Bovine respiratory syncytial virus: infection dynamics within and between herds

Abstract

The infection dynamics of bovine respiratory syncytial virus (BRSV) were studied in randomly selected Norwegian dairy herds. A total of 134 herds were tested twice, six months apart. The herds were classified as positive for BRSV if at least one animal between 150 and 365 days old tested positive for antibodies against BRSV, thereby representing herds that had most likely had the virus present during the previous year. The prevalence of positive herds at the first and second sampling was 34 per cent and at 41 per cent, respectively, but varied greatly between regions. Negative herds were found in close proximity to positive herds. Some of these herds remained negative despite several new infections nearby. Of the herds initially being negative, 42 per cent changed status to positive during the six months. This occurred at the same rate during summer as winter, but a higher rate of animals in the herds was positive if it took place during winter. Of the herds initially being positive, 33 per cent changed to negative. This indicates that an effective strategy to lower the prevalence and the impact of BRSV could be to employ close surveillance and place a high biosecurity focus on the negative herds.

Bovine respiratory syncytial virus and bovine coronavirus antibodies in bulk tank milk – risk factors and spatial analysis

“…The study region was selected as it was believed it would contain a mix of BTM positive and negative herds. The large variation in prevalence across regions is in agreement with a study performed by Klem et al (2013).…”

“…The overall apparent prevalence of seropositive herds in the study area was 46.2% for BRSV and 72.2% for BCoV, which is low compared to reports worldwide (Paton et al, 1998;Uttenthal et al, 2000;Ohlson et al, 2010). This is also lower than estimates from previous studies in Norway using serologic methods (Gulliksen et al, 2009;Klem et al, 2013). The present study classified herds according to detection of antibodies measured in a milk sample taken from the BTM.…”

“…Serology of individual animals, either using milk or blood samples, can give a more recent picture of the herds' infection history than BTM samples, depending on the age and number of animals sampled. (Ohlson et al, 2009;Klem et al, 2013). The ideal method for classifying herds with respect to detecting virus circulation would be to detect the virus; however, this is demanding on a larger scale (Klem et al, 2013).…”

“…(Ohlson et al, 2009;Klem et al, 2013). The ideal method for classifying herds with respect to detecting virus circulation would be to detect the virus; however, this is demanding on a larger scale (Klem et al, 2013).…”

“…Previous studies in Scandinavia have indicated large variations in prevalence of BRSV and BCoV between regions (Elvander, 1996;Tråvén et al, 1999;Beaudeau et al, 2010a;Klem et al, 2013), but spatial analyses involving BRSV and BCoV infections are infrequently reported. For control-and eradication purposes, locating high and low risk areas is important in order to know which control strategies should be applied to different regions.…”