Том 9

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Browsing Том 9 by Subject "avian pathogenic E. coli (APEC)"

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    Coinfection of avian pathogenic Escherichia coli and infectious bursal disease virus in broiler chickens
    (Національний університет "Києво-Могилянська академія", 2026) Nechypurenko, Oleksii; Furtat, Iryna; Dreval, Denis; Avdeeva, Liliya
    Infectious bursal disease virus (IBDV) is the main immunosuppressive agent in the poultry industry that stimulates the development of secondary bacterial infection. However, the avian pathogenic E. coli (APEC) could be a primary agent that induces the development of colibacillosis, nevertheless the absence of immunosuppression. The depletion of bursa after viral replication is crucial for starting bacterial dissemination because of devastation of systemic and local humoral immunity. Therefore, the aim of the work was to investigate the correlation between APEC and IBDV infection in broiler chickens. The bursal atrophy was observed from 21 days with further level depletion from 60 to 90% at the final stage of research. Moreover, APEC strains were isolated from birds at 28–42 days which is correlated with chronical immunosuppression. All E. coli isolates showed resistance to beta‑lactams (amoxicillin, amoxiclav), tetracyclines, and trimethoprim, highlighting the risk of multidrug‑resistant strains. There were no resistant strains to colistin and florfenicol. The IBDV strains were detected in the bursa of 21, 28 and 35 broilers with Ct level 22.8; 25.8; and 32.2 points, respectively that indicates decreasing the viral load. Based on partial nucleotide sequences of the VP2 gene, the pathogen was identified as very virulent United Kingdom 2019 strain. However, analysis of the samples from 42-day-old broilers revealed that the nucleotide sequence belonged to the vaccine strain. Therefore, coinfection of APEC and IBDV in broiler chickens enhances immunosuppression, creating conditions for secondary bacterial infections. The susceptibility to colibacillosis correlates with the stage of bursal depletion and may persist even during replication of the vaccine strain of IBDV after primary infection.