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BRSV spread in cattle can be controlled
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A study published this week in the journal Veterinary Record from a research group in the Norwegian School of Veterinary Science suggests that the prevalence of respiratory diseases in cattle could be controlled. The study examined incidence of infection of cattle herds in Norway with the bovine respiratory synctial virus (BRSV), which is a major cause of respiratory infection in cattle.

BRSV is an enveloped, negative sense, single-stranded RNA virus of the pneumovirus genus and Paramyxoviridae family. Alone, this virus causes severe disease in calves. It also predisposes calves to secondary infections with bacteria including Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, resulting in bovine respiratory disease complex. This is the major cause of feed-lot cattle morbidity and mortality. It is reckoned it can cause losses to the cattle industry approaching $1 billion annually, with deaths to cattle along with reduced feeding efficiency, reproductive impact and milk production loss, as well as costs of vaccinations and treatments. On an immunological level, BRSV infection inhibits the CD8 T cytotoxic cell response and promotes a Th2 response, which can in turn further dampen the Th1 response. There have been some promising developments in terms of safe, stable, attenuated virus vaccine candidates. However, the epidemiology and evolution of the virus and the mechanisms by which it establishes infection are not fully understood.

The current Norwegian study looked at 134 herds. The herds were tested twice at intervals of six months and were classified as BRSV-positive if at least one animal between 150 and 365 days old tested positive for antibodies against BRSV. While the prevalence of positive herds at both samplings was high, at 34 per cent and 41 per cent, respectively, there was variation between regions. Importantly, negative herds were found in close proximity to positive herds and some of these remained negative even when new infections arose nearby, implying that it is possible to avoid herd infection even in proximity to infected herds nearby. In addition, one third of the herds that originally tested positive managed to get rid of the virus and tested negative on the next test.

The authors of the study suggest that prevalence and impact of BRSV could be reduced by employing effective surveillance of herds and putting a high biosecurity focus on the negative herds. Research on mechanisms of BRSV infection are therefore even more imperative.

Sources

GERSHWIN, L.J., 2012. Immunology of bovine respiratory syncytial virus infection of cattle. Comparative immunology, microbiology and infectious diseases, 35(3), pp. 253-257

KLEM, T.B., GULLIKSEN, S.M., LIE, K.- I. , LOKEN, T.,OSTERAS, O., and STOKSTAD, M., 2013. Bovine respiratory syncytial virus: infection dynamics within and between herds. Veterinary Record, 2013; DOI: 10.1136/vr.101936

SACCO, R.E. et al., 2013. Respiratory Syncytial Virus Infection in Cattle. Veterinary pathology, 2013

SARMIENTO-SILVA, R., NAKAMURA-LOPEZ, Y. and VAUGHAN, G., 2012. Epidemiology, molecular epidemiology and evolution of bovine respiratory syncytial virus. Viruses, 4(12), pp. 3452-3467

Norwegian School of Veterinary Science. "The prevalence of colds and pneumonia in cows can be controlled." ScienceDaily, 5 Nov. 2013. [Accessed 7 Nov. 2013]
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BRSV spread in cattle can be controlled - by mtwalsh01 - 11-08-2013, 05:26 AM
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