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 Togaviridae have spherical virions 70 nm in diameter, with a lipid envelope containing glycoprotein spikes. The genome consists of linear, positive-sense single-stranded RNA which is 11 to 12 kb in size in the genus Alphavirus (from Gr. alpha = letter ‘a’, for the original name of group A arboviruses), and 9,7 kb in the genus Rubivirus (from L. rubeus = reddish, for the rubella rash). The 31 currently recognized members of the genus Alphavirus are typically spread by insect vectors, those that infect mammals being transmitted by mosquitoes.  

Only three alphaviruses are associated with significant livestock disease, namely Eastern, Western and Venezuelan equine encephalitis viruses in the Americas, although related Getah and Ross River viruses sporadically cause systemic disease in horses in Asia and Australia respectively. Rubella virus of humans is the sole member of the genus Rubivirus.


  1. International Committee for Taxonomy of Viruses (accession date: 16/06/2017)
  2. MACLACHLAN N.J. & DUBOVI, E.J. (eds.), 2016. Veterinary Virology, 5th edition, Academic Press.

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