EN
The value of different methods used for isolation and identification of parainfluenza (PI-3) virus and infectious bovine rhinotracheitis (IBR) virus was compared. The following tests were used for the diagnosis of infections: the haemadsorption (Had), haemagglutination (Ha) and immunofluorescence (IF) tests and cytopathic effects on infected calf kidney cell cultures. In the IF test, preparations made of undiluted and diluted nasal discharge, its sediment and supernatant after centrifugation were used. This test proved to be useful method for the early diagnosis of pneumotropic viral infection in cattle. The main causative factor in these infections was PI-3 virus.