Page 290 - Avian Virology: Current Research and Future Trends

Avian Adenoviruses

Juan Carlos Corredor and Eva Nagy* 10

Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.

*Correspondence: enagy@ovc.uoguelph.ca
https://doi.org/10.21775/9781912530106.10

Abstract worldwide. Inclusion body hepatitis (IBH) is caused by fowl ade-
Avian adenoviruses are ubiquitous worldwide in avian species. noviruses (FAdVs), although they can be isolated from healthy
Although many of these viruses are isolated from healthy birds, chickens as well, and FAdVs are considered ubiquitous on poultry
some cause diseases associated with significant economic losses farms (Hess, 2013). Hydropericardium syndrome (HPS) is the
in the poultry industry, including egg-drop syndrome (EDS), result of infection with pathogenic serotype 4 FAdVs. Gizzard
inclusion body hepatitis (IBH), inclusion body hepatitis/hydrop- erosion, mainly attributed to FAdV-1, is more frequently seen in
ericardium syndrome (IBH/HPS) in chickens and haemorrhagic recent years (Gjevre et al., 2013; Ono et al., 2003). Quail bronchi-
enteritis (HE) of turkeys. Avian adenoviruses are classified into tis is an important disease of bobwhite quail. Egg drop syndrome
three genera based on genome organization, phylogenetic rela- (EDS) is caused by an atadenovirus, egg drop syndrome virus
tionships and host: Aviadenovirus, Atadenovirus and Siadenovirus. (EDSV). Haemorrhagic enteritis (HE) of turkeys is associ-
The viral genome consists of genus-common and genus-specific ated with turkey adenovirus 3 (TAdV-3) and together with the
genes. Genus-common genes, such as those involved in DNA causative agent of marble spleen disease of pheasants and avian
replication and encoding structural proteins, are conserved and adenovirus splenomegaly virus they belong to the siadenoviruses.
present in all adenoviruses. Genus-specific genes, on the other In addition, adenovirus infections have been described in turkeys,
hand, are unique for each genus. The functions of most early viral geese, ducks, pigeons, guinea fowls and wild birds. The descrip-
genes of avian adenoviruses remain unknown. Some of these tions of the diseases can be found in the appropriate chapters of
genes, such as Gam-1 and ORF22, have functions similar to those Diseases of Poultry (Swayne et al., 2013).
described for human adenoviruses – stimulation of cell cycle The first unintentional isolation of an avian adenovirus was
progression, modulation of apoptosis and counteraction of the in 1949, when material from a bovine case suspected for lumpy
host’s innate immunity. Studies on virus–host interactions at the skin disease was inoculated into embryonated chicken eggs
molecular level are limited to a few viruses [e.g. fowl adenovirus (Van Den Ende et al., 1949). The chicken embryo lethal orphan
(FAdV)-1, FAdV-4 and FAdV-9]. The virulence determinants for (CELO) virus, now designated FAdV-1, was first observed in
these viruses are unknown. However, some candidate viral genes 1957 (Yates and Fry, 1957). Isolation of the first avian adeno-
associated with virulence have been described in some aviad- virus from a diseased bird, a bobwhite quail occurred in 1950
enoviruses (e.g. FAdV-4 and FAdV-8) and a siadenovirus (duck (Olson, 1951). IBH was first described in the USA in 1963
adenovirus 1). Non-pathogenic aviadenoviruses, such as fowl by Helmboldt and Frazier (Helmboldt and Frazier, 1963).
adenoviruses 1, 4, 8, 9 and 10, have been described as virus vec- Isolation of aviadenovirus from broilers with hydropericardium
tors for potential use as recombinant poultry vaccines and gene syndrome was reported from Pakistan in 1988 (Cheema et al.,
delivery. 1989) and very recently numerous outbreaks are identified in
China (Zhao et al., 2015; Niu et al., 2016). Egg drop syndrome
(EDS) was described in 1976 in the Netherlands (van Eck et al.,
Introduction and history 1976), and the viral aetiology was shown a year later (McFerran
Adenoviruses can infect and be isolated from humans and a wide et al., 1977). HE was first mentioned in 1937 (Pomeroy and
range of mammals, birds and other vertebrate species, although Fenstermacher, 1937), and its viral aetiology was considered
they appear to be host specific and co-evolved with their hosts. by Domermuth and Gross in 1971 (Domermuth and Gross,
Adenoviruses were first mentioned in connection with human 1971), and since then the disease was reported in many coun-
adenoid tissues by Rowe and colleagues in 1953 (Rowe et al., tries including North America (Carlson et al., 1974; Itakura et
1953), hence the origin of the name of this group of viruses, sub- al., 1974).
sequently the virus was isolated in 1954 (Huebner et al., 1954). The focus of this chapter is mainly on aviadenoviruses;
The avian adenoviruses are associated with important clini- however, other avian adenoviruses will be discussed where appro-
cal diseases, causing substantial losses to the poultry industry priate.