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