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National Veterinary Services Lab Pivotal in Avian Flu Fight

posted on August 18, 2006

Influenza is believed to have existed for thousands if not millions of years. Typically, the virus that causes other species to become ill rarely affects humans. But there are exceptions to this rule. The most recent flu virus that crossed from animals to humans appeared in Hong Kong in 1997. In that outbreak, 18 people died. The major concern these days is a potential pandemic of Avian flu. A highly pathogenic strain of the virus has killed more than half of the 200 people worldwide it infected over the past decade. This week, USDA officials confirmed that two wild swans in Michigan had tested positive for Avian flu. But initial testing ruled out the deadly Asian strain of the virus. The birds were sent to America's only nationally recognized avian flu testing facility for further diagnosis. David Miller toured the lab recently and filed this report.

National Veterinary Services Lab Pivotal in Avian Flu Fight

Currently, there is no evidence the H5N1 strain of avian influenza has mutated and can pass directly from human-to-human. But work goes on to keep track of where the virus might appear next.

Larry Granger, Associate Deputy Administrator for Emergency Management and Diagnostics: "We don't have high pathonogenic avian influenza in this country in commercial poultry and we don't have any low path avian influenza either. And so we have a monitoring program that demonstrates that."

To identify the cause of the deaths in 1997, samples were sent more than half way around the world to the United States Department of Agriculture's National Veterinary Services Laboratory, or NVSL, in Ames, Iowa. The doctors and technicians at the secure Ames facility were able to isolate the virus and identify the killer strain as H5N1 Asian.

Since that time, the NVSL has become the laboratory where other international health agencies, including the preeminent French OIE and the United Nations FAO, send avian flu samples for confirmation.

Beverly Schmitt, NVSL: "If we're given a call and it's given a high priority we will prepare ourselves to have the reagents, everything ready to go."

In a worst case scenario, a rapid die-off of 500 or more birds would trigger an alert for samples to be taken and analyzed. If the event were to happen in the United States, the initial sample would be sent to one of 46 sanctioned National Animal Health Network laboratories around the country and a test would be performed for the presence of an avian flu virus. If the result is positive, the sample would be rushed to NVSL in Ames.

Technicians would begin by preparing the samples for a real time polymerase chain reaction or PCR test. The machine which performs this test heats and cools the sample. Computer analysis would identify if an H5 flu virus were present. At the same time, doctors and lab technicians would begin inoculating chicken eggs with a refined version of the sample. This would be followed by identifying the virus as one of the 144 possible combinations of H-types and N-types. If necessary, live chickens would be inoculated with more of the sample to perform further research.

Beverly Schmitt, NVSL: "The PCR test will take approximately three hours for one PCR, but depending on what we find, we'll do some additional testing for sub-types and then if it is a suspect Asian then we will run N1 primers. So, all together it takes up to 12 hours to do all those tests. And the virus isolation can take 2 to 10 days but for the Asian H5 strain it is probably much shorter because it grows so well in eggs and kills the embryos quickly."

If the H5N1 strain were present confirmation would likely take 2 to 4 days.

Scientists at NVSL believe the virus will be carried by migrating ducks or shore birds coming from Asia. Infected birds would theoretically arrive in Alaska and mingle with other birds that fly south for the summer. According to the same scientists, the reason the virus may not have show up in North America is that birds contracting the deadly H5N1 strain are dying before they can fly across the Pacific.

The biggest threat currently is to U.S. free range poultry. If an infected bird carrying the disease were to survive and mingle with an outdoor flock it could infect the entire group.

If, by chance, a bird were to survive and it was purchased at a farmers market, chances of contracting the disease can be eliminated by thorough hand washing, the cleaning of all work surfaces with warm soapy water, and, most importantly, cooking the bird to an internal temperature of at least 165 degrees Fahrenheit.

Scientists at the NVSL believe there is possibility that the H5N1 strain will change enough that it could pass easily among humans.

Dr Dennis Senne, NVSL: "there's no question it will happen again but when and what event will trigger that...will be the next pandemic virus...We just have to be vigilant, have to be alert, to make sure we are looking at all the possibilities and not focusing all of our attention only on the high path H5N1 because something could come back, through the back door when we are not looking and bite us.

As part of the fight against the spread of H5N1 or any other avian flu virus, a baseline is being established by testing of wild birds. Aided by the US Fish and Wildlife Service and the United States Geological Survey, between 80 and 100 thousand samples will be taken and sent to many of the labs in the National Animal Health Network. And if one of them were to test positive it would travel to the NVSL as part of USDA's continuing efforts to fight the spread of avian flu.

For Market to Market, I'm David Miller


Tags: agriculture Ames animals birds diseases government influenza Iowa news USDA