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H5N1 Wild Bird Flu Confirmed in Seven Kazakhstan Villages
Recombinomics Commentary
August 23, 2005
"The H5N1 strain has been detected in all seven villages," Asylbek Kozhumratov, director of the ministry's Veterinary Department, told reporters.
"The western region is now in the risk zone because (migratory) birds are starting to fly to the Caspian Sea and Urals-Caspian basin," he said.
The confirmation of H5N1 in all seven villages in Kazakhstan is not a surprise. The current series of H5N1 wild bird flu outbreaks began in May at Qinghai Lake in China (see May map). 16 isolates were sequenced and all were very similar. Although there were sequences that traced back to Europe, the isolates were clearly related to H5N1 detected throughout Asia in 2004 and 2005. Three of the genes were similar to isolates from Guangdong Province, while the other five genes were related to isolates from South Korea and Japan.
However, the Qinghai isolates were quite unique and many polymorphisms traced back to sequences found in migratory birds. All isolates had the PB2 polymorphism E627K which is found in all human isolates but had never been isolated directly from H5N1 in birds. The isolates also had polymorphism that traced back to European swine, which added to the acquisition of mammalian polymorphisms. These isolates were quite lethal in chickens, killing experimental chickens in 20 hours. The isolates also killed mice in 3-4 days and had the unusual property of killing water fowl. The H5N1 die off at Qingahi lake was without precedent. Over 6000 birds died, including the five species described in the OIE report.
The death of water fowl was seen again in the following month with outbreaks at Tacheng and Changji in Xinjiang Province (see June map). The following month there was an outbreak near Chany Lake in Novosibirsk, Russia and the adjacent site at Pavlador in Kazakhstan (see July map). Sequencing of the isolates from Chany Lake showed that the H5N1 was closely related to the isolates from Qinghai Lake. The affected farms were scattered and those most affected were generally near water reservoirs frequented by migratory birds.
Similarly, dead waterfowl (whooping swans and bar headed geese) were found at the remote Erkhel Lake in Mongolia. These isolates were also shown to be H5N1. Additional testing of the isolates in Siberia showed that they were all closely related to the isolates from Novosibirsk.
Thus, finding H5N1 in the Kazakhstan isolates is not surprising. The outbreaks in northern Kazakhstan paralleled those in southern Siberia and now new outbreaks are being reported further south as the birds prepare to fly to the Caspian Sea area.
In addition, there are new outbreaks to the north of the migratory path, supporting the notion that migratory birds that are leaving northern Siberia are arriving into southern Siberia with H5N1.
The birds from northern Siberia may also be moving H5N1 further toward western Europe. As the September migration period approaches, the migratory trails of H5N1 should become more pronounced.
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