon as possible. Human to human transmission is not known to occur.

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