Avian Zoonoses: beyond Avian Flu

PSITTICOSIS Also known as parrot fever and ornithosis, psittacosis is caused by Chlamydophila psittaci, an obligate intracellular bacterial infection of birds that can cause severe pneumonia and other serious disease in humans (on average 250 reported cases per year in the US). Most cases resulted from exposure to infected pet birds, (cockatiels, parakeets, parrots, and macaws). Infected birds shed bacteria through feces and ocular/nasal discharges. Disease in humans is called psitticosis, parrot fever, or ornithosis. In a survey conducted by this author of 100 households with infected birds, humans only suffered disease in two households. Apart from exposure to infected pet birds, other persons at risk include pigeon fanciers and employees in poultry slaughtering and processing plants; veterinarians and technicians; zoo, laboratory and avian quarantine employees; farmers; game-keepers; and wildlife rehabilitators. Humans can be infected from brief, passing exposure to infected birds or their excretions so infection can arise from brief contact with an infected bird, eg, in a shop, zoo, or restaurant, where contact was so short that the patient has forgotten it. This problem is compounded as patients are often ‘confused.’ Person-toperson transmission has been suggested but not proven. Onset of illness typically follows an incubation period of 5 to 14 days (longer periods have been reported). Disease ranges from subclinical to systemic illness with severe pneumonia. Disease is fatal in less than 1% of properly treated humans; however, where a diagnosis is not made and no appropriate antimicrobials are provided, fatality levels can reach 15% to 20%. Human patients demonstrate sudden onset fever, headache, malaise, and myalgia. They usually develop a nonproductive cough that can be accompanied by breathing difficulty and chest tightness. Splenomegally, and a nonspecific rash are sometimes observed and are suggestive of psittacosis in patients with communityacquired pneumonia. The differential diagnoses include Coxiella burnetii, Mycoplasma pneumoniae, Legionella spp, other Chlamydiaceae, and respiratory viruses, eg, influenza. Chlamydophila psittaci can also endocarditis, myocarditis, hepatitis, arthritis, keratoconjunctivitis, and encephalitis. Severe illness with respiratory failure, thrombocytopenia, hepatitis, and fetal death has been reported among pregnant women.