“Frozen Evolution” Of An RNA Virus Suggests Accidental Release as a Potential Cause off Arbovirus Re-emergence

Pascall D.J. et al., PLoS Biology 2020 Apr 28;18(4):e3000673. doi: 10.1371/journal.pbio.3000673. eCollection 2020 Apr.

Bluetongue is a major disease of domestic ruminants, mainly affecting sheep and caused by the bluetongue virus (BTV), an arbovirus belonging to the family Reoviridae (genus Orbivirus).

The epidemiology of BTV serotype 8 (BTV-8) is somewhat peculiar, two major outbreaks having occurred in Europe since the turn of the millennium. The first one, spanning from 2006 to 2010, originated in the Netherlands and then widely spread across Europe, where it was controlled through a pan-continental vaccination campaign. The second outbreak occurred in France in 2015 and subsequently involved several neighboring countries.

The source of BTV-8 re-emergence in France is still obscure. To solve that issue, Pascall et al. examined more than 150 viral samples collected from sheep and cattle during both outbreaks, using full genome sequencing. On the basis of such extensive investigation, Authors interestingly speculate that contaminated, frozen semen and/or embryos could have acted as the source of infection.

Overall, the paper remarks the usefulness of pathogen genomic epidemiology, as well as the need for more accurate controls of frozen materials, even when intended for local trading.

Giuseppe Marruchella