In recent years, the global burden of viral infections has greatly increased. Infections are easily spread internationally, are difficult and costly to control and contain. In 1997 an outbreak of avian influenza occurred in Hong Kong. Since then, similar events took place all over the world: in Italy, Netherlands, Canada, Russia, Thailand, Mongolia, etc. In these cases the spread of influenza coincided with the routes of migratory birds. Long term studies revealed that birds have been natural reservoirs of influenza A for millions of years. The primary reservoirs of influenza are considered to be the orders Anseriformes (wild geese and ducks) and Charadriiformes(herons, sea-swallows, plovers). Since 1961, avian influenza was isolated from 90 species of 12 orders, including 40 of 149 species of Anseriformes (with no symptoms of illness associated with avian influenza), and 20 species of Charadriiformes. Charadriiformes are mostly represented by long— distance migratory birds with a worldwide habitat. Other birds are not considered as long— term natural reservoir of avian influenza.
Waterfowls act as natural reservoirs of all 16 influenza A HA subtypes. In wild ducks influenza reproduces mainly in the cells of gastrointestinal walls, causes no symptoms and is shed in high quantity in feces. Influenza was successfully isolated from fresh feces and lake water, which means that waterfowls are able to transmit influenza through feces and lake water with high efficacy. Non virulent nature of influenza in ducks and swamp birds may be caused by centuries— long accommodation to the host. Thus, Ducks and swamp birds play an important role in the history of influenza evolution by continuously sustaining virus population. To date, avian influenza is known to have caused epidemics among seals, whales, swine, minks, horses and poultry.
Genetic studies of influenza in different bird species showed that influenza evolved independently in Eurasia and America. Thus, latitudal migration between the two continents plays almost no role in influenza transmission, while longitudal migration is, supposedly, key to continuous evolution of influenza. In 1999 a group of Swedish researchers studied the spread of influenza in Northwestern Europe. More than 10000 birds migrating from Ö land to the Southwest of Sweden, where an ornithological base was located, were examined. It was established that 10–20% of wild ducks were influenza A carriers, with subtype varying by season. A new H16 subtype was isolated from Larus ridibundus (Fouchier et al 2005). Influenza A was for the first time found in guillemot (Wallensten et al 2005). It was shown that influenza subtypes H5 and H7 are widely spread among wild birds and are genetically similar to highly pathogenic viruses which caused epizootic outbreaks in Russia and Europe. Avian influenza surveillance is vital for prediction and prevention of influenza outbreaks in poultry.
Little is known about the spread of influenza A in the northern region of the Pacific. During the Beringia 2005 Expedition, specimens were collected from birds in nesting places of the Alaskan tundra and Northeast Russia. An Influenza A virus of Eurasian and North— American origin, previously obtained from guillemot in the Baltic Sea (Wallensten et al 2005), was isolated. We assume there exists an unknown marine transmission route of influenza, possibly through razorbills. Detection of influenza in remote locations can be the key to understanding its transmission routes. A study in Antarctic (Wallensten et al 2006), for instance, provided serological evidence of the presence of influenza in penguins.
The Commander Islands, located 180 km from Kamchatka coast, are ideal place for such studies. The islands boast a variety of species and huge populations of birds, which are endemic to this place and seldom engage in contact with continental species. The absence of poultry makes these islands a pristine environment for influenza virus. The Islands also offer an opportunity of collecting specimens from razorbills and seagulls.
Borrelia burgdorferi is an etiological agent of Lyme disease spread by ticks. It is predominant in the northern hemisphere. Previous studies showed that birds infested with ticks spread the disease in the Baltic and Atlantic regions (Olsen et al 1995, Comstedt et al 2006, Larsson et al accepted). Our expedition was aimed at finding out whether the birds and animals of the Northern Pacific are carriers of the Lyme disease.
In the course of the expedition, more than 1100 specimens from blood sera and anal swabs of wild birds were collected. More than 10 different bird species were studied, including glaucous-winged gull, black-headed gull, tufted puffin, pigeon guillemot, red-faced cormorant, pelagic cormorant, black-legged kittiwake, red-legged kittiwake and rock sandpiper. Molecular biological analysis indicated no presence of influenza A antibodies in blood sera, which means that local birds didn’t carry influenza A.
More than 30 strains of Borrelia burgdorferi were collected and studied from tufted puffins and their nesting places.
