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Infection of psittacine birds with Chlamydia psittaci is widespread.^1,2 Pet bird, pet shop, and breeder situations encompass the many facets and variables likely to be encountered when dealing with chlamydiosis (psittacosis) in pet birds.

Chlamydiosis in a pet bird

An adult, blue-front, Amazon parrot was in apparent good health when purchased. However, one month after being purchased, the parrot began sitting quietly in its cage with its feathers ruffled and subsequently developed depression, dyspnea, and lime-green diarrhea. The diet of various types of food items offered to the bird was considered to be nutritionally satisfactory.

Physical examination indicated that the bird had wasting of the pectoral musculature, and feathers around the vent were soiled with greenish yellow fecal material. Radiography indicated that the air sacs were thickened and that the liver and spleen were enlarged. The WBC count and serum aspartate transaminase activity were greatly above normal.

Direct complement fixation (DCF) for antibody activity against chlamydial antigen indicated a titer of 256; the titer by latex agglutination (LA) was 64.

Bacterial pathogens were not isolated aerobically from fecal specimens, and chlamydiae were not isolated from fecal material expressed from a swab of the cloaca; however, chlamydiae were isolated from a cloacal swab specimen collected the day after collection of the first swab. Chlamydiosis was diagnosed. The case was reported to the proper state health authorities. The owner of the parrot had the following questions for the attending veterinarian.

Q: What is the proper treatment for chlamydiosis?

A: Forty-five days of feeding chlortetracycline-medicated (1%) pellets. Commercial sources provide medicated feed in the form of pellets for large birds such as macaws, parrots, and cockatoos, antibiotic-impregnated seed for small birds such as cockatiels, lovebirds, and budgerigars, and liquid for nectar-eating species.

Q: Could the antibiotic be administered to the parrot's drinking water?

A: This is not recommended. Parrots do not consume enough medicated water to result in a therapeutic blood concentration of the antibiotic.

Q: What is a therapeutic blood concentration of tetracycline?

A: One microgram per milliliter of blood.

Q: Is there another antibiotic effective against Chlamydia that might be used on a single bird?

A: Yes. Doxycycline can be administered IV to severely ill birds for 1 or 2 days or it can be given orally twice daily for 18 to 20 days.

Q: If Chlamydia had not been isolated from fecal specimens of the parrot, would the DCF and IA results, clinical signs, and hematologic findings have been sufficient to diagnose chlamydiosis?

A: Probably. The DCF titer alone was of sufficient magnitude to indicate a current infection or a very early recovery stage of the disease.³ The titer detected by LA is even more indicative of a current infection.⁴

Q: Then, why culture for Chlamydia if serologic testing for Chlamydia is being done?

A: Because, early in the disease, antibody activity may not be detectable, but the organism may be isolated. Although a second (paired) serum sample could be collected and evaluated for antibody against C psittaci, this could require a 2- or 3-week delay in making a definitive diagnosis,³ whereas isolation of the organism (if isolated) could provide a definitive diagnosis earlier.

Q: Do all infected birds eventually develop high antibody titers?

A: Not necessarily. Individuals and species differ in the way they respond to chlamydial infection.^5,6

Q: Can one be assured that a particular bird does not have chlamydiosis when serologic and culture results are negative for Chlamydia?

A: Not entirely. A small percentage of birds may be culture-positive, but may not have detectable antibody activity.^3,4 That is one aspect that causes C psittaci infections to be such an enigma. Therefore, repeated culturing and serologic testing may be indicated when disease signs are consistent with chlamydiosis.

Q: How long do serologic titers against C psittaci persist?

A: Although DCF titers of 64 to 128 may persist for several months, LA titers usually decrease rapidly over a period of several weeks.^3,4

Q: Are antibody titers against Chlamydia still detectable after antibiotic treatment?

A: In some cases, antibody activity may decrease to an undetectable level. Normally, however, once the immunologic system has been stimulated, some antibody persists in serum, probably indefinitely.

Q: Were the clinical signs in my parrot specific for chlamydiosis?

A: No. Similar clinical signs may develop with other bacterial infections. Therefore, making a definitive diagnosis is essential to specifically treat the disease.

Q: Are there any factors that may aggravate chlamydial infections?

A: A subclinical infection may become a clinical infection if the bird is stressed by crowding during shipment, changes in environmental conditions or diet, or concomitant infections (especially with Salmonella spp).

Chlamydiosis in a pet shop situation

After public health authorities received the report of chlamydiosis in the parrot, personnel concerned with zoonotic diseases questioned the parrot's owner and learned that the bird had been purchased at a local pet shop. Evidence of chlamydiosis in the family members or friends of the bird's owner was not found.

The pet shop was found to be clean. The proprietor was conscientious about his responsibilities regarding public health and good business practices. Two cockatoos and 2 African gray parrots, 1 macaw, and 3 Amazon parrots were housed 1 or 2/large cage. The parrot in which chlamydiosis had been diagnosed had been kept in a cage with a red-headed Amazon parrot that subsequently was caged alone. A single large cage contained 10 cockatiels of various species. Twenty finches of various species were kept in one cage, 6 canaries were kept in another cage, and 2 mynah birds were kept in yet another cage. The various birds were purchased from local breeders and wholesalers who dealt with approved and inspected quarantine stations. Although the pet store owner had not noticed illnesses or deaths that could be attributed to chlamydiosis in the birds in his pet shop, the pet shop was quarantined (requiring cessation of selling birds until further notice). Blood was collected from all psittacine birds in the pet shop, and serologic tests for antibody against C psittaci were done. The red-headed Amazon parrot had a DCF titer of 64 and an LA titer of 16. The 2 Amazon parrots that were caged together did not have detectable antibody activity (ie, titers < 8). Of the 2 African gray parrots caged together, one (a new arrival) had a DCF titer of 8, whereas the other had a DCF titer < 8; both parrots had IA titers of < 8. One cockatoo had a DCF titer of 16 and the other cockatoo had a DCF titer of < 8; both cockatoos had IA titers of < 8. The blue and yellow macaw did not have detectable antibody titer by either testing method. Of the 10 cockatiels, 3 had DCF titers of 16, 2 had titers of 32, and 5 had titers of < 8. Antibody activity was not detectable by LA in the 10 cockatiel sera (titers < 8).

Chlamydiae were isolated from fecal specimens from the red-headed Amazon parrot caged alone and from pooled fecal specimens of the African gray parrots. Results of cultures of separate cloacal swabs from each African gray parrot indicated that the new arrival was shedding chlamydia. Chlamydiae were not isolated from pooled cockatiel fecal specimens.

All birds were treated for 45 days with chlortetracycline-medicated feed. Selling of birds was allowed if the buyer was given instructions to continue treating the bird with medicated feed provided by the pet shop owner The pet shop owner had the following questions for the public health veterinarian.

Q: Was it unusual for the red-headed Amazon parrot to have detectable antibody activity and to be shedding chlamydiae?

A: Not especially. Some birds are able to cope quite well with these infections, but may develop overt disease when severely stressed.

Q: Is a low DCF titer to Chlamydia ever indicative of a current infection?

A: Yes, it can be. A low DCF titer of 8 or 16 may be particularly important in African gray parrots and cockatiels,^3,4 but also may be important in other avian species. Therefore, paired serum samples from highly suspect birds with such low titers should be evaluated for antibody against C psittaci.

Q: If low DCF titers are important in cockatiels, why were chlamydiae not isolated from the cockatiels that were evaluated? Also, what about the low titer in the cockatoo?

A: The cockatiels may have been shedding so seldom or in such low numbers that the organism was missed; however, low titers (and even a moderate titer of 32) have been detected in cockatiels that have recovered from chlamydiosis and have ceased shedding chlamydiae. The low DCF titer in the cockatoo also may have been the result of a previous infection.

Q: Why were the finches, canaries, and mynah birds not serologically evaluated?

A: Although susceptible to C psittaci, these birds are somewhat like sentinels and probably would die acutely rather than develop infections of long duration.

Q: Why did the smaller, nonpsittacine birds not become infected?

A: Chlamydia psittaci is considered to be primarily aerosol transmitted. Therefore, a lack of strong air currents in the pet shop may have been a factor. Infection also is dose dependent. Because the cages were kept clean, feces did not accumulate and dry thereby precluding aerosolization of the organism.

Q: What is the best disinfectant for treating Chlamydia-contaminated material and objects?

A: Quaternary ammonium compounds are the disinfectants of choice. Although hypochlorite (bleach) is chlamydiacidal, it is caustic to certain metals, and the chlorine is toxic for animals.

Q: Are birds kept in quarantine stations for the prescribed time (45 days) and provided with chlortetracycline-medicated feed free of chlamydial infections?

A: Not necessarily. Medicated feed made available to birds ad libitum is not always eaten. Wild-caught birds often will not accept unfamiliar food. If a bird with subclinical infection is stressed during shipment, the bird's immunologic system may become suppressed. This enables the numbers of C psittaci to increase in the bird, resulting in illness, particularly if the bird does not consume enough medicated feed to develop an anti-infective blood concentration of the antibiotic. Therefore, despite quarantine and provision of medicated feed, some infected birds can enter the pet trade.

Q: Is it possible for a buyer to determine when birds are sick from chlamydial infections?

A: Not always. A sick bird sometimes is considered to be tame by an unsuspecting potential pet owner. However, a wholesaler or retailer should be aware that the bird is sick and should not sell an infected bird while hoping that the bird will live beyond the short guarantee period.

Chlamydiosis in a bird breeding operation

The breeding operation that supplied cockatiels to the pet shop provided well-kept housing for budgerigars, cockatiels, and lovebirds. The operation was family-owned and -operated, with some extra hired help. Although the various kinds of birds were housed separately, the flight cages were in close proximity with each other. The owners exercised good husbandry, but were not always strict in caretaking when manpower was low.

Sick birds were kept together in small cages, separate from the breeding pairs. Often, sick birds were treated by trial and error, using various antibiotics until an effective antibiotic was found. The practice of administering antibiotics in the drinking water was considered unacceptable.

When questioned about illness in any of the workers, the owner stated that his adolescent son had been hospitalized with a respiratory tract problem and had been treated successfully by a physician. Also, one of the hired workers had a chronic cold that would worsen at times and then improve. A suggestion was made that the hired worker be examined by a physician for possible chronic chlamydiosis.

The owners indicated that several birds (especially nestlings) had died, but the owners considered the deaths to be a routine occurrence in raising these birds. Examination of the birds indicated that most of the birds were healthy, except for a few obviously ill cockatiel fledglings. These sick fledglings were evaluated serologically for Chlamydia. One fledgling had DCF and LA titers of 16, and C psittaci was isolated from a fecal specimen from this bird. Another sick cockatiel had a DCF titer of 128 and an LA titer of 32, and C psittaci was isolated from its feces. The remaining sick cockatiels had low titers (8 to 32), but C psittaci was not isolated from their feces. A few sick budgerigars and lovebirds were not evaluated serologically; however, C psittaci was isolated from pooled cloacal swab specimens from these birds.

The breeder agreed to treat his birds with chlortetracycline and asked the public health veterinarian the following questions.

Q: Is chlamydiosis unusual in a domestic avian-breeding facility?

A: No. Such facilities are a continuous source of chlamydiae.

Q: If a group of breeding birds does not have chlamydial infection, what can be done to keep them Chlamydia-free?

A: Great care should be taken to prevent the potential introduction of the organism by wild birds. Even more important, new breeder birds should not be introduced into the breeding group unless it can be ascertained that they are free of infection. In addition, other bird raisers should not be allowed on the premises, and all workers should stay away from other bird-breeding facilities.

Q: Are all human cases of chlamydiosis alike? Why would one person have to be hospitalized and another person have a less severe but chronic illness?

A: As with birds, all people do not respond the same to C psittaci. Differences in response may be attributable to biologic differences in susceptibility, dosage, or the pathogenicity of different strains of chlamydiae.

Discussion

Chlamydia psittaci is a common inhabitant of psittacine birds that probably can be controlled to a great extent by a cooperative effort of all concerned. Individual birds and different species of birds respond differently to C psittaci. This is attributable in part, to differences in the pathogenicity among isolates. Definitively diagnosing chlamydiosis in an individual bird may be difficult. In addition to standard techniques for isolation of Chlamydia, a peroxidase-antiperoxidase method can be used to detect Chlamydia in tissues.⁷

Chlamydia psittaci is a potentially serious public health hazard. Human populations in England and Norway may have become colonized with C psittaci allowing for person-to-person transmission of C psittaci.^8,9 A human-adapted C psittaci can cause pneumonia in people.¹⁰ Nevertheless, transmission of C psittaci from birds to man should not be ignored because of the sequelae that may develop as a consequence of untreated infections.

References

1. Grimes JE. Enigmatic psittacine chlamydiosis: results of serotesting and isolation attempts, 1978 through 1983, and considerations for the future. J Am Vet Med Assoc 1985; 186:1075-1079.

2. Grimes JE. Chlamydia psittaci infections of pet and other birds in the United States in 1984. J Infect Dis 1986; 153:374-375.

3. Grimes JE. Direct complement fixation and isolation attempts for detecting Chlamydia psittaci infection of psittacine birds. Avian Dis 1985; 29:873-877.

4. Grimes JE. Chlamydia psittaci latex agglutination antigen for rapid detection of antibody activity in avian sera: comparison with direct complement fixation and isolation results. Avian Dis 1986; 30:60-66.

5. McDonald SE, Bayer EV. Psittacosis in pet birds. Calif Vet 1981; 35:6-17.

6. Mohan R. Epidemiologic and laboratory observations of Chlamydia psittaci infection in pet birds. J Am Vet Med Assoc 1984; 184:1372-1374.

7. Moore FM, Petrak MS. Chlamydia immunoreactivity in birds with psittacosis: localization of chlamydiae by the peroxidase-antiperoxidase method. Avian Dis 1985; 29:1036-1042.

8. Bruu A, Aasen LS, Tijaland S, et al. An outbreak of ornithosis in Norway in 1981. Scand J Infect Dis 1984; 16:145-152.

9. Nagington J. Psittacosis/ornithosis in Cambridgeshire 1975-1983. J Hyg (Camb) 1984; 92:9-19.

10. Grayston JT, Kuo CC, Wang SP, et al. A new Chlamydia psittaci strain, TWAR, isolated in acute respiratory tract infections N Engl J Med 1986; 315:161-168.

Addendum (1994)

The first method of testing recommended in cases of avian chlamydiosis is serologic, because of the newly developed and evaluated elementary body agglutination (EBA) test, which detects IgM activity in birds with Chlamydia psittaci infections whether the birds are ill or clinically normal.^1-3 The EBA is used in conjunction with an improved latex agglutination (LA) method, which detects only IgG activity.⁴ Direct complement fixation (DCF) detects only IgG activity, and is most useful for identifying birds that have had chlamydial infections in the past, when results of EBA and LA tests are negative (titer < 10).⁴ Determination of leukocyte count or serum liver enzyme activities, or both may be helpful in association with serologic tests.

For confirmation of infection, chlamydial culture of or antigen-detection ELISA on choanal slit/oropharyngeal swab specimens is recommended rather than testing of fecal samples or cloacal swab specimens.^a This may be most important in the early stage, when antibody activity may be undetectable and in the case of clinically normal birds that have antibody activity indicative of infection.

Some clinically normal birds maintain titers, as detected by EBA, LA, and DCF tests, for inordinately long periods.^1,2,5 Such cases may require determination of leukocyte count or serum liver enzyme activities, or use of culture or antigen-detection ELISA to rule out chlamydial infection. The long-term maintenance of titer seems to be directly related to the titer attained before chlamydiastatic antibiotics are administered or before spontaneous resolution of infection. Presently, this phenomenon remains an enigma.

For confirmation of chlmaydiosis in dead birds, direct microscopic examination of Gimenez-stained touch impressions of spleen and liver capsular surfaces, antigen-detection ELISA on splenic and hepatic parenchymal swab specimens, or use of both methods is recommended. Culture and histologic examination should be done in unusual situations, especially in the case of determining new avian hosts. A positive culture result is incontrovertible. The latest known avian hosts of C psittaci in North America are the ratites, especially the rheas, in which sudden death is attributable to a "pigeon-like" strain.

Test results in cockatiels sometimes are questionable when a diagnosis of chlamydial infection is attempted, and use of multiple methods may be required.¹⁶ Recent publications have pointed out some of the problems (and possible answers to those problems) encountered in using some of the recently developed test methods.^17,18

Footnote

(a) Anderson AA. Comparison of fecal, cloacal, and oral samples for the diagnosis of chlamydiosis (abstr). Proc Annu Meet Am Assoc Vet Lab Diagn 1988; 55.

References

1. Grimes JE, Arizmendi F. Elementary body agglutination: A rapid clinical diagnostic aid for avian chlmamydiosis, in Proceedings. Annu Conf Assoc Avian Vet 1993; 30-40.

2. Grimes JE. Interpretation of avian host chlamydial titers using various serologic methods. Semin Avian Exotic Pet Med 1993; 2:161-166.

3. Grimes JE, Tully TN Jr, Arizmendi F, et al. Elementary body agglutination for rapidly demonstrating chlamydial agglutinins in avian serum with emphasis on testing cockatiels. Avian Dis 1994; (in press).

4. Grimes JE, Phalen DN, Arizmendi F. Chlamydia latex agglutination antigen and protocol improvement and psittacine bird anti-chlamydial immunoglobulin reactivity. Avian Dis 1993: 37:817-824.

5. Grimes JE, Arizmendi F. Bases for interpretation of chlamydia serology results, in Proceedings. Annu Conf Assoc Avian Vet 1992; 59-71.

6. Grimes JE, Arizmendi F. Serology, culture, and antigen capture in the diagnosis of chlamydial infections in psittacine birds, in Proceedings. Annu Conf Assoc Avian Vet 1990; 272-282.

7. Ley DH, Flammer, K, Cowen P, et al. Performance characteristics of diagnostic tests for avian chlamydiosis. J Assoc Avian Vet 1994; 7:203-207.

8. Brown PA, Newman JA. Diagnosis of avian chlamydiosis: Questions, answers, questions, in Proceedings. Annu Conf Assoc Avian Vet 1992; 42-47.