The first avian adenovirus (AAV) associated with clinical disease was isolated
from an outbreak of respiratory disease in quail in 1950 (Olson, 1950). Since
that time, AAVs have been found in all types and breeds of chickens and from a
variety of other avian species. The infections may be asymptomatic or
associated with several clinical and pathological conditions. Vertical
transmission via the egg is the most common way of transmission. Also
horizontal transmission through faeces, contaminated egg trays, crates and
trucks play a role in the infection route. Studies have demonstrated the
presence of antibodies in healthy poultry, and viruses have been isolated from
normal birds. Avian adenoviruses in chickens are the etiological agents of 2
diseases known as inclusion body hepatitis (IBH) and hydropericardium syndrome
(HP). In some cases each condition is observed separately, however, recently
the 2 conditions have frequently been observed as a single entity; therefore,
the name hepatitis hydropericardium has been widely used to describe the
pathologic condition. The syndrome is an acute disease of young chickens
associated with anemia, haemorrhagic disorders, hydropericardium and high
mortality. Egg-Drop-Syndrome (EDS) is caused also by an adenovirus. The
disease is characterised by a severe drop in egg production as well as the
production of shell-less, thin-shelled, discoloured or misshapen eggs in
apparently healthy birds. Ducks and geese are the natural host of the EDS
virus. It was first described in chickens in the 1970s and spread to several
countries world wide. The birds usually do not show any other signs of
disease, and mortality is not expected. There is no specific treatment of the
AAV infections. Active immunization by vaccination using an inactivated is
wide spread
