Chlamydiosis (also known as psittacosis, parrot fever, chlamydophilosis or ornithosis) is a disease of birds that can also cause respiratory disease in humans. It is caused by Chlamydia psittaci, a germ that is a bit bigger than a virus and a bit smaller than most bacteria. Birds do not contract nor do they carry Chlamydia trachomatis the organism that causes sexually transmitted chlamydia in people.
Birds or people generally contract chlamydiosis/psittacosis by inhaling particles of infected material shed by chlamydia infected birds. There have been no cases where the bird chlamydia organism has been transmitted directly between humans. Bird chlamydia may be excreted in droppings, discharge from the eyes or nostrils or exhaled air. To develop chlamydiosis a bird must initially be exposed to the chlamydia organism through contact with a chlamydia infected bird or its droppings or discharges. It is possible for the organism to be carried by birds in a dormant state and then be activated by some stressing factor such as moulting, extremes in weather conditions (e.g. a cold snap), transportation, changes in husbandry or concurrent illnesses. Some birds may carry the organism for years without showing any clinical signs. There has been a case of a solitary pet bird, seemingly well and isolated from other birds for over ten years, dying from chlamydiosis/ psittacosis. Chlamydosis is widespread in Australia’s wild bird population and is a cause of illness in wild birds .
Chlamydia in parrots and birds
Clinical signs of chlamydiosis are quite variable and can range from sudden death in apparently healthy birds, to simply showing a lack of energy. Often birds show signs of chlamydiosis like conjunctivitis, respiratory, liver or intestinal disease. These may include any of the following: lethargy, depression, ‘fluffed’ feathers, depression, loss of appetite, weight loss, diarrhoea, biliverdinuria (green droppings due to bile pigments), laboured respiration, eye discharge, seizures or neurological symptoms. Some birds may show feather colour change (green to yellow or grey to black). Others birds with chlamydiosis may chew at their feathers or bodies, possibly due to discomfort associated with internal organ damage. Species of birds that may be affected with psittacosis include cockatoos, cockatiels, budgerigars, parrots, finches, chickens and ducks.
Diagnosis of chlamydiosis in birds and parrots
Because clinical signs of chlamydiosis/psittacosis are highly variable and can be the same as those caused by other diseases, avian chlamydia diagnosis needs to be confirmed by laboratory testing and/or post mortem examination. Common tests done in live birds check for the
• presence of the psittacosis organism. This is generally done by a PCR test that needs to be sent away to a laboratory and takes two weeks.
• presence of antibodies in the blood to the avian chlamydia organism. This test is done at the clinic and results are ready in several hours.
It is important to understand that neither these tests are 100% accurate. A bird may not shed the bird chlamydia organism constantly, in which case there could be a negative PCR test result but the bird could still be infected. Some birds that have been exposed to the psittacosis organism may not produce antibodies against it because it is early in the infection or their immune system is poor. Some birds who have been exposed to the chlamydia organism may have eliminated the virus but still show some antibodies against it. Your Melbourne avian veterinarian can advise you as to which tests to do. Positive avian chlamidia test results, in conjunction with other characteristic parrot chlamydia symptoms, are generally strong evidence of the disease. Sometimes we will recommend treatment in birds with characteristics symptoms even though test results are negative.
Treatment of avian chlamydia
There is no treatment currently available that will 100% guarantee the elimination of the psittacosis organism. The main difficulty is that the organism can go into a dormant phase against which antibiotics are ineffective. The most effective current treatment is a course of the antibiotic doxycyline given orally or by weekly injections for 30 days. Drinking water medication is less effective as birds may not drink the medicated water, but it may be the only practical means of treatment in an aviary outbreak.
Sick birds should also receive good supportive care including a stress-free, warm (26 degree) environment and crop feeding if needed.
In the majority of cases 30 days of doxycyline administered at the appropriate dose rate will resolve the disease. On rare occasions, because of the problems in treating the organism when it is in a dormant phase, a bird may show recurrent symptoms months or years after the treatment has finished, even though treatment has been carried out correctly. Birds do not develop lasting immunity following infection from Ch;lamydia psittaci so it is possible for the same bird to contract the disease more than once.
Psittacosis in humans
In humans psitacosis is rare. the onset of psittacosis is abrupt with fever, chills, headache, muscle aches, general malaise and respiratory tract infections. Cough is often, but not always, a feature. The illness usually lasts for 7-10 days and is generally mild or moderate but may be severe or fatal in older, immunocompromised or untreated patients. The incubation period is 4-15 days. Relapses can occur. It is important to consult your doctor if you or anyone coming into contact with your bird(s) develops signs. Even birds without obvious clinical signs can pass this disease on to humans.
Because even apparently healthy birds may shed the psittacosis organism, it is very difficult to completely eliminate the risk of psittacosis in humans . This risk of transmission to humans is obviously greater in a bird that has been diagnosed as having the disease. If you are considering treating a bird with psittacosis you should be aware of the possible human health risk and discuss any concerns with your doctor.
Control measures that will reduce the risk of spreading psittacosis include the following:
• Have all birds tested for psittacosis by an avian veterinarian
• Follow veterinary advice regarding isolation and treatment of individual sick birds
• Do not introduce any new birds until treatment has been completed
• Minimise stress and focus on good husbandry, good nutrition and regular cleaning
• Bleach, F10 or quaternary ammonium compounds are effective disinfectants
• Avoid creating dust or aerosols. Wearing a mask may reduce the risk of infection in humans
• Treat every bird as a potential carrier. Only introduce new birds of known origin. Quarantine and treat new birds, as advised, for 4 weeks before introducing them to previously treated birds.