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Sensitivity of Real Time –PCR in comparison with conventional methods for detection of AI virus

Sensitivity of Real Time –PCR in comparison with conventional methods for detection of AI virus

Lamiaa M. Omar, Mohamed A. Abdrabo, Dali M. Omar, Nermeen A. Marden


Background: Avian influenza virus (AIV) infection, an important but difficult pathogen to control in
poultry. Vaccination might reduce the risk of bird infection virus transmission by reducing virus
shedding. Challenge of vaccinated birds with AI vaccines under strictly controlled condition with
virulent HPAI virus may also be used to predict flock response to AI infection. The reduction in
challenge virus replication can be quantified using classical virus isolation (VI) and titration methods
in (ECE) or by molecular assay for detection AI virus specific nucleic acids such as (rRT-PCR).
Methods: Titration of the HPAI virus for infection of SPF chicken. The tracheal swabs were collected
from diseased chicken for virus isolation and quantification by ECE inoculation and rRT-PCR.
Results: the titer of original HPAI virus was 1010.3 EID50/ml. The AI titers after experimental
infection of chicken and viral re-isolation were 1010.3 EID50/ml in ECE and 1.6×107 copies/ml by
rRT-PCR to sample (1), 105.4 EID50/ml in ECE and 1.2 ×106 copies/ml by rRT-PCR to sample (2),
and 106.2 EID50/ml in ECE and 4×105 copies/ml by rRT-PCR to sample (3). The egg inoculation
method detect a gradual decrease in percentage of positive egg for AI infection which were 100, 80,
80, 60,20 and 0 %for the viral dilutions 6,7,8,9,10 and11 respectively. While the rRT-PCR give 100%
positive results with all the sample dilutions. The reduction in viral shedding with values of 3.4, 2.9
and 2.4 when measured by ECE from the vaccinated chicken with inactivated H5N1, H5N2 and
inactivated recombinant vaccines respectively. While, the ranges from 102, 102 and 10 when measured
by rRT-PCR respectively. Also, the live recombinant vaccine could not reduce the viral shedding
when measured by both egg inoculation and rRT-PCR.
Conclusion: Depending on the previous phenomena this study showed that despite the expensive and
latency of VI, it is more sensitive and accurate for detection of AI infection and titer of viral shedding
in vaccinated chicken.

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Journal of Virological Sciences


Vol. 3, Iss. 1


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