Keywords
Adenovirus, inclusion body hepatitis, broiler, histopathology, PCR
INTRODUCTION
Fowl adenoviruses (FAdVs) cause many diseases in chickens like inclusion
body hepatitis (IBH), hydropericardium hepatitis syndrome (HHS), and
adenoviral gizzard erosion (AGE), leading to economic losses everywhere
in the world (Schachner, Matos, Grafl, &
Hess, 2018).
Fowl adenoviruses (FAdVs) belong to the genus Aviadenoviruswithin the family Adenoviridae. They are non-enveloped double-stranded
DNA viruses (De Luca et al., 2020). The
International Committee on Taxonomy of Viruses separated Adenoviridae
members into five genera (Zhao, Zhong,
Zhao, Hu, & Zhang, 2015). The Mastadenovirus genus contains mammalian
adenoviruses like humans, bats, dogs, horses, mice, -ruminants, and
swine. The genus Aviadenovirus, formerly designated as a gaggle I avian
adenoviruses (AAV), contains 11 of the 12 recognized European adenovirus
serotypes classified into five molecular groups (A to E) and other
related viruses (Hafez, 2011). Fowl
adenovirus is immune to many several disinfectants and is comparatively
tolerant to heat and pH changes. Iodophor and aldehyde disinfectants
seem to be effective if they can contact the virus for an extended time
(Rahimi & Haghighi, 2015).
The first IBH report was from the USA in 1963. Helmboldt and Frazier
described the disease as necrotizing hepatitis in seven-week-old
chickens (Helmboldt & Frazier, 1963).
After that, the disease was reported in many areas. In 1988, a new
broiler disease, called Angara Disease, was reported from Angara Goth
near Karachi in Pakistan. The disease course and clinical signs were
almost similar to IBH. The pathological findings included the
accumulation of clear, straw-colored fluid in the pericardial sac;
hence, it was called Hydropericardium Syndrome
(Yasmeen et al., 2017). The disease has
subsequently been recorded in Iraq
(Abdul-Aziz & Al-Attar, 1991).
IBH is transmitted by vertical and horizontal means, but the former is
reported as a very effective means of spreading from parent birds to
offsprings (Asthana, Chandra, & Kumar,
2013). Horizontal infection occurs through the oral-fecal route, and
further spread by mechanical means and contamination with infected feces
occurs (Gomis, Goodhope, Ojkic, & Willson,
2006).
Over the last two decades, increasing IBH outbreaks have been reported
in several geographic locations, stressing the disease’s worldwide
spread. IBH mainly affects broilers aged up to 35 days, but the disease
has also been described periodically in layers and broiler breeders. The
disease has been reported in birds as young as seven day-olds and as old
as 20 weeks (Erny, Barr, & Fahey, 1991).
In natural outbreaks, IBH is characterized by sudden mortality of 2-40%
in chickens. High death rates occur when the affected birds are younger
than three weeks. Depending on the virus’s pathogenicity, chicks’ immune
status, and simultaneous secondary infections, mortality as high as 80%
may occur. In general, mortality peaks within 3–4 days and falls in
9–14 days (Schachner, Marek, Grafl, &
Hess, 2016).
In most cases, the liver is the primarily affected organ. Gross lesions
of IBH include an enlarged pale and friable liver, sometimes with
necrotic foci. Ecchymotic hemorrhages might also be observed in the
liver and muscles of the leg and breast. Clinical signs are not
conclusive, including lethargy, huddling, ruffled feathers, and appetite
loss (Hafez, 2011).
The definitive diagnosis of IBH is primarily based on polymerase chain
reaction, histopathological examinations, or virus or antigen detection
using immunofluorescence test or electron microscopy
(Steer, O’Rourke, Ghorashi, &
Noormohammadi, 2011). Histopathological lesions include the presence of
focal necrotic areas and intra-nuclear inclusion bodies in some
hepatocytes. The inclusion bodies might be eosinophilic, large, round,
or irregularly shaped with a clear pale halo or occasionally basophilic
(Schachner et al., 2018).
Most avian adenoviruses are considered opportunistic pathogens that do
not produce clinical signs when inoculated into birds. However,
researchers have noted that some viruses are considered primary
pathogens, like those liable for inclusion body hepatitis,
hydropericardium syndrome, respiratory disease, necrotizing
pancreatitis, and adenoviral gizzard erosion in chickens and other
birds. Moreover, infection with infectious bursal disease virus (IBDV)
has been suggested as a significant predisposing factor in the
development of IBH (Ojkic et al., 2008).
According to our knowledge, IBH or similar cases characterized by
hepatitis and occurrence of hepatocytic intra-nuclear inclusion bodies
have not been documented in poultry in Kurdistan of Iraq. Therefore, the
case of adenovirus-like inclusion body hepatitis in a broiler farm in
Kurdistan of Iraq is reported here for the first time.
METHODS