The efficacy of simultaneous successive classic and variant infectious bronchitis virus vaccines versus circulating variant II Egyptian field virus.

Background: Being a ubiquitous, highly contagious virus with a continuous mutation and a large number of evolutions worldwide, the infectious bronchitis virus (IBV) continues to wreak problems among Egyptian chickens and generate economic losses. The commonly applied IBV vaccination protocols in broilers include alternatives to classic and/or variant attenuated live virus vaccines. Aim: The current study targeted to assess the protective efficacy of concurrent and successive Ma5 and 4/91 vaccine strain regimens against the field variant II IBV strain (IBV-EGY-ZU/Ck-127/2021) in chickens. Methods: Commercial broiler chickens were vaccinated with Ma5 and 4/91 strains simultaneously at 1 and 14 days of age. The evaluation parameters included clinical protection and humoral and early innate immunity aspects in the renal tissues of vaccinated and infected birds. Results: The vaccine regimen ameliorated the clinical and histopathological lesions against variant II IBV and enhanced body gain as well as succeeded in preventing tracheal shedding and minimizing cloacal shedding of the field virus. The IL-1ß mRNA gene expression was evident as early as 24 hours, with highly significant upregulation at 48 hours post vaccination and 24 hours post challenge (PC) in vaccinated birds. Remarkable upregulation was observed in oligoadenylate synthetases (OAS) expression 48 hours PC in vaccinated and unvaccinated infected birds. The vaccinated birds developed a significant antibody titer of 704.0 ± 111.98 at 28 days of age, with a consistent antibody titer increase after the challenge. Conclusion: Overall, a combination of heterologous protectotype commercial vaccines achieved good protection against the Egyptian variant II IBV strain. This vaccine program could be an effective protocol against the threat posed by IBV viruses circulating in the Egyptian field.

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.

Avian Paramyxovirus Type 1 in Egypt: Epidemiology, Evolutionary Perspective, and Vaccine Approach.

Avian orthoavulavirus 1, formerly known as avian paramyxovirus type-1 (APMV-1), infects more than 250 different species of birds. It causes a broad range of clinical diseases and results in devastating economic impact due to high morbidity and mortality in addition to trade restrictions. The ease of spread has allowed the virus to disseminate worldwide with subjective virulence, which depends on the virus strain and host species. The emergence of new virulent genotypes among global epizootics, including those from Egypt, illustrates the time-to-time genomic alterations that lead to simultaneous evolution of distinct APMV-1 genotypes at different geographic locations across the world. In Egypt, the Newcastle disease was firstly reported in 1947 and continued to occur, despite rigorous prophylactic vaccination, and remained a potential threat to commercial and backyard poultry production. Since 2005, many researchers have investigated the nature of APMV-1 in different outbreaks, as they found several APMV-1 genotypes circulating among various species. The unique intermingling of migratory, free-living, and domesticated birds besides the availability of frequently mobile wild birds in Egypt may facilitate the evolution power of APMV-1 in Egypt. Pigeons and waterfowls are of interest due to their inclusion in Egyptian poultry industry and their ability to spread the infection to other birds either by presence of different genotypes (as in pigeons) or by harboring a clinically silent disease (as in waterfowl). This review details (i) the genetic and pathobiologic features of APMV-1 infections in Egypt, (ii) the epidemiologic and evolutionary events in different avian species, and (iii) the vaccine applications and challenges in Egypt.