Capture of Northern Pintails at Lake Izunuma-Uchinuma, Japan

A female Northern Pintail marked with a solar-powered satellite transmitter. Photo credit: Dr. Tetsuo Shimada, Izunuma-Uchinuma Environmental Foundation

Locations in Japan where Northern Pintail Ducks where captured and radiomarked.

Evaluating exchange of avian-borne pathogens between Asia and North America by migratory birds requires an understanding of patterns of contact among birds from each continent. Biologists at the Alaska Science Center (USGS) are comparing neutral nuclear and mitochondrial genetic similarities between Asian and North American pintails to evaluate the degree of reproductive isolation between these populations, and are assessing transcontinental transmission of avian influenza by comparing genetic similarities of low pathogenic (non-H5N1) virus strains in pintails wintering in California to those from Japan. Collaborators include the Laboratory of Biodiversity Science (University of Tokyo), USGS National Wildlife Health Center, Western Ecological Research Center, and the U.S. Fish and Wildlife Service.

Read about genetic analyses of avian influenza in Northern Pintails at following Progress Report:

Movements of Northern Pintail Ducks and Whooper Swans Marked with Satellite Transmitters in Japan

For more information contact Dirk V. Derksen, Alaska Science Center.

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Common shellduck (Tadorna tadorna) carrying a satellite transmitter as part of avian influenza surveillance efforts in Egypt. Photo credit: Eric C. Palm, USGS

Efficient methods for the detection of avian influenza (AI), particularly those subtypes that are lethal to humans, poultry and wild birds, are necessary for the prevention of outbreaks. Rapid detection methods also represent a breakthrough for research that seeks to unravel the role of wild birds in the spread of the virus. The ability to determine the host status of wild birds at the time of field sampling, makes it possible to deploy satellite transmitters to track the movement of the host. This information would enhance understanding of whether wild birds can act as vectors for highly pathogenic subtypes such as the lethal subtype, H5N1. Recently developed molecular methods, such as real-time reverse transcriptase polymerase chain reaction (rRT-PCR) offers one of the most accurate and sensitive techniques for diagnosis of AI in the laboratory. Most rRT-PCR assays are capable of characterizing the AI subtype, even at the low titer levels shed by wild birds. However, maintenance of wet PCR reagents at a constant cold temperature has prohibited the use of rRT-PCR in field settings. Our current work aims to validate the use of various portable rRT-PCR units that use freeze-dried reagents, eliminating the need for refrigeration in the field. Such technologies would lend themselves to use in remote locations throughout Eurasia where avian influenza H5N1 has become entrenched.

For more information view Satellite Tracking Migratory Birds: Determining Migratory Connectivity and Routes for Distinct Populations and contact John Y. Takekawa and Nichola J. Hill, Western Ecological Research Center.

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Examining Virus Isolates from Birds in the North Atlantic for Eurasian Strains of Avian Influenza

Avian influenza. Photo Credit: Cynthia Goldsmith, Centers for Disease Control and Prevention

Avian influenza is thought to be spread in part, by migrating wild birds. The risks of introduction of HPAI H5N1 into North America are generally believed to be greatest in Alaska. However, many birds migrate from Eurasia into the North Atlantic where they mingle with migrants from North America and could transmit the virus to birds that would be able to carry the virus to the U.S. We will examine virus isolates from birds in the North Atlantic for genetic evidence of Eurasian strains of AI being introduced into these populations. These data will provide information on the risks of HPAI being introduced into N. America by this route.

For more information contact Jeffrey S. Hall, National Wildlife Health Center.

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Understanding the Dynamics of Avian Influenza: Transmission, Spread, and Potential Risk

Bird in flight. Photo credit: Don Becker, courtesy the USGS National Wildlife Health Center Avian Influenza Photo Gallery

A highly pathogenic strain of avian influenza (HPAI) virus subtype H5N1 emerged in Asia and is circulating in Asia, Europe, and Africa causing mortality in domestic birds, wild waterfowl, and causing human deaths. Numerous avian and mammalian species have been shown to be susceptible to infection and mortality in the field and laboratory, but little is known about the full spectrum of species susceptible to the virus, transmission among wildlife species, or factors that determine immunity or resistance, and whether long-term carriers may exist for some species. This task will examine these dynamics in a selected variety of wildlife species, using both low and high pathogenicity AI viruses, to better understand the potential effect H5N1 HPAI may have on North American wildlife, and the dynamics of infection that will enable us to better understand its transmission, spread, and potential risk to domestic fowl and humans should it be introduced to the U.S. We also study the within-host population genetics of influenza viruses to shed light on recombination, reassortment, virus variation and mutation of these viruses.

For more information contact Jeffrey S. Hall, National Wildlife Health Center.

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Swabbing sea gulls for H5N1 virus detection. Photo credit: Hon Ip, USGS

Rapid advances in the detection of genetic material (both DNA and RNA) from viral pathogens have greatly aided in the identification and the study of viruses in wild animals.  The Diagnostic Virology Laboratory in the National Wildlife Health Center has worked, in collaboration with the USDA National Veterinary Services Laboratory and the USDA Southeast Poultry Research Laboratory, to improve the real time RT-PCR test for the detection of the H7 subtype avian influenza viruses in North American wild birds.  The previous test was developed to detect H7 viruses from domestic sources and failed to detect H7 viruses from wild birds. The new test can detect viruses from both groups with equal efficacy and has since been deployed to network laboratories.  Molecular methods are also amenable to high throughput strategies.  As part of the national surveillance program, a sustained capacity of over 1,000 samples can be tested for avian influenza per day has been established.  Molecular testing can also help in situations when viable samples are difficult or impossible to obtain.  In a study performed by collaborators at the University of Kansas and the USDA, it was not possible to send samples from Chinese tree birds containing viable viruses to the US. Instead samples were preserved in alcohol, which preserved the genetic material and had the added advantage of allowing for room temperature storage and shipping.  Using molecular techniques, we were able to determine that tree birds in China may be significant reservoirs of avian influenza viruses.  This is contrary to the current paradigm of passerine birds having few viruses.  Moreover, the study found that the majority of the tree birds that were positive were migratory species, raising the possibility of these birds being able to transmit the highly pathogenic H5N1 virus during migration.

For more information, please contact Hon S. Ip at the National Wildlife Health Center in Madison, Wisconsin.

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Using mist nets to catch passerine birds for avian influenza virus testing. Photo credit: Hon Ip, USGS

The Diagnostic Virology Laboratory at the National Wildlife Health Center works on the identification and characterization of emerging and established viruses that affect wildlife from around the world.  Besides the use of viral phylogenetic analysis to validate the basis of the nation avian influenza surveillance program (see USGS National Wildlife Health Center Avian Influenza), we use the genetics of viruses to understand their relationship to those from historic outbreaks.  For example, large-scale sequencing and phylogenetic studies have been conducted in the evolution of Newcastle Disease Virus (NDV) in collaboration with the US Department of Agriculture (USDA), and on the worldwide distribution of avian poxviruses with the Szent István University in Hungary.  Such studies allow us to put into perspective the viruses isolated from new mortality events to inform resource managers whether they are dealing with resurgence of an existing disease or confronting the introduction of a novel virus.  Moreover, detailed sequence analysis coupled with experimental studies can identify mutations that are associated with virulence or host-range expansion.

For more information, please contact Hon S. Ip at the National Wildlife Health Center in Madison, Wisconsin.

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Distribution of P. multocida serotype 1 isolates cultured from wild birds and environmental samples collected in Central California.  Isolates are represented on the map according to their collection location using dendrogram branch designations from figure 3a.  Collection sites are indicated with triangles. Larger view

Principal components analysis of P. multocida serotype 1 isolates cultured from wild birds and environmental samples.  Each isolate is designated according to its collection location and the cluster encompassing 49 of the 61 Central California P. multocida isolates is circled. Larger view

Birds affected by avian cholera. Photo credit: USGS

Avian cholera, an infectious disease caused by the bacterium Pasteurella multocida, kills thousands of North American wild waterfowl annually.  Pasteurella multocida serotype 1 isolates cultured during a laboratory challenge study of mallard ducks (Anas platyrhynchos) and collected from wild birds and environmental samples during avian cholera outbreaks were characterized using amplified fragment length polymorphism (AFLP) analysis, a whole-genome DNA fingerprinting technique.  Comparison of the AFLP profiles of 53 isolates from the laboratory challenge demonstrated that P. multocida underwent genetic changes during a three month period. 

Analysis of 120 P. multocida serotype 1 isolates collected from wild birds and environmental samples revealed that isolates were distinguishable from one another based upon regional and temporal genetic characteristics.  Thus, AFLP analysis had the ability to distinguish P. multocida isolates of the same serotype by detecting spatiotemporal genetic changes and provides a tool to advance the study of avian cholera epidemiology.  Further application of AFLP technology to the examination of wild bird avian cholera outbreaks may facilitate more effective management of this disease by providing the potential to investigate correlations between virulence and P. multocida genotypes, to identify affiliations between bird species and bacterial genotypes, and to elucidate the role of specific bird species in disease transmission.

For more information contact David S. Blehert, National Wildlife Health Center.

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