GENERAL INTRODUCTION: PARVOVIRIDAE

PARVOVIRIDAE

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 Parvoviridae (parvus = small in Latin) are some of the smallest viruses (about 25 nm in diameter) that infect a wide range of vertebrates and invertebrates. On this basis they are divided into two subfamilies, i.e. those that infect invertebrates (Densovirinae) and vertebrates (Parvovirinae). 1

The subfamily Parvovirinae, which currently contains 41 viruses,is further divided into 8 genera, 7 of which infect mammals (Amdoparvovirus, Bocaparvovirus, Capiparvovirus, Dependoparvovirus, Erythroparvovirus, Protoparvovirus, Tetraparvovirus); the eighth (Aveparvovirus) infect birds. Dependoparvoviruses contain adeno-associated viruses of mammals (e.g. humans, cattle, dogs, bats, seals) that have so far not been associated with disease. These viruses require the presence of an adenovirus in the infected cell to complete their life-cycle.

The current classification system of Parvoviridae is complicated and – for non-specialists in this field – sometimes difficult to follow.

Of the viruses that infect domestic mammal species, porcine parvovirus (new species name – Ungulate protoparvovirus 1) is an important cause of reproductive failure in gilts and young sows throughout the world. The pathogenic potential of bovine parvoviruses (Ungulate bocaparvovirus 1) is less well understood. Feline parvovirus (Carnivore protoparvovirus 1) causes a devastating disease of cats (Feline panleukoenia), and variants of this virus are pathogenic in a number of other carnivore species such as dogs (Canine parvovirus 2), mink and raccoons.

Parvoviridae replicate in cells in the S-phase of mitosis and therefore require rapidly dividing cells in order to propagate themselves efficiently. Members of the family are also remarkably resistant to a range of environmental conditions that most other viruses are unable to survive, e.g. lipid solvents, pH 3 to 9, and heating to 56 °C for 60 minutes.1, 2

Virions are unenveloped, isometric with icosahedral symmetry; the capsid being comprised of three (four in the case of Densovirinae) polypeptides derived from a common sequence. The genome comprises a molecule of linear, single-stranded DNA. Most parvoviruses encapsidate only  negative sense DNA, whereas virions of other parvoviruses include both positive and negative sense DNA  molecules.1

References

  1. International Committee for Taxonomy of Viruses https://talk.ictvonline.org/taxonomy/ (accession date – 26/05/2017)
  2. MACLACHLAN N.J. & DUBOVI, E.J. (eds.), 2016. Veterinary Virology, 5th edition, Academic Press.