H5N1 in Migratory Birds in New Zealand
Recombinomics Commentary 19:29
September 17, 2008

A surveillance programme researching the presence of avian influenza in New Zealand has found low pathogenic (LPAI) H5N1 virus in two samples taken from mallard ducks. Tests indicate that the virus is closely related to viruses found in the past and has been here for some time.

Sampling of healthy wild birds took place at seven locations across New Zealand in February this year, as part of MAFBNZ's ongoing avian influenza surveillance programme. A total of 1241 samples were collected from mostly mallard ducks and some migratory bird species in Paparoa, the mouth of Kaituna River, Lake Aniwhenua, Reparoa, Napier, Temuka and Invercargill.

The above comments describe the detection of low path H5N1 in New Zealand.  These data are similar to data reported for Canada in 2005, when H5N1 was detected across southern Canada in young mallards.  The result was followed by increased surveillance in North America, which led to more H5 positives the United States and Canada.

These assays however lack sensitivity, especially for high path H5N1.  Beginning in the spring of 2005, high path H5N1 was widely distributed by migratory birds.  Prior to 2005, all reported cases of the “Asian” versions of H5N1 would limited to China and countries to the east.  However, the expansion that began in 2005 lead to reports of clade 2.2 H5N1 in over 50 countries west of China.

Recent outbreaks in South Korea, Japan, and southeastern Russia have signaled a wild bird expansion of another H5N1 sub-clade, which has a clade 2.3.2 HA and clade 2.3.4 for the other 7 gene segments.

Several full sequences, in clued those from two recent isolates from Aomori have been published,  The sequences from multiple locations in northern Japan and southeastern Russia are virtually identical.  Reports from South Korea suggest those isolates are also more than 99.7 identical to these sequences.

Monitoring of the newly acquired polymorphisms in these sequences identifies multiple locations in the East Asian flyway, stretching from Australia and New Zealand in the south, to Alaska and the rest of North America to the north. Include were a number of polymorphisms in PB1, which were recently published from Korean swine, which had many clear examples of homologous recombination, including the PB1 gene.  In the swine the PB1 gene was human and it had recombined with avian sequences from low path wild birds or clade 2.2 H5N1.

The PB1 gene in the clade 2.3.2 sequences had a large number of polymorphisms from H3 isolates from New Zealand and Australia (seelist here or here) raising concerns that the PB1 in the H5N1 was also acquiring polymorphisms from human serotypes.

These data highlight the importance of monitoring these acquisitions and expanding the wild bird database in New Zealand and Australia, including the recently described H5N1 isolates.

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