Two protocols of hyperimmunisation through marker vaccines reduce the incidence of seroconversion against the bovine herpesvirus 1 in dairy livestock: results of a field study.

A 28 months long cohort study was organized in dairy herds in Belgium, to assess the efficacy of hyperimmunisation as a tool for the control of infectious bovine rhinotracheitis. Two protocols of hyperimmunisation in which glycoprotein-E deleted marker vaccines were repeatedly administered were compared to a positive control group in which the usual vaccination protocols were authorised. The two hyperimmunisation protocols differed in the primovaccination : the first group was treated with an attenuated vaccine firstly given intra-nasally then by intramuscular route whereas the second group was given an inactivated vaccine by subcutaneous injection. Afterwards, booster vaccinations were the same in both groups : an inactivated vaccine was administered by subcutaneous route every 6 months. In the control group, as a rule, part of the herd was vaccinated annually. For each group, 6 half-yearly reports specify : 1. the evolution of the population, categorized by birth half-year, 2. the incidence of seroconversion against gE in the cohorts and 3. the evolution of the gE seroprevalence. The survival curves of the hyperimmunised groups show a significantly higher proportion (P < 0,001) of animals remaining seronegative against glycoprotein- E compared to the positive control group. No significant difference was shown between the two protocols of hyperimmunisation. Both of them could then be used as tools for the control of infectious bovine rhinotracheitis