Background and Aim: Foot-and-mouth disease virus (FMDV) serotypes A, O and South African Territories (SAT2) are endemic in Egypt; each is presented by a number of partially related topotypes and lineages, depending on their geographical origin. Continuous mutations and the emergence of new topotypes that lead to occasional vaccination failures were frequently recorded, so this study aimed to genetically characterize the circulating FMD virus strains in Egypt during 2013 and 2014 outbreaks, focusing on amino acids variations in VP1 region. Materials and Methods: A total of 51 oral tissue samples were collected from cattle and buffaloes in 13 farms, and 38 individual cases showed clinical signs suspected to be FMD in six Egyptian Governorates (Cairo, Giza, Qaliubia, Fayoum, Sharquia, and Assiut). FMDV in collected samples was characterized by reverse transcription-polymerase chain reaction (RT-PCR) amplification of full VP1 region, sequencing, and phylogenetic analysis. Results: Out of 51 samples, 44 (86.27%) were positive by RT-PCR using universal primers. Serotype O was predominant and detected in 31 samples (70.45%), serotype A was detected in 9 samples (20.45%), and then serotype SAT2 was identified in 4 samples (9.10%). Sequencing and phylogenetic analysis of VP1 demonstrated clustering of serotype O, A, and SAT2 in EA-3 topotype, ASIA topotype, and topotype VII, respectively. Serotype O is closely related to O/SUD/8/2008 with 94.6% identity but showed 14.6% differences from vaccine strain (O/PanAsia-2) of ME-SA topotype. Furthermore, Serotype A and SAT2 were closely related to recent circulating Egyptian isolates and vaccine strains type A/EGY/1/2012 (Asia topotype, lineage Iran-05) with identity 96.4% and vaccine strain of SAT2/EGY/A/2012 (topotype VII, lineage SAT2/VII/ALX-12) with identity 95.3%, respectively. Conclusion: The present study recommended further studies of serotype O to determine the immunogenic relationship between the vaccine strain and the new strains to attain maximum protection against circulating viruses.
Newcastle disease viruses (NDV) represent a major threat to poultry production worldwide. Recently in Egypt NDV circulated extensively, even in vaccinated farms. In the present study samples were collected from sixteen vaccinated broiler farms in animals exhibiting the typical gross lesions of NDV. Virus isolation and pathogenicity studies for positive samples were carried out in accordance to reference procedures and phylogenetic analysis was carried out based on partial sequences of the Fusion gene. Furthermore, in vivo investigation of the ability of heterologous antibody, induced by commercially available lentogenic strain-based vaccines, to efficiently reduce viral shedding was examined. Results revealed that all the sixteen farms were positive for the presence of NDV. Out of these fifteen were confirmed to due to velogenic viruses, based on a main death time (MDT) ≤ 48 hours and partial sequencing of the F gene that showed the presence of a polybasic amino acid motif. However, three patterns in the cleavage site of these velogenic viruses were identified in the present study. Phylogenetic analysis revealed that all fifteen isolates were clustered with class II genotype VIIb while the remaining isolate (B81) was class II genotype II. Results of the in vivo study revealed that adequate heterologous antibody levels, induced by the proposed vaccination program, sufficiently protected birds from morbidity and mortality. However, virus shedding was quantitatively affected in relation to the time of challenge after vaccination. Altogether, with an absence of vaccines able to induce homologous antibody to the presently circulating viruses, higher antibody levels, which depend on efficient and timely implementation of the vaccination program, are considered as highly important in relation to the reduction of virus shedding.
Infectious bronchitis virus (IBV) affects both vaccinated and unvaccinated flocks worldwide, with a significant impact on the poultry industry. The aim of the present study is to characterize an emerging variant pathogenic IBV originating from field outbreaks in vaccinated Egyptian layer flock. Samples were collected from disease-suspected flock with a history of administration of live and inactivated IBV vaccines (Ma5 type). Virus propagation in embryonated chicken eggs (ECEs), after three successive passages, revealed typical IBV lesions such as curling and dwarfism. The reported isolate was identified by a real-time reverse transcriptase PCR assay targeting nucleocapsid (N) gene and, further characterized by full-length spike (S1) gene sequencing. Phylogenetic analysis revealed clustering of the isolated virus within 4/91 genotype of GI-13 lineage. Deduced amino acid sequences identity revealed 75-76% and 88-90% similarity with the currently used classic (H120, Ma5, and M41) and variant vaccine strains (4/91 and CR88) in Egypt, respectively. Recombination analysis gave an evidence for distinct patterns of origin for the studied isolate providing another example of intra-genotypic recombination among IBVs and the first example of recombination within the GI-13 lineage in the Egyptian field. The studied isolate (IBV/CK/EG/ Fadllah-10/2019) emerged as a result of recombination between the variant group (Egy/var I genotype, GI-23 lineage) as a major parent and the CR88 variant vaccine strain (4/91 genotype, GI-13 lineage) as minor parent. Our data suggest that both mutation and recombination may be contributing to the emergence of IBV variants which ascertain the importance of disease monitoring in vaccinated flocks as well as re-appropriation for the current vaccine strategies.
Newcastle disease virus (NDV), the type member of the species Avian avulavirus 1 (formerly known as avian paramyxovirus serotype 1), causes a highly contagious and economically important disease in a myriad of avian species around the globe. While extensive vaccination programs have been implemented in ND-endemic countries, the disease is continuously spreading in commercial, backyard, and wild captive poultry. In order to investigate the evolution of the virus and assess the efficiency of the vaccine regimens that are currently being applied in commercial poultry, four wild-bird-origin NDV strains were characterized biologically, based on mean death time and intracerebral pathogenicity index, and genetically, based on the cleavage motif (RRQKRF) in the fusion (F) protein. Based on these features, all of the isolates were characterized as velogenic strains of NDV. Phylogenetic analysis based on the complete genome sequence revealed clustering of these isolates within class II, genotype VII. This class of NDV remains the predominant genotype in the Egyptian poultry industry, as well as in those of many Asian and African countries. To investigate the potential of these wild-bird-origin NDV isolates to cause infection in domesticated poultry and to assess the efficacy of currently available vaccines for protection of commercial poultry, an extensive animal challenge experiment was performed. Cumulative clinicopathological and immunological investigations of virus-challenged chickens indicate that these isolates can potentially be transmitted between chicken and cause systemic infections, and the currently applied vaccines are unable to prevent clinical disease and virus shedding. Taken together, the data represent a comprehensive evaluation of the ability of Egyptian wild-bird-origin NDV strains to cause infection in commercial poultry and highlights the need for a continuous and large-scale surveillance as well as revised vaccine approaches. These integrated and multifaceted strategies would be crucial in any efforts to control and eradicate the disease globally.
Since the first report of low pathogenic avian influenza (LPAI) H9N2 virus in Egypt in 2011, the Egyptian poultry industry has suffered from unexpected economic losses as a result of the wide spread of LPAI H9N2. Hence, inactivated H9N2 vaccines have been included in the vaccination programs of different poultry production sectors. The optimal antigen content of avian influenza virus vaccines is essential to reach protective antibody titers. In this study, the correlation between antigen content (based on hemagglutinating units [HAU]) and postvaccination (PV) antibody response of H9N2 inactivated vaccine was studied. Five different vaccine antigen loads (128, 200, 250, 300, and 350 HAU formulas/dose) were investigated in commercial broiler and specific-pathogen-free (SPF) chickens. Vaccine safety and PV antibody responses were monitored. At the fourth week PV only SPF vaccinated groups (128, 200, 250, and 300 HAU/dose) were challenged using LPAI H9N2 (A/Ck/EG/114940v/NLQP/11) virus with 10(6) EID50/bird. Oropharyngeal swabs were used to monitor virus shedding at 2, 4, 6, and 10 days postchallenge. Results showed that all vaccine formulations were well tolerated, and the highest antibody titers were observed in birds vaccinated with higher HAU. Vaccines containing 128 and 200 HAU/dose did not induce the required protective HI titers by 3 wk PV. Meanwhile, the challenge experiment in SPF chickens showed that 250 and 300 HAU vaccine doses were required to reduce the level and duration of virus shedding. Study results thus suggest that inactivated H9N2 vaccines containing at least 250 HAU/dose will induce the optimal protective titers and minimize virus shedding in SPF chickens.
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