GENERAL INTRODUCTION: FLAVIVIRIDAE

FLAVIVIRIDAE

A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria /protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

Members of the family Flaviviridae (from L. flavus = yellow, for the type species which is yellow fever virus). The family currently includes 4 genera, specifically, Flavivirus, Pestivirus, Hepacivirus and Pegivirus.1  

Flaviviridae have spherical virions, 40 to 60 nm in diameter, with a lipid envelope containing protein spikes which are known to incorporate glycoproteins in the genera Flavivirus and Pestivirus. The virions contain a single molecule of linear, positive-sense, single-stranded RNA ranging in size from approximately 9,5 kb for members of the genus Hepacivirus (hepatitis C virus), through 10,7 kb for members of the genus Flavivirus, to 12,5 kb for the genus Pestivirus (from L. pesti = plague or pestilence).

All members of the genus Flavivirus are believed to be arthropod-borne, utilizing either mosquitoes or ticks as vectors, and  all of these viruses are antigenically related; currently 53 flavivirus species are placed in seven  distinct serogroups of closely related viruses.  Only four members of the genus have been associated with significant diseases in livestock: louping ill, Japanese encephalitis, Wesselsbron and West Nile viruses.2

The genus Pestivirus contains three pathogens of livestock: bovine viral diarrhoea virus, border disease virus of sheep, and hog cholera (classical swine fever) virus, however a substantial and increasing number of new pestivirus species of uncertain pathogenic significance have recently been described. Similarly, several “non-primate” hepaciviruses and pegiviruses of uncertain pathogenic significance have been identified recently in animals.

References

  1. International Committee for Taxonomy of Viruses https://talk.ictvonline.org/taxonomy/ (accession date: 13/06/2017)
  2. MACLACHLAN N.J. & DUBOVI, E.J. (eds.), 2016. Veterinary Virology, 5th edition, Academic Press.