Efficacy of Five Commercial Available Inactivated Avian Influenza Vaccines in both Specific Pathogen Free (SPF) and Commercial Broiler Chicks against Challenging with the Current Recently Isolated HPAI H5N1 (A/duck/Egypt/CLEVB-24_N00238/2015) Field Strain

Abstract: The endemic highly pathogenic H5N1 avian influenza viruses (A/H5N1) of clade 2.2.1 in Egypt
compromise the poultry industry and pose a serious public health threat. In spite of vaccination, infections of
commercial poultry flocks have been frequently reported. The 2.2.1.2 viruses were isolated from vaccinated
commercial poultry and are postulated to be immune escape variants (IEV). In a trial to control the wide spread
of Highly pathogenic avian influenza (HPAI) H5N1 virus outbreaks among poultry flocks in Egypt this study
has been pursued to Evaluate the efficacy of possible available AI (H5N1, H5N2 and H5N3) vaccines against
challenging with the current recently isolated HPAI H5N1 (A/duck/Egypt/CLEVB-24_N00238/2015) field
strain this trail was planned to explain why some poultry farms are vaccinated against AI and suffered from
outbreaks of HPAI infection. in this study 5 commercially available inactivated avian influenza vaccines were
evaluated for their efficacy using both SPF and broiler chickens, SPF groups were vaccinated at 21st
day old
while broiler groups were vaccinated at 10th
day old to simulate field condition, the groups were serologically
monitored on a weekly basis post vaccination (PV) using HI test, then challenge test were conducted at 28th

PV for SPF groups and at 28th
day old for broiler groups using the recently isolated (A/duck/Egypt/CLEVB-
24_N00238/2015) field strain s challenge virus, oropharyngeal swab samples were collected for detection of
virus shedding titer by real time RT- PCR). The results of HI against the homologous antigens for each vaccine
showed positive seroconversion for the 5 H5 AI vaccines in both SPF and broiler chickens, Meanwhile only 3
H5 vaccines included positive seroconversion against the heterologous A/duck/Egypt/CLEVB-24_N00238/2015
HPAI antigen with mean HI titers of 5.9, 4.7 and 3.9 log2 in broiler chickens and 7.5, 5.1 and 4 log2 in SPF
chickens for poulvac H5N3, Nobilis H5N2 and Re-5 H5N1 AI vaccines respectively. While the two local Re-
H5N1 AI vaccines included HI titers < 3 (negative seroconversion) in both broiler and SPF chickens. These
mean HI values were reflected on the protection percentages which were 90%, 85%, 85%, 50% and 40% in
broiler chickens and 90%, 85%, 90%, 55% and 45%, in SPF chickens vaccinated with poulvac H5N3, Nobilis
H5N2, Re-H5N1, Mevac H5N1 and serovac H5N1 AI vaccines, respectively. Finally concerning the reduction
on the challenged HPAI H5N1 virus shedding, only the same 3 vaccines (poulvac H5N3, Nobilis H5N2 and Re
H5N1 – induced significant reduction in the titer of the shedding virus (more than 2 logs) compared to the non-
vaccinated challenged groups in both broiler and SPF chickens while the rest two did not provide significant
reduction in the titer of shedding virus compared to the non-challenged control group in both boiler and SPF
chickens.
URL
Publication year 2016
Pages 379-385
Organization Name
Author(s) from ARC
Publication Type Journal
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