Psittacosis: Avian Infection Transmittable to Humans

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A large number of human infections are airborne and cause diseases of the respiratory tract. One of these is psittacosis, actually an avian infection that is transmitted to humans by way of the respiratory route. Some mammals also may harbor the agent.

The causative organisms belong to the genus Chlamydia; they are completely dependent upon actively metabolizing host cells for growth and produce elementary bodies in reticuloendothelial (relating to the mononuclear phagocyte system) cells.

In humans, psittacosis (also known by three other names: chlamydiosis, ornithosis, or parrot fever) develops after an incubation period which varies from seven to fourteen days. When transmitted to humans, psittacosis produces symptoms that may be confused with atypical pneumonia, pneumonia, or typhoid fever. These include headache, fever, chills, sore throat, dry cough, loss of appetite, and muscle pain.

The onset of psittacosis is rapid, and its symptoms may appear suddenly or gradually. Usually in psittacosis, the lungs develop a spotty consolidation. Convalescence, with possible relapses, usually begins after about three weeks of the disease; but in extreme cases, death may occur instead.

While psittacosis is rare among children, it is common among poultry workers and those who handle pets. The virus is carried by dust particles and can be inhaled by any individual in contact with an infected bird. Diagnosis of suspected cases of human psittacosis can be confirmed by injecting mice with sputum or throat washings. The complement-fixation test can be used to determine increase in antibody titer in specimens of blood serum taken at five-day intervals after the onset of symptoms.

The history of the infected individual’s association with infected birds is useful in interpreting the clinical signs. Control of psittacosis in humans depends on regulation of trade to ensure that only healthy birds are sold. This is important especially since most human cases of psittacosis originate from close contact with birds. The possibility that caged birds will harbor or spread the disease-causing organisms can be reduced by feeding them with antibiotics.

Poultry workers who may be exposed to the organisms can minimize the risk of infection by working in sanitary, well-ventilated establishments. Spread of psittacosis from person to person is prevented by proper sanitation and hygienic practices.

Inasmuch as some cases of human psittacosis are serious, the care of the infected individual should be directed by a physician. Certain antibiotics, such as the tetracyclines, provide excellent results, as in treating the disease and in eliminating the organisms from the body.

It is preferable to have the infected person in a hospital. If the person is cared for at home, treatment is similar to that for pneumonia. This includes strict bed rest, simple remedies for relief of symptoms, fomentations to the chest (done morning and evening), and oxygen inhalations as indicated.


1. “Psittacosis in Pet Birds and People” by Lianne McLeod, DVM, Exotic Pets

2. “Psittacosis/ Chlamydiosis/ Ornithosis/ Parrot Fever”, on

3. “Psittacosis (ornithosis, parrot fever, chlamydiosis)”, on the New York State Department of Health (online)


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