Avian influenza virus H9N2 survival at different temperatures and pHs.

The H9N2 avian influenza virus (AIV) subtype has become endemic in Israel since its introduction in 2000. The disease has been economically damaging to the commercial poultry industry, in part because of the synergistic pathology of coinfection with other viral and/or bacterial pathogens. Avian influenza virus viability in the environment depends on the cumulative effects of chemical and physical factors, such as humidity, temperature, pH, salinity, and organic compounds, as well as differences in the virus itself. We sought to analyze the viability of AIV H9N2 strains at three temperatures (37, 20, and 4 C) and at 2 pHs (5.0 and 7.0). Our findings indicated that at 37 C AIV H9N2 isolate 1525 (subgroup IV) survived for a period of time 18 times shorter at 20 C, and 70 times shorter period at 4 C, as measured by a decrease in titer. In addition, the virus was sensitive to a lower pH (pH 5.0) with no detectable virus after 1 wk incubation at 20 C as compared to virus at pH 7.0, which was viable for at least 3 wk at that temperature. The temperature sensitivity of the virus corresponds to the occurrence of H9N2 outbreaks during the winter, and lower pH can greatly affect the viability of the virus.

H9N2 influenza viruses from Israeli poultry: a five-year outbreak.

Since 2000, hundreds of H9N2 viruses have been isolated from all types of domestic birds. Although H9N2 is a low-pathogenicity virus, disease has been observed in all types of poultry in the field. Clinical signs ranged from very mild disease to high morbidity and mortality when the virus was associated with a secondary pathogen. Because of the wide range of the virus and the great losses it caused, initially a local vaccination program was implemented, but mass vaccination was quickly authorized. A local strain, isolated in 2002 was selected and is currently in use as an inactivated vaccine. An intensive operation is in progress to characterize the isolates. Several genes (hemagglutinin [HA], neuraminidase, nonstructural protein, nucleoprotein, and matrix) were sequenced, revealing three main groups: the first group included two isolates from 2000, the second group included isolates from 2001 to the beginning of 2003, and the third group included all isolates from 2003 to date. The differences between the second and third groups, in a part of the HA gene, ranged from 3.49% to 6.97% (average 4.57%) of the nucleotides. Similar differences were recorded in the other tested genes. These data could indicate the probable introduction of distinct progenitor viruses into the Israeli poultry population. Furthermore, sequencing of the HA protein of some Israeli isolates revealed the presence of L216 in the binding site; this finding was typical of the H9N2 viruses isolated from humans, which raises the possibility of an influence on host specificity and virulence.

Naegleria fowleri in cooling circuits of industrial and power plants in North Moravia.

Both nonvirulent (15 strains) and virulent (1 strain) variants of Naegleria fowleri were isolated from the cooling circuits in seven of ten examined plants in North Moravia. No amoebae were found in waters with a high salinity (electric conductivity more than 614 microseconds) and with a low content of phosphates (less than 0.37 mg . 1(-1)) and oxygen (less than 7.4 mg . 1(-1)). Other results of the physical, chemical and bacteriological examinations showed no direct bearing on the occurrence of N. fowleri.