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Commentary
Abysmal MN Fujian
H5N2 WB Surveillance Raises
Concerns
Recombinomics Commentary
April 28, 2015 10:15
Carstensen reported on Apr 25 that the DNR has submitted 2,314 fecal samples for testing, including 1,740 from waterfowl in areas near infected farms and 574 from control sites. Test results on 915 of these revealed no HPAI viruses and just seven low-pathogenic viruses, she said.
DNR officials said earlier they had collected 148 fecal samples from wild birds in the vicinity of the western Minnesota outbreak. Wild birds have been widely suspected of spreading H5N8 from Asia to the United States and diffusing both strains within the country, but some experts have questioned that thinking.
The above comments (in red) describe the Minnesota DNR efforts to detect Fujian clade 2.3.4.4 H5 in wild bird feces in Minnesota. The detection frequency of 0.77% for influenza A is abysmal, and lower than earlier efforts (in blue) where 1.3% of samples were influenza A positives.
Avian influenza is common in wild birds and 10-20% of ducks have detectable influenza A.
When HPAI H5N2 was reported in Fraser Valley in British Columbia in December, the USDA launched enhanced surveillance in the administrative Pacific Flyway. Most samples were from throat and cloacal swabs from hunter killed birds and in December and January these efforts identified Fujian H5 (H5N1, H5N2, H5N8) in 51 wild birds (in 12 species).
However, at the end of hunting season, the positives abruptly stopped and no H5 has been reported in any of the positives states since January 23. The sole subsequent positive was a cinnamon teal in New Mexico detected through routine surveillance in a February 19 collection.
During enhance surveillance in the Pacific Flyway multiple national agencies (USDA-APHIS, USGS-NWHC, USDA-SEPRL) as well as local agencies (WA-DFW, OR-DFW, ID-DFG, WY-GFD, UC Davis) were involved.A USGS-NWHC January 26 report on the agency data through mid-January cited collection of tracheal and cloacal swabs from over 1200 birds in the Pacific Flyway (largely from Washington) and 167 (13.9%) were influenza A positive (based on PCR positive M gene), which is a common frequency for ducks, which are infected with a wide range of influenza serotypes. The 167 influenza A positives yielded 7 that were Fujian H5 confirmed (4.2%).
These numbers indicate that the Minnesota DNR is detecting influenza A at a rate that is strikingly low, signaling serious concerns about sample integrity due to degradation, transport, storage, packaging, or a host a possible factors that create false negatives. Unfortunately, these low numbers have been cited in multiple CIDRAP reports claiming that wild birds are not responsible for the outbreaks in Minnesota, which has been echoed in ProMED reports.
In addition to false negatives associated with highly suspect testing, the absence of positives due to an absence of testing has been used to claim that the H5N2 had “jumped” from the Northwest to Midwest or was “hopscotching” around the US, terminally inconsistent with wild bird spread.
Moreover, the delayed testing in the Midwest was also used to note that positives in wild birds in the Midwest were lower than the numbers generated through enhanced surveillance in the Pacific Flyway during hunting season.
The most recently reported wild bird positives were snow geese that were confirmed on April 10, but had been collected on March 5 in St Charles County in Missouri. Thus, the spatial and temporal parameters matched the outbreaks in Missouri, Arkansas, and Kansas on commercial turkey and backyard mixed farms (H5N2 map ), but the confirmed wild bird cases is low because the number of samples collected were limited and testing/reporting was delayed (the April 10 confirmations were reported on April 17, the last wild bird update).
The failure to detect Fujian H5N2 in wild birds in Minnesota, coupled with confusion over the relationship between the three Fujian H5 serotypes with the parental H5N1 bird flu strain (clade 2.3.4), that has been killing humans in China since 2005, increases the likelihood of human cases.
Poultry workers have decline prophylactic oseltamivir (Tamiflu) and media reports downplay the likelihood of Fujian H5N2 human infections linked to culling and management in large poultry farms in the Midwest, which includes the calling up of the National Guard to transport water used to activate foam used in the culling of more than 13 million (and counting) birds in the United States.
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