In recent weeks – after a prolonged absence of bird flu reports out of Japan - the H5N1 virus has been detected in several wild birds (ducks, swans) and at a poultry farm.
Recent blogs on those events include:
Now, we’ve reports of four sick or dying hooded cranes at the national reserve in Izumi City, Kagoshima Prefecture Japan, where 80% of the world’s hooded cranes overwinter.
Of those, one has tested positive for the H5N1 virus, and tests are being conducted on the others.
First, an English language report (and video) from NHK news, and then I’ll return with some thoughts on why all of this matters.
Wed, 22 Dec 2010
The Environment Ministry is analyzing bird flu virus detected in a wild crane in southwestern Japan to confirm what measures should be taken to prevent the virus from spreading.
There are estimated to be fewer than 10,000 hooded cranes in the world, and the International Union for Conservation of Nature (IUCN) lists the species as Vulnerable (one step up from Endangered).
Their habit range is basically the northern end of the great East Asian - Australasian Flyway.
Breeding grounds are primarily in Siberia (and to a lesser extent, Mongolia) and the birds over winter in parts of Korea and China, but primarily in southern Japan.
You can find extended information on the Hooded Crane at the International Crane Foundation website.
Given their apparent ill effects from the H5N1 virus, and the long migratory distances involved, it doesn’t necessarily follow that these sick cranes were exposed to the virus in Siberia or Mongolia and subsequently brought it to Japan.
However, we do know that some species of birds (certain types of ducks, for instance) are perfectly capable of carrying the infection asymptomatically, with little or no ill effect.
Which suggests that these cranes may have been exposed either en route to Japan or perhaps after their arrival, via another migratory species.
Although we’ve not heard a lot about bird flu in Russia recently, in 2007 and 2008 we saw surveillance reports of wild birds in Siberia showing the presence of the H5N1 virus (see Siberian Birds Test Positive For H5N1 Antibodies and Siberian Birds Show H5N1 Antibodies).
The gist of these reports was that up to 2% of the birds sampled in Siberia showed antibodies to the H5N1 virus.
These birds, alive and healthy, were exposed at some point in their lives to the virus and either recovered or were never sickened to begin with.
In 2008, the following news story appeared in the Korean press (link is now dead).
Researchers have found that strains of bird flu found in Korea and Japan this year are almost genetically the same. The National Veterinary Research and Quarantine Service said Wednesday that the genetic makeup of a strain of bird flu sampled from chickens in Gimje, South Jeolla Province was 99.7 percent identical to a sample from swans found in Japan's Akita prefecture.
The finding gives grounds to analysis that the latest outbreak of avian influenza may have originated from migratory birds.
And according to the OIE Report filed on Japan’s poultry outbreak last month (see OIE Notification On Japan’s H5N1)", the strain detected in November was very close to the strain detected in Hokkaido, Japan in 2008.
On 2 December 2010, the institute confirmed the cases as highly pathogenic avian influenza because the isolate caused 75 % mortality in 4-week-old chickens infected intravenously, and the amino acid sequence of the connecting peptide of the haemagglutinin was the same as that observed for the highly pathogenic avian influenza viruses isolated from faeces of wild ducks in Hokkaido in October 2008.
The emergence of similar strains of H5N1 over a period of years, and across great distances (Siberia to Izumi City = 2,000 miles) strongly supports the notion that the virus keeps being re-introduced to Japan (and Korea) by some species of migratory birds – probably coming out of Siberia, Mongolia, and China.
It should be noted that the East Asian - Australasian Flyway also encroaches on western Alaska, providing a potential air-bridge for the virus to migrate to North American birds as well.
The USGS and the Alaska Science Center track birds that migrate between Alaska and Asia, and from Alaska to the rest of the Americas, and test them for avian influenza viruses.
Thus far, the highly pathogenic H5N1 has not been detected in North America.
Four migratory species (see USGS Tracking Animal Movements with Radio Telemetry) of particular interest are:
Common Eider - Eiders move from Alaska's North Slope to Russia and back.
Long-tailed Ducks - These waterfowl migrate to Japan via Russia from Alaska's North Slope and also around the state of Alaska.
Black Brant - These geese migrate from Western Alaska to Baja Mexico and back.
Loons - Loons are wide-ranging from Alaska to Mexico and Alaska to China and Japan.
The discovery of a few dead cranes from the H5N1 in some remote marsh or wildlife preserve halfway around the world may not sound like a big story, but it serves as an early warning system that the virus is on the move.
And that not only endangers wildlife and poultry interests, it poses a potential hazard to humans as well.