Understanding Avian Chlamydiosis

Cause

Chlamydia psittaci is an obligate intracellular bacterium that can infect a wide range of bird species, including domesticated and wild birds. It is a zoonotic pathogen, meaning that it can be transmitted from animals to humans. The bacterium can survive in the environment for long periods and can be transmitted via the respiratory route, ingestion of contaminated material, or direct contact with infected birds or their droppings.

Significance

Avian chlamydiosis is a significant disease of birds and humans worldwide. In birds, the disease can cause respiratory disease, conjunctivitis, and systemic illness, leading to weight loss, diarrhea, and death. In humans, the disease can range from mild flu-like symptoms to severe pneumonia and can be fatal in some cases. Psittacosis is a notifiable disease in many countries, meaning that it is a reportable disease to health authorities.

Species Affected

Avian chlamydiosis affects a wide range of bird species, including pigeons, parrots, canaries, finches, and poultry. The disease is more prevalent in birds that are kept in captivity or in close proximity to humans,  such as pet birds or birds kept in aviaries or poultry farms. Urban areas where birds are likely to gather around food sources are particularly likely to spread chlamydiosis which represents only one of several risks for wild birds in urban areas.

Distribution

Chlamydia psittaci is a globally distributed pathogen, and avian chlamydiosis has been reported in many countries worldwide. The disease is more common in areas with high bird density or where birds are kept in close proximity to humans. This includes zoos where many wild birds also deal with the stress of captivity which can lead to a compromised immune system.

Transmission

Transmission of avian chlamydiosis can occur via the respiratory route, ingestion of contaminated material, or direct contact with infected birds or their droppings. Birds that are carriers of the bacterium can shed it in their droppings for extended periods, making environmental contamination a potential source of infection. Humans can become infected with the bacterium via inhalation of contaminated dust or droplets, direct contact with infected birds or their secretions, or ingestion of contaminated food or water.

Clinical Signs

In birds, the clinical signs of avian chlamydiosis can vary from mild respiratory disease to severe systemic illness. The disease can cause conjunctivitis, nasal discharge, coughing, sneezing, and diarrhea. Birds may also exhibit lethargy, anorexia, and weight loss. In severe cases, the disease can cause death. In humans, the clinical signs of psittacosis can range from mild flu-like symptoms to severe pneumonia. Other symptoms may include headache, fever, chills, and muscle aches.

Diagnosis

Diagnosis of avian chlamydiosis can be challenging, as the clinical signs can be similar to those of other respiratory diseases. Laboratory testing is required for a definitive diagnosis. The most commonly used diagnostic test is PCR, which can detect the presence of the bacterium in swab or tissue samples. Serological testing can also be used to detect antibodies to the bacterium in blood samples. In humans, a diagnosis of psittacosis can be confirmed with serological testing or PCR of respiratory secretions.

Treatment

Treatment of avian chlamydiosis involves the administration of antibiotics, such as doxycycline or azithromycin. Treatment should be initiated early in the course of the disease to increase the chances of recovery. In birds, treatment may need to be continued for several weeks to ensure complete eradication of the bacterium. Infected birds should be isolated and treated, and their environment should be thoroughly cleaned and disinfected to prevent further spread of the disease.

In humans, the treatment of psittacosis involves the administration of antibiotics, such as tetracycline or doxycycline. Treatment should be initiated early in the course of the disease to prevent complications, and hospitalization may be required in severe cases. Patients with psittacosis should be advised to avoid contact with birds and their droppings during treatment and until complete recovery.

Management

Prevention of avian chlamydiosis involves good husbandry practices, including regular cleaning and disinfection of bird cages, aviaries, and poultry farms. Birds should be kept in well-ventilated areas, and handlers should use appropriate personal protective equipment, such as masks and gloves. It is also essential to identify and isolate infected birds and to monitor the health of bird populations to detect outbreaks early.

Closing

In conclusion, avian chlamydiosis is a significant disease of birds and humans worldwide and it’s one of several respiratory illnesses affecting wild birds. It is caused by the bacterium Chlamydia psittaci, which can infect a wide range of bird species and can be transmitted to humans. The disease can cause respiratory disease, conjunctivitis, and systemic illness in birds and can range from mild flu-like symptoms to severe pneumonia in humans. Diagnosis of avian chlamydiosis can be challenging, and laboratory testing is required for a definitive diagnosis. Treatment involves the administration of antibiotics, and infected birds should be isolated and their environment thoroughly cleaned and disinfected.

Prevention of avian chlamydiosis involves good husbandry practices and early detection of outbreaks. By understanding the cause, significance, species affected, distribution, transmission, clinical signs, diagnosis, treatment, and management of avian chlamydiosis, we can work together to prevent and control this important disease.

Sources

1. World Organisation for Animal Health. (2020). OIE terrestrial manual: Psittacosis (Chlamydophila psittaci). https://www.oie.int/en/what-we-do/standards/codes-and-manuals/terrestrial-manual-online-access/
2. Centers for Disease Control and Prevention. (2018). Psittacosis. https://www.cdc.gov/pneumonia/atypical/psittacosis.html
3. Kaleta, E. F., & Taday, E. M. (2003). Avian host range of Chlamydophila spp. based on isolation, antigen detection and serology. Avian Pathology, 32(5), 435-461. doi: 10.1080/03079450310001593697
4. Stewardson, A. J., Grayson, M. L., & Korman, T. M. (2014). Psittacosis. Infectious Disease Clinics of North America, 28(1), 103-115. doi: 10.1016/j.idc.2013.10.002
5. Ley, D. H. (2010). Chlamydiosis in birds: A review with emphasis on zoonotic implications. Avian Diseases, 54(2), 479-497. doi: 10.1637/8910-043009-Review.1