New testing technique collects bird feces from wetland sediment to check for virus presence and determine strain
The spread of a highly pathogenic avian influenza virus has researchers taking a closer look at migratory birds.
The wild animals, which aren’t affected by the flu, are believed to be a vector for the virus, which can quickly wipe out commercial poultry flocks.
The H5N2 virus identified in British Columbia’s Frasier Valley in December led to the deaths or destruction of 240,000 birds on 11 commercial farms and saw trade restrictions placed on some Canadian poultry products.
The H5N2 virus has since been identified in avian influenza cases in commercial flocks in Ontario and several U.S. states.
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More than two dozen Ontario poultry farms were under quarantine last week after the H5N2 strain was identified on a turkey farm near Woodstock, Ont., earlier in the month.
“It certainly raises concerns: is this year out of the ordinary or is this the start of a trend? With one year, we can’t really say,” said Chelsea Himsworth, leader of veterinary science and diagnostics with the B.C. agriculture ministry’s Animal Health Centre.
Each case brings further trade and transportation restrictions for Canadian and U.S. producers as well as challenges for those who rely on American suppliers for eggs and live animals.
The trail of outbreaks has officials tracing the flight paths of migratory birds.
“I know one of the things that makes me concerned … is that we know that things like climate change alter migratory bird patterns. We’re starting to see flyways intersect that have never intersected before,” said Himsworth.
“Birds are commingling and potentially trading viruses that have never had contact with each other.… I think there is the potential for us seeing more and more of these virulent viruses coming into North America.”
Himsworth said it’s too early to draw connections between the H5N2 virus found in B.C. and those identified elsewhere. Researchers don’t know what species it’s travelling in, although they’re paying closest attention to waterfowl, she added.
Researchers believe the H5N2 virus came from the mixing of a North American virus and a Eurasian one.
“My hypothesis would be that it probably originated up north where these birds were coming from and where they were intermingling,” she said.
“That kind of Arctic area, where the birds fly through and commingle, that would be the most likely starting place that would allow the birds to then travel to all sorts of different destinations.”
Himsworth is co-leader of a project studying how the virus spread in B.C. The project could also lead to the development of an improved surveillance system.
“These outbreaks seem to really catch us by surprise,” she said. “It’s surprising that they are so surprising, given that they occur with relative frequency in the Frasier Valley. You think we would be able to develop a good way to predict it, but when you look at how the tools that we currently have, you can see where these viruses could fall through the cracks.”
Current monitoring efforts focus on testing wild birds that die from other causes. Samples can be taken from live animals, but there are logistical challenges, she added.
Himsworth’s project is trying something new.
Researchers are using sediment collected from wetlands near the affected B.C. farms to hone molecular techniques that will identify the DNA of the virus in the animal’s feces.
“You might have a hundred birds making a donation to one sediment sample,” she said.
“We thought that would be a good idea, but then it’s really like searching for a needle in a haystack, if you can imagine.”
Patrick Tang, a microbiologist with the B.C. Centre for Disease Control and a contributor to the project, said researchers have identified avian influenza within the 250 samples they have collected but are still working to separate the highly pathogenic strain from the less serious ones.
Tang said the work should wrap up by fall, in time for another influx of birds.
