Study may show how bluetongue virus survives winter

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A virus that sickens and kills ruminants may survive winter in temperate regions by reproducing inside female midges, according to a recent scientific article.

During the past two winters, researchers at the University of California-Davis found viable bluetongue virus inside female Culicoides sonorensis midges that appeared to have fed on infected dairy cattle in Northern California. The results were published Sept. 12 in the article “Seasonal and interseasonal dynamics of bluetongue virus infection of dairy cattle and Culicoides sonorensis midges in northern California—implications for virus overwintering in temperate zones” in the online journal PLoS One.

The report and a related announcement from UC-Davis indicate that the study results could solve a century-old mystery, help in predicting bluetongue’s occurrence, and help in controlling the disease.

The article authors state that it has been unclear how the bluetongue virus, also listed in the report as BTV, persisted during winter months that restricted vector activity and reproduction.

“For the first time, this study documented the presence of BTV RNA of parous female C sonorensis midges collected during the interseasonal period in 2013 and again in 2014, which potentially explained the mechanisms for overwintering of BTV on this farm,” the article states.

The study began in August 2012 and concluded in March 2014. Bluetongue virus infections typically occur in temperate zones of the Northern Hemisphere from July through November.