During the month of July 2007 a joint Russian and Swedish research expedition set out to investigate the presence of microbial agents of zoonotic potential in the fauna of the Commander Islands, a small group of islands bordering the Bering Sea in the North Pacific Ocean. The geographic position of the Commander Islands is of key interest as they are isolated from the North East Asian mainland, but are in close proximity to the North American continent forming a continuation of the Aleutian chain of islands. In December 2002 the Commander Islands received the status of an international biosphere reserve and are thus considered a part of the world’s natural heritage. The coastal waters of the islands are inhabited by many species of whales and cetaceans, while the islands themselves support large colonies of fur seals and sea lions, great numbers of sea otters as well as over 500,000 rare northern birds. The islands host large populations of both migratory and stationary bird species. Due to isolation, some populations have even developed into subspecies found only on these islands, such as subspecies of Rock Sandpiper (Calidris ptilocnemis quarta), Commander Rock Ptarmigan (Lagopus mutus ridgwayi Stejneger) and Winter Wren (Troglodytes troglodytes pallescens Ridgw.). Many marine birds such as auks, gulls, fulmars and shearwaters come to the islands in thousands to breed while others such as the emperor goose use the islands as wintering ground.

In search of avian flu viruses

The expedition’s main focus of interest was to screen for the presence of influenza viruses among the large marine bird populations on the islands. Influenza viruses exist in different types and subtypes and cause disease in many different species of animals (Webster et al., 1992, Stone, 2000 and 2002, Wallensten, 2007a). The seasonal and occasional pandemic (world wide) spread of influenza virus in humans is of major public health importance. The subject has received massive attention since the start of the outbreak of highly pathogenic avian influenza subtype H5N1 in poultry in South East Asia in 2003. This outbreak has had an enormous negative impact on the poultry industry worldwide. It has also proved to be highly lethal when transmitted to humans and has raised concerns over an imminent pandemic (Wallensten et al., 2007b). Historically influenza pandemics have had a devastating impact. The worst known pandemic, the Spanish Influenza of 1918, is thought to have caused the death of more than 40 million people (Oxford 2000). Although stable lineages of influenza viruses exist in different species such as humans, horses and pigs, all influenza viruses in these species are thought to have originated from those circulating in wild birds (Ito and Kawaoka, 2000). Wild birds have been shown to harbour a multitude of different influenza viruses but only a few of these have been involved in outbreaks in other species. Influenza viruses have been isolated from several bird species, but are most frequently isolated from dabbling ducks such as mallards and in some parts of the world from certain species of waders (Olsen et al. 2006, Wallensten et al., 2007c). Influenza viruses are isolated from these species around the world and there has even been serological evidence of infection in Antarctic penguins (Wallensten et al., 2006). Very little is known about the circulation in marine birds such as shearwaters and auks although there have been sporadic reports (Wallensten et al., 2005, Sazonov et al., 1977, Mackenzie et al. 1984, Yamnikova et al., 2003), but the relevance of these sporadic findings in marine birds in relation to the total circulation of influenza viruses in wild birds is still unclear. Many marine bird species live nomadic lives at sea and are therefore difficult to catch other than on their breeding grounds. Therefore breeding places such as the Commander Islands are ideal for sampling marine birds. The relative isolation of the Commander Islands from the mainland East Asian migratory bird flyways and the limited impact of poultry production also make these islands interesting for sampling. The current expedition aimed to fill the final gap in an influenza screening project that was part of the multidisciplinary research expedition named “Beringia 2005”, organized by the Swedish Polar Research Secretariat in collaboration with Russian and American authorities. During Beringia 2005, sampling for influenza took place on the Russian mainland further north including Wrangel Island and also at the Alaskan coast, in order to map the prevalence of influenza viruses in the Bering Sea area.

Zoonotic gut bacteria and antibiotic resistance

However, influenza A viruses are not the only agents of zoonotic potential that birds can harbour and during both Beringia 2005 and the current expedition, simultaneous sampling for bacterial agents were also performed in order to benefit studies on the prevalence of Campylobacter, Salmonella and Chlamydophila psittaci among wild birds. These samples will also be used for studies on the presence of antibiotic resistance in bacteria from these remote echo systems. Previous studies by Professor Olsen’s group have discovered antibiotic resistance in bacteria from other remote places such as the South Georgian Islands, in spite of the limited human presence on those islands (Olsen et al. 1996, Palmgren et al., 2000, Broman et al., 2000).

Seabirds perpetuate specific bird-tick borrelia cycles

In addition, ticks were collected from birds and from the birds’ nests. Ticks will be analysed for the presence of Borrelia burgdorferi sensu lato, tick-borne spirochetes that can cause Lyme borreliosis in humans. Migratory birds have been shown to act as long distance vectors for Borrelia and different sea birds, nesting in large colonies, are known to perpetuate specific bird–tick Borrelia cycles with dedicated tick species (Olsen, Jaenson et al., 1993, Olsen, Duffy et al., 1995, Comstedt, Bergstrom et al., 2006). Mapping Borrelia isolates from these remote islands and comparing them to strains isolated from birds and rodents as well as humans can provide new knowledge on the global distribution and spread of the Borrelia spirochetes.

Field work

The expedition was carried out by participants from the Institute of Influenza in Saint Petersburg and a joint Swedish crew with representatives from Kalmar University, Lund University and Umeå University. The team was fortunate to have stable weather during the whole expedition (not always the case on these misty and cold islands) and with expert help from the rangers of the reserve, they managed to capture and sample birds from both the east and west coast of Bering Island, as well as from the small Toporkov Island. In addition, a smaller number of specimens were collected from black-headed gulls in the river delta of Petropavlovsk. All together, specimens from some 530 birds of different key species were collected, as well as a large number of ticks, mainly from birds’ nests. As a side project, Dr. Marina Stukova also performed voluntary blood sampling of the local population at Bering Island for seroepidemiological investigations.

All specimens were put in appropriate protective media in the field, and then placed in stainless steel dewars of liquid nitrogen at a temperature of about -197°C. The dewars provided a simple and effective means of rapid freezing and safe storage during fieldwork and transportation across the 11 time zones back to Sweden. Laboratory investigations regarding Influenza viruses and Influenza serology will be carried out as a collaboration between Kalmar and Saint Petersburg, while ticks and bacterial specimens will be processed in Umeå and Kalmar, respectively. All results will be published jointly and feedback on the outcome of the investigations also provided to the Director of the Komandorskiy State Nature Biosphere Reserve for reference.

In conclusion, this international, multidisciplinary research expedition may provide new knowledge in several important areas of research regarding silvatic zoonotic diseases, i.e. infectious diseases and propagation of infectious agents in wild animals that can eventually affect humans. Knowledge about the propagation of antibiotic-resistant bacteria from human and agricultural sources back into nature is also of major concern in the context of the long-term usefulness of antibiotics in the battle against infectious diseases.