The reemergence of Bluetongue in Europe may have been caused by 'human activities' such as storing frozen bull semen samples, according to new research.
Bluetongue virus (BTV) is transmitted by midge bites and affects cattle, goats, sheep and other camelids such as llamas.
It does not affect people or food safety, but outbreaks of the virus can result in restrictions on livestock movement and trade.
The virus can also reduce milk yield and cause infertility, and in the most severe cases is fatal for infected livestock.
New research by University of Glasgow, published in the journal PLOS Biology, shows that the recent re-emergence of BTV in France could have been caused by 'human activities'.
Scientists compared genomes of the virus before and after it re-emerged in France in 2015. BTV first arrived in Europe in 2006 from unknown sources.
It was controlled through mass vaccination by 2010, and no cases were reported until it re-emerged in 2015, the study highlights.
The authors' genome analyses revealed that during both the 2006 and 2015 outbreaks, BTV accumulated novel mutations in a manner expected for a rapidly evolving virus.
During the period in between the two outbreaks, however, the researchers noted a curious lack of mutations, indicating that the virus was likely not circulating during this period.
The genetic similarity between the original and re-emergent viruses suggests that the 2015 outbreak was caused by infectious material that somehow arose from the first outbreak.
A plausible scenario, the researchers argued, is that the virus resurfaced after being stored in frozen bull semen samples.
And since artificial insemination and embryo transfer are widely used in the livestock industry, this transmission mechanism should be evaluated by future work, they said.
Professor Massimo Palmarini, one of the senior authors of the study, explained: "In order to survive, to be transmitted and to find new hosts, viruses need to replicate.
"New mutations are an inevitable consequence of this, so viruses can't remain 'frozen in time'.
"While there is still lots for us to learn about virus biology, the most plausible explanation for our findings is that exposure to infectious material, stored from the earlier outbreak, caused the most recent emergence of this virus in Europe."
