Psittacosis infections associated with livestock and human

  11 April 2022

By Ofeh Augustine Seun


Psittacosis is a zoonotic infectious disease caused by the bacterium Chlamydophilia Psittaci formerly known as  Chlamydia psittaci. They are obligate, intracellular, aerobic, gram-negative like organism that is usually coccoid to rod shape morphologically. They have some virus and bacteria characteristics. This infection affects birds Such as pigeons, ducks, parrots, etc

Mode of transmissions.

In Humans: Infections occur when a person inhales the organism which has been aerosolized from dried feces or respiratory secretions of infected birds. The infection can also be acquired by the bite of infected birds and the handling of infected birds’ plumage and tissue. Person-to-person transmission has been suggested but not proven, it occurs during acute illness with paroxysmal cough.

In Birds: The organism is excreted in feces and nasal discharges of  infected birds. The organism is environmentally labile but can remain infectious for several months if protected by organic debris such as litter and feces. Shedding can be activated by stress factors such as relocation, overcrowding, malnutrition, etc. Some birds have a latent infection but shed the organism intermittently.


It was first reported in Europe in 1878 among pet store owners. Chlamydophilia psittaci  can infect 465 avian species in 30 avian order Psittaciformes. From 1988 through 2003 a total of 935 human cases of infection were reported by the United State Center for Disease Control and Prevention. The mortality rate for untreated psittacosis range from 15 to 20% but after the administration of antibiotics the mortality rate is less  by 1 or 2%. The incidence of psittacosis in men seems to be increasing in industrialized countries because they involve in the importation of exotic birds.


In Birds: Chlamydophilia psittaci strain infects mucosal epithelial cells and macrophages of the respiratory tract. Septicemia eventually develops and the bacteria are localized in the epithelial cells and macrophages of most organs and the Gastrointestinal tract (GIT).

In Humans: When a person inhales the organism, the lungs’ defense mechanism attempt to neutralize them. The bacteria that avoided this defense starts causing infection. The incubation period is 5 to 19 days after entering the respiratory tract. The bacteria are transported to the cells of the liver and spleen. They multiply rapidly with these cells and then invade the lungs, where they cause inflammation, hemorrhaging, pneumonia, and hepatitis.

Signs and symptoms.

In Humans: Fever, myalgia, chills, malaise, and headache

In Birds: The signs in birds depend on the following: Species of birds, Virulence of the strain, age of birds, and stress factors

The signs include: Lethargy, Anorexia, Diarrhea, Ruffled fever, serious Or mucopurulent nasal discharge


Diagnosis can be undertaken using the polymerase chain reaction(PCR). It can also be diagnosed using a direct fluorescent antibody test.


In Birds: Doxycycline and tetracycline are used for treating infected birds. They are present drugs of choice. Doxycycline can be administered in the following way. Orally administered doxycycline, doxycycline medicated water, injectable doxycycline.

 In Humans: Tetracycline is used for treating infected humans. The drug is administered orally.

Prevention and control: 

Protect birds from undue stress such as chilling, unnecessary relocation, poor husbandry, and malnutrition. Sick birds may consume inadequate an amount of medicated food or water, so they should be initially treated with medication delivered directly by mouth or by injection. Observe the birds daily and them weigh for 3 to 7days. If there is a reduction in n weight call the attention of a veterinarian. Isolate birds that are to be treated in clean and uncrowded cages.


Since there is no vaccine against Psittacosis, pet birds owner free use tetracycline and doxycycline for treatment or prevention of respiratory disease. Thus, a vaccine and information on the sensible use of antimicrobial drugs in Psittaciformes are needed to prevent psittacosis in humans and the development of drug-resistant bacteria strains. Good husbandry practices should be followed to prevent opportunistic infections. Good husbandry practices such as cleaning up all spilled food promptly, and washing food and water container daily.

What is going on with AMR?
Stay tuned with remarkable global AMR news and developments!

Keep me informed