Psittacosis

Psittacosis—also known as parrot fever, and ornithosis—is a zoonotic infectious disease in humans caused by a bacterium called Chlamydophila psittaci and contracted from infected parrots, such as macaws, cockatiels, and budgerigars, and from pigeons, sparrows, ducks, hens, gulls and many other species of birds. The incidence of infection in canaries and finches is believed to be lower than in psittacine birds. Psittacosis—also known as parrot fever, and ornithosis—is a zoonotic infectious disease in humans caused by a bacterium called Chlamydophila psittaci and contracted from infected parrots, such as macaws, cockatiels, and budgerigars, and from pigeons, sparrows, ducks, hens, gulls and many other species of birds. The incidence of infection in canaries and finches is believed to be lower than in psittacine birds. In certain contexts, the word is used when the disease is carried by any species of birds belonging to the family Psittacidae, whereas 'ornithosis' is used when other birds carry the disease. In humans, after an incubation period of 5–19 days, the symptoms of the disease range from inapparent illness to systemic illness with severe pneumonia. It presents chiefly as an atypical pneumonia. In the first week of psittacosis, the symptoms mimic typhoid fever, prostrating high fevers, joint pains, diarrhea, conjunctivitis, nose bleeds, and low level of white blood cells. Rose spots called Horder's spots can appear. Spleen enlargement is common towards the end of the first week. It may become a serious lung infection. Diagnosis can be suspected in case of respiratory infection associated with splenomegaly and/or epistaxis. Headache can be so severe that it suggests meningitis and some nuchal rigidity is not unusual. Towards the end of the first week, stupor or even coma can result in severe cases. The second week is more akin to acute bacteremic pneumococcal pneumonia with continuous high fevers, headaches, cough, and dyspnea. X-rays show patchy infiltrates or a diffuse whiteout of lung fields. Complications in the form of endocarditis, liver inflammation, inflammation of the heart's muscle, joint inflammation, keratoconjunctivitis (occasionally extranodal marginal zone lymphoma of the lacrimal gland/orbit), and neurologic complications (brain inflammation) may occasionally occur. Severe pneumonia requiring intensive-care support may also occur. Fatal cases have been reported (less than 1% of cases). Blood analysis usually shows a normal white cell count, but marked leukocytosis is occasionally apparent. Liver enzymes are abnormal in half of the patients, with mild elevation of AST. The erythrocyte sedimentation rate and C-reactive protein can be markedly elevated. Differential diagnosis must be made with typhus, typhoid, and atypical pneumonia by Mycoplasma, Legionella, or Q fever. Exposure history is paramount to diagnosis.Diagnosis involves microbiological cultures from respiratory secretions of patients or serologically with a fourfold or greater increase in antibody titers against C. psittaci in blood samples combined with the probable course of the disease. Typical inclusions called 'Leventhal-Cole-Lillie bodies' can be seen within macrophages in BAL (bronchoalveolar lavage) fluid. Culture of C. psittaci is hazardous and should only be carried out in biosafety laboratories. The infection is treated with antibiotics; tetracyclines and chloramphenicol are thchoice for treating patients. Most people respond to oral therapy doxycycline, tetracycline hydrochloride, or chloramphenicol palmitate. For initial treatment of severely ill patients, doxycycline hyclate may be administered intravenously. Remission of symptoms is usually evident within 48–72 hours. However, relapse can occur, and treatment must continue for at least 10–14 days after fever subsides. Psittacosis was first reported in Europe in 1879. In 1929, a highly publicized outbreak of psittacosis hit the United States. Although not the first report of psittacosis in the United States, it was the largest up to that time. It led to greater controls on the import of pet parrots. The aftermath of the outbreak and how it was handled led to the establishment of the National Institutes of Health.