An evaluation of an intradermal test for the diagnosis of bovine herpesvirus type 1 (BHV-1) infection in cattle.

An intradermal (ID) test (a delayed-type hypersensitivity test) was used for the diagnosis of BHV-1 infection in cattle. A threshold value for the test positive results was established based on the analysis of the agreement between the results of ID test and those of virus neutralization (VN24) assay. Linear regression analysis revealed no correlation between the intensity of the skin reaction (expressed as an increase in skin-fold thickness) and the VN24 antibody titre. The sensitivity and specificity of the ID test compared to VN24 one, were 86.6% and 98.3% respectively. Of the 487 cattle with an age of over 6 months, 25 (5.1%) reacted discordantly by ID and VN24 tests, i.e. 19 seropositive animals expressed little or no skin reaction, whereas 6 seronegative individuals were positive by ID. Neither of the calves, with passively acquired antibodies in contrast to experimentally infected ones, showed distinctive skin reaction.