The unique wildlife of Antarctica is considered to be particularly sensitive to environmental hazards because of the extremes in climate and because of the limited choice of feed available. One important topic that has attracted growing concern during the last decades is the potential risk of humans involuntarily introducing infectious diseases novel to the indigenous Antarctic fauna. Such new pathogens, to which the animals would have no immunity, could be rapidly transmitted within the dense animal populations and have devastating effects on the fauna. The most likely risk factors for the introduction of infectious diseases are contaminated food and untreated sewage let out from research stations and tourist or commercial ships. There are only a few human settlements in Antarctica, all devoted to scientific research, and the majority of staff stays at the research stations only for short periods of the year. The population of scientists in Antarctica has remained fairly constant in the last decade, and the Antarctic Treaty regulates the number of residents at each research station. Nevertheless, the total number of visitors to the area is steadily increasing, because of rapidly increasing numbers of ship borne tourists infectious agents in bird populations on the Antarctic Peninsula (at present exceeding 10,000 tourists annually; Provic, 1998). The Antarctic Treaty, as well as some research stations and tourist companies, have made regulations to safeguard the environment from harmful effects of the human presence. This involves, for instance, regulations regarding waste disposal and maximum numbers of visitors to penguin breeding colonies.

Current knowledge is limited regarding the natural microbial flora and the occurrence of disease-causing organisms among animals in the region. However a few reports have been published on mass mortality in seal and bird populations, where infectious diseases have been the suspected cause. An incident with accidental pollution by sewage in 1990–1991 at the Scott base on Ross Island had devastating effects on the sea fauna in the affected area, with a high mortality of marine animal species (Meyer-Rochow, 1992). Avian cholera caused by Pasteurella multocida was the suspected death cause in an incident with 90% mortality in a population of skuas in 1981. In 1998, sea lions on a New Zealand sub-Antarctic island died of an unknown cause, but a new Campylobacter-like bacterial species was suspected of causing the epizootic. Furthermore, several different pathogens have been isolated from Antarctic animals: Salmonella (Oelke, 1973, Olsen, 1996 and Palmgren, 2000), Pasteurella multocida (Parmelee, 1978 and Lisle, 1990), Mycobacterium tuberculosis (Bastida, 1999), Campylobacter jejuni (Broman, 2000), and avian paramyxovirus (the Newcastle disease agent; Morgan, 1981). These reports might be the tip of an iceberg, since only a few studies reflecting these issues have been carried out in the Antarctic and sub-Antarctic regions.

The aim of our project in Antarctica was to further investigate the occurrence of different pathogens (primarily Salmonella and Campylobacter) in the Antarctic wildlife, and, with aid of modern molecular techniques, elucidate epidemiological relationships between humans and wild animals. We took part in a commercial cruise on the ship Polar Star, arranged by the Swedish tourist agent Äventyrsresor. The blending of a scientific operation and a commercial cruise had many advantages, and both scientists and tourists benefited mutually from each other. We visited seven penguin colonies during a 5-day long cruise along the Antarctic Peninsula. Faecal samples for detection of various bacterial and viral infections, and blood samples for detection of blood borne viral diseases were taken from a variety of animals (table 1). In an investigation such as this, limiting the time between sampling and the actual culturing of the samples in the laboratory is very important, as this influences the likelihood of isolating live pathogens. This has been a problem when working in the Antarctic, as the nearest laboratory is situated in South America. To overcome this problem we set up a small mobile microbiological laboratory on the ship. This enabled us to cultivate certain bacteria (Campylobacter and Helicobacter, which are particularly sensitive to prolonged transportation times and thereby prone to high level of die-off during transport) already on the cruise.

Preliminary results

The results must still be considered preliminary, since not all isolated bacteria have been phenotypically and genotypically determined to species and strain level. We have screened the samples for several different pathogens. No isolation was made in any of the samples of the following: Influenza A virus, Salmonella, Yersinia, VRE (Vancomycin Resistant Enterococci) or EHEC (Enterohemorr-hagic E. coli). However, 19 isolates of Campylobacter spp. and two isolates of Helicobacter spp. were found. We have compared the DNA sequences of the 16S rRNA gene from the Antarctic Campylobacter isolates to published sequences in a database. There are no indications that any of the Campylobacter isolates belong to the species C. jejuni. All data at hand show that they are C. lari. Some are most likely classical representatives for the species, while some are atypical. More complex typing schemes are needed to clarify this, and the isolates are now being investigated by such methods. The DNA sequences of the two Helicobacter isolates show relatedness to previously described species, but preliminary data from other methods indicate that the Antarctic Helicobacter isolates have features not previously described among intestinal Helicobacter spp.

Discussion

In 1996 and 1998 we investigated faecal samples from seals and birds at Bird Island in the South Georgian archipelago, an area where there is human activity all year round. In both years, and especially in 1998, we found a surprisingly high number of Salmonella among the samples. It is noteworthy that the Salmonella isolates from Bird Island, South Georgia, belonged to serotypes commonly found in the urbanised world. On both sampling occasions we also found a few Campylobacter isolates originating from birds, including C. jejuni (Broman, 2000), the species most commonly associated with human disease. In the light of the previous findings it is most interesting that no Salmonella or C. jejuni were found in the collected samples from this year’s expedition. The absence of these organisms indicates that they may not be part of the natural microbial flora of Antarctic birds. This finding not only strengthens the theory of Salmonella spp. and C. jejuni having been introduced to the animal populations of Bird Island, it also shows the importance of obedience to the strict regulations on handling of sewage and wastes that are imposed on all parties involved in different activities in the Antarctic region.