[Characterization of strains of Bordetella bronchiseptica isolated from animal housing air and of the airborne infection pressure proceeding from them].

Strains of B. bronchiseptica were isolated from the air in farrowing and weaned piglet houses within the framework of follow-up investigations in an intensive pig breeding and fattening farm with 2600 productive sows. The strains were tested for their biological properties. The results show that virulent B. bronchiseptica-strains have been present as an aerosol in the air of both husbandry systems which refers to the infectious pressure of the animal house air. The number of isolated strains of B. bronchiseptica increases during both rearing phases of piglets. The toxin-forming ability of the strains from weaned piglet houses is higher in comparison with such from farrowing houses. This is a proof for the increasing infectious pressure during the rearing period. One has to take the transmission of virulent strains from animal houses with older pigs to such with younger one into account in case of a common air space. This could result in a lower impact of disinfection during the servicing period. The morbidity rate of atrophic rhinitis could be reduced by 60% in consequence of the application of a B. bronchiseptica-live vaccine. P. multocida couldn't be found neither on nasal mucous membrane nor in animal house air over the whole investigation period. All results as a whole point out that within the framework of the elaboration of a strategy for atrophic rhinitis control in pig houses with a high animal density one has to pay more attention to virulent B. bronchiseptica-strains in addition to toxinogenous strains of P. multocida.