Abstract

The San Diego Wild Animal Park (SDWAP) has maintained a very popular, public interactive exhibit with a flock of free-flighted rainbow lorikeets (Trichoglossus haematodus haematodus) since 1995. In October 1999, the exhibit featured 59 rainbow lorikeets. Following the death of two lorikeets due to Clostridium perfringens, six birds were selected at random for health examination. Each bird was tested for C. perfringens and opportunistically sampled for zoonotic and psittacine-specific diseases as per our disease surveillance protocol. Fecal samples from all birds were negative for C. perfringens enterotoxin by ELISA (IDEXX Veterinary Services, Inc., West Sacramento, CA, USA). One of the six birds was positive for Campylobacter jejuni and was treated successfully using oral erythromycin (EryPed 400 oral suspension, Abbott Laboratories, North Chicago, IL, USA) at 10 mg/kg, twice daily for seven days. Birds were negative for polyomavirus and psittacine beak and feather disease virus by DNA probe of heparinized whole blood (Research Associates Laboratory, Inc., Milford, OH, USA). Two of the six birds were positive for Chlamydophila psittaci (formerly Chlamydia psittaci) by DNA probe of heparinized whole blood (Research Associates Laboratory, Inc.).⁴

All birds were re-sampled 7 days later with a triad of C. psittaci tests. Serum was submitted for elementary body agglutination (EBA) antibody titer (Texas Veterinary Medical Diagnostic Laboratory, College Station, TX, USA); heparinized whole blood for C. psittaci by DNA probe (Research Associates Laboratory, Inc.); and a combination cloaca/choanal swab for C. psittaci by DNA probe (Research Associates Laboratory, Inc.).

The four originally negative birds were negative on the triad of tests. The two originally positive birds were once again found to be positive for C. psittaci DNA in whole blood and for DNA in the combination orifice swab. These birds were separated and immediately placed on treatment using oral doxycycline (Vibramycin oral suspension, Pfizer, Inc., New York, NY, USA) at 50 mg/kg mixed into fluid nectar once daily for 45 days.² Avian chlamydiosis (AC) is a reportable zoonotic disease^7,8; therefore, local veterinary public health officials were contacted immediately.

The remaining 53 birds in the exhibit were screened using the same triad of C. psittaci tests. Twenty-seven birds (51%) were positive for at least one of the C. psittaci tests; 22 (82%) were positive by DNA in the combination orifice swab only; two (7%) were positive for EBA antibody only; one (4%) was positive by DNA in whole blood only; and two (7%) were positive on the EBA antibody and DNA combination orifice swab. Therefore, a total of 29 of 59 (49.2%) lorikeets in the flock were positive for AC by one of the tests. A decision was made to close the exhibit to the public until further notice and local public health officials were contacted again.

The laboratory results and treatment protocols obtained from the two originally positive lorikeets during the 45-day doxycycline treatment period (study 1) are summarized in Table 1. These birds had elevated white blood cell (WBC) counts on the first day of treatment but normal aspartate aminotransferase (AST) and creatinine kinase (CK) levels.¹ Creatinine kinase levels remained normal (150–350 IU/L) for the duration of treatment. On the tenth day of treatment both birds had significantly elevated AST, and high normal WBC count. Hepatocellular damage due to doxycycline toxicity seemed a more likely explanation for the elevated AST than C. psittaci infection. In response, the total daily dose of doxycycline was divided to 25 mg/kg twice daily.

Table 1. Laboratory results of two rainbow lorikeets on oral doxycycline for treatment of avian chlamydiosis

^aVibramycin®, doxycycline oral suspension, placed in fluid nectar
^bWhite blood cell count/µL; normal 6,000–14,000
^cAspartate aminotransferase, IU/L; normal 130–280
^dBile acids, µmol/L; normal 20–65
^ePositive for C. psittaci by DNA probe of whole blood and combination orifice swab
^fNegative for C. psittaci by EBA antibody, DNA probe of whole blood and combination orifice swab

Since evidence of hepatocellular damage continued on the seventeenth day of treatment, the daily dose of doxycycline was decreased to one-half of the original, or 25 mg/kg once daily. On the thirty-sixth day of treatment, bile acid levels were significantly elevated.¹ On the thirty-eighth day of treatment, liver biopsies from both birds revealed hepatocellular dissociation and multinucleation with mild bile duct hyperplasia, suggestive of a toxic insult. Histologic lesions suggestive of chlamydiosis were not seen. A swab of the liver biopsy site was submitted for C. psittaci DNA probe analysis (Research Associates Laboratory, Inc.) but was negative. Aspartate aminotransferase (AST) levels were still significantly elevated on the forty-fourth day of treatment, 1 day before the last treatment. The birds remained clinically normal throughout the treatment. Following treatment, both birds’ bile acid and AST levels returned to normal and they were negative on the triad of C. psittaci tests.

A study using three different doxycycline doses was conducted to further evaluate the safety and efficacy of this antibiotic in the remaining 27 positive birds (study 2). Ten birds in treatment group A received 25 mg/kg doxycycline orally twice daily; six birds of group B received 25 mg/kg once daily; and 11 birds in group C received 12.5 mg/kg twice daily. Medication was mixed in the fluid nectar and fed individually for 45 days. Two birds from each treatment group served as principals and were sampled prior to treatment and on days 7, 14, 21, 28, 35, 42 and 6 days following completion of treatment.

The hematologic and biochemistry results of the principal birds in each treatment group of study 2 were similar to the two birds in the study 1. Each bird had a normal AST level prior to treatment which increased significantly during treatment and returned to normal levels post-treatment. All birds remained clinically normal for the duration of the study.

Post-treatment, 24 (89%) of the 27 birds were negative on the triad of tests; three (11%) were positive on at least one of the tests. Two of 10 (20%) birds in group A and one of six (17%) birds from group B remained positive. These three lorikeets were euthanatized. Necropsy and histopathology of tissues did not reveal lesions consistent with C. psittaci or hepatotoxicity.

Preliminary observations from these studies:

1.  Routine testing of birds in free-contact, public aviaries for zoonotic diseases is highly recommended. Management staff must understand the zoonotic disease potential of this type of animal interactive exhibit.

2.  Diagnosis of AC remains difficult despite numerous diagnostic methods available.^3-6 Sensitivity and specificity of tests are problematic, and interpretation of results are often equivocal and open to criticism. A combination of tests is recommended.

3.  Treatment of AC with oral doxycycline at published doses appears to cause hepatocellular damage as seen by elevated AST and bile acid levels as well as on liver biopsy in rainbow lorikeets. Further investigation is necessary to better define pathogenesis.

4.  The management of AC, and other zoonotic diseases, in a flock of public contact birds necessitates an aggressive, sound, and diplomatic response due to public health implications as well as the safety of other susceptible avian species in the collection.

Literature Cited

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8.  Smith, K.A., M. Eidson, W.B. Johnson, and M.G. Stobierski. 2002. Compendium of Measures to Control Chlamydophila psittaci (formerly Chlamydia psittaci) Infection among Humans (Psittacosis) and Pet Birds, 2002. National Association of State Public Health Veterinarians (NASPHV). American Veterinary Medical Association website at www.avma.org.