The calibration, control and use of a diluted bovine tuberculin (PPD) for testing cattle in areas free from tuberculosis.

In order to reduce the number of the so-called non-specific reactors of cattle in areas attested to be free from tuberculosis a 500 IU dilution of polysorbate-stabilized bovine PPD has been produced since 1971. This dilution is the result of field trials in such an area. The preparation is standardized according to the Requirements for Tuberculins. The stability of each batch is controlled in comparison with a lyophilized reference preparation during the whole time of its use. The use of this diluted tuberculin was regulated by instructions of our national veterinary authority in 1971 and 1975 as follows: Use only for testing cattle in areas where all herds have been attested free from tuberculosis for 2 years or more, not to be used on cattle for sale or in comparative tests. Maximal interval between tuberculin treatment 1 year. Notice of each reaction. Documentation according to the regulations of veterinary law of the GDR. Depending on the kind and level of mycobacterial sensitization in a definite area and on the mode of keeping cattle, the number of cross reactors has been reduced as a rule to 1/3 by the use of the diluted bovine PPD in comparison with the normal mammalian PPD "Dessau".