Implementation of surveillance programme for bovine respiratory syncytial virus (BRSV) and bovine corona virus (BCoV) in the Norwegian cattle population

Bovine respiratory syncytial virus (BRSV) is the dominating cause of veterinary-treated disease among calves, and an important cause of antimicrobial use in dairy herds. Bovine coronavirus (BCoV) is a widely distributed pathogen, causing respiratory disease and diarrhea in calves and winter dysentery in adult cattle (Oma et al., 2016). Both BRSV and BCoV are considered widespread among cattle in Norway and worldwide. These two viral diseases have a negative impact on animal welfare, growth rate, feed utilization, reproduction performance, milk quality and use of antibiotics (Klem et al., 2016). A voluntary control-programme was therefore launched in 2016 by a joint cattle industry. The control programme is based on classification of herds as positive or negative based on antibodies against BRSV and BCoV, using a multiplex antibody ELISA (MVD-Enferplex BRSV/BCoV multiplex). Initial classification of dairy herds is based on bulk tank milk (BTM) testing, while pooled serum samples of young stock (4 individuals over 6 months of age) are used in beef herds or for follow-up samples in dairy herds with a positive BTM test. The current classification of all herds is available through the Norwegian Dairy Herd Recording Scheme (NDHRS). The core principle of the programme is to protect negative herds from introduction of virus through biosecurity measures. Negative herds are encouraged to only purchase animals from other negative herds. Animals from negative and positive herds are transported separately, and truck-drivers are encouraged to not enter the barn at pick-up. All producers are encouraged to have biosecurity barriers in place and must provide boots and change of clothes for visitors, including veterinarians. The aim of this thesis was to give an overview of the control programme of BRSV and BCoV in Norway with focus on the occurrence of herds testing negative and positive today