Model of sanitary management for the eradication of bovine herpesvirus 1 (HVB-1) in a dairy herd

Abstract

This paper describes the efficacy of sanitary management on the eradication of HVB- 1 by means of hyperimmunization, that consists in infected animals vaccination in order to decrease the level of viral reactivation in carriers. Seroneutralization in microplates was the technique used for HVB-1 diagnosis in a dairy herd bred extensively. In the first year of the studies the occurrence of seroreagents older than six month old was 44.5% (166/373). After that, other evaluations were performed in non-reagents cows and calves. From the second year on, hyperimmunization was performed every six months on seropositive animals older than six months of age, using the inactivated monovalent vaccine with oily adjuvant. The greatest occurrence of seroreagents was observed in older animals in productive and reproductive phases. The rate of seroreagents decreased with the gradual culling of these animals, and three years after the establishment of the sanitary program, the number of seroreagents decreased to zero. In the first year, incidence was equal to 0.5% (2/371), in the second year, 0.8% (3/387), and was zero in the third year. Calves born from seroreagent cows became non-reagent after the disappearance of colostral immunity. Annual reduction in the number of reagent animals was due to the culling of seropositive females, substituted by non-reagent heifers. Fight against HVB-1 by monitoring non-reagent individuals, hyperimmunization and progressive culling of seroreagents, associated with other prophylactic procedures, such as the use of virus-free semen and animal traffic control made gradual culling of infected animals a rational procedure until eradication was completed.