Disease ecology refers to the study of host-pathogen interactions within the context of their environment and evolution. To understand the universal role of pathogens in ecosystems, pathogen transmission and spread in both time and space and the impact on host populations are key features. Besides emerging diseases, which are often invasive species, outbreaks of infections can often be caused by environmental factors affecting the hosts and/or the pathogens singly and/or in combination (e.g. temperature, agro-chemicals). Therefore, understanding the incidence and impact of diseases requires understanding of the ecological conditions and their interactions.
At the Vetsuisse Faculty Bern, disease ecology questions are addressed in the research on bees, fish, and wildlife.
Bees
Bees and other insects, provide crucial ecosystem services for human food security and maintenance of biodiversity. It is therefore not surprising that major declines in wild insects, combined with losses of managed bees, have recently raised great concern.
Diseases are playing an apparent key role for the disastrous health situation of managed European honey bee subspecies, Apis mellifera, globally. In particular, the ubiquitous ectoparasitic mite Varroa destructor, an invasive species from Asia, is the primary biological cause of managed honey bee colony mortality worldwide. This is mainly because it is a very efficient vector of several honey bee viruses, generating a disease epidemic within the colony, which dwindles until it dies. Other disease are also involved, e.g. small hive beetles Aethina tumida or microsporidians Nosema ceranae. Theses pathogens originally described from honey bees can spill over to other species, e.g. bumblebees, Bombus spp. The extent and role of such pathogen spill over for the decline of wild species is not well understood at present. Likewise, the role of interactions between factors from the individual bee, over the colony and apiary to the landscape level is not clear as are the mechanisms behind those interactions.
Our hypothesis-driven research therefore aims to better understand the basic biology of both bee hosts and their pathogens in order to shed light on the fundamental mechanisms underlying the impact of disease on ecosystem service providing insects.
Fish
We aim at the understanding of the mechanisms through which aquatic contaminants interfere with the fish immune system. Emphasis is given on chemical effects that are mediated via endocrine receptors, in particular arylhydrocarbon receptors (AhR), membrane-bound and nuclear estrogen receptors (ER), and thyroid receptors (TR). The research questions addressed by our group iare (i) which immune cell types express AhR, ER or TR?, (ii) which immune cell functional changes are induced by the ligand-dependent activation of these receptors?, (iii) does the contaminant-related immunomodulation translate into altered immunocompetence and pathogen resistance of the fish?, and (iv) to what extent does the physiological status of the fish (developmental stage, reproductive cycle, nutritional status, stress) influence the receptor-mediated immunomodulating effects of environmental contaminants? Experimentally, we rely on two model fish species, rainbow trout and zebrafish, and we use both in vitro and in vivo approaches. The research is funded by the Swiss National Science Foundation and the European Commission.
The myxozoan parasite, Tetracapsuloides bryosalmonae, has a multi-host life cycle, involving both vertebrae (cold-water salmonids) and invertebrate (bryozoan) hosts. In salmonids, T. bryosalmonae causes the proliferative kidney disease (PKD) of cold-water salmonids. Recent studies suggest that PKD is an emerging disease in Europe and Northern America, and that the emergence is linked to increasing temperatures and eutrophication. Our research incorporates ecological, genetic, immunological and epidemiological studies across the entire life-cycle (fish and bryozoans) of the disease agent to understand disease maintenance, emergence and spread in river networks and to create predictions for scenarios of future environmental change in aquatic systems. The research is funded by SNF-Sinergia.
Wildlife
A number of infectious diseases such as bovine tuberculosis, sarcoptic mange, canine distemper, infectious keratoconjunctivitis of wild Caprinae or leptospirosis may be maintained in free-ranging wildlife populations. Pathogen maintenance in the wild represents a potential threat to wildlife conservation, domestic animal and human health. There are strong indications that animal densities, game management strategies and climatic factors are drivers of infection dynamics in wildlife populations. We carry out harmonized epidemiological investigations in wildlife populations in different Swiss and European regions with various disease patterns and host abundance to track the anthropogenic and natural environmental factors contributing to disease emergence and maintenance in the wild. In the framework of multidisciplinary collaborations, we also investigate host and pathogen factors and merge the results obtained with different approaches to perform integrative data analyses, with the aim of formulating recommendations for disease prevention and control. The research is supported by the Federal Food Safety and Veterinary Office, the Federal Office of Environment, EMIDA-Eranet, COST, and additional funding sources.
