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Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

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  • #16
    Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

    Originally posted by tompe View Post
    I interrupt my vacation to pose a challenge to Dr. Niman. Please develop a scenario based on accepted evidence from the peer-reviewed literature about stopover ecology, flight physiology, migratory pathways, reasonable timing, wildlife disease ecology etc. that can explain the spread of H5N1 from Asia to Europe. Please base as many statements as possible on literature references. So for example, it it will not be enough to state that a grebe or some other species was found to be asymptomatically infected with the virus. Based on age and sex of the individual, the time of year it was found and where it has been found a reasonable guess needs to be made if the bird is in fact migratory, where it was coming from and where it is likely to go to. Is it likely that the bird actually has made a long migratory flight? To find a virus in a wild bird is simply not enough.

    There's absolutely no propaganda in the article which started this thread. It doesn't actually say that wild birds are absolutely blameless. It just reviews the state of knowledge in ecological immunology and claims that this knowledge makes it unlikely, but not impossible, that migratory movements are responsible for the long distance spread of H5N1. Dr. Niman hasn't countered convincingly any pertinent point made in this article. I am looking forward to an answer to my challenge.
    I really didn't read beyond the opening straw man statement on requirements for asymptomatic birds. The paper isn't serious.

    For something serious, look at the figures here



    There are over 230 Qinghai H5N1 isolates from Europe, the Middle East, and Africa. All were isolates after Qinghai in May, 2005 and most of the isolates in Europe are from wild birds (the names of the isolate includes species, location, and year of isolation). None of the countries represented had H5N1 prior to Qinghai.

    However, these are all icing on the cake. As soon as H5N1 was found (for the first time) in Chany Lake in Russia in July, 2005 and remote Erhel Lake in Mongolia in August, 2005 and the Qinghai strain was identified (in the summer of 2005), the "dead birds don't fly" debate was over.
    Last edited by sharon sanders; August 17, 2007, 04:30 PM. Reason: edited quote as referenced above

    Comment


    • #18
      Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

      I was warned and now it's sure: there's absolutely no point discussing seriously with Dr. Niman. He displays complete and utter ignorance about avian migration. Strong words, but I stand by them. Still, my challenge stands.
      Concerning the relay hypothesis: what happens to the infected birds? There should be a trail of dead birds along the migratory pathway. This has never been shown.
      Concerning short flights vs. long flights: even short flight can be very long. But this really depends on the distribution of stopover sites and their quality (and it's not a good option for birds migrating in flocks where departure is to a large extent controlled socially). It is likely that a migrant choosing this strategy will arrive very late, if at all at it's breeding ground.

      Comment


      • #19
        Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

        Originally posted by tompe View Post
        I was warned and now it's sure: there's absolutely no point discussing seriously with Dr. Niman. He displays complete and utter ignorance about avian migration. Strong words, but I stand by them. Still, my challenge stands.
        Concerning the relay hypothesis: what happens to the infected birds? There should be a trail of dead birds along the migratory pathway. This has never been shown.
        Concerning short flights vs. long flights: even short flight can be very long. But this really depends on the distribution of stopover sites and their quality (and it's not a good option for birds migrating in flocks where departure is to a large extent controlled socially). It is likely that a migrant choosing this strategy will arrive very late, if at all at it's breeding ground.
        Please. H5N1 migrated out of China 2 years ago. Case closed.

        Comment


        • #20
          Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

          Tompe -

          As you may not be aware, we do not allow "name calling" on this site.

          Also, Niman is an expert on avian migration, as are many participants of this forum. Degree status is irrelevant.

          Thank you for keeping the disagreements civil.

          Comment


          • #21
            Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

            I promise to keep the disagreements civil in the future.

            As I am rather new in the forum, I did not yet have the time to peruse all threads in detail, but I am sorry to say that from an ornithologist's perspective the expertise in avian migration evinced here in the forum is rather sketchy. The debate in ornithology is ongoing and controversial. One might argue that ornithologists may want to keep their study animal free of blame, but this would be very unfair. There is no consensus, but the evidence for the involvement of wild wird in the long-distance spread of H5N1 is very weak.
            I recommend the following articles:
            M. Gauthier-Clerc et al. (2007) Recent expansion of highly pathogenic avian influenza H5N1: a critical review. Ibis 149: 202-214
            C.J. Feare (2007) The Role of Wild Birds in the Spread of HPAI H5N1. Avian Diseases 51: 440-447

            Comment


            • #22
              Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

              Thanks Tompe.

              We have ornithologists who post regularly here. I find them fair. There is no bias here for or against them.

              We encourage vigorous, but civil, debate.

              Comment


              • #23
                Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                Here are some expansions of a few of the articles mentioned by gsgs above. This is presented not only for the possible (probable) role that wild birds play in the spread of H5N1 and other influenza viruses but also to suggest that Indonesia may have some valid points in using a human vaccine. With the somewhat optimistic time frame of 4-6 months to develop and distribute a vaccine a 'perfectly matched pandemic vaccine' may become a 'post-pandemic vaccine'

                Some excerpts on this Feb2006 article by Webster et al....



                Six HPAI H5N1 viruses were isolated from apparently healthy migratory ducks at Poyang Lake on two sampling occasions (January and March 2005) just before their migration north.

                These findings suggest that migratory ducks at Poyang Lake may have first been exposed to low pathogenic H5-subtype viruses that may have provided partial protection against HPAI H5N1 infection.

                Thus, all eight gene segments of viruses from the Qinghai Lake outbreak in central China can be traced to the H5N1 viruses isolated from migratory ducks at Poyang Lake in southeast China, 1,700 km distant, indicating that migratory birds can disseminate the virus over long distances.

                As revealed by virus neutralization and pathogenicity tests ( Table 3), these HPAI H5N1 viruses isolated from apparently healthy migratory ducks are not invariably fatal, and surviving ducks may shed virus for as long as 7 days after infection in those experimental ducks.

                We have shown that H5N1 virus has persisted in its birthplace, southern China ( 1), for almost 10 yr and has been repeatedly introduced into neighboring (e.g., Vietnam) and distant (e.g., Indonesia) regions, establishing "colonies" of H5N1 virus throughout Asia that directly exacerbate the pandemic threat.

                The antigenic diversity of viruses currently circulating in Southeast Asia and southern China challenges the wisdom of reliance on a single human vaccine candidate virus for pandemic preparedness; the choice of candidate viruses for development of human vaccines must reflect the antigenic diversity observed across this wider region. Furthermore, antigenic drift observed over time within those H5N1 sublineages highlights the necessity of continually updating the candidate virus chosen for future H5N1 vaccines. These concepts are critical for the control of this pandemic threat.

                Poyang Lake, located in north Jiangxi Province, is the largest freshwater lake in China. Mai Po Marshes are in northwestern Hong Kong, at the border with mainland China. Both are major over-wintering sites for migratory birds in eastern Asia ( 11). Migratory birds usually arrive in September and leave in April.

                BIOLOGICAL SCIENCES / MICROBIOLOGY
                Establishment of multiple sublineages of H5N1 influenza virus in Asia: Implications for pandemic control

                H. Chen ,, G. J. D. Smith ,, K. S. Li , J. Wang , X. H. Fan, J. M. Rayner , , D. Vijaykrishna, , J. X. Zhang ,, L. J. Zhang , , C. T. Guo, C. L. Cheung , , K. M. Xu, , L. Duan ,, K. Huang , K. Qin ,, Y. H. C. Leung , W. L. Wu ,, H. R. Lu , Y. Chen , N. S. Xia, T. S. P. Naipospos?, K. Y. Yuen , S. S. Hassan||, S. Bahri?, T. D. Nguyen**, R. G. Webster , , , J. S. M. Peiris ,, and Y. Guan, ,

                Joint Influenza Research Centre (Shantou University Medical College and Hong Kong University), Shantou University Medical College, Shantou, Guangdong 515031, China; State Key Laboratory of Emerging Infectious Diseases, Department of Microbiology, University of Hong Kong, Faculty of Medicine Building, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China; Research Center for Medical Molecular Virology of Fujian Province, Xiamen University, Xiamen, Fujian 361005, China; ?Ministry of Agriculture and Animal Health, Government of Indonesia, Pasar Minggu, Jakarta Selatan 12550, Indonesia; ||Veterinary Research Institute, 31 400 Ipoh, Malaysia; **National Institute of Veterinary Research, Dong Da, Hanoi, Vietnam; and Virology Division, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38105

                Contributed by R. G. Webster, December 23, 2005







                and

                I thought this was a very useful article substantiating the role wild bird migration appears to have played in the spread of the virus from Qinghai. This one takes a very good look at the bird ecology with a detailed look at the migration patterns, stopover periods to accomplish feather moultings, mixing with immune naive juvenile birds, intersection of migration pathways, concentration patterns of poultry, etc... One of the interesting things is the difference in susceptibility of different bird species (ie asymptomatic carriers) I'm reminded of what veterinarian Illaria Capua said in that a duck may be as different from a gull as an elephant from a tiger. And there are even many species of ducks....


                Volume 12, Number 11?November 2006
                Perspective
                Anatidae Migration in the Western Palearctic and Spread of Highly Pathogenic Avian Influenza H5N1 Virus
                Marius Gilbert,* Xiangming Xiao,? Joseph Domenech,? Juan Lubroth,? Vincent Martin,? and Jan Slingenbergh?
                *Universit? Libre de Bruxelles, Brussels, Belgium; ?University of New Hampshire, Durham, New Hampshire, USA; and ?Food and Agriculture Organization of the United Nations, Rome, Italy

                Suggested citation for this article

                Abstract
                During the second half of 2005, highly pathogenic avian influenza (HPAI) H5N1 virus spread rapidly from central Asia to eastern Europe. The relative roles of wild migratory birds and the poultry trade are still unclear, given that little is yet known about the range of virus hosts, precise movements of migratory birds, or routes of illegal poultry trade. We document and discuss the spread of the HPAI H5N1 virus in relation to species-specific flyways of Anatidae species (ducks, geese, and swans) and climate. We conclude that the spread of HPAI H5N1 virus from Russia and Kazakhstan to the Black Sea basin is consistent in space and time with the hypothesis that birds in the Anatidae family have seeded the virus along their autumn migration routes.

                The spread of highly pathogenic avian influenza (HPAI) H5N1 virus during 2003?2004 in eastern and southeastern Asia, and, in 2005?2006 westward across Asia into Europe, the Middle East, and Africa is not typical of other HPAI epizootics. Until recent events, HPAI outbreaks or epizootics were assumed to first require transmission of a low pathogenic avian influenza (LPAI) virus from wild birds to domestic poultry ( 1). Preventive measures thus focused on surveillance and control in poultry and on stopping transmission to noninfected premises. Usually this strategy successfully extinguished an outbreak, often within the year ( 2). The spread of the disease back to wild birds from domestic fowl was considered relatively rare. The HPAI H5N1 virus is unusual in that virus infections in wild bird populations may cause a high proportion of deaths ( 3?5). A list of species that have been infected with HPAI H5N1 virus can be found in Appendix Table. The virus also is persisting in Asia longer than most previous HPAI epizootics, which suggests a local reservoir ( 6,7).

                Epidemiologic studies during 2004?05 mainly focused on HPAI H5N1 virus persistence in relation to the agro-ecology of poultry and duck production systems ( 6), and little attention was paid to the role of wild birds in local viral persistence or long-distance spread during that period. Because of 3 major events during mid- to late 2005, wild birds are now suspected of spreading the HPAI H5N1 virus over long distances through migration ( 8,9). First, in May 2005, a major HPAI HN51 virus outbreak was discovered in wild birds in Lake Qinghai (western People's Republic of China), an important breeding place for migratory bird species in eastern Asia. Within a few weeks, several hundred birds, mainly bar-headed geese, had died of the disease ( 4,10). Eventually, other bird species also became affected, and several virus introductions may have occurred. Soon after the Lake Qinghai episode, HPAI H5N1 virus was detected in wild birds in Mongolia, to the north of Lake Qinghai along the central migration route, and in an area where domestic poultry were scarce ( 11). Second, in October 2005, HPAI H5N1 virus spread westward across Eurasia; outbreaks were recorded in Turkey, Romania, and Ukraine, usually in or near known wintering sites for migratory birds. This long-distance spread took place through areas with no record of any virus presence. Third, in spring 2006, the virus infected large numbers of mute swans and other wild bird species across western Europe, also in areas where no outbreaks had previously been detected in domestic poultry, despite continual and intensive surveillance. These incursions occurred after unusual waterfowl movements that were associated with a spell of cold weather in the Black Sea area where HPAI H5N1 virus is believed to have been endemic since autumn 2005.

                Arguments may also be raised against the hypothesis that HPAI H5N1 virus is transmitted by wild birds. Invariably, wild birds found to be infected with the virus were either dead or moribund and may not have been able to spread the virus over long distances. Furthermore, in several cases, no straightforward match was found between the appearance of the virus and the presence of the wild birds suspected of spreading it. For example, HPAI H5N1 virus outbreaks that took place in Russia and Kazakhstan during summer 2005 were distributed along important trade routes that link western People's Republic of China to Russia ( 12 ), rather than any direct migration pathway.

                We document and discuss the possible role of migratory birds in the spread of HPAI H5N1 virus during the second half of 2005, on the basis of information and data concerning the role of waterfowl in the ecology of avian influenza viruses; the pattern of Anatidae bird migrations across the western Palearctic, and contemporary, satellite-derived temperature data.

                Role of Migratory Waterfowl in Ecology of Avian Influenza Viruses
                Avian influenza viruses (AIVs) have been recorded in most bird families ( 3), but the prevalence and diversity of AIV subtypes is not evenly distributed among them ( 13). AIVs have been isolated in 12 bird orders, but most isolations have been reported in the orders Anseriformes (in particular in the family Anatidae : ducks, swans, geese) and Charadriiformes (shore birds, gulls, terns). Although a wide variety of AIV subtypes have been isolated from Charadriiformes ( 13,14), they are believed to belong to a somewhat different genetic pool from those isolated in Anseriformes ( 15).

                Species from the Anatidae family, in particular, the Anatinae subfamily (ducks), represent the highest risk for transmission to domestic poultry ( 16,17 ) for the following reasons: 1) Anatids harbor the most diverse and highest prevalence of avian influenza viruses ( 13,14); 2) historical outbreaks of HPAI in poultry have been linked mainly to strains circulating in ducks, rather than in members of other species ( 18,19); 3) domestic ducks (mallards) can excrete large amounts of HPAI H5N1 virus while remaining relatively healthy and are thus able to move the virus across large distances ( 7 ); and 4) direct contacts between wild anatids and domestic aquatic poultry are believed to be relatively more common than with other groups of wild birds ( 20).

                Most waterfowl migrate seasonally, to exploit temporary feed resources during spring and summer, while escaping harsh winter conditions ( 21 ). An important evolutionary incentive for these migrations is the prolific spring growth in the Arctic, which provides plants and insects rich in the calcium and protein required for egg production ( the female mallard duck produces 8?12 eggs) and juvenile growth ( 22 ). However, the favorable season for breeding is very short in these higher latitudes, and migratory bird populations soon start migrating southward with their juveniles to escape the frosts that occur from midsummer onward ( 23). This frequently results in premigration concentrations of many species of waterfowl south of the breeding areas, where juvenile maturation and adult molting take place before the main southward migration in the autumn. This seasonal aggregation mixes many species with high densities of immunologically naive juveniles alongside adult birds, which are unable to fly for up to 1 month while they molt; this setting is ideal for AIV transmission and redistribution. Previous work on AIV ecology has shown that premigration concentrations of waterfowl, together with the high recruitment rate of immunologically naive juveniles, induce a seasonally and geographically distinct pattern in AIV prevalence with peaks observed just before autumn migrations in interspecies concentration areas ( 13 , 24). During the subsequent southwest wards migration, AIV prevalence declines as a result of increased flock immunity and progressive dispersal of bird populations ( 13, 24,25). Although AIV is more difficult to detect in waterfowl during winter and spring, several studies reviewed by Stallknecht and Shane ( 13) reported that AIV isolates persist until spring. De Marco et al. (26 ) demonstrated that AIV circulated continually from November to March in wintering areas. The high level of flock immunity and the relatively low level of AIV isolation during winter and spring raise the question of AIV survival during this time in the annual cycle ( 13 ). The survival of the virus in water and ice ( 27) may play a critical role, in terms of virus persistence and in terms of facilitating fecal-oral AIV transmission ( 16). The possible overwintering of AIV in shallow and cold water ( 28 ) in the Pan-Arctic region and the concentrations during postsummer-breeding and transmission of AIV between subpopulations and bird species during premigration may help sustain the natural AIV cycle. A redistribution of AIV among birds that use different migration routes may well contribute to the survival of the virus across a wide geographic range.

                Anatidae Migration Patterns in the Western Palearctic
                Figure 1

                Figure 1. Map showing the spread of highly pathogenic avian influenza (HPAI) H5N1 virus and its environmental context...


                Figure 2

                Figure 2. Distribution overlay of migratory flyways of Anatidae bird species in the western Palearctic...


                Appendix Figure

                Appendix Figure. Population of Anatidae in the western Palearctic.

                Northeastern Russia and Siberia are major breeding areas for many migratory Anatidae species in the Palearctic. Birds arrive during the spring, traveling different routes from Europe, Asia, and Africa. Of particular importance is the west Siberian lowlands (WSL), which has an area of 2,745,000 km 2 and is by far the largest wetlands in the world ( Figure 1). WSL is an important breeding area, along with several other large wetlands located in northwestern Russia and northern Scandinavia ( Figure 1). In western Europe, the main wetlands that support wintering waterfowl are found along the coastal areas of Denmark, the Netherlands, United Kingdom, France (the Rh?ne delta), Spain, and northern Italy. In central Europe and western Asia, major wetland areas are found around the Black Sea in Ukraine, Romania (the Danube delta), and Turkey; around the Caspian Sea in Russia and Iran; and in the southeastern part of Iraq. Three recognized routes, or flyways, connect breeding areas to wintering areas in the western Palearctic ( 29) are shown on the overlay of individual species flyways in Figure 2A . The North Sea flyway joins the wetlands of northwestern Russia to western Europe wintering sites and runs through Scandinavia, the Baltic basin, and the North Sea. The Black Sea and Caspian Sea flyways run from the WSL, leading to Mediterranean Europe and western Asia, respectively. When weighted according to the number of birds that use them ( Figure 2B), the North Sea flyway stands out as the most important, followed by the Black Sea; the Caspian Sea flyway is of least consequence. ( The estimated population of Anatidae in the western Palearctic is shown in the Appendix Figure.)

                Migration Patterns and Spread of HPAI H5N1 Virus across the Western Palearctic
                During July and August 2005, several HPAI H5N1 virus outbreaks were reported in Russia and Kazakhstan ( Figure 1). These occurred in domestic poultry, but the strains were genetically related to the Lake Qinghai strain ( 30). Early in October 2005, HPAI H5N1 virus was first encountered in wild fowl and in poultry in Turkey and Romania and in dead swans in Croatia. Again, the sequenced virus was found to be identical to that from Lake Qinghai. This same virus was detected in Ukraine in December 2005 ( 31).

                A mission of the World Organization for Animal Health (OIE) to Kazakhstan established that the first outbreaks were located near important molting sites for migratory waterfowl. This finding is further illustrated in Figure 1, which depicts the WSL breeding area, where the first frost took place as early as July ( the pale green pixels). The premigration concentration of wild bird populations for molting takes place just south of the WSL. HPAI H5N1 virus may have been brought into southern Siberia through the poultry trade and related traffic, in particular, through the trans-Siberian commercial route ( 12 ), and, from there, may have entered the wild bird population. However, the observed patterns of virus circulation are also consistent with the critical steps in AIV transmission and redistribution ( 13 ), and HPAI H5N1 virus may have already been present in the wild bird population during the 2005 spring season in the WSL or at the molting sites and transmitted from there to domestic poultry at the time of main virus transmission in the premigration concentration areas.

                The initial outbreaks of HPAI H5N1 virus in Romania, Turkey, and Ukraine occurred close to wetlands frequented by overwintering migratory waterfowl. These locations were clearly far from any known location where HPAI H5N1 virus had been recorded, while the timing and location match the autumn wildfowl migration ahead of the approaching wave of frost ( Figure 1).

                Figure 2C illustrates the population-weighted overlay of all Anatidae species flyways that coincide with locations of HPAI H5N1 virus in Russia and Kazakhstan observed during the summer 2005, i.e., the spread to be expected if only the bird species using the Caspian Sea flyway had been responsible for further spread. Figure 2D shows the population-weighted overlay of species flyways in relation to locations of HPAI H5N1 virus until January 2006. This figure suggests that the Black Sea flyway was also infected if anatids did indeed spread HPAI H5N1 virus through their autumn migration. This apparent discrepancy between HPAI H5N1 virus outbreak locations ( Figure 2D) and the pattern of spread that could have been expected from the summer outbreaks locations ( Figure 2C ) requires further attention. First, the northern limits of the 2 flyways are so close that a figure similar to Figure 2D is obtained just with the summer outbreaks if one simply allows for a 200-km variation in the flyway border or if HPAI H5N1 virus presence is assumed to have occurred 200 km further westward. Second, the boundaries between the flyways are arbitrary; these flyways mainly represent directions taken by subpopulations, representing most diffusive migration paths. A large fraction of wild bird populations distributed across the area with locations of HPAI H5N1 virus reported presence in Russia and Kazakhstan connect to the Black Sea basin (actually, the number of anatids flying from Siberia down to the Black Sea is higher than the number flying to the Caspian Sea basin; Figure 2B). Given the above uncertainties, one may reasonably assume that waterfowl from both flyways may have become infected when they met in premigration concentration areas.

                If these flyways are assumed to be used by infected birds, their geographic extent may be used to estimate an index of risk for virus transmission from wildfowl to domestic poultry. The population-weighted overlay of individual waterfowl species' ranges intersecting with HPAI H5N1 virus locations ( Figure 2B) can, in turn, be intersected with the wintering areas' boundaries (rescaled from 0 to 1 as an index of wintering site suitability) to delineate the areas where migrating birds are more likely to concentrate. This layer can then be multiplied by overall poultry population density ( 32) to derive a coarse measure of risk for an HPAI H5N1 virus outbreak to occur in domestic poultry ( Figure 2E). The resulting display highlights the high-risk areas on the Black Sea coast, in particular, areas adjacent to the wintering areas in Romania, Turkey, and Russia, but also parts of Greece, along the Adriatic coast, the Nile delta, and along the southern edges of the Caspian Sea. A relatively high risk is found across western Europe, which reflects not only the high density of poultry but also the fact that a cluster of 3 westernmost outbreaks in Russia intersect with multiple western European flyways.

                Discussion
                Our results indicate that the broad-scale pattern of spread of HPAI H5N1 virus from Russia to the Black Sea basin is consistent with the spatial and temporal pattern of Anatidae migration from Siberia. Given that the first recorded signs of HPAI H5N1 virus in Turkey, Romania, and Ukraine took place in the direct vicinity of important waterfowl overwintering sites, Anatidae could have been implicated in the spread of HPAI H5N1 virus to the Black Sea basin. The search for wild bird species carrying HPAI H5N1 virus is in progress and awaits further classification. Several species demonstrably carry the virus without showing clinical signs, as has been recently reported from studies in Russia ( 30) and People's Republic of China ( 8). Most wild birds found dead were geese, swans, and, rarely, wild ducks (when domestic ducks were found infected with, and sometimes dead from HPAI H5N1 virus, this occurred in conjunction with disease outbreaks in terrestrial poultry), which supports the hypothesis that not only mallards but also several other duck species are healthy carriers of HPAI H5N1 virus. The postulate that migratory anatids can spread the disease over long distances by no means excludes the role of the poultry trade as an important, complementary transmission pathway.

                It could be argued that an important contradiction of the hypothesis that wild birds spread HPAI H5N1 virus along their migration paths stems from our "false-positive" predictions ( e.g., Figure 2E, Spain, Morocco, Greece). We propose 3 possible explanations for these deviations. First, as well as being along flyways of infected wild bird, establishment of HPAI H5N1 virus in domestic poultry may require additional conditions: 1) an aggregation of waterfowl for a sufficient period (more risk for transmission within wintering areas than at more transient stopover sites), 2) a high proportion of small poultry farms and backyard poultry, and 3) extensive (aquatic) poultry units in contact with waterfowl populations and habitat, i.e., floodplain or other forms of wetland agriculture in close proximity to natural wetlands used as wildfowl wintering sites. Such conditions have been shown to be associated with HPAI H5N1 virus persistence in Southeast Asia ( 6) and were certainly also met in parts of Romania, Turkey, and Ukraine. Second, the overall prevalence of HPAI H5N1 virus found in wild bird populations was very low, usually <1% ( 8). This finding suggests that virus persistence in wild bird populations may be subject to stochastic fluctuation. Also, few infected individual birds are likely to be evenly distributed in the population; i.e., the distribution of infected birds is probably clustered. The scarcity of infected individual birds and their likely clustering produce a pattern in which several regions exposed to equivalent wintering populations may have been exposed to different levels of virus exposure. Finally, HPAI H5N1 virus was found either in dead and apparently healthy ducks, which suggests a dichotomy in wild bird susceptibility. The exact status of species, as sentinels or spreaders, and precise migratory pattern may help explain any inconsistencies that arise from considering all species at equal risk for transmission.

                One could also mention here the discrepancies between the geographic spread of HPAI H5N1 virus and overall pattern of wild bird migrations: the virus has never been reported in the Philippines and in several countries farther south such as New Zealand and Australia (although these 2 countries have no migratory anatid populations connecting them to Southeast Asia, they do have many shore bird and wader species in common [ 20]). Conversely, with the possible exception of African countries, HPAI H5N1 virus was established in domestic poultry only in countries connected by flyways with existing infected countries. The introduction in Nigeria is inconclusive. Two species of dabbling ducks, Anas querquedula and A. acuta, have large wintering concentrations in and near Lake Chad and in the Niger delta, both under the western Siberia/Black Sea flyways, and are presumed to be infected by HPAI H5N1 virus. However, Nigeria imported large numbers of poultry from Turkey and People's Republic of China until a ban was imposed, and illegal trade may well have continued after the ban and brought in infected animals or products ( 33).

                The broad approach adopted in this study has clear limitations, given the uncertainties regarding the host range of HPAI H5N1 virus within the Anatidae family, the sizes and distribution of the bird populations, their precise migratory patterns, and the demarcation of the summer and winter habitat. A comprehensive retrospective analysis of HPAI H5N1 virus spread in the western Palearctic would require a better description of the dynamic distribution of wild birds (breeding range, wintering sites, stopover sites, migration pathways) as well as more detailed domestic poultry data (distribution, production structure, species composition, movements through trade) to map the contact points between wild and domestic birds. In addition, local studies could focus on possible introduction points and characterize and detail the specific ecologic conditions in the wild birds?domestic poultry interface that support establishment of the virus, including the local landscape structure (wild bird habitat and farming), climate ( e.g., virus survival in the environment), and other agro-ecologic conditions.

                Experimental Procedure
                Imagery
                We used the land surface temperature (LST) data products derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on board the National Aeronautics and Space Administration's Aqua satellite ( 34). The Aqua satellite acquires daytime images (a local pass time of 1:30 p.m. at the equator) and nighttime images (a local pass time of 1:30 a.m . at the equator). A day/night algorithm was applied to a pair of MODIS daytime and nighttime observations to extract average temperature (when multiple observations are available), and the method yields an accuracy of 1?K with known emissivities ( 34).

                Daily LST products were aggregated (averaged) to generate 8-day composite LST product (MYD11A2), and 46 of these 8-day composite LST products are generated per year. The LST product has a spatial resolution of 1 km. We downloaded the 8-day composite LST data (MYD11A2) in 2005 from the US Geological Survey Earth Resources Observation and Science (EROS) Data Center. For each individual 1-km pixel, we analyzed time series data of nighttime LST in 2005 and identified the first 8-day period that experienced frost (LST <0?C) in the fall/winter seasons. We assume that the date of early frost events in fall/winter seasons is one of many factors that affect the starting date of wild bird migration from north to south.

                Distribution Overlays
                Distribution data regarding the winter feeding areas and summer breeding areas were extracted from the Global Registry of Migratory Species CD-ROM ( 35). The data on migration flyways were digitized directly from Scott and Rose ( 36 ). All boundaries were smoothed by a 2.5-decimal degrees filter to avoid sharp edges in distribution boundaries. The population estimates from Delany and Scott ( 37) were assigned to each flyway. In the population-weighted, each flyway contribution was estimated as its relative contribution to the total population of Anatidae along all flyways multiplied by 100 (100? Popflyway/PopAnatidae). The species included in the analysis are the following: Anas acuta, Anser albifrons, Anser anser, Anser brachyrhynchus, Anas clypeata, Anas crecca , Anser erythropus, Anser fabalis, Aythya ferina, Aythya fuligula, Aythya marila, Aythya nyroca , Anas penelope, Anas platyrhynchos, Anas querquedula , Anas strepera, Branta bernicla, Bucephala clangula , Branta leucopsis, Branta ruficollis, Cygnus columbianus, Cygnus cygnus, Clangula hyemalis , Cygnus olor, Mergellus albellus, Marmaronetta angustirostris , Melanitta fusca, Mergus merganser, Melanitta nigra, Mergus serrator, Netta rufina, Oxyura leucocephala, Polysticta stelleri, Somateria mollissima , Tadorna ferruginea, Tadorna tadorna. The data on HPAI locations were extracted from HPAI H5N1 virus reported presence, as recorded in the FAO Empres-I database ( 31) between July 1, 2005, and January 16, 2006.

                Acknowledgments
                We thank William Wint for his help with the editing of this article.

                Dr Gilbert is a postdoctoral fellow at the laboratory of Biological Control and Spatial Ecology in Brussels. He focuses his research on patterns and processes affecting the spatial dynamics of invasive organisms, in particular, the conditions of persistence and spread of highly pathogenic avian influenza in Southeast Asia.

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                Gilbert M, Chaitaweesub P, Parakamawongsa T, Premashtira S, Tiensin T, Kalpravidh W, et al. Free-grazing ducks and highly pathogenic avian influenza, Thailand. Emerg Infect Dis. 2006;12:227?34.
                Hulse-Post DJ, Sturm-Ramirez KM, Humberd J, Seiler P, Govorkova EA, Krauss S, et al. Role of domestic ducks in the propagation and biological evolution of highly pathogenic H5N1 influenza viruses in Asia. Proc Natl Acad Sci U S A. 2005;102:10682?7.
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                Lvov DK, Shchelkanov MY, Deryabin PG, Grebennikova TV, Prilipov AG, Nepoklonov EA, et. al. Isolation of influenza A/H5N1 virus strains from poultry and wild birds in West Siberia during epizooty (July 2005) and their depositing to the state collection of viruses (August 8, 2005) [Russian]. Vopr Virusol. 2006;1:11?4.
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                Riede K. Global register of migratory species: database, GIS maps and threat analysis. Munster (Germany): Landwirtschaftsverlag; 2001.
                Scott DA, Rose PM. Atlas of Anatidae populations in Africa and western Eurasia [cited 2006 Sep 11]. Wageningen ( the Netherlands): Wetlands International; 1996 Available from http://www.wetlands.org/
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                Figures
                Figure 1. Map showing the spread of highly pathogenic avian influenza (HPAI) H5N1 virus and its environmental context...
                Figure 2. Distribution overlay of migratory flyways of Anatidae bird species in the western Palearctic...
                Appendix Figure. Population of Anatidae in the western Palearctic.

                Table
                Appendix Table. Family and species found to be positive for highly pathogenic avian influenza H5N1 virus as of May 15, 2006

                Suggested Citation for this Article
                Gilbert M, Xiao X, Domenech J, Lubroth J, Martin V, Slingenbergh J. Anatidae migration in the western Palearctic and spread of highly pathogenic avian influenza H5N1 virus. Emerg Infect Dis [serial on the Internet]. 2006 Nov [ date cited]. Available from http://www.cdc.gov/ncidod/EID/vol12no11/06-0223.htm

                Attached Files

                Comment


                • #24
                  Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                  Tompe, I would like to echo Florida1?s sentiments that for the most part there is no bias for or against a particular position here at FluTrackers. Most members and readers here are searching for the best possible explanations of the data we have before us. <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:p></o:p>
                  <o:p></o:p>
                  Niman?s position is straight forward because in a very parsimonious way it explains the current worldwide geographic distribution of the clades of H5N1 among various bird species.<o:p></o:p>
                  <o:p></o:p>
                  It is not sufficient to say that ?the evidence for the involvement of wild bird in the long-distance spread of H5N1 is very weak.? Following the principal of Occam?s razor, what alternative mechanism(s) do you then propose to explain the current geographic distribution of H5N1? <o:p></o:p>
                  http://novel-infectious-diseases.blogspot.com/

                  Comment


                  • #25
                    Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                    Originally posted by Laidback Al View Post
                    Tompe, I would like to echo Florida1’s sentiments that for the most part there is no bias for or against a particular position here at FluTrackers. Most members and readers here are searching for the best possible explanations of the data we have before us.

                    Niman’s position is straight forward because in a very parsimonious way it explains the current worldwide geographic distribution of the clades of H5N1 among various bird species.

                    It is not sufficient to say that “the evidence for the involvement of wild bird in the long-distance spread of H5N1 is very weak.” Following the principal of Occam’s razor, what alternative mechanism(s) do you then propose to explain the current geographic distribution of H5N1?
                    The transport and transmission of Qinghai H5N1 by migratory birds goes well beyond Occam's razor. I have not gone through the detail, because much of the evidence was covered in 2005, shortly after the Qinghai strain was reported at Qinghai Lake. Initially, in early May, there were 189 dead bar-headed geese which subsequently were positive for H5N1.



                    By the time the first OIE report was filed, the number was up to 519 and included 5 species of long range migratory birds (two geese, two gulls, and cormorants).



                    In May 2005, some of the issues were somewhat open because the level of death in waterfowl was unprecedented and H5N1 had never been reported west of China. Thus, it was possible that the Qinghai strain would burn out at Qinghai Lake (i.e. dead birds don't fly).

                    However, the debate really ended a couple of months later. H5N1 was reported at Chany Lake in southern Siberia (and adjacent Kazakhstan), and Erhel Lake in northern Mongolia. Since none of these countries had reported H5N1 previously, it seemed likely that there was a relationship to the Qinghai outbreak, because it was known that many migratory birds that are at Qinghai Lake in the spring, spend the summer in Siberia. When it was confirmed that the H5N1 in Russia, Mongolia, and Kazakhstan was the Qinghai strain, the debate was over.



                    Novosibirsk Russia and Qinghai Lake China H5N1's are Similar

                    Recombinomics Commentary
                    August 11, 2005

                    Genetic sequencing of a particular fragment of the virus relating to its virulence shows it is "analogous to the sequence of the highly virulent [H5N1 sub-type] found in three species of migratory water birds during the epidemic in May and June on Qinghai Lake in China, writes Evgueny Nepoklonov, head of the main veterinary department at the Russian ministry.

                    The turkey virus was also subjected to a phylogenetic analysis, which shows evolutionary history, of a crucial flu gene - the neuraminidase gene. This provides additional evidence of link to the Chinese migratory bird outbreak. "The preliminary data on the neuraminidase structure show that it is practically identical to that of the isolate from bar-headed geese (Anser indicus) from Qinghai Lake," says Nepoklonov......


                    Since southern Siberia lies within multiple overlapping flyways and H5N1 had already moved from Qinghai Lake to central China to Chany Lake in southern Siberia in a couple of months, it was clear that H5N1 would then move into new regions it had never been previously, such as Europe, the Middle East, and Africa. That happened by the end of 2005 and all H5N1 isolated was the Qinghai strain and initial isolates were in wild waterfowl at the Volga Delta, the Danube Delta, the Crimea penninsula, and the Nile Delta.

                    There are many additional arguments (lack of any other clade anywhere outside of eastern Asia and re-emergence of H5N1 throughout Germany in the middle of the summer), but these just add to a story that was VERY clear in 2005.

                    Anyone bringing the "dead birds don't fly" argument in 2007 simple doesn't know the history, at best, or is in the "religious fanatic" category at worst. Unfortunately, my posts frequently attract the latter (which has been ongoing since May, 2005, when the Qinghai H5N1 was reported).

                    Comment


                    • #26
                      Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                      I am sorry that it took me so long to respond to the numerous contributions, but I?ve just returned from my vacation and only now had the chance to consult some references.

                      @kent nickell
                      The 2006 paper by Chen et al. illustrates quite well the weaknesses of some of the arguments that implicate wild birds. In this paper the birds are only identified as ?migratory ducks?. There are three possible species at the sampling location and one, the spot-billed duck, includes resident and migratory individuals. The study does not show whether the tested birds were in fact migratory.
                      The pathogenicity tests were not conducted on exercising migrants, and that this may matter very much is one of the main points of the paper by Weber & Stilianakis.

                      The paper by Gilbert et al. is not very substantial, but only correlative and does not explicitly consider alternative hypotheses. So, how might an alternative hypothesis look like? Spread along major human transport routes is such an alternative and previous epizootics of AI subtypes were shown to be caused by trade in poultry and poultry products. I summarise here parts of the argument made by Gauthier-Clerc et al. (2007, Ibis, 149, 202-214).
                      Let?s start with the infamous bar-headed geese at Lake Qinghai. By February 2004 the virus was well established along the major highway from Shanghai to Urumqi in the province of Xinjiang in the nort-west, by way of Liujlapu, Jinguyan and Zhonghe. Lake Qinghai is situated to the west of Zhonghe. In spring 2005 the geese arrived in an area where the virus was established for more than a year. (They might have caught the virus in 2004 and brought it back in 2005, but why were there not outbreaks in the wintering areas in India, Nepal, Pakistan and Bangladesh?)
                      The westward expansion of the virus started in July 2005 in Novosibirsk, which is a major road and railway hub. The first dates by administrative regions of Russia are on 22 July in the region of Novosibirsk, on July 23 in the Territory of the Altai, on 27 July in the region of Omsk, on 28 July in the region of Tiumen, on 4 August in the region of Kurgan, on 13 August in the region of Tcheliabinsk, on 19 October in the region of Tula, on 24 October in the region of Tambov, on 22 November in the region of Astrakhan, and on 12 December in Kalmykia along the Caspian Sea. The expansion of H5N1 follows thus exactly the trans-Siberian railway and major main highways and not the flight and stop-over pattern of any migrant. There are many more examples: in Turkey the spread was mainly along the road from Anatolia to Ankara, and the introduction into sub-Saharan Africa was clearly by trade.

                      Comment


                      • #27
                        Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                        the Qinghai virus emerged by reassortment, probably in late 2004 or early 2005 , probably in one single host and all Qinghai viruses probably
                        descend from this one host.
                        The viruses from Qinghai-lake have probably died - they had some
                        special markers which were never found elsewhere.
                        The migration in Siberia in summer,autumn is north-->south
                        I'm interested in expert panflu damage estimates
                        my current links: http://bit.ly/hFI7H ILI-charts: http://bit.ly/CcRgT

                        Comment


                        • #28
                          Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                          Originally posted by gsgs View Post
                          the Qinghai virus emerged by reassortment, probably in late 2004 or early 2005 , probably in one single host and all Qinghai viruses probably
                          descend from this one host.
                          The viruses from Qinghai-lake have probably died - they had some
                          special markers which were never found elsewhere.
                          The migration in Siberia in summer,autumn is north-->south
                          Please, you have no data on clade 2.2 (Qinghai) H5N1 in northern China, South Korea, or Japan for 2005/2006/2007 (and ONE isolate from southern China and VERY limited data from Mongolia).

                          Conclusions from a VERY biased database can be dangerous (and are usually wrong).

                          Comment


                          • #29
                            Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                            Originally posted by tompe View Post
                            I am sorry that it took me so long to respond to the numerous contributions, but I?ve just returned from my vacation and only now had the chance to consult some references.

                            @kent nickell
                            The 2006 paper by Chen et al. illustrates quite well the weaknesses of some of the arguments that implicate wild birds. In this paper the birds are only identified as ?migratory ducks?. There are three possible species at the sampling location and one, the spot-billed duck, includes resident and migratory individuals. The study does not show whether the tested birds were in fact migratory.
                            The pathogenicity tests were not conducted on exercising migrants, and that this may matter very much is one of the main points of the paper by Weber & Stilianakis.

                            The paper by Gilbert et al. is not very substantial, but only correlative and does not explicitly consider alternative hypotheses. So, how might an alternative hypothesis look like? Spread along major human transport routes is such an alternative and previous epizootics of AI subtypes were shown to be caused by trade in poultry and poultry products. I summarise here parts of the argument made by Gauthier-Clerc et al. (2007, Ibis, 149, 202-214).
                            Let?s start with the infamous bar-headed geese at Lake Qinghai. By February 2004 the virus was well established along the major highway from Shanghai to Urumqi in the province of Xinjiang in the nort-west, by way of Liujlapu, Jinguyan and Zhonghe. Lake Qinghai is situated to the west of Zhonghe. In spring 2005 the geese arrived in an area where the virus was established for more than a year. (They might have caught the virus in 2004 and brought it back in 2005, but why were there not outbreaks in the wintering areas in India, Nepal, Pakistan and Bangladesh?)
                            The westward expansion of the virus started in July 2005 in Novosibirsk, which is a major road and railway hub. The first dates by administrative regions of Russia are on 22 July in the region of Novosibirsk, on July 23 in the Territory of the Altai, on 27 July in the region of Omsk, on 28 July in the region of Tiumen, on 4 August in the region of Kurgan, on 13 August in the region of Tcheliabinsk, on 19 October in the region of Tula, on 24 October in the region of Tambov, on 22 November in the region of Astrakhan, and on 12 December in Kalmykia along the Caspian Sea. The expansion of H5N1 follows thus exactly the trans-Siberian railway and major main highways and not the flight and stop-over pattern of any migrant. There are many more examples: in Turkey the spread was mainly along the road from Anatolia to Ankara, and the introduction into sub-Saharan Africa was clearly by trade.
                            Looks like a new "dead birds don't fly" propaganda campaign has been launched

                            Comment


                            • #30
                              Re: Ecologic Immunology of Avian Influenza (H5N1) in Migratory Birds

                              Looks like a new "dead birds don't fly" propaganda campaign has been launched
                              The latter part of my most recent posting has nothing at all to do with a "dead birds don't fly"-argument.

                              I'd still appreciate a substantive reply to the findings cited in my posting and not just empty dismissals. Dr. niman, please answer the following question: Which bird species migrates between July and December from Novosibirsk to the Caspian Sea along the major transport routes and stops over at the specific times and the specific places where the first cases in the different regions have been reported?

                              Comment

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