Experimental co-infection of infectious bronchitis and low pathogenic avian influenza H9N2 viruses in commercial broiler chickens

Abstract

In this study, commercial broilers were experimentally infected with single (classical IBV, variant IBV or AIV-H9N2) or mixed AIV-H9N2 with classical, variant or vaccine strains of IBV. Birds were monitored for clinical and pathological outcomes and virus shedding for 10days post infection (DPI). Clinical signs were limited to the respiratory tract in all challenged groups and varied from mild to moderate mouth breathing to severe respiratory signs with snorting sound and extended head. Mortalities were only recorded in mixed AIV-H9N2/variant IBV challenge group. AIV-H9N2 challenge caused tracheal petechial hemorrhage that progressed to tracheal congestion and caseation. In mixed AIV-H9N2/IBV vaccine challenge, severe tracheitis with bronchial cast formation was observed. In mixed AIV-H9N2/variant IBV challenge severe congestion of the tracheal mucosa and excessive exudates with a tendency to form tubular casts were observed. Kidney ureate deposition was only observed in variant IBV challenge group. Histopathologically, tracheal congestion, severe degeneration, and deciliation were noticed in all groups of mixed infection. Interestingly, hemorrhage and atrophy were observed in thymus gland of birds challenged with single AIV-H9N2 or mixed AIV-H9N2/IBV. There was no difference in the tracheal shedding level of variant IBV between single and mixed infected groups while classical IBV shedding increased in mixed infection group. Interestingly, the AIV-H9N2 showed constantly high shedding titers till 7DPI with variant or vaccine IBV co-infection. In conclusion, co-infection of IBV and AIV-H9N2 induced severe clinical outcome and high mortality. Also, IBV co-infection increased the shedding of AIV-H9N2 in experimentally infected birds.

Genetics, antigenicity and virulence properties of three infectious bronchitis viruses isolated from a single tracheal sample in a chicken with respiratory problems

“…Previous studies have indicated the synergistic mechanism between IBV and AIV-H9N2, possibly by trypsin-like proteases encoded by coronaviruses that enhance the AIV-H9N2 hemagglutinin cleavage (Haghighat-Jahromi et al, 2008;Hassan et al, 2017), which increases replication and pathogenicity of AIV-H9N2. In this study, we did not find any synergistic effects on pathogenicity when different types of IBV co-infected SPF chickens.…”

“…Evidence from epidemiological studies has revealed that co-infection with IBV and other respiratory pathogens, such as avian influenza virus (AIV) H9 subtype, is widespread in poultry in Jordan and Egypt (Roussan et al, 2008;Hassan et al, 2017). It is also reported that coinfection with different IBV serotypes is occasionally observed in the same chicken flock (Dolz et al, 2008).…”

Co-infections of chickens with avian influenza virus H9N2 and Moroccan Italy 02 infectious bronchitis virus: effect on pathogenesis and protection conferred by different vaccination programmes

“…Likewise, co-infections of LPAIV H9N2 with other respiratory pathogens, particularly with IBV, Mycoplasma gallisepticum, Staphylococcus aureus, Avibacterium paragallinarum, Escherichia coli, Ornithobacterium rhinotracheale and/ or immunosuppressive agents can exacerbate LPAIV H9N2 infections and result in severe clinical disease with different rates of mortality (Nili & Asasi, 2002;Kishida et al, 2004;Perk et al, 2006). Previous studies have demonstrated longer H9N2 virus shedding, more severe clinical signs and higher mortality rates caused by a co-infection with LPAIV H9N2 and IBV, either as a vaccine or as a wild-type virus (Seifi et al, 2012;Hassan et al, 2017;Ismail et al, 2018).…”

Viral interference between H9N2-low pathogenic avian influenza virus and avian infectious bronchitis virus vaccine strain H120 in vivo

“…Such cell receptor also serves as a receptor protein determinant for primary attachment of group 3 corona viruses [7], allowing fusion events and entry of both viruses. Huang et al have described as it is unknown whether co-infections with AIV and IBV exacerbate clinical signs of the disease in infected birds or produce viral interference, masking infections by either virus [8], even though it is reported that co-infection of IBV with AIV increased not only the severity of AIV-H9N2 clinical sings and gross lesions, but also the mortality rate with extended viral shedding period of AIV [9][10][11].…”