A field trial with a multicomponent inactivated respiratory viral vaccine.

An inactivated virus vaccine containing strains of parainfluenza type 3 (PI3), bovine adenovirus type 3, reovirus type 1, bovine virus diarrhoea (BVD) and infectious bovine rhinotracheitis (IBR) viruses was tested in a group of 58 calves reared in a semi-intensive management system. Following vaccination, 1/30, 14/30 and 17/30, showed significant rises in antibody titre to reovirus type 1, adenovirus type 3 and IBR respectively. None of the animals showed significant serological response to PI 3 and BVD. In the control group, 2/28, 1/28, 6/28 and 3/28 developed antibody responses to reovirus type 1, BVD, adenovirus type 3 and IBR respectively. Microbiological examination revealed the presence of a wide variety of commensal bacteria and Mycoplasma bovirhinis in both groups. Analysis of the records of clinical examinations indicated that the respiratory tract infections occurred among the calves at between 50 and 80 days after arrival at the farm, and that there was no significant difference between the test and the control groups. A number of animals had maternal antibodies to the various components of the vaccine present before the trial commenced and these antibodies appeared to interfere with the subsequent serological response to the antigen challenge. The vaccination schedule recommended by the manufacturer does not entirely circumvent this problem.