Aviadenoviruses are adenoviruses that affect birds—particularly chickens, ducks, geese, turkeys and pheasants. There are 15 species in this genus. Viruses in this genus cause specific disease syndromes such as Quail Bronchitis (QB), Egg Drop Syndrome (EDS), Haemorrhagic Enteritis (HE), Pheasant Marble Spleen Disease (MSD), and Inclusion Body Hepatitis (IBH). Avian adenoviruses have a worldwide distribution and it is common to find multiple species on a single farm. The most common serogroups are serogroup 1, 2 and 3.
No evidence of transmission from birds to humans has been identified. The virus is mainly spread horizontally by the oro-fecal route, but vertical transmission can occur in serogroup 1. Once it has infected the bird the virus may remain latent until a period of stress, when it may then cause clinical disease.
Infections are normally subclinical, however clinical disease can occur—especially in young birds as maternal antibody levels begin to wane.
Signs of gastrointestinal disease (Haemorrhagic Enteritis) include diarrhea, anorexia, melena and hematochezia. Anaemia and dehydration may develop secondary to this haemorrhagic enteritis. Signs of reproductive disease (Egg Drop Syndrome) include low egg production/hatching and the laying of abnormal eggs (size, shape, colour, texture). Adenovirus infection may infect other organs, causing splenitis, inclusion body hepatitis, bronchitis, pulmonary congestion ventriculitis, pancreatitis, or oedema, depending on the species of bird infected.
Diagnosis of aviadenovirus is by histopathology, electron microscopy, viral isolation, ELISA and PCR. In addition, virus antigen can be detected double immunodiffusion. Postmortem examination may reveal a variety of clinical signs relating directly to the organ affected. Specifically, Egg Drop Syndrome can be diagnosed by hemagglutinin inhibition and the virus causes haemagglutination in chickens and ducks.
Vaccines for HE and EDS are available (ATCvet codes: QI01AA05 (WHO) for the inactivated vaccine, QI01AD05 (WHO) for the live vaccine, plus various combinations). Disease incidence may be reduced by minimising stress levels, using appropriate hygiene measures and providing adequate nutrition.