By Dr. Valerie Campbell, DVM
CHLAMYDIA PSITTACI is a rickettsial organism, a bacteria, that causes the clinical disease psittacosis, ornathosis and chlamydiosis. The disease was first discovered in 1930 when several people and birds died after a bird show in South America.
Chlamydia psittaci is well-adapted to the avian host and is endemic in many bird populations in this country and many others. Serious illness occurs mainly under conditions of crowding and stress both in the wild and in captivity.
Shedding of the agent occurs after a latent or carrier infection is reactivated – through feather dust and fecal contamination. The organism appears in the droppings 10 days prior to the bird becoming ill, and intermittent shedding can occur for months with no illness. Dogs, cats, horses, humans, cattle, sheep, frogs and goats all are susceptible to infection.
Psittacosis can exist as a completely asymptomatic condition or acute, systemic fatal disease. Different strains vary in virulence. The shortest incubation time is 42 days up to 1.5 years or longer. The clinical illness is caused primarily by a toxin that affects the liver and kidneys. Diarrhea and respiratory signs (unilateral conjuntivid, rales, and sinusitis) occur as well as excessive thirst. The bird is lethargic, dehydrated, hypothermic, anoretic and puffed. Droppings appear watery and yellowish-green with the urates and feces intermixed. Central nervous system signs such as tremors, convulsions, paralysis and twisted neck can occur.
Diagnosis of the dead bird is by histopathology (microscopic examination of the tissues) – diagnosis in the live bird is difficult and may be impossible for healthy carriers.
Various tests exist – electron micropscopy, fluorescent antibody of the feces, ELISA (enzyme linked immunosorbent assay), BELISA (blocking ELISA), latex agglutination, direct complement fixation (DCF), tissue culture and egg inoculation. Treatment with chloramphenical (palmitate) penicillin, tylosisn erythromycin, tetracyclines (including doxycycline) and baytril will cause a false negative result. So it is important to test prior to treatment of any sort. The two best tests at this point for cockatiels are the ELISA antigen test and the BELISA. At this time there is no test that is 100% accurate and false negatives are common. False positives are possible with the ELISA.
The only effective treatment is prolonged medication with tetracyclines. The problem with the 45-60 day regime of tetracyclines is that the antibiotic can cause immunosuppression and intestinal flora alterations that foster fungal overgrowth. Also, tetracyclines are inactivated by calcium and other metallic ions that bind it and prevent absorbtion. The eventual elimination of Chlamydia psittaci is by host cell sloughing and replacement by uninfected cells over the 45-60 day period. The antibiotic will not affect the inactive state of the organism. Chlortetracycline oxytetracycline (oral and injectable), and doxcycline (oral and injectable) are the only forms of treatment available. Baytril may cause some improvement in clinical signs, but it will not keep the organism from multiplying.
Psittacosis is a reportable disease in many states since it can infect humans. Various actions occur secondary to notification which mainly involve quarantine, notification of people who have purchased birds within the last 45 days, inspection to insure the birds have been adequately medicated and occasionally destruction of the birds (i.e. the treatment is more expensive than the birds).
Some avian experts recommend periodic treatment of breeding flocks with tetracyclines once to twice yearly. The benefits must outweigh the risks in these situations, since medicating the birds is not without some problems. Pet shops and bird importation facilities generally may benefit from such a program, but care must be taken, especially with birds actively breeding or being handfed.
Lastly, do not expect the USDA quarantine facilities to provide you with Psittacosis-free birds. Although tetracyclines are given in the feed, in cush facilities, birds are frequently not eating well, and the medication may be interrupted if the birds are not eating – so that the carrier state is maintained.
Valerie Campbell, DVM is an avian and small animal specialist graduating from Virginia Tech’s Virginia-Maryland Regional College of Veterinary Medicine. Dr. Campbell works with Bird Clubs of Virginia and bird clubs throughout the states of Virginia, Maryland and the District of Columbia. She practices veterinary medicine at the Blue Ridge Veterinary Associates in Purcellville, VA.