Vaccination is the major control measure for rabbit haemorrhagic disease virus (RHDV). The co-circulation of different RHDV genotypes in Egypt has led to the need to determine the most effective vaccine strain and the cross-protection between these genotypes. Rabbits seronegative for RHDV were vaccinated with the commercial GI.1a (RHDVa) vaccine strain Giza2006 and the GI.1d (G5) vaccine strain Giza97. The rabbits were challenged three weeks post vaccination with GI.1a (RHDVa) strains Giza2010 and Kal2012 and GI.1d (G5) RHDV Giza97 and RHDV2014 to determine the degree of cross-protection and evaluate immunity and cross-reactivity by haemagglutination inhibition (HI) and indirect enzyme-linked immunosorbent assay (iELISA). Both vaccines were fully protective three weeks post vaccination, with 95% protection for the GI.1a vaccine and 94.7% for the GI.1d vaccine, with no direct relationship between mortality rates and the genotype of the challenge strain. The antibody titres obtained using the HI test were one log higher for the GI.1a compared with the GI.1d vaccine, but post-challenge titres showed increased responses, expressed as 1−3 log 2 higher titres, for the GI.1d vaccine. Sequence and phylogenetic analysis of the Egyptian strain RHDV2014 revealed its relatedness to the GI.1d genotype and showed no evidence of the presence of GI.2 in Egypt until 2014. In conclusion, both GI.1d (G5) and GI.1a (RHDVa)-based vaccines are protective against both RHDV genotypes present in Egypt but continuous monitoring of circulating strains is essential because the arrival of GI.2 in Egypt will require new vaccination strategies.
Riemerella anatipestifer (R. anatipestifer) infection and duck virus hepatitis (DVH) are enormous dangers for the duck industry and its investment. So, in the current study, a combined inactivated vaccine against both of them was prepared to combat their adverse effect. One hundred and thirty-three ducks of one-day-old of age were used and grouped randomly into four groups. Group (1) was vaccinated with R. anatipestifer vaccine, group (2) was vaccinated with DHV vaccine, group (3) was vaccinated with the prepared combined vaccine of both and finally, group (4) was kept as a negative control. Vaccination was at one day old of age. The vaccinated groups with Riemerella vaccine had 72.7% protection against challenges with the virulent strain with the highest antibody titers in 6 th week as measured by the indirect Hemagglutination test. The control group had 90.9% mortality when challenged against R. anatipestifer, with no detectable antibody titers. DVH-vaccinated groups exhibited their highest serumneutralizing antibody titers by the 5 th and 6 th weeks post-vaccination. The Control group had no detectable antibody titers against DVH. Statistically, it was clear that there were no significant differences between the results of different groups vaccinated with combined or single vaccines of the same agent. Briefly, combined vaccines of R. Anatipestifer and duck viral hepatitis have harmonized effects with the priority to decrease the stress on birds and workers. Besides its efficiency, the economic side as providing one-shot vaccines instead of each one separately.
Newcastle disease (ND) is a highly contagious disease causing huge economic losses to the poultry industry due to high morbidities and mortalities. This study was aimed to isolate and characterize the new sub-genotype NDV strains in Qalybia Governorate during 2017 and 2019. Sixty-eight samples were collected from Sixty-eight broiler chicken flocks suffering from high mortality reach to 80% with distinctive clinical signs and post-mortem lesions of NDV. NDV strains isolated through inoculation in specific pathogen free (SPF) eggs and were identified by hemagglutination (HA) and hemagglutination inhibition (HI) techniques. There were 16/20 (about 80%) of selected suspected farm were positive for NDV With HI test. These hemagglutinating agents were confirmed as NDV strains through molecular characterization using one step RT-PCR targeting the partial F-gene of NDV. Sequencing and phylogenetic analysis were successfully performed with eight NDV isolates which possessed the motif 112 R/K-R-Q-K/RR116 at the C-terminus of the F2 protein and F (phenylalanine) at residue 117, indicating that they are velogenic genotype. The present study revealed the circulation of NDV class II genotype VII in Qalybia chicken flocks F protein Cleavage site
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