The primary goal of this research is to understand the ecological determinants of transmission of the pathogen Toxoplasma gondii from terrestrial hosts to the threatened southern sea otter (Enhydra lutris nereis) population and to use these data in predictive models to evaluate the impact of changes in host abundance, infection prevalence, water management, habitat structure (terrestrial and aquatic) and prey selection. The study and model development will focus on this protozoan parasite because T. gondii is the major cause of death in southern sea otters, and otters serve as a valuable sentinel for marine pollution with this important human pathogen. Focusing on two coastal sites where T. gondii infections and mortality in sea otters are prevalent, this integrated study has three components that link terrestrial ecology to land use patterns and ultimately to sea otter ecology. Investigators from University of California at Davis, California State University at Fresno, Institute of Ecosystems Study, and University of British Columbia will predict terrestrial environmental contamination with oocysts and risk of exposure to T. gondii based on the prevalence of infection in domestic felids and wild rodent populations. The investigators hypothesize that there is a distinct spatial pattern of risk for otters because land runoff forms well-defined zones at specific locations in coastal waters, and high oocyst concentrations are expected in these zones. Finally, they propose to study whether individual otter diet and movements can predict the risk of exposure and death from protozoal encephalitis caused by T. gondii infection. Data from the three components will permit evaluating the impact of alternative control strategies using simulation modeling to test whether reduction of putative risk factors will reduce site-specific incidence and prevalence of T. gondii in otters. This project is unique in its multidisciplinary and comprehensive approach - incorporating terrestrial and marine ecologists, oceanographers, epidemiologists, and parasitologists to investigate the ecology of an important environmental pathogen at the interface of terrestrial and aquatic systems.
In terms of the broader impacts of this study, this project emphasizes graduate student training in research and outreach. Overall, 4 Ph.D. and 2 Masters students will be mentored in research and outreach efforts. The simulation model will permit evaluation of different control strategies to reduce pathogen pollution of the near shore marine environment. This will benefit the threatened southern sea otter population that is struggling to recover, as well as other marine wildlife and humans in coastal areas. Sea otters are a flagship species with extremely high visibility, which provides a unique opportunity to inform the public about the land-sea interface and pathogen pollution. A public website www.seaotterresearch.org will be expanded to include specific information on the goals of this study and to publicize the findings in a public-friendly format with special interactive sections devoted to younger students (K-8), land and water resource managers, and cat owners. A brochure explaining risks of toxoplasmosis, suggested best practices for cat owners, and methods to reduce environmental exposure to T. gondii will be provided to the cat-owning public through pet product retailers and veterinarians in coastal areas. Sea otter bookmarks with the web address will also be provided at no cost through pet product retailers and schools in the high impact areas. Public town hall meetings will be organized and attended by senior personnel and students at both study sites to inform and discuss with local residents the rationale, design and findings of the study. Each of the graduate students involved in the project will be trained in public relations/speaking and will be required to make at least 2 presentations per year at schools and public meetings in high-risk communities. In addition, to original research publications, students will present the results of this research at national scientific conferences.
