[Mycobacterium avium infections in poultry--a risk for human health or not?]

Avian tuberculosis is an animal disease notifiable for statistical purposes in Germany. Cases notified (between 130 and 230 annually) were primarily related to private flocks of pedigree poultry and layers consisting of less than 20 animals and individual animals in game enclosures and zoological gardens. Mycobacterium (M.) avium infection does not play any role in modern intensive poultry husbandry. Human M. avium infections have considerably gained in importance in the last two decades, mainly in HIV-infected patients. Due to the ubiquitous character of MAIC (Mycobacterium avium intracellulare-Complex), it is difficult to establish confirmed epidemiological associations with infections in humans. Surface and drinking water, soil and also foods as well as direct contact with infected birds (pet birds) have been discussed as possible sources of infection. Recently, strains of the serovars 1, 2 and 3 which have often been isolated from birds (bird-type strains) could be defined as a taxon on its own right among MAIC by using molecular-biological methods for MAIC typing (RFLP--restriction fragment length polymorphism and PFGE-pulsed field gel elektrophoresis). In exceptional cases only, strains of this character have been isolated from humans. Consequently, poultry-to-man transmission of M. avium appears to be a very improbable event. In contrast, extensive conformity has been found to exist between M. avium isolates of human origin and isolates from pigs. This fact has rightly given rise to assumptions of either the presence of epidemiological links between pigs and humans or of infection from common sources. In a summarizing view, it can be stated that M. avium infection of farm poultry is hardly of any importance for poultry production as well as for human disease. The importance of MAIC for infections in other farm animals (cattle and swine) is outlined and discussed.