a1 Clinic for Poultry, Hannover School of Veterinary Medicine, Bünteweg 17, 30559 Hannover, Germany
Chlamydiosis of domestic poultry (chickens, pheasants, guinea fowl, quail, ducks, geese, and turkeys) is reviewed with emphasis on psittacosis as an occupational disease. The article covers literature from 1940 to 1994. The potential risks of transmission of C. psittaci from poultry to man are discussed, and clinical diseases caused by C. psittaci infection in man are briefly reviewed. Ducks, sometimes without clinical signs, and turkey flocks usually conspicuous for ornithosis during transport or processing, are the most likely sources for poultry transmitted psittacosis. Isolation of the chlamydia, both from man and birds, is the best method for confirmation of the diagnosis. In humans an easier, but less reliable, way is the demonstration of a significant titre rise in properly spaced paired serum samples combined with clinical symptoms. False positive results can occur with the complement fixation test (CFT) commonly used. It has to be remembered that there is a high prevalence of antibodies to different Chlamydia spp. in the population, and that the genus-specific antigen used in the CFT recognizes antibodies to all these pathogens and antibodies resulting from prior infections. More specific serological tests should be favoured, and highly sensitive and specific DNA detection methods, currently mostly used in research, will probably replace tests like the CFT. Case reports of outbreaks of the disease especially among poultry plant workers are compared. With awareness of the problem, employees knowing the clinical signs of psittacosis both in poultry and man, modern abattoir machinery, good sanitary conditions, and early treatment with effective drugs when necessary, the disease risks can be minimized.