Evaluation of the economic impact and description of a BRSV-outbreak in a dairy herd

Abstract: Bovine respiratory syncytial virus (BRSV) is globally one of the most important causes of respiratory disease in beef and dairy cattle of all ages and results in considerable costs for cattle farmers and significant suffering for the affected animals. The BRSV-infection can be subclinical to severe, and even fatal. There is no effective treatment and no commercially available vaccine that induces satisfying duration of protection, though promising vaccine candidates are under development. In addition to treatment costs and animal loss BRSV is associated to reduced production, such as reduced growth, reduced milk yield and fertility disorders. The virus can be transmitted directly and indirectly by respiratory secretion. Spread between and within herds is often rapid. The contagious nature of the virus together with its severe impact on animal welfare and economy necessitate effective preventive measures. To develop cost-efficient prevention strategies against BRSV evaluation of the economic impact caused by the virus is necessary. This study aimed to estimate the economic impact of BRSV by analyzing the short-term costs associated to a BRSV-outbreak in a Swedish dairy herd. The parameters investigated were veterinary care, drug treatment, diagnostic tests, milk production, death and extra labor. The sum of the estimated budget items was 71,464 SEK, which rounded corresponded to 130 SEK per animal housed in the farm during the outbreak, or 270 SEK per cow. Out of the investigated costs milk loss (23,234 SEK, 32,5%), death (21,000 SEK, 29,4%) and extra personnel (17,112 SEK, 23,9%) were the three major budget items (61,346 SEK, 85,8%). Veterinary cost (2656 SEK, 3,7%), medicine costs (5399 SEK, 7,6%) and costs for diagnostic tests (2063 SEK, 2,9 %) were comparably small costs (10,118 SEK, 14,2%). Due to the possible long-term consequences such as reduced growth and reproduction disorders not being included, the estimated sum of 71,464 SEK is most likely an underestimation of the true cost for the farm. The estimated cost in this study is an example of the short-term economic impact of a BRSVoutbreak. By seemingly small changes of an outbreak’s characteristics the economic impact can change greatly. The investigated outbreak in the present study was for example characterized by relatively low mortality, 0,37%. In literature outbreaks of up to 20 % mortality are described. The clinical illness in the present herd was also relatively low, which was explained mainly by high inter-herd biosecurity and overall good cattle management and air quality resulting in minimized viral exposure and consequently less severely affected animals. The economic estimations and the epidemiologic observations presented in this study are in agreement with other papers emphasizing the economic impact and animal suffering of BRSV. Further, the epidemiologic observations presented in this study indicates that decreased feed consumption and decreased milk yield can be used as early warning signs of an upcoming BRSV-outbreak. In conclusion more research is needed to gain broader and more in-depth knowledge about the economic impact of BRSV, both for different kinds of herds and in terms of long-term economic consequences.