Bacteria, viruses and parasites have always been part of human life. The hopes once cherished, that we through antibiotics would win the battle against infectious diseases is not realistic anymore. Rather the contrary, the last centuries' enormous population expansion, utilization of new habitats and swift methods of travel have made us more exposed and more vulnerable to the emergence of novels pathogens. And at the same time, antibiotics and antivirals are becoming less effective because of the development of resistance.
In the intricate web of disease, pathogens and hosts, it is important to remember that most human infections are zoonoses. This means that they occur mainly in animals but have the capacity to cross species boundaries and infect humans. However, the education and research systems have traditionally been divided into veterinary and human medicine, with only little crossover between disciplines. Bridging this gap was the fundamental idea behind the founding of the Zoonotic Ecology and Epidemiology research group at Linnaeus University.
We work on the following research topics:
Influenza virus – from birds to people
Influenza A virus is one of the most important and devastating zoonotic pathogens in the world. It is a RNA virus and occurs in many different subtypes and genetic lineages. Characterization is based on genetic and antigenic variation in two surface proteins: the hemagglutinin (H1-H16) and the neuraminidase (N1-N9). Wild birds, especially ducks, constitute the natural reservoir of the virus. In these hosts, the influenza A virus appears to be a sub-clinical gastrointestinal infection. High loads of virus are excreted in the feces of infected ducks, and can spread between individuals via the fecal-oral route.
Some influenza A virus subtypes (most notably H5 and H7) can infect poultry and undergo genetic changes and transform into highly pathogenic variants, causing high mortality in infected populations. Although devastating for the poultry industry, outbreaks can be stopped if culling is undertaken.
The virus pool in wild birds constitutes the ancestors to the influenza circulating in humans. The virus requires several adaptations in order to efficiently infect and spread between people. Such host shifts have been rare, and in the last century occurred three times: the Spanish Flu in 1918 (H1N1), the Asian Flu in 1957 (H2N2) and the Hong Kong Flu in 1968 (H3N2). Each of these pandemics caused the deaths of several million people.
After being introduced to humans, the influenza A virus adapts to its new host and herd immunity in the human population builds up. Continued virus circulation is manifested by yearly seasonal respiratory influenza outbreaks which are milder than the original pandemic strain. Due to the virus' ability to change its antigenic properties by mutation, yearly vaccination is required for protection from the disease.
In our research, we study the influenza A virus in its wild bird reservoir. This work runs along several lines, but we are particularly interested in the natural dynamic of the virus in different bird species and if there are any ecological costs from being infected. Further, we study the molecular interaction between viruses and host cells, the viral evolution and the induction of antiviral resistance mutations.
Campylobacter jejuni ecology and evolution
Campylobacter jejuni is an example of a multihost pathogen with large zoonotic potential. It is common in food production animals, particularly in poultry, but also infects a range of wild animals, including different species of wild birds. In humans, infections are caused by consumption of contaminated food items, particularly undercooked poultry products. Although rarely causing deaths, the costs to society in terms of lost working days, healthcare costs, reduced productivity and human suffering is very large and make this pathogen an important topic to study.
In our research, we focus particularly on the epidemiology of Campylobacter in the wild bird reservoir. By whole genome sequencing of wild bird isolate and comparative genomics we strive to get a deeper understanding on how host populations shape population genetics of this pathogen. Based on the genome information we hope to identify genes that determine specific adaptations and functional traits, such as why certain genotypes have a high degree of host specificity.
Antibiotic resistance in natural bacterial flora
Bacteria date back at least 3 billion years. They are found everywhere in our environment as well as in and on our bodies. Their unique adaptability is directly related to their short generation time which, under optimal conditions, may allow 1000 generations in 10 days, corresponding to 20,000 – 30,000 human evolutionary years. This allows bacteria to adapt to changes in their environment and to develop mechanisms to protect them against toxic compounds.
The ability of bacteria to develop resistance mechanisms to antimicrobial agents is rendering more and more human infections that are difficult or impossible to treat. The overuse of antimicrobial agents during the past decades has taken resistance beyond hospitals, farms, daycare centers and homes for the elderly, and may leave irreversible footprints in antimicrobial ecology.
Quite recently, there has been an increasing interest in the presence of antibiotic resistance in bacteria from natural environments. Commensal bacteria could constitute a hidden reservoir of antimicrobial resistance. The presence of antimicrobial resistance in the normal microbiota of migrating birds has been poorly investigated so far. The role of birds as vectors for various infectious agents is well known, and not least their ability to introduce and spread diseases to new geographical areas. Our research investigates the geographic connectivity of antibiotic resistant bacteria and bird migration.
Zoonotic pathogens in Polar regions
The extreme climate and the limited choice of available feed make the wildlife of Polar Regions particularly sensitive to environmental hazards. In Antarctica, breeding colonies of penguins and other animals may harbor a million pairs or more. Similarly in the Arctic, isolated islands are the homes of millions of auks and other seabirds. Such dense aggregations of animals facilitate rapid transmission of infectious agents between individuals and may result in large epizootics, especially if a novel pathogen is introduced.
The human presence is increasing in both Polar Regions, in part due to a growing ship-borne tourism. The Antarctic continent is remote, but still holds several permanent scientific bases, which together with tourism and fishing vessels pose a threat for introduction of human-associated infectious agents to the Antarctic fauna. Microorganisms originating from human activities have been detected around Antarctic stations; several that potentially may have devastating effects on the indigenous animals.
The most likely risk factors for introduction of pathogenic bacteria and viruses are contaminated food and untreated sewage. In the Antarctic, the Antarctic Treaty has enforced regulations to minimize any possible harmful effects caused by the human presence. These involve, for instance, regulations regarding waste disposal and maximum numbers of visitors to penguin colonies. The legislation in the Arctic differs between countries.
During the last decade, we have investigated the presence of zoonotic pathogens in both Antarctic and Arctic wildlife. We have participated in expeditions to South Georgian and to the Antarctic Peninsula in the south, and to expeditions to the Faroe Islands and the Bering Strait Region in the north.
We have a broad interest in Polar pathogens, with studies ranging from tick-borne infections such as Borrelia, to viral and bacterial diseases such as Influenza A virus, Campylobacter and Salmonella.
Ecology of Ticks and Tick-borne Diseases
Ever since Borrelia burgdorferi was identified as the causative agent of Lyme disease in 1982, new tick-borne pathogens have been described. Tick-borne diseases increase in incidence and geographic range and are thus considered emerging infections.
In Scandinavia, tick-borne diseases are the most important vector-borne diseases, surpassing even mosquito-borne illnesses. Tick-borne diseases present in Sweden include Lyme disease (borrelia), tick-borne encephalitis (TBE), human granulocytic anaplasmosis (fästingfeber) and Candidatus Neoehrlichia mikurensis.
Our research group studies the ecology of ticks and the epidemiology of tick-borne diseases, often focusing on the role different animal hosts play for spatial and temporal transmission. At present, we focus most of our efforts on the newly found Candidatus Neoehrlichia mikurensis, trying to characterize host range, distribution and risk for humans to acquire infections.
- Daniel Bengtsson, Linnaeus University, Stopover ecology of mallards – where, when and how to do what? March 11, 2015. ISBN 978-91-88357-00-7.
- Michelle Wille, Linnaeus University, Viruses on the wing: evolution and dynamics of influenza A virus in the Mallard reservoir, 8 May 2015. ISBN 978-91-87925-56-6.
- Johan Stedt, Linnaeus University, Wild birds as carriers of antibiotic resistant E. coli and Extended-Spectrum Beta-Lactamases, 13 June 2014. ISBN: 978-91-87427-93-0.
- Petra Griekspoor, Linnaeus University, Exploring the epidemiology and population structure of Campylobacter jejuni in humans, broilers and wild birds, 28 May 2013. ISBN 978-91-87427-83-1.
- Jorge Hernandez, Uppsala University, Human pathogens and antibiotic resistant bacteria in the Polar regions, 10 October 2014. ISBN 978-91-554-9016-4.
- Neus Latorre-Margalef, Linnaeus University, Ecology and epidemiology of influenza A virus in Mallards Anas platyrhynchos, 8 June 2012. ISBN 978-91-86983-61-1.
- Goran Orozovic, Linnaeus University, Resistance to neuraminidase inhibitors in influenza A virus isolated from mallard, 8 April 2011. ISBN 978-91-86491-66-6.
- Jonas Bonnedahl, Uppsala University, Wild birds as indicators of antibiotic resistance pressures in the environment, 25 March 2011. ISBN 978-91-554-8000-4.
- John Wahlgren, Karolinska Institute, Influenza A virus in natural and artificial environments, 8 October 2010. ISBN 978-91-7457-028-1.
- Diana Axelsson-Olsson, University of Kalmar, Protozoa and their involvement in Campylobacter epidemiology, 8 May 2009. ISBN 978-9185993-26-0.
Former group members
A research group is a living entity, changing in composition over time. What we are today is a product of those that worked with us before. The alumni listed below are PhD students, postdocs and faculty that were part of the research group from 2002 and onwards, first at Kalmar University and later at Linnaeus University.
Björn Olsen, professor
Martin Andersson, postdoc
Richard Williams, postdoc
Alexis Avril, postdoc
Joanne Chapman, postdoc
Patrik Ellström, postdoc
Elsa Jourdain, postdoc
Lovisa Svensson, postdoc
Diana Axelsson Olsson, PhD student
Jonas Bonnedahl, PhD student
Daniel Bengtsson, PhD student
Petra Griekspoor-Berglund, PhD student
Badrul Hasan, PhD student
Jorge Hernandez, PhD student
Neus Latorre Margalef, PhD student
Goran Orozovic, PhD student
Johan Stedt, PhD student
Anders Wallensten, PhD student
Anu Helin, PhD student
Our research relies on the financial support that we receive from funding agencies. Without this funding most of our studies would have been impossible to conduct and we would like to thank all financial sponsors for their contributions.