Adenoviruses

Adenoviruses are double-stranded DNA viruses of animals. The prefix adeno comes from the Greek word meaning "gland," reflecting the first isolation of a virus of this type from human adenoid tissue over a half a century ago. Adenoviruses have been since isolated from many animals, from fish to mammals. Some human and animal adenoviruses can cause disease and even death, but most are not pathogenic in healthy individuals.

Adenoviruses have become one of the most popular vector systems for virus-based gene therapy and vaccination and have potential and have potential as antitumor tools.1

Classification

By tradition, adenoviruses have been classified by their hemagglutination (clumping of red blood cells caused by the presence of a virus) and oncogenic (cancer-causing) properties. Adenoviruses belonging to subgenus A are highly oncogenic and induce tumors in newborn hamsters within a few months.

Human Adenoviruses

The human adenoviruses are now classified into six subgenera, A to F, containing 49 serotypes.

  • Subgenus A - This consists of Ad12, Ad18, and Ad31. All three members can be isolated from the stool of healthy humans. Ad31 has frequently been isolated from children with diarrhea, but a definitive relation is yet to be established.
  • Subgenus B Ad3, Ad7 and Ad21 primarily cause outbreaks of respiratory disease, but can also cause a more generalized infection. Ad11, Ad34, and Ad35 can persistent infections in the urinary tract.
  • Subgenus C - Ad1, Ad2, Ad5, and Ad6 represent nearly 60% of all adenoviruses reported by WHO; they are commonly isolated from lymphoid tissue in which they can persist for years.
  • Subgenus D - This family consists of 23 established serotypes, the most important being 8 and 19 which are associated with epidemic keratoconjunctivitis.
  • Subgenus E - Ad4 has been associated with epidemic follicular conjunctivitis and respiratory disease.
  • Subgenus F - This family consists of serotypes Ad40 and Ad41; both were isolated from children with diarrhea.


Non-Human Adenoviruses

The non-human adenoviruses are currently divided into two genera: Mastadenovirus (mammalian adenoviruses) and Aviadenovirus. Tests indicate multiple serotypes exist in most animal species. Currently there are 2 equine, 9 bovine, 4 porcine (pig), 6 ovine (sheep), 2 caprine (goat and antelope), 2 canine, 11 chicken, 4 turkey, 3 goose, 2 mice, and 25 simian serotypes of adenovirus. Adenoviruses have also been isolated from quail, pheasants, opossum, rabbits, tree shrews, guinea pigs, rats, and sea lions. They are usually isolated from the upper respiratory tract, conjunctiva, gastrointestinal tract, and feces. Most of these adenoviruses do not produce signs of disease, but pneumonia, conjunctivitis, diarrhea, and hepatitis are frequently observed in animals infected with adenoviruses.2

Diseases Caused by Adenoviruses

Diseases in domestic mammals caused by adenoviruses include respiratory or enteric disease in cattle Bos taurus caused by bovine adenovirus 1-6; in sheep Ovis aries caused by ovine adenoviruses 1-6; and hepatitis in dogs Canis familiaris caused by canine adenovirus type 1 (CAV-1).

Some adnoviruses that commonly infect domestic animals can also infect wild animals. For example, infectious canine hepatitis virus of dogs also infects wild members of the Canidae, including coyotes Canis latrans and wolves Canis lupus. Important nondomestic mammalian adenovirus diseases that can manifest as epidemics include fox encephalitis (sometimes called fox distemper) caused by CAV-1, and the recently described adenovirus hemorrhagic disease of deer Odocoileus spp.3

References

  1. Desk Encyclopedia of Human and Medical Virology. Brian W.J. Mahy, Marc H.V. van Regenmortel
  2. Viral Diarrheas of Man and Animals. Linda J. Saif, Kenneth Thiel
  3. Infectious diseases of wild mammals. Elizabeth S. Williams, Ian K. Barker





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