PREVALENCE OF BOVINE VIRUS DIARRHEA (BVD) IN 19 DANISH DAIRY HERDS AND ESTIMATION OF INCIDENCE OF INFECTION IN EARLY-PREGNANCY

A survey of all cattle in 19 Danish dairy herds with unknown status of bovine virus diarrhoea virus (BVDV) infection showed that 1.4% of the animals were persistently infected with BVDV. Persistently infected animals were detected in ten herds (53%), in numbers varying from one to ten animals per herd. The prevalence of neutralizing antibody-seropositive animals in herds with one or more persistently infected animals was 87%, whereas the prevalence in herds without persistently infected animals was 43%. Seropositive animals were found in all herds. There was a logarithmic relationship between age and prevalence of seropositive animals. The theoretical risk of fetal infections occurring during the first 3 months of pregnancy was estimated to be 3.3%, close to the observed prevalence (2.9%) of persistently infected animals less than 1 year of age.