Occurrence of Mycobacteria in Sawdust, Straw, Hay and Their Epizootiological Significance

Pa vias, M., Patlokova, Vlasta: Occurrence of Mycobacteria in Sawdust, Straw, Hay and Their Epizootiological Significance. Acta vet. Bmo, 54, 1985: 85-90. The occurrence of mycobacteria in sawdust and straw used as bedding material in cattle and pig herds was investigated using 147 sawdust and straw samples from 47 farms. The most important epizootiological finding was the demonstration of nine strains of Mycobacterium intracellulare (serotypes 4, 6, 8 and 9) and of one strain of Mycobacterium avium (serotype 1) in samples of sawdust and wood shavings, which accounted for a quarter of all these samples examined, no matter whether they were collected directly in wood-processing plants or from stores on the farms. In view of the virulence of M. intracellulare for pigs, in which active excretion is very rare, the aforementioned bedding material should be regarded as one of the most important sources of mycobacteriosis in pigs. A large number of atypical avirulent mycobacteria found in straw and hay suggests that this bedding material and roughage may be involved in the occurrence of non-specific reactions to avian or possibly mammalian tuberculin particularly in cattle. Atypical mycobacteria, bedding material, swine mycobacteriosis. The current favourable situation as to bovine tuberculosis in farm animals in our country suggests that a majority of sources of Mycobacterium bovis have been eliminated. A comprehensive investigation into the causes of reaction to mammalian and avian tuberculins in cattle, pigs and other farm animals showed that most importance among individual pathogenic mycobacterial species should be ascribed to Mycobacterium avium and atypical mycobacteria with biological and chemical properties similar to those of avian mycobacteria. These atypical mycobacteria are, for the most part, of low virulence for a majority of farm animal species. Horizontal transmission of these mycobacteria is therefore very rare and is limited to a very short period of time after infection. The importance of a typical mycobacteria emerges from the results of tuberculin testing in cattle in Czechoslovakia in 1979 where specific reaction was shown by 125 animals (17.8 per cent) out of 700 positive reactors to mammalian PPD tuberculin on 8 farms in 6 districts. On the other hand, the reactions to mammalian PPD tuberculin in 575 cattle in 34 districts were found to be caused not by Mycobacterium bovis, but by Mycobacterium avium or atypical mycobacteria present in the environment. According to Kuker and Zettl (1964), Beer:werth and Popp (1971), Kauker and Rheinwald (1972, Kleeberg and Nel (1973) the major source of mycobacteria involved in the tuberculosis in pigs is sawdust. The presence of mycobacteria in bedding was also pointed out by Piening et al. (1972) who isolated 67 strains, three of them having the properties of M. avium, from sawdust used as bedding for pigs. Beerwerth and Popp (1971), studying the mode of contamination of sawdust with mycobacteria, demonstrated a majority of group III and group IV atypical mycobacteria in samples originating from wood that had laid in wood stores for a considerable length of time before pro~ cessing. On examination of 225 sawdust samples collected at local saw mills they isolated 3 strains of Mycobacterium intracellulare serotype 8 which is most important for pigs from the epizootiological point of view. Group III mycobacteria having the properties of M. intracellulare serotypes