Impact of single and mixed infections with Escherichia coli and Mycoplasma gallisepticum on Newcastle disease virus vaccine performance in broiler chickens: an in vivo perspective.

AIMS: This study was designed to investigate, in an in vivo setting, the effects of single and combined infections with either Mycoplasma gallisepticum (MG) and/or Escherichia coli on the chicken immune response induced by Newcastle disease virus (NDV) vaccine. METHODS AND RESULTS: Humoral immunity was measured through detection of NDV antibody and anti-NDV IgG titres using haemagglutination-inhibition test and enzyme-linked immunosorbent assay, respectively. In addition, the expression levels of pro-inflammatory cytokines' genes (interleukin (IL) 6, IL4 and interferon (IFN) γ) were analysed using quantitative reverse transcription PCR. Significant (P < 0·05) results in all immunological parameters were detected in the vaccinated noninfected chicken group in comparison with those in groups exposed to bacterial infections. Bacterial infection along with vaccination hampered the NDV antibodies production and reduced the vaccine upregulated cytokine genes. The vaccinated mixed infection group reported lower antibody titres and cytokines expression levels compared to those in the single infection groups. All the previously enhanced immunological parameters reflected the maximum protection post challenge with velogenic viscerotropic NDV in the vaccinated noninfected chicken group. CONCLUSIONS: These findings provide novel insights into the immunosuppression activities of MG and E. coli infection in chickens vaccinated against NDV. SIGNIFICANCE AND IMPACT OF THE STUDY: This study hopes to provide a better insight to the immunosuppressive action of bacterial pathogens in chickens. This will help to improve biosecurity strategies during NDV vaccination in the future.

Salmonella enterica in imported and domestic day-old turkey poults in Egypt: repertoire of virulence genes and their antimicrobial resistance profiles.

Globalisation and international trade facilitate the rapid spread and transmission of foodborne pathogens. This study was designed to determine the serovars, distribution of virulence genes (invA, avrA, ssaQ, mgtC, siiD, sopB, gipA, sodC1, sopE1, spvC, bcfC) and antibiotic resistance profiles in salmonellae recovered from imported and domestic day-old turkey poults in Egypt. The prevalence of salmonellae in the imported poults was 4% (6/150): S. Enteritidis was the most frequent isolate (1.3%; 2/150), followed by Typhimurium, Virchow, Larochelle and a non-typeable strain, each with 0.7% (1/150) prevalence. The prevalence of salmonellae in the domestic poults was < 2% (2/150) and serotyping indicated a prevalence of 1.3% (1/150) for both Typhimurium and Altona. In polymerase chain reaction screening, the genes invA, sopB and bcfC were detected in all the Enteritidis, Typhimurium, Virchow, Larochelle, Altona and non-typeable isolates (100%); the gene gipA was absent from all isolates. Carriage of invA, sopB and bcfC among the Enteritidis, Typhimurium, Virchow, Larochelle, Altona and non-typeable isolates was associated with a core pattern of resistance to three antibiotics: streptomycin, nalidixic acid and chloramphenicol. The detection of S. Enteritidis, Typhimurium, Virchow, Larochelle, and Altona in turkey poults has important implications because these serovars are a significant cause of foodborne illness and enteric fever in humans.

Isolation of highly pathogenic avian influenza H5N1 from table eggs after vaccinal break in commercial layer flock.

In May 2009, during routine monitoring of a commercial layer flock of about 87,000 birds kept in cages in 4 different houses that had been vaccinated 3 times with an inactivated H5N1 vaccine at weeks 1, 7, and 16, highly pathogenic avian influenza (HPAI) virus of subtype H5N1 was isolated and detected by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) in tracheal and cloacal swabs collected from houses 3 and 4; 7 days after onset of clinical signs, there was an increase in mortality accompanied by a decrease in egg production and egg quality. In addition, using RT-PCR, the viral RNA could be detected from albumin and eggshell as well. Seven days after the onset of the clinical signs, the hemagglutination inhibition (HI) titers in the affected houses were 3.2 and 1.9 log2. In the other two houses, there were no clinical signs, and all tested samples were negative using virus isolation and real-time RT-PCR. The HI titers were 6.6 and 7.0 log2 in nonaffected houses. The isolated virus from egg albumin showed high nucleotides and amino-acid identities and clustered with viruses from recently H5N1-confirmed human infections and poultry from different places in Egypt. Moreover, several amino-acid substitutions of viral H5 protein were observed. The vaccinal break seems to be associated with immune escape mutants and/or improper vaccination. The role of contaminated eggs as a source of infection and as a vehicle for spread of the virus should be considered in area with avian influenza outbreaks.

Introduction and enzootic of A/H5N1 in Egypt: Virus evolution, pathogenicity and vaccine efficacy ten years on.

It is almost a decade since the highly pathogenic H5N1 avian influenza virus (A/H5N1) of clade 2.2.1 was introduced to Egypt in 2005, most likely, via wild birds; marking the longest endemic status of influenza viruses in poultry outside Asia. The endemic A/H5N1 in Egypt still compromises the poultry industry, poses serious hazards to public health and threatens to become potentially pandemic. The control strategies adopted for A/H5N1 in Egyptian poultry using diverse vaccines in commercialized poultry neither eliminated the virus nor did they decrease its evolutionary rate. Several virus clades have evolved, a few of them disappeared and others prevailed. Disparate evolutionary traits in both birds and humans were manifested by accumulation of clade-specific mutations across viral genomes driven by a variety of selection pressures. Viruses in vaccinated poultry populations displayed higher mutation rates at the immunogenic epitopes, promoting viral escape and reducing vaccine efficiency. On the other hand, viruses isolated from humans displayed changes in the receptor binding domain, which increased the viral affinity to bind to human-type glycan receptors. Moreover, viral pathogenicity exhibited several patterns in different hosts. This review aims to provide an overview of the viral evolution, pathogenicity and vaccine efficacy of A/H5N1 in Egypt during the last ten years.