Abstract:
This study was to determine the persistence of isolated avian influenza subtype H5N1 from the central and eastern parts of Thailand between January and February 2004 (the 1 [superscript st] outbreak) and October 2004 (the 2 [superscript nd] outbreak) against various conditions including disinfectants, temperature and pH. Lungs, intestines, tracheas and livers of suspected chickens were isolated and identified as avian influenza virus (AIV) H5N1 by inoculation of 11 days old of chicken embryonated eggs (CEE) hemagglutination test, hemagglutination inhibition test and polymerase chain reaction. The AIV H5N1 propagation and virus titration were done by inoculation of CEE. The allantoic fluid (AF) of CEE containing AIV H5N1 was stored at -80 degree Celsius until used. The AF containing AIV H5N1 was extracted for RNA, which was submitted for nucleotide sequencing of hemagglutinin (HA) and neuraminidase (NA) genes followed by sequencing analysis by BioEdit software version 7.0.5.3. Three AIV H5N1 isolates, each containing 1.0 x 10[superscript 8] ELD[subscript 50]/ml, were determined the persistence of virus with recommended concentration of disinfectants including glutaraldehyde (GLu)< hydrogenperoxide, quatermary compounds (QAC), Glu+QAC, iodine, chlorine, formalin and phenol at 25 and 37 degree Celsius, stored for 0, 5, 7, and 14 days. The exposure time of treated AIV H5N1 with disinfectants was 10 min. The physical methods including various temperatures at 55, 60, 65 70 and 75 degree Celsius for 10, 15, 30, 45 and 60 min an the pH at 3, 5, 7, 9 and 12 were determined. The treated AIV H5N1 were inoculated into six 11 days old of CEE. The inoculated CEE were incubated, observed and recorded for 7 days. The death of inoculated CEE was harvested for the AF, which was isolated and identified as AIV H5N1 as previously described. Results revealed that the 1 [superscript st] and 2 [superscript nd] outbreak found AIV H5N1 for 8 and 1 isolates, respectively. Numbers of nucleotides and the homology of nucleotide sequences of H5 and N1 genes of all 9 isolates were 1638-1670 and 1306-1321, and 99.32%-99.88% and 99.16%-100%, respectively. Three AIV H5N1 isolates, 2004.1, CUK-2/04 and 2004.2, showed the low or no persistence against Glu, Glu+QAC, chlorine and phenol at 25 and 37 degree Celsius. The temperatures at 65 degree Celsius for 60 min and/or at least 70 degree Celsius for at least 10 min could inactivate, where as all ranges of pH could not inactivate all 3 isolates. In this study, CUK-2/04 was more persistent against disinfectants, temperatures, and pH compared to other isolates.