GENERAL INTRODUCTION: CALICIVIRIDAE AND ASTROVIRIDAE

CALICIVIRIDAE AND ASTROVIRIDAE

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.

Caliciviridae and Astroviridae are considered together because they have morphological and genomic similarities. Neither family contains viruses that are so far known to cause important diseases of mammalian livestock. Nevertheless, some of these viruses are widespread infections of a wide variety of animals including mammalian livestock.
Well-known members of the family Caliciviridae (calyx = cup) are vesicular exanthema of swine virus, closely related San Miguel Sea Lion viruses and feline calicivirus (all members of the Genus Vesivirus). Vesicular exanthema has so far only occurred in the Western Hemisphere, along the Californian coast particularly and is likely derived from marine environments.

 The Caliciviridae include 4 other genera, Lagovirus (infections of lagomorphs), Nebovirus (enteric infections of cattle; the type species being Newbury-1 virus), Norovirus (infections of humans, including Norwalk virus that is an important cause of human food poisoning) and Sapovirus (also associated with food poisoning in humans; this genus also putatively contains porcine enteric viruses and a virus of mink)1.

Caliciviruses and Astroviruses have small non-enveloped virions with icosahedral symmetry and genomes of single-stranded, positive-sense RNA.

Astroviridae are mainly associated with gastro-enteritis in children but viruses within this family also occur widely in many avian and mammalian species, both wild and domestic. Currently, there are two genera within Astroviridae – Astrovirus with three species (1-3) that infect avian species and Mamastovirus which contains 19 species numbered 1-191. The latter are infections of humans (types 1-8), mammals such as cattle, cats, mink, sheep, pigs and, possibly, other vertebrates. As far as disease association is concerned, Mamastoviruses have so far been associated with sporadic encephalomyelitis of cattle and in mink.2

References

  1. International Committee for Taxonomy of Viruses https://talk.ictvonline.org/taxonomy/ (accession date: 26/05/2017)
  2. MACLACHLAN NJ, DUBOVI EJ (Eds). Veterinary Virology, 5th edition, Academic Press, 2016