EN
Virologic examinations to detect the BHV 1 and seroogical studies to determine the titre of anti BHV 1 antiodies and the content of serum immunoglobulins were lone on bulls aging 2—4 and 6—10 months naturally nfected with BHV 1 and showing clinical symptoms of he respiratory tract inflammation. For control healthy .nimals uninfected were included. It was found that bulls nfected with BHV 1 excrete the virus for a relatively ong time (42-—56 days). In some animals the SN titres 1:2—1:8 were noted only in some periods of studies, respectively of the age of bulls serum content of IgGt nd IgG increased and IgG. decreased. The level of IgM nd IgA was stable and it was not related to the age of nimals.