|By JANE HOUIN
WASHINGTON, D.C. — The USDA announced last week that routine surveillance discovered the presence of H5 and N1 avian influenza subtypes in samples from two wild mute swans in Michigan, but testing has ruled out the possibility of this being the highly pathogenic H5N1 strain that has spread through Asia, Europe and Africa.
Thus far, test results indicate this is a low pathogenicity avian influenza, which poses no threat to human health. Avian influenza is a virus that can cause a varying amount of disease among birds, including chickens, turkeys, pheasants, quail, geese and ducks as well as a variety of other birds. Virus strains can be either low or high pathogenic, based on the severity of the illness they cause in poultry.
The swans were sampled as part of the expanded avian influenza surveillance program. They were showing no signs of sickness. Genetic analysis of the virus conducted at USDA’s National Veterinary Services laboratories (NVSL) in Ames, Iowa, suggests that it is similar to a low pathogenicity strain that has been found in North America.
According to the Michigan Department of Agriculture, low-path avian influenza viruses have been found for decades and are most often found in migratory waterfowl, such as ducks, geese and swans.
Susceptible birds can become infected with avian influenza virus when they have contact with nasal secretions of fecal material from infected birds.
The occurrence of low-path strains in wild birds is seasonal with the highest rate of infection typically occurring in late summer in juvenile waterfowl when they assemble for their first southward migration. The number then decreases in the fall as the birds migrate south to their wintering grounds.
USDA officials said it is possible these birds were not infected with an H5N1 strain, but instead with two separate bird flu viruses, one containing H5 and the other containing N1.
The confirmatory testing underway at NVSL will clarify whether one or more strains of the virus are present, the specific subtype, as well as pathogenicity. These results are expected within two weeks and will be made public when completed.
Wild birds are known to harbor many influenza viruses, and the finding of one or more of these viruses during routine testing is not unusual.
The swans were sampled Aug. 8 at the Mouillee state game area located on the coast of Lake Erie in Monroe County, Mich. The samples were taken by USDA Animal and Plant Health Inspection Service personnel as part of an expanded wild bird monitoring program.
The USDA and the U.S. Department of Interior are working collaboratively with states to sample wild birds throughout the country for the presence of highly pathogenic avian influenza.
The Michigan Department of Natural Resource’s Wildlife Disease Laboratory is conducting three types of surveillance: examination of carcasses from wild bird die-offs, sampling of live-caught birds and sampling of hunter-harvested wild birds.
Initial screening tests on the swan samples were conducted by Michigan State University’s Diagnostic Center for Population and Animal Health - part of USDA’s National Animal Health Laboratory Network. These tests indicated the presence of an H5 avian influenza virus. Confirmatory testing at NVSL confirmed the H5 and the N1.
This testing also suggests, but has not yet confirmed, that this is low pathogenicity avian influenza.
Evidence of LPAI H5N1 has been found on two occasions in wild birds in the United States. In 1975 and 1986, it was detected in wild ducks. These detections occurred as part of routine sampling. LPAI H5N1 has also been detected in Canada, most recently in 2005.
If Michigan citizens discover six or more sick or dead waterfowl in one area, they should call the Michigan DNR Wildlife Disease Laboratory at 517-336-5030. If a single dead bird is discovered, citizens should either fill out a dead bird form at www.michigan.gov/emerging diseases or call a DNR field office.
USDA has also implemented a reporting system to answer calls and inquiries from the public regarding dead or sick wild birds. The toll-free number, 866-4 USDAWS. In addition, USDA is conducting AI surveillance in wild migratory birds in Alaska and 10 other states. Initial AI screening tests are performed by one of more than 45 USDA approved laboratories in the National Animal Health Laboratory Network (NAHLN). In the case of wild bird samples, the U.S. Department of the Interior’s National Wildlife Health Center also performs initial screening tests.
USDA has developed the National Avian Influenza Response Plan to ensure a quick and decisive response when any surveillance system detects any serious poultry disease. In June, USDA’s Draft Summary of the National Avian Influenza Response Plan was posted on the Animal and Plant Health Inspection Service website for review and comment by federal, state and industry leaders. The 180-day report on USDA’s Avian Influenza efforts is available at www.usda.gov/documents/PandemicPlanningReport180.pdf
This farm news was published in the August 23, 2006 issue of Farm World, serving Indiana, Ohio, Illinois, Kentucky, Michigan and Tennessee.