Scientists have analysed the re-assortment patterns of the bluetongue virus (BTV) in Europe, which reveals the mixing of viral genomes is not strictly random and re-assortment is commonly followed by novel adaptive changes in the progeny virus.
Scientists from the University of Glasgow and The Pirbright Institute made the discovery and their research is published in the journal PLoS Pathogens.
Roman Biek, who was involved in the study, said: “While re-assortment has received a lot of attention in certain segmented viruses, especially influenza A, its frequency and biological consequences remain poorly understood for most of the others.”
“This study of the bluetongue virus confirms earlier reports re-assortment is common and can involve segments derived from live vaccines used to control outbreaks.
He added: “Our findings have important implications for the classification and control of segmented viruses and generate new insights and hypotheses about the biological interactions among different parts of the bluetongue virus genome.”
The study confirms genetic re-assortment is common and widespread and has had a major impact on the genomic composition of European BTV strains. Genetic mixing occurs easily and appears to be the norm whenever multiple strains coexist.
The attenuated vaccine viruses that have been used in southern Europe have also contributed segments to circulating field strains.
Creating novel strains
Peter Mertens of the Pirbright Institute, who was also involved in the research said: “This study has important implications for the emergence and evolution of segmented-genome viruses and even whole virus populations, within new or previously uninfected ecosystems.
“By introducing live attenuated virus vaccines, we may be contributing to the genetic variation of BTV and the creation of novel strains whose properties we know nothing about. This needs to be considered during the design and implementation of control strategies.”
BTV infects ruminants and is transmitted via biting midges, causing a range of symptoms that can be fatal. Indirect impacts including weight loss, reduced milk production, abortion and deformed calves.
Most of Europe was considered to be BTV-free until the late 1990s, but since then multiple strains of the virus have invaded, with new strains arriving annually, causing outbreaks across the continent.