ABSTRACT
A purified concentrated BHV1 antigen that had been tested in field trials was also tested under isolated conditions in BHV1 positive and negative cattle. The antigen proved to act specifically even after storage for 2 years at +4 degrees C or for 6 months at 37 degrees C. The best results were obtained when the test was read 48-72 hours after the injection, which is in agreement with the field trials. The increase in skin thickness decreased unless boosted by infection or vaccination gradually. The test is unsuitable to control a vaccination programme. There was no correlation between the increase in thickness and humoral antibody titers. Repeated application of the intradermal injection of the antigen did not result in seroconversion in seronegative cattle. The biological limits of the test evaluation are discussed.
Subject(s)
Herpesvirus 1, Bovine/isolation & purification , Infectious Bovine Rhinotracheitis/microbiology , Intradermal Tests/veterinary , Skin Tests/veterinary , Animals , Cattle , Enzyme-Linked Immunosorbent Assay , Neutralization TestsABSTRACT
An intradermal test (delayed hypersensitivity test) for the diagnosis of BHV1 infection was evaluated in 791 cattle of 16 dairy farms. The skin reactions were compared with the results of serological examinations using a commercial BHV1 ELISA kit (Trachitest). As antigen concentrated, purified and inactivated BHV1 was used. The skin reaction (increase of the skin fold thickness) was used for the interpretation of test results. The best results were obtained with the control of the skin reaction on the third day after injection of the antigen. From 393 serologically BHV1 negative cattle with an age of more than 6 months 391 (99.5%) had a skin reaction up to 1.0 mm and 2 animals (0.5%) had a reaction of 1.3 and 1.9 mm, respectively. The mean increase of skin fold thickness was 0.2 mm. Out of 291 serologically BHV1 positive cattle with an age of more than 6 months 270 had antibodies from natural infection and, partially, from additional vaccination with inactivated BHV1 vaccine. 266 (98.5%) of these animals showed a skin reaction of more than 2.0 mm, in 3 animals (1.1%) a skin reaction up to 1.0 mm was observed and 1 animal (0.4%) had a reaction of 2.0 mm. The mean increase of the skin fold thickness was 6.3 mm. 21 animals had BHV1 antibodies only because of vaccination with inactivated BHV1 vaccine. Only 4 animals had a skin reaction of more than 2.0 mm. Among 107 animals with an age up to 6 months 30 were serologically BHV1 positive and 77 were BHV1 negative. In all animals the skin reaction was less than 1.0 mm, the mean was 0.2 mm.
