An intradermal test for the diagnosis of BHV-1 infection. The effect of repeated testing on the immune status of cattle.

The effect of the repeated delayed-type hypersensitivity (DTH) testing (an intradermal test--ID) on virus neutralizing (VN) antibody and DTH responses has been studied. Repeated intradermal injection of inactivated BHV-1 antigen elicited neither the virus neutralizing antibody nor positive skin reaction in cattle free from BHV-1 infection. On the other, hand, the same manipulation carried out in a herd infected with BHV-1 provoked seroconversion and/or positive DTH reaction in some of the animals without detectable pre-existing VN antibody. Cattle initially positive by VN and intradermal tests showed steady increase in antibody titre, and some of them developed little or no skin reaction following repeated DTH testing.