INTRODUCTION
NICOLA DECARO AND CANIO BUONAVOGLIA
Department of Veterinary Public Health, Faculty of Veterinary Medicine of Bari, Valenzano (Bari), Italy
Adenoviruses belong to the family Adenoviridae, which is divided into four genera, namely Mastadenovirus, Aviade- novirus, Atadenovirus and Siadenovirus.
These have 19, 6, 4 and 2 serogroups respectively, each organized in several serotypes. The genus-, serogroup- and serotype-specific antigen determinants are localized on the virion surface structures (hexons and fibres). The genus Mastadenovirus includes adenoviruses infecting mammals — for example, human adenoviruses, canine adenoviruses, most ruminant adenoviruses and squirrel adenovirus. Most adenoviruses of birds, including fowl adenoviruses and goose adenovirus, belong to the genus Aviadenovirus. Viruses of mammalian (some ovine and bovine adenoviruses, possum adenovirus and cervid adenovirus) and avian (Duck adenovirus 1, or egg drop syndrome virus) origin with an exceptionally large content of adenine and thymine in their genome constitute the genus Atadenovirus, whereas genus Siadenovirus comprises adenoviruses of amphibians (Frog adenovirus 1) and birds (Turkey adenovirus 3, or marble spleen disease virus).Adenoviruses are medium-sized (80—110 nm in diameter), naked icosahedral particles, with a linear, doublestranded DNA of about 35,800—36,200 nucleotides. The capsid is formed by 252 capsomeres consisting of 240 hexons and 12 pentons at the vertices of the icosahedron. To each penton base capsomere one or two antenna-like fibres are attached, which bind to cell receptors and which, in some adenoviruses, have haemagglutination activity. Five different proteins are associated with the viral DNA, forming a nucleoprotein core. The genome encodes for at least 10 polypeptides, including the structural proteins forming the capsid, fibres and core, and a few non- structural proteins, such as DNA-associated enzymes, the viral replicase and an internal protein.
Adenoviruses replicate in the cell nuclei, and their replication is not always associated with a clear cytopathic effect. However, basophilic intranuclear inclusion bodies are observed consistently in the infected cells. Adenoviruses are stable at room temperature and between pH 5—6, and are resistant to lipid solvents. They are usually inactivated at 56°C for 10—15 minutes and by disinfectants containing chlorine and formol.Adenoviruses can cause various clinical signs involving the respiratory system, gastroenteric and urinary tracts, eyes, central nervous system, spleen and liver. Some avian and bovine adenoviruses are able to induce tumours in newborn hamsters infected experimentally, but their oncogenicity is usually absent in the natural hosts.
Infectious Diseases of Wild Mammals and Birds in Europe, First Edition. Edited by Dolores Gavier-Widen, J. Paul Duff, and Anna Meredith. © 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd. Material authored by Paul Duff remains Crown Copyright.