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Avian Chlamydiosis

Ornithosis, Psittacosis, Parrot Fever, Louisiana Pneumonitis, Chlamydophilosis

Avian chlamydiosis is a bacterial disease caused by the Chlamydia genus, which is well known for its high zoonotic potential for infection in huamns. The genus are widely distributed throughout the world, and known to contain 11 species, each having it's own specific range of hosts. Ducks are most commonly infected with C. ornithosis and C. psittaci. Ducks infected with C. psittaci most often develop enteric disease or act as subclinical carriers, displaying no signs of disease. Whether symptoms develop in ducks depends on the virulence of the chlamydial strain and immune status of the bird.

C. psittaci are most commonly spread to ducks through ingestion or inhalation of the organism from contaminated environments, feed, or water. Contamination occurs from carriers (infected or recovered birds that shed the organism within their feces, nasal or eye secretions). In some cases, ducks can get infected but display no clinical signs of being infected, however they will still shed C. psittaci in their feces. C. psittaci is very hardy and is able to survive in the environment, including airborne particles and dust, for several months. They can also be transmitted through respiratory secretions and fecal material of infected birds. Many birds are often asymptomatic carriers (meaning they are infected and regularly shed the bacteria in their feces, however show no clinical signs of infection.


Body tremors
Loss of appetite
Nasal discharge
Eye discharge
Weight loss
Yellow to greenish diarrhea
Ruffled feathers
Unthrifty appearance


  • History
  • Clinical signs
  • Fluorescent antibody
  • CI
  • Immunohistochemistry
  • ELISA - detection of antigens
  • Histopathology


MethodMethod Summary
Supportive careIsolate the bird from the flock and place in a safe, comfortable, warm location (your own duck "intensive care unit") with easy access to water and food. Limit stress. Call your veterinarian.
Doxycycline (Vibramycin)400-800 mg/L drinking water, made fresh daily for 21 days or 25-50 mg/kg PO q12-24h, for 21 to 45 days
Doxycycline (Vibravenos)50-100 mg/kg SC, IM q5-7d x 5-7 doses
Oxytetracycline2500 mg/L drinking water and 2500 mg/kg feed

Reported Cases

  • Case 1: Chlamydiosis in a Finch In May 2018, avian chlamydiosis was diagnosed in a 1-year-old male Gouldian finch at the Turlock Branch of the California Animal Health and Food Safety Laboratory System. The bird belonged to an outdoor aviary with mixed avian species, including Gouldian finches, doves, and psittacines. Severe respiratory distress and mortality were noted among the finches. Gross and histopathologic lesions were concentrated in the liver and spleen, with a mild involvement of the upper respiratory tract. Chlamydia spp. were detected in the spleen and kidney by real-time PCR and were further confirmed by immunohistochemistry. Subsequently, Chlamydia psittaci was isolated from the liver and spleen and characterized as a CP3-like strain (genotype B). In addition, viral particles compatible with circovirus were identified in the liver by direct electron microscopy. Ref

  • Case 2: Avian chlamydiosis in a Parrot A two-year-old Congo African grey parrot was examined since the bird had shown clinical signs of anorexia, depression, diarrhea, and mild dyspnea and based on biochemical and hemathological analysis the bird was diagnosed as having anemia, leukocytosis, heterophilia, lymphopenia and monocytosis. With regards to clinical and paraclinical findings, the case was diagnosed to be carrying Chlamydiophila spp. In addition, choanal cleft and cloaca swabs were positive for Chlamydiophila spp. in a diagnostic polymerase chain reaction (PCR) (600 bp amplicon). Polymerase chain reaction products were typed by ompA gene-based PCR, using CTU/CTL primers (1050 bp amplicon). The PCR product sequence was compared with the sequences obtained from GenBank. The phylogenetic tree has revealed 100% identity with genotype B obtained from previous studies. The bird was hospitalized and treated with doxycycline regimen for 45 days, with a weekly sampling process to trace the presence of C. psittaci DNA in faecal and choanal swabs, this process continued to the point where the specimens turned negative after two weeks. Laboratory and radiology results were within normal limits after the treatment. Genotype B is predominantly isolated from Columbidae and there have not been any reports regarding the clinically affected African gray parrot with this genotype. Ref

  • Case 3: Avian chlamydiosis in a Turkeys Chlamydiosis affecting only the nasal glands was observed in less than 1% of 24-week old turkey hens in a flock of 5,000 birds. The disease was clinically manifested by mild to moderate swelling above the eyes and was diagnosed based on FAT, PCR and immunohistochemistry. They killed the birds to prevent it from spreading. Ref

  • Case 4: Avian chlamydiosis in a Turkeys Ornithosis caused swelling over the eyes in 13-week-old, female turkeys. Ten percent of 36,000 birds were affected. Histologically, there was nasal gland inflammation and chlamydia was detected only in the nasal gland by immunohistochemistry and fluorescent antibody (FA) testing. The birds were otherwise healthy. Testing of wild pigeons on a neighboring farm confirmed the presence of chlamydia by FA. Ref

  • Case 5: Avian chlamydiosis in a Penguin An outbreak of Chlamydophila psittaci occurred in an outdoor colony of 63 Magellanic penguins at the San Francisco Zoo. Affected penguins presented with inappetence, lethargy, and light green urates. Hematologic and serum biochemical findings were consistent with chronic inflammation. Penguins did not respond to initial supportive and antimicrobial therapy, and 3 died. Necropsy results of the 3 birds revealed hepatomegaly and splenomegaly, and histologic lesions included necrotizing hepatitis, splenitis, and vasculitis. Chlamydophila psittaci infection was confirmed by results of Gimenez staining, immunohistochemistry, and tissue polymerase chain reaction assay. As additional birds continued to present with similar clinical signs, the entire colony of penguins was prophylactically treated with a 30-day minimum course of doxycycline, administered orally or intramuscularly or as a combination of both. Despite treatment, 9 additional penguins died during a 3-month period. Pathologic results from these birds revealed renal and visceral gout (n = 4), cardiac insufficiency (n = 2), sepsis from a suspected esophageal perforation (n = 2), and no gross lesions (n = 1). During the outbreak, 4 birds presented with seizures, 5 developed dermatitis, and nearly 90% of birds in the colony showed severe keratoconjunctivitis, believed to be related to drug therapy with doxycycline. We report the clinical and pathologic features of Chlamydophila psittaci infection in an outdoor colony of penguins and the associated challenges of treatment. Ref

  • Case 6: Conjunctivitis and rhinitis in a Duck Chlamydia psittaci was isolated from the eyes of domestic ducks with conjunctivitis and rhinitis. Ref


  • Quarantine any new birds
  • Don't mix Psittaciformes (cockatoos, parrots, parakeets, and lories) or Columbiformes (pigeons and doves) with ducks or house in the same location.


Risk Factors

  • Exposure to Psittaciformes (cockatoos, parrots, parakeets, and lories) or Columbiformes (pigeons and doves)
  • Recently adopted a bird who was kept in an area where Psittaciformes (cockatoos, parrots, parakeets, and lories) or Columbiformes (pigeons and doves) are also kept.