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Joel A. Schmutz, U.S. Geological Survey, Alaska Science Center, Anchorage, AK
Jerry W. Hupp, U.S. Geological Survey, Alaska Science Center, Anchorage, AK
J. Christian Franson, U.S. Geological Survey, National Wildlife Health Center, Madison, WI
Alaska can provide insights on transcontinental transmission of viruses, and would be useful to understand the likelihood that those species could serve as conduits for transmission of highly pathogenic Asian H5N1 virus to North America. Such comparisons would be especially useful if recent migration history of sampled individuals could be determined. Contrasting virus populations in Alaskan birds known to have recently visited Asia to those that have not could be used to estimate the likelihood that Asian migrants will carry Old World stains of avian influenza to North America.
Emperor geese (Chen canagica) regularly migrate between Alaska and Asia, making them a priority species for monitoring occurrence of the H5N1 virus in North America. Each year >20,000 adult emperor geese (>28% of the adult population), that fail in their breeding attempt or that forego breeding entirely may migrate from the Yukon-Kuskokwim Delta (YKD), Alaska to the northern Chukotka Peninsula, Russia to molt their flight feathers (Hupp et al. 2007). The number of molt migrants may be much higher in years of poor reproductive success or if birds that have not reached their breeding age of three years (Schmutz 2000) also migrate from Alaska to Russia. Also, there are small numbers of Emperor Geese that breed in Russia and that likely migrate to Alaskan staging or wintering areas after breeding (Eisenhauer and Kirkpatrick 1977, Schmutz and Kondratyev 1995). Whether distinctions between Eurasian and North American varieties of influenza A viruses (Ito 1995, Olsen et al. 2006) are evident in a population that moves freely between continents is unknown. Evaluating influenza populations in Emperor Geese could provide insights into how Asian and North American influenza strains are modified through regular contact.
Examination of virus strains in Emperor Geese is also of interest because of the seasonal variation in distribution and population density. After nesting on the YKD, >85% of the population is concentrated on a small number of coastal staging areas on the Alaska Peninsula for 2-3 months in fall (Petersen and Gill 1982). During winter Emperor Geese are widely distributed from Kodiak Island, Alaska to the Commander Islands, Russia (Petersen et al. 1994). In spring they are again concentrated on the same coastal staging areas used in fall on the Alaska Peninsula. Measuring the incidence of influenza A viruses in Emperor Geese at these different periods would improve understanding of how viruses propagate at different population densities. Further, Emperor Geese that molt in Chukotka appear to migrate directly to Alaska Peninsula staging areas in fall (Hupp et al. 2007) where they would come in contact with birds that originated from Alaskan nesting areas. Likewise some Emperor Geese that nest in Russia may also use staging areas (Schmutz and Kondratyev 1995). By sampling known Russian migrants at fall staging areas we could determine whether their virus populations differ from birds that remained in Alaska. Through further sampling in winter and spring we could potentially trace transmission of those strains through the population. An understanding of virus transmission will be necessary for any effort to model spread of the H5N1 virus should it reach North America.
Sampling influenza viruses across the winter range of Emperor Geese could also provide insights of how viruses may be transmitted from Asia to North America. Although all satellite-based migration data indicate Emperor Geese that successfully nest, migrate from the Alaska mainland westward across the Aleutian Islands in autumn, there are also observations of some Emperor Geese arriving on wintering areas in the western Aleutians from the direction of Russia (Kondratyev and Byrd, pers. comm.). This suggests that some Emperor Geese molting and/or breeding in Asia may migrate to Alaska wintering areas by traveling west to east along the Aleutian Islands. Thus the potential for Emperor Geese to be in Alaska and harboring influenza A viruses of Asian origin may be a function of where they winter.
We propose to sample avian influenza strains carried by Emperor Geese on their nesting, staging, and winter areas. The study will consist of three components. In the first, we will examine virus populations and the effects of avian influenza on survival and reproduction of Emperor Geese in a marked population on the Yukon Delta where long-term demographic studies have been conducted. In the second component we will examine incidence of avian influenza on staging and winter areas to assess the influence of population density on virus occurrence, and whether differences in influenza populations are apparent in recent Asian migrants versus birds that have remained in Alaska. We will also assess geographic variation of virus strains across the 2500 km east to west distribution of Emperor Geese on their winter range. In the third component satellite telemetry will be used to examine whether Emperor Geese that have not reached breeding age migrate from Alaska to molting areas in Russia. This is necessary to fully understand the magnitude of Emperor Goose migration between Asia and North America.
Background/Rationale:
Most studies of avian influenza virus (AIV) have focused on detection and prevalence, but little effort has been devoted to understanding the demographic consequences of AIV on wild bird populations. For Emperor Geese, because of the existence of a marked sample of birds in a tractable study area representative of the population, there is an opportunity to relate future survival probability of individuals to the existence and strain of AIV. Because impacts on survival from AIV may be proximally manifested through changes in physiological status of birds, we also have the opportunity to measure various correlates, such as indexed body condition of incubating birds and indirect (isotopic) measures of nutrient investment (reliance on stored reserves from staging/wintering areas vs local foods from YKD). Prior work has shown that body condition and nutrient investment are linked (Schmutz et al. 2006). Further, nest parasitism is very prevalent in this species (80% of nests; ~40% of all eggs; Yff, Schmutz, and Talbot unpublished), and may also be related to body condition and nutrient investment. If there is a relation between AIV prevalence and these attributes of reproductive investment (body condition, nutrient source, egg production/parasitism), this would have important impacts on the general perception of the ecological relevance of AIVs.
Finally, given the interest of AIV transmission between Asia and North American waterfowl populations, it would be of interest to ask, at the individual level, if a bird’s probability of harboring AIV was related to whether it was recently in Asia. Such an opportunity may exist with Emperor Geese, given that a large fraction of them migrate to Chukotka annually to undergo molt. The latitudinal separation between the YKD and Chukotka molting areas may result in differences in isotopic signatures of flight feathers (Bowen et al. 2005) that could enable us to discern a bird’s migration history. Further, satellite telemetry data indicate that Emperor Geese on Chukotka molting areas develop flight feathers in coastal lagoons (Hupp et al. 2007), and thus their feathers should have a stronger marine signature than feathers of Emperor Geese that molt on the more inland habitats of the YKD. We presently have primary feathers gathered from females nesting on the YKD and known to have grown their primaries the previous summer on the YKD (n=7) and in Chukotka (n=2), that we can use to test for differences in isotopic signatures. Museum specimens could supplement the Asian sample, and we will ask Russian colleagues to collect samples of primary feathers from molting Emperor Geese on brood-rearing areas in the Anadyr region. If primaries are markedly different isotopically, then that would suggest that we could identify which nesting birds (or hunter harvested birds in spring) spent their previous summer in Chukotka versus in the YKD. If we used this potential natural marker, then we could ask if subtype prevalence (and other physiologic/reproductive metrics) were related to the most recent molt migration history.
Objectives and Hypotheses:
H1: Annual survival is related to prevalence of exposure to AIV and subtype composition.
H2: Body condition during incubation and nutrient investment into eggs varies in relation to evidence of exposure to AIV.
H3: Probability of nest parasitism is related to the presence of AIV in the maternal host.
H4: Subtype prevalence of AIV in emperor geese is related to whether they were predicted to have molted the previous year in Russia
H5: Survival differs between geese that were predicted to have molted the previous year in Russia vs YK Delta.
H6: Goslings will exhibit a higher prevalence AIV than adults.
Methods:
We will locate all Emperor Goose nests in an approximate 20 km2 area along the Manokinak River. For birds already marked, we will primarily rely on resightings (rather than physical captures) and pair such sightings with fecal samples gathered by following gently flushed birds and waiting for them to defecate. Unmarked birds will be captured on nests, blood and primary samples taken for AIV and isotopic analysis, and measurements taken to assess body condition. From all nests, host breast feathers and egg membranes will be gathered, to allow for analysis of nutrient investment and parasitism. Molt drives will be conducted to allow sampling goslings for AIV and will also facilitate adding marked birds to the population for FY07.
Background and Rational:
One may expect prevalence of Asian forms of AIV to be greater on fall staging areas and in early winter than later winter, as geese in fall and early winter would have most recently been in Asia. However, if austere wintering conditions impact individual susceptibility to viral infection, than sampling in late winter may also indicate significant prevalence. Also, incidence of possible Asian strains of avian influenza may be greater in the more western portion of the wintering distribution if some Russian Emperor Geese migrate from west to east along the Aleutian Islands. Further, incidence of all strains of avian influenza may be higher on staging than on winter areas due to higher population densities at the former. Feather isotopic signatures (above) may provide us a means of determining whether an Emperor Goose has migrated from Asia or remained in Alaska. We will examine influenza strains during the early period of fall staging and determine if variation in influenza strains are associated with differences in feather isotopic signatures. If we find evidence of continental differences in influenza strains, we will examine whether transmission of Asian forms to Alaskan birds increasingly occurs over the staging and winter periods, and whether there are longitudinal differences in influenza strains along the winter range. Examination of influenza strains of Emperor Geese on staging and wintering areas also provides us with the opportunity to assess how habitat, or physiological condition of birds may interact with the incidence of influenza strains to affect overwinter survival.
Hypotheses:
H1: Does AIV subtype prevalence, as determined from feces or cloacal sampling, vary geographically (western vs central vs eastern Aleutians) and temporally (fall staging vs winter vs spring staging).
Rationale for a geographic examination of influenza viruses is given above.
H2: Does AIV subtype prevalence differ between family groups and non-family groups.
Prevalence of AIV is typically highest in juvenile waterfowl (Hanson et al. 2003). Further, as raising young exerts a physiologic and survival cost to parent birds (Golet et al. 2004), adult geese in family flocks may also exhibit higher AIV prevalence than adults in flocks without young.
H3: Does AIV subtype prevalence of emperor goose flocks correlate with average abdominal profiles (body condition).
Although there is little study in birds to document whether AIV infection is related to physical condition of an individual, human biology would suggest this is likely. We therefore will pursue examining whether there is such a linkage in Emperor Geese. As stated, this hypothesis reflects an examination based on observations of geese and sampling feces. More direct and sensitive measures of this will be possible if live capture methods are successful.
H4: Is there a relation between viral prevalence and type of intertidal community used for foraging.
Vulnerability and exposure to AIV may be influenced by habitat use for two reasons. First, related to H3, physical condition may be related to what intertidal resources Emperor Geese can gain access to. Second, they will be more spatially proximal to other waterfowl species (e.g, eiders, harlequin ducks) in some habitats than others.
H5: Is viral profile related to over-winter survival of juvenile geese (dependent on successful development of live capture techniques).
Survival of juvenile geese appears to vary geographically (Eldermire et al. MS). Despite varying degrees of pathogenicity of subtypes of AIV, little demographic work has been done to relate survival rates to viral prevalence. If a relation exists, this could be quite important to population demography.
Methods:
Fresh fecal samples will be obtained at roost sites located on or near beaches on wintering and staging areas. Prior to gathering fecal samples, age ratio, abdominal profile, and behavioral data of observed flocks will be obtained. We also will experiment with nightlighting and mist nets to live capture geese. If successful, we will mark all birds with tarsal bands and follow their fates during periodic resighting periods. Cloacal swabs will be gathered from all captured birds. We will visit Shemya, Adak, Unalaska, and Kodiak islands, during both early and late winter. One to two weeks will be spent at each site in each time period. We will visit Izembek and Nelson lagoons to collect data from staging Emperor Geese during autumn (September-October) and spring (April). We will clip 1-2 cm from secondary feathers of captured birds for isotopic evidence that Emperor Geese spent summer months in Alaska versus Russia. All cloacal samples will be screened for the presence of influenza A subtypes. Subtypes of positive samples will be identified and compared between Russian and Alaskan migrants. The incidence of positive samples will be compared between staging and wintering areas. Similar subtypes will genetically sequenced to contrast differences in virus populations that may be related to migration history of Emperor Geese.
Background and Rationale:
From 2000-2004, most (15 of 16) adult female Emperor Geese that were marked with satellite transmitters on the YKD and that did not successfully nest, migrated to the north coast of Chukotka to molt remegies (Hupp et al. 2007). During aerial surveys in 2002, Russian colleagues observed >21,000 emperor geese molting in the same areas of Chukotka used by birds with satellite transmitters (Hupp et al. 2007). This was a conservative estimate because surveys were not complete and were not corrected for detection likelihood. A much larger number of Emperor Geese may migrate from Alaska to Asia if Emperor Geese that are not of breeding age use the same molting areas as adults. Emperor Geese believed to be yearlings have been reported to depart the YKD on a northward migration in early summer (Blurton Jones 1972, Eisenhauer and Kirkpatrick 1977). Because Emperor Geese are unlikely to breed until three years of age (Schmutz 2000), Hupp et al. (2007) estimated that as many 49,000 1-2 year old birds may migrate between Alaska and Chukotka. We propose to mark juvenile Emperor Geese with satellite transmitters in order to evaluate molt migration of birds that are not of reproductive age. This will improve our understanding of the magnitude of Emperor Goose migration between Alaska and Russia, and enable us to determine whether the likelihood that a bird harbors Asian strains of influenza is age-related.
H1. Distribution of juvenile Emperor Geese during wing molt is similar to that of adult Emperor Geese.
Methods:
We will capture juvenile emperor geese at winter areas on Kodiak, Unalaska, Adak, and Shymeya islands. This will occur concurrently with efforts to sample incidence of avian influenza across winter areas (above). Capture will be via floating mist nets, noose carpets, or nightlighting. Capture efforts will be made in late winter (Feb-Mar). We will identify juveniles on the basis of plumage. At each capture site, we will mark up to 10 juvenile birds (5 male and 5 female) with platform transmitting terminal (PTT) transmitters, and will deploy a total of 30 PTTs in each of two winters (2008 and 2009). We will use a 35-g implantable PTT that will be programmed to transmit for 6 hours at 72 hour intervals. Data collection will be via the Argos Data Collection and Location System (Lago, Maryland). We will assess spring migration chronology of juvenile emperor geese, estimate the proportion that depart the YKD to molt remegies elsewhere, and test whether summer distribution of juveniles on molting areas is same as previously observed for adults. We will observe return migration dates of juveniles from molting areas and determine whether they migrate directly to staging areas. We will use their return date to staging areas as an indication of when migrants may introduce possible Asian strains of influenza to birds that have remained in Alaska.
- Alaska Maritime, Izembek, and Kodiak National Wildlife Refuges (bunk house and vehicle access).
- Eareckson Air Station-USAF (transport to and room and board at Shemya).
- Simon Fraser University (Dr. Dan Esler and student)
- National Wildlife Health Center (Dr. Chris Franson)
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