The Occurrence of Mycobacteriosis in Free-Living Birds at Different Epizootological Situation of Poultry Tuberculosis

Veterinarni Medicina 38, 1993, 305-317

The occurrence of tuberculosis in free-living birds was studied in relation to a certain epidemiological situation in a long-term study from 1966 to 1990. A total of 3210 birds were examined. Mycobacteria were isolated in five cases from free-living birds in the environment of six poultry rearing farms where tuberculosis was found in domestic fowl. At individual localities, the occurrence of mycobacteria was 3.5 - 50.0 %. Generalized tuberculosis was found in one case in house sparrow (Passer domesticus). On the investigated poultry rearing farms, the distribution of tuberculosis infection in free-living birds was directly related to the distribution and stage of tuberculosis in poultry or to the achieved extent of eradication. On a poultry rearing farm where no mycobacteria were isolated from free-living birds, a successful eradication of tuberculosis by flock exchange was in progress. During the examination of free-living birds on three farms, mycobacteria were found at two localities where poultry infected with tuberculosis was kept either on the farm or in its immediate vicinity. On the third farm, where no mycobacteria were found in free-living birds, only sporadic reactors to tuberculin were found during survey in spatially separated flocks. No mycobacteria were isolated from birds examined on two farms in whose vicinity poultry was not reared at all. Similarly, bacteriological cultures were negative in a group of 298 birds examined during five years in the environment of a poultry enterprise farm free from tuberculosis. No mycobacteria were found in a large group of 2303 free-living birds taken in the wild except four rooks (Corvus frugilegus). However, this is a migratory species which is noted for its considerable longevity. It is thus more probable that these birds were infected outside the locality which the specimens were taken from. Out of the isolated strains of mycobacteria that were further examined by a biological experiment, 86.6 % were pathogenic to domestic fowl, serotype M. avium 2. The results of these examinations suggest that the presence of tuberculosis-infected poultry as a major source of M. avium is necessary for the infection of free-living birds. The infectious agent apparently does not persist and spread within the flocks of free-living birds

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