Pathogenesis of Velogenic Genotype VII.1.1 Newcastle Disease Virus Isolated from Chicken in Egypt via Different Inoculation Routes: Molecular, Histopathological, and Immunohistochemical Study

Protective effectiveness of two vaccination schemes against the prevalent Egyptian strain of Newcastle disease virus genotype VII

Background

Despite the strict preventive immunization used in Egypt, Newcastle disease remained a prospective risk to the commercial and backyard chicken industries. The severe economic losses caused by the Newcastle disease virus (NDV) highlight the importance of the trials for the improvement and development of vaccines and vaccination programs.

Aim

In the present study, we evaluated the effectiveness of two vaccination schemes for protection against the velogenic NDV (vNDV) challenge.

Methods

Four groups (A-D) of commercial broiler chickens were used. Two groups (G-A and G-B) were vaccinated with priming live HB1 GII simultaneously with inactivated GVII vaccines at 5 days of age, then boosted with live LaSota GII vaccine in group A and live recombinant NDV GVII vaccine in group B on day 16. Groups A to C were challenged with NDV/Chicken/Egypt/ALEX/ZU-NM99/2019 strain (106 Embryo infective dose 50/0.1 ml) at 28 days of age.

Results

Two vaccination schemes achieved 93.3% clinical protection against NDV with body gain enhancement; whereas, 80% of the unvaccinated-challenged birds died. On day 28, the mean HI antibody titers were 4.3 ± 0.33 and 5.3 ± 0.33 log2 in groups A and B, respectively. As well as both programs remarkably reduced virus shedding. The two vaccination schemes displayed close protection efficacy against the vNDV challenge.

Conclusion

Therefore, using the combination of a live attenuated vaccine with an inactivated genetically matched strain vaccine and then boosting it with one of the available live vaccines could be considered one of the most effective programs against current field vNDV infection in Egypt.

Characterization of Chicken-Derived Genotype VII Newcastle Disease Virus Isolates from Northwest China

Newcastle disease virus (NDV) threatens global poultry production, with genotype VII the most prevalent strain in China. However, little information is available regarding viral multiplication and pathogenicity based inoculation route. The objectives of this study were to sequence NDV VII isolates and to analyze their biological characteristics in detail. A total of 86 oral and cloacal swabs were collected from Shaanxi and Gansu provinces in northwest China. Identification of genotype VII NDV based on the M gene was performed by qPCR. Viral multiplication and pathogenicity were assessed as a function of route of infection. We observed increased morbidity and mortality using intravenous injection, whereas intranasal, intraocular, and cloacal infections resulted in slower progression and milder clinical disease, with viral proliferation obvious in different tissues. These results provide an important basis for the clinical control and prevention of NDV epidemics in poultry.

Newcastle Disease Genotype VII Prevalence in Poultry and Wild Birds in Egypt

Newcastle Disease Virus (NDV) genotype VII is a highly pathogenic Orthoavulavirus that has caused multiple outbreaks among poultry in Egypt since 2011. This study aimed to observe the prevalence and genetic diversity of NDV prevailing in domestic and wild birds in Egyptian governorates. A total of 37 oropharyngeal swabs from wild birds and 101 swabs from domestic bird flocks including chickens, ducks, turkeys, and pelicans, were collected from different geographic regions within 13 governorates during 2019–2020. Virus isolation and propagation via embryonated eggs revealed 91 swab samples produced allantoic fluid containing haemagglutination activity, suggestive of virus presence. The use of RT-PCR targeted to the F gene successfully detected NDV in 85 samples. The geographical prevalence of NDV was isolated in 12 governorates in domestic birds, migratory, and non-migratory wild birds. Following whole genome sequencing, we assembled six NDV genome sequences (70–99% of genome coverage), including five full F gene sequences. All NDV strains carried high virulence, with phylogenetic analysis revealing that the strains belonged to class II within genotype VII.1.1. The genetically similar yet geographically distinct virulent NDV isolates in poultry and a wild bird may allude to an external role contributing to the dissemination of NDV in poultry populations across Egypt. One such contribution may be the migratory behaviour of wild birds; however further investigation must be implemented to support the findings of this study. Additionally, continued genomic surveillance in both wild birds and poultry would be necessary for monitoring NDV dissemination and genetic diversification across Egypt, with the aim of controlling the disease and protecting poultry production.

In vitro investigation of the antiviral activity of propolis and chitosan nanoparticles against the genotype VII Newcastle disease virus

The Newcastle disease virus (NDV) is considered a serious threat to global poultry production. Despite the availability of vaccines, it remains a major devastating epidemic responsible for great economic losses. The development of novel virus-controlling strategies is therefore an urgent need. The present study investigated for the first time the antiviral efficacy of propolis and chitosan nanoparticles against two NDV isolates, MW881875 and MW881876, recovered from vaccinated commercial broiler farms in KafrEl Sheikh Governorate, Egypt. The polygenetic analysis focused on the F and M genes, with one isolate having a 97% identity with the genotype VII NDV Israeli strain. On the other hand, the identified isolates showed high genetic variation and only 76% identity with the LaSota vaccine (genotype II). More interestingly, the cell cytotoxic concentrations of chitosan, propolis, and a propolis–chitosan mixture against Vero cells were 327.41 ± 12.63, 109.48 ± 8.36, and 231.78 ± 11.46 μg/ml, respectively. The median tissue culture infectious dose (TCID50) assay demonstrated that the nanoparticles have antiviral effects after NDV exposure resulting in significant decrease in viral titer (TCID50) by 2, 2.66, and 2.5 log10 at 62 μg/ml of chitosan, 13 μg/ml of propolis, and 30 μg/ml of the propolis–chitosan mixture, respectively, compared with the control TCID50 value of 4 log10. Taken together, the results provide novel insights into the potentially promising roles of propolis and chitosan as novel, safe, and effective antiviral agents against NDV.