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Don't Ask Don't Tell H5N1 Surveillance in Alaska

Recombinomics Commentary 13:51
May 2, 2008

No. of samples: Total of 400 samples, including 200 fecal samples from nesting birds and 200 cloacal swabs from brood flocks.

Sampling locations: Samples will be collected at different Islands in the Aleutian chain, including Buldir, Shemya and Agattu where Alaska Maritime NWR will have crews in place for seabird monitoring.

Sampling timeframe: Primary time frames will be late May to early June when birds are on nests, and late July and early August when adults with young are flightless.

Sample demographics: Geese of all age and sex classes will be sampled. Fecal samples of nesting birds will only include adults.

Methods of capture: Samples of nesting birds will likely be restricted to fecal specimens obtained in areas where nesting birds have recently foraged. Flightless birds will be captured be a field crew on Buldir Island by using long-handled nets.

Other targeted species: Sampling during the nesting period on Agattu will be done in conjunction with sampling for Common Eiders. Asiatic species are abundant on the Aleutian Islands and it may be possible to obtain fecal samples from a number of them.

The above comments are from the public protocol for collecting samples from Aleutian Cackling Geese.  These procedures have become of interest because of recent H5N1 positives in South Korea, southeastern Russia, and northwestern Japan (see satellite map).  The most recent collections in northeastern Japan are the closest confirmed H5N1 cases relative to North America.  The bird flu in Hokkaido is 800 miles northeast of the record outbreaks in South Korea and 800 miles southwest of the Aleutian Islands.  The Aleutian Cackling geese winter in Japan and then fly to the Aleutian Islands in late spring, raising the possibility of transport of H5N1 to North America.

However, sampling of fecal samples and cloacal swabs is not an efficient method for detecting H5N1 in live wild birds.  The H5N1 in South Korea last season was the clade 2.2.3 Uvs Lake strain, which was found in the massive Uvs Lake outbreak in wild birds in the summer of 2006.  It is likely that the H5N1 in South Korea, Russia, and Japan is also clade 2.2 and is likely clade 2.2.3 Uvs Lake strain.

It has been known for several years that H5N1 levels are higher in pharyngeal swabs.  These higher levels are even more applicable to clade 2.2, since the vast majority of clade 2.2 isolates have had PB2 E627K, a polymorphism found in seasonal flu, and associated with higher polymerase activity at lower temperatures (33 C).  Consequently levels will be higher in nose and throat swabs where the body temperature of the host is lower.

The latest detection of H5N1 in northeastern Asia has much in common with events in 2005 in central Asia.  On May 9, 2005 dead bar headed geese were noted at Qinghai Lake, the largest lake in China.  Although the initial reports were on 178 bar headed geese, the OIE report filed near the end of May included five long range migratory bird species.  In June, China reported H5N1 on farms in northeast China, on a line connecting Qinghai Lake to Chany Lake in southern Siberia.  By mid-July H5N1 was reported at farms surrounding Chany Lake.  Sequence analysis showed that the H5N1 was clade 2.2 (Qinghai strain)., including H5N1 from a healthy crested grebe.

The Chany Lake outbreak was followed by an outbreak at Erhel Lake in Mongolia in August.  H5N1 was again detected in dead birds and was also clade 2.2, but conservation groups failed to detect H5N1 in live wild birds when fecal samples and cloacal swabs were collected.  These data highlighted the shortfalls of this approach, but these same groups have now tested 350,000 fecal samples, which are largely negative.

Recent lab controled infections of a number of wild bird species also showed similar results.  H5N1 could be detected in pharyngeal swabs but was rare in cloacal swabs.  Similarly, H5N1 was not detected in the intestines.  Isolation of H5N1 was limited to a single 24 hour collection, highlighting the fact that the majority of daily collections failed to yield H5N1 isolates, even under ideal lab conditions.

The surveillance of H5N1 in North America has produced similar results.  There are 46 samples listed that tested positive for H5N1.  However, virus was isolated from 20 of the samples, while only 11 of the 20 were H5N1, which were low path H5N1.  Thus, more than 75% of H5N1 positive samples fail to yield H5N1 virus, and in many instances the isolated virus did not have H5 or N1.  All of these samples were from live (or hunter killed birds).

H5 was detected in a dead gosling on Prince Edward Island.  Since low path H5N1 rarely kills waterfowl, the three goslings with neurological symptoms followed by rapid death were likely to have been clade 2.2 H5N1 positive.  However, the sample was held on Prince Edward Island for 10 days, and the degraded sample failed to yield a PCR positive or virus when shipped to the National labs in Winnipeg.

Although fecal samples do occasionally test positive for clade 2.2 H5N1 testing of 400 fecal or cloacal swabs is unlikely to yield positive data, even if these birds are H5N1 infected, because detection is limited to a very small time frame, even when pharyngeal swabs are collected.

Similar limited testing of fecal samples is planned for Japan, where all positives reported this season have been from dead or dying waterfowl.  Therefore positive results from the surveillance in Japan is also likely to yield an over abundance of false negative.

This “don’t ask, don’t tell” approach of H5N1 surveillance remains a cause for concern.

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