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Conference abstract2008

Prevalence and geographic distribution of BRSV and BCV in dairy herds in two neighbouring veterinary districts in Sweden

Ohlson, Anna; Tråven, Madeleine; Emanuelson, Ulf; Alenius, Stefan

Abstract

The purpose of this study was to investigate the prevalence of antibodies to bovine respiratory syncytial virus (BRSV) and bovine corona virus (BCV) in dairy herds in two neighbouring veterinary districts in Sweden, and to explore the association between antibody status and some herd characteristics. Forty-one herds were sampled from district A and 38 from district B. A pooled milk sample from five primiparous cows and bulk tank milk (BTM) was obtained from each herd and analysed for IgG antibodies to BRSV and BCV with an indirect ELISA. The location of the herds was mapped using a geographical information system. Data on herd size, artificial insemination (AI) strategy, breed and milk production were accessed from the Official Milk Recording Scheme. We used chi-square test to analyse prevalence and t-test to analyse herd size differences. To analyse milk production we used a linear regression model correcting for breed and herd size. The seroprevalence for BRSV in the pooled samples was 83% in district A and 73% in district B. For BCV the prevalence was 61% and 55% in district A and B, respectively. Ten herds were negative for both BRSV and BCV. The prevalence in BTM was 95.1% for BRSV in district A and 92.1% in district B, and 100% for BCV in district A and 81.6% in district B. None of the herds were antibody negative to both viruses in BTM. There were no differences in herd size and milk production between positive and negative herds, both with respect to the pooled sample and the bulk tank milk. Negative herds were located in close proximity to positive, indicating that airborne transmission between herds is not of great importance for these infections and that it is possible to stay negative although virus is circulating in the area. Another interesting finding is that there were significantly (p<0.01) more herds using professional AI-technicians rather than AI performed by farm personnel amongst the herds negative to BCV both with respect to the pooled sample and bulk tank milk. In fact all seven herds negative to BCV in BTM used external AI-technicians. This suggests that it is possible to avoid infection although having regular visitors in the herd

Conference

World Buiatrics Congress, WBC XXV