Prevalence of avian respiratory viruses in broiler flocks in Egypt

Abstract

In this study, respiratory viral pathogens were screened using real-time RT-PCR in 86 broiler chicken flocks suffering from respiratory diseases problems in 4 Egyptian governorates between January 2012 and February 2014. The mortality rates in the investigated flocks ranged from 1 to 47%. Results showed that mixed infection represented 66.3% of the examined flocks. Mixed infectious bronchitis (IBV) and avian influenza (AI)-H9N2 viruses were the most common infection (41.7%). Lack of AI-H9N2 vaccination and high rates of mixed infections in which AI-H9N2 is involved indicate an early AI-H9N2 infection with a potential immunosuppressive effect that predisposes for other viral infections. High pathogenic AI-H5N1 and virulent Newcastle disease virus (vNDV) infections were also detected (26.7% and 8.1%, respectively). Interestingly, co-infection of AI-H9N2 with either AIV-H5N1 or vNDV rarely resulted in high mortality. Partial cell-mediated immunity against similar internal AI genes, as well as virus interference between AI and vNDV, could be an explanation for this. Highly prevalent IBV and AI-H9N2 were isolated and were molecularly characterized based on S1 gene hypervariable region 3 ( HVR3: ) and hemagglutinin gene (HA) sequences, respectively. IBV strains were related to the variant group of IBV with multiple mutations in HVR3. Though AI-H9N2 viruses showed low rate of evolution in comparison to recent strains, few amino acid substitutions indicative of antibody selection pressure were observed in the HA gene. In conclusion, mixed viral infections, especially with IBV and AI-H9N2 viruses, are the predominant etiology of respiratory disease problems in broiler chickens in Egypt. Further investigations of the role of AI, IBV, and ND viruses' co-infections and interference in terms of altering the severity of clinical signs and lesions and/or generating novel reassortants within each virus are needed.

Phylogenetic and antigenic analysis of avian infectious bronchitis virus in southwestern China, 2012–2016

“…In recent years, outbreaks of IB have been reported frequently in southwestern China Zou et al, 2010). Although the mortality rate of a single infection has been low, it could increase as a consequence of secondary infections or co-infection with E. coli, AIV, and NDV (Dwars et al, 2009;Hassan et al, 2016). In our study, rates of co-infection of IBV and bacteria accounted for 25.0% of total cases.…”

Natural Reassortants of Potentially Zoonotic Avian Influenza Viruses H5N1 and H9N2 from Egypt Display Distinct Pathogenic Phenotypes in Experimentally Infected Chickens and Ferrets

“…The likelihood of the importance of these scenarios is low, as the cocirculation of both viruses on the same poultry farms at the same time, the coinfection of chickens with both viruses, and the presence of both viruses in the same poultry field samples have been repeatedly reported (27)(28)(29), However, the emergence and perpetuation of the now extinct HPAIV H5N1 2.2.1.1 clade of vaccine escape mutants from 2008 to 2011 were highly restricted to industrial poultry farms. These viruses did not spill over to backyard holdings, where viruses of another clade (2.2.1.2) prevailed (25).…”

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

“…Chicks infected with IBV then super-infected with AIV-3 days later, showed no IBV shedding either in TC or CL, during the experimental period (Figs. [2][3][4][5]. When comparing the kinetics of AIV or IBV virus replication at different time points after chick inoculations, the patterns of TC and CL viral titers were different depending on the virus exposure, as shown for AIV or IBV viral gene copy numbers detected by qRT-PCR ( Figs.…”

“…They are considered the most economically important respiratory viral diseases, and they threaten the poultry industry worldwide [1]. Mixed infection or co-infection with AIV and IBV has been described as a natural infection in different countries in Asia and the Middle-East [2,3]. More, the IBV vaccine is used extensively in chicken farms in many countries worldwide where both IBV and low pathogenic AIV H9N2 are endemic [3,4].…”

“…Mixed infection or co-infection with AIV and IBV has been described as a natural infection in different countries in Asia and the Middle-East [2,3]. More, the IBV vaccine is used extensively in chicken farms in many countries worldwide where both IBV and low pathogenic AIV H9N2 are endemic [3,4]. The H120 strain of IBV was one of the earliest live attenuated IBV vaccines to be developed and has continued to be use in most parts of the world.…”