Abstract :
Rapid spreading of the low pathogenic avian influenza virus (AIV)
caused by the H9N2 subtype and the highly pathogenic AIV caused by
H5N1 have caused serious economic losses in the poultry industries ofAsia.
Therefore, the early detection of AIVs is crucial for the control of the
disease. In the present study, the applicability of a rapid
immunochromatographic (RIC) assay, which specifically detected type A
antigens ofAIVs, was evaluated. This assay detected H9N2 viruses at 103.2
ELD50/ml and H5, H7 and H9 antigens at 128 HA titers, but did not react
with other respiratory viruses. The assessment of cloacal swab samples
prepared from 1 to 10 d post-inoculation (PI) revealed that the first positive
samples were detectable on day 2 and 3 PI, and the last positive samples
were detectable on day 10 and 9 PI, by the virus isolation (VI) and RIC
assays, respectively. Collectively, the relative specificity, sensitivity,
positive predictive value, negative predictive value, accuracy and
correlation rate of the RIC and VI assays, were 100%, 71.5%, 100%, 78.5%,
0.86, and 0.98, respectively. There was also a good correlation (? > 0.81)
between the results of the haemagglutination (HI), VI and RIC assays of
cloacal/tracheal swab samples that were obtained from broiler flocks
involved with viral respiratory diseases. Overall, RIC showed a low
sensitivity and high specificity for the rapid diagnosis of H9N2 isolates in
both experimental and clinical infections.
