Efficacy of the Newcastle Disease Virus Genotype VII.1.1-Matched Vaccines in Commercial Broilers

Class II genotype VII Newcastle disease viruses (NDV) are predominant in the Middle East and Asia despite intensive vaccination programs using conventional live and inactivated NDV vaccines. In this study, the protective efficacies of three commercial vaccine regimes involving genotype II NDV, recombinant genotype VII NDV-matched, and an autogenous velogenic NDV genotype VII vaccine were evaluated against challenge with velogenic NDV genotype VII (accession number MG029120). Three vaccination regimes were applied as follows: group-1 received inactivated genotype II, group-2 received inactivated recombinant genotype VII NDV-matched, and group-3 received velogenic inactivated autogenous NDV genotype VII vaccines given on day 7; for the live vaccine doses, each group received the same live genotype II vaccine. The birds in all of the groups were challenged with NDV genotype VII, which was applied on day 28. Protection by the three regimes was evaluated after infection based on mortality rate, clinical signs, gross lesions, virus shedding, seroconversion, and microscopic changes. The results showed that these three vaccination regimes partially protected commercial broilers (73%, 86%, 97%, respectively, vs. 8.6% in non-vaccinated challenged and 0% in non-vaccinated non-challenged birds) against mortality at 10 days post-challenge (dpc). Using inactivated vaccines significantly reduced the virus shedding at the level of the number of shedders and the amount of virus that was shed in all vaccinated groups (G1-3) compared to in the non-vaccinated group (G-4). In conclusion, using closely genotype-matched vaccines (NDV-GVII) provided higher protection than using vaccines that were not closely genotype-matched and non-genotype-matched. The vaccine seeds that were closely related to genotype VII.1.1 provided higher protection against challenge against this genotype since it circulates in the Middle East region. Updating vaccine seeds with recent and closely related isolates provides higher protection.

Isolation and phylogenetic analysis of Avian orthoavulavirus 1 sub-genotypes VII.2 and XXI.1.2 from caged birds in the Lahore district, Pakistan – Short communication

In this study, the prevalence of Avian orthoavulavirus-1 (AOAV-1) (also commonly known as Newcastle disease virus) was investigated in caged birds kept in bird markets in the Lahore district of Pakistan. A total of 354 swab samples were obtained from 14 different species of clinically healthy birds. The overall virus prevalence was 12.7% in 9 out of the 14 species. Phylogenetic analysis of the complete fusion protein (F) gene showed that 23 isolates from different avian species belonged to sub-genotype VII.2 while three isolates of pigeon origin clustered with sub-genotype XXI.1.2. The VII.2 viruses isolated had a high nucleotide identity to viruses repeatedly isolated from poultry in Pakistan from 2011 to 2018. To date, sub-genotype XXI.1.2 viruses have only been identified in Pakistan. These findings suggest that the Newcastle disease (ND) outbreaks occurring in Pakistan involve multiple hosts and environments. The study emphasises the importance of continuing to monitor multiple avian species for the presence of AOAV-1s and implementing effective ND control strategies.

Single-Dose Vaccination of Recombinant Chimeric Newcastle Disease Virus (NDV) LaSota Vaccine Strain Expressing Infectious Bursal Disease Virus (IBDV) VP2 Gene Provides Full Protection against Genotype VII NDV and IBDV Challenge

Newcastle disease virus (NDV) and infectious bursal disease virus (IBDV) are the two most important and widespread viruses causing huge economic losses in the global poultry industry. Outbreaks of genotype VII NDV and IBDV variants in vaccinated poultry flocks call for genetically matched vaccines. In the present study, a genetic matched chimeric NDV LaSota vaccine strain expressing VP2 gene of IBDV variant, rLaS-VIIF/HN-VP2 was generated for the first time, in which both the F and HN genes of LaSota were replaced with those of the genotype VII NDV strain FJSW. The cleavage site of the FJSW strain F protein in the rLaS-VIIF/HN-VP2 genome was mutated to the avirulent motif found in LaSota. Expression of IBDV VP2 protein was confirmed by western blot. The rLaS-VIIF/HN-VP2 maintained the efficient replication ability in embryonated eggs, low pathogenicity and genetic stability comparable to that of parental LaSota virus. One dose oculonasal vaccination of one-week-old SPF chickens with rLaS-VIIF/HN-VP2 induced full protection against genotype VII NDV and IBDV lethal challenge. These results indicate that the rLaS-VIIF/HN-VP2 is a promising bivalent vaccine to prevent infections of IBDV and genotype VII NDV.

Effectiveness of vaccines produced by the Federal State-Financed Institution “ARRIAH” against topical genotype VII Newcastle disease viruses

In 2019, the situation regarding Newcastle disease in the Russian Federation worsened radically due to the spread of NDV subgenotype VII-L throughout the country from the Primorsky Krai to the Kursk Oblast. As a result, 17 infected settlements with backyard farms where unvaccinated poultry was kept were registered. In this study, immunogenicity of the vaccines produced by the FGBI “ARRIAH”, as well as the effectiveness of various vaccination schedules to prevent genotype VII NDVs, relevant for the Russian Federation, was studied. It is known that the currently circulating ND agent is significantly more virulent compared to the viruses isolated in previous years, and it is able to bypass the immunity provided by live vaccines. Test results demonstrated that the vaccines against genotype VII NDVs produced by the FGBI “ARRIAH” are highly immunogenic, which allows to effectively prevent the disease when using them as part of a standard vaccination schedule. A 2-dose vaccination schedule using live vaccine from the La Sota strain as well as the “complete” vaccination schedule using inactivated vaccines provides immunity in 100% of chicks. The use of live vaccines in a single- and double-dose vaccination schedules prevents mortality and clinical disease in poultry, but does not prevent virus replication, while the addition of an inactivated vaccine to the immunization schedule does prevent the replication of the virulent virus. Thus, the use of domestically produced live and inactivated vaccines, primarily the ones containing the La Sota strain, with the following control of the immunity level and booster vaccination, if required, is the main tool for the disease control.

Molecular Characterization of Velogenic Newcastle Disease Virus (Sub-Genotype VII.1.1) from Wild Birds, with Assessment of Its Pathogenicity in Susceptible Chickens

Newcastle disease (ND) is considered to be one of the most economically significant avian viral diseases. It has a worldwide distribution and a continuous diversity of genotypes. Despite its limited zoonotic potential, Newcastle disease virus (NDV) outbreaks in Egypt occur frequently and result in serious economic losses in the poultry industry. In this study, we investigated and characterized NDV in wild cattle egrets and house sparrows. Fifty cattle egrets and fifty house sparrows were collected from the vicinity of chicken farms in Kafrelsheikh Governorate, Egypt, which has a history of NDV infection. Lung, spleen, and brain tissue samples were pooled from each bird and screened for NDV by real-time reverse transcriptase polymerase chain reaction (RRT-PCR) and reverse transcriptase polymerase chain reaction (RT-PCR) to amplify the 370 bp NDV F gene fragment. NDV was detected by RRT-PCR in 22 of 50 (44%) cattle egrets and 13 of 50 (26%) house sparrows, while the conventional RT-PCR detected NDV in 18 of 50 (36%) cattle egrets and 10 of 50 (20%) of house sparrows. Phylogenic analysis revealed that the NDV strains identified in the present study are closely related to other Egyptian class II, sub-genotype VII.1.1 NDV strains from GenBank, having 99.7–98.5% identity. The pathogenicity of the wild-bird-origin NDV sub-genotype VII.1.1 NDV strains were assessed by experimental inoculation of identified strains (KFS-Motobas-2, KFS-Elhamoul-1, and KFS-Elhamoul-3) in 28-day-old specific-pathogen-free (SPF) Cobb chickens. The clinical signs and post-mortem changes of velogenic NDV genotype VII (GVII) were observed in inoculated chickens 3 to 7 days post-inoculation, with 67.5–70% mortality rates. NDV was detected in all NDV-inoculated chickens by RRT-PCR and RT-PCR at 3, 7, and 10 days post-inoculation. The histopathological findings of the experimentally infected chickens showed marked pulmonary congestion and pneumonia associated with complete bronchial stenosis. The spleen showed histocytic cell proliferation with marked lymphoid depletion, while the brain had malacia and diffuse gliosis. These findings provide interesting data about the characterization of NDV in wild birds from Egypt and add to our understanding of their possible role in the transmission dynamics of the disease in Egypt. Further research is needed to explore the role of other species of wild birds in the epidemiology of this disease and to compare the strains circulating in wild birds with those found in poultry.

Efficacy of a Turkey Herpesvirus Vectored Newcastle Disease Vaccine against Genotype VII.1.1 Virus: Challenge Route Affects Shedding Pattern

The control of Newcastle disease (ND) highly relies on vaccination. Immunity provided by a ND vaccine can be characterized by measuring the level of clinical protection and reduction in challenge virus shedding. The extent of shedding depends a lot on the characteristics of vaccine used and the quality of vaccination, but influenced also by the genotype of the challenge virus. We demonstrated that vaccination of SPF chicks with recombinant herpesvirus of turkey expressing the F-gene of genotype I ND virus (rHVT-ND) provided complete clinical protection against heterologous genotype VII.1.1 ND virus strain and reduced challenge virus shedding significantly. 100% of clinical protection was achieved already by 3 weeks of age, irrespective of the challenge route (intra-muscular or intra-nasal) and vaccination blocked cloacal shedding almost completely. Interestingly, oro-nasal shedding was different in the two challenge routes: less efficiently controlled following intra-nasal than intra-muscular challenge. Differences in the shedding pattern between the two challenge routes indicate that rHVT-ND vaccine induces strong systemic immunity, that is capable to control challenge virus dissemination in the body (no cloacal shedding), even when it is a heterologous strain, but less efficiently, although highly significantly (p < 0.001) suppresses the local replication of the challenge virus in the upper respiratory mucosa and consequent oro-nasal shedding.