PSITTACOSIS (Chlamydofila spp)

Note for Pet Owners:

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Psittacosis is a disease that can be transmitted to humans (a zoonosis) and precautions should be taken to prevent the transmission of the disease from infected animals or birds.

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Psittacosis is the term given to an infectious disease which is endemic in birds (both psittacines and ornithines) worldwide. In ornithines the disease is called "ornithosis". The infection is transmissible to other species and regularly causes disease in humans, cattle, sheep, pigs, and cats. Occasional infections of dogs have been reported.

The cause is an infective agent, Chlamydofila (previously Chlamydia) psittaci
,which is an obligate intracellular bacterium consisting of RNA and DNA.. There are many varieties which are species specific eg Chlamydofila felis affects cats.

Breed Occurrence
There is no specific breed predisposition to develop psittacosis.

linical signs depend upon the species involved :

  • Birds
    • Infected birds can appear healthy
    • Depression
    • Inappetance
    • Respiratory disease - rapid breathing rate, open mouth breathing/gasping
    • Eye discharge
    • Nose discharge - sneezing
    • Watery green diarrhoea
    • Ruffled feathers
    • Weight loss
    • Sudden death in severe acute forms of the disease
  • Cats
    • Conjunctivitis
  • Cattle
    • Pneumonia
    • Arthritis
  • Dogs
    • Cough 
    • Fever
    • Lameness
  • Humans
    • Chest pain (common)
    • Cough (common)
    • Conjunctivitis
    • Flu-like disease
    • Headache
    • Fever
    • Muscle pain
    • Pneumonia
    • CNS signs
    • Diarrhoea - uncommon
    • Vomiting
    • Renal failure
    • Death -  mortality rates of up to 20% have been reported
  • Pigs
    • Pneumonia
    • Arthritis
  • Sheep
    • Abortion (called enzootic abortion)

Spread of infection is through direct contact with secretions from infected animals, or aerosol spread.

Stress often precipitates the disease in animals which are carrying the organism but which are otherwise healthy. So, capture and transportation of wild parrots commonly causes sufficient stress for them to succumb to the disease. Animals that recover from infection may remain carriers of the organism and can relapse later.

Diagnosis depends upon isolation and identification of the organism from samples of faeces, swabs eg taken  from eyes (eg in cats) , or tissue collected at post-mortem. At post-mortem attempts to prevent transmission to humans should involve wearing protective clothing and masks and wetting the carcase to reduce aerosol spread.

There is a serious human health risk so a decision to treat an infected animal or bird must not be taken lightly.

The treatments of choice for psittacosis are tetracyclines. Dosing through water intake is unsatisfactory as it is necessary to maintain high therapeutic levels in the blood and this cannot be guaranteed by adding antibiotic to water supply.

  • Birds
    • Up to 45 days therapy with chlortetracycline 5g/L water is usually recommended.
    • Doxycycline given at 75mg/kg by intramuscular injection every 5 days for 45 days
  • Cats (C.felis)
    • Doxycyline by mouth 5mg/kg 1-2 times daily for 6 weeks
    • Oxytetracycline by subcutaneous or intramuscular injection 10mg/kg
  • Cattle
    • Oxytetracycline by depot injection intramuscularly 20mg/kg every 2-4 days or 30mg/kg every 6 days.
  • Dogs
    • Doxycycline by mouth 10mg/kg
    • Oxytetracycline by mouth 25mg/kg twice daily
    • Oxytetracycline by injection (subcutaneous/intramuscular) 2-10 mg/kg daily
  • Pigs
    • Oxytetracycline by mouth 10-30mg/kg 1-2 times daily
  • Sheep
    • Oxytetracycline by depot injection intramuscularly 20mg/kg every 2-4 days or 30mg/kg every 6 days.

If tetracyclines are contraindicated in a patient erythromycin may be an alternate subject to medicines licensing regulations.



There is a vaccine available for use in cats.

The prognosis is guarded for infected individuals

Long term problems
Latent carrier state is common, particularly in birds.


Update in Preparation 2013