Progress 10/01/06 to 09/30/08

Outputs
OUTPUTS: The primary objective of our research has been to identify the ecological and environmental parameters associated with S. neurona transmission in two high risk sites in California. Our findings are the first step towards developing control strategies to help minimize the risk of S. neurona infection in sea otters and horses. This project greatly benefited from a multi-collaborative working environment which included input and assistance from several ecologists, veterinarians, pathologists, epidemiologists, and microbiologists. Being a wildlife study, extensive field work and subsequent laboratory analyses were required to accomplish our goals. Over 60 days were spent trapping and sampling opossums in field. The data gathered from live-trapping in addition to data gathered from other opportunistically sampled opossums allowed us to quantitatively analyze multiple risk-factors associated with S. neurona infection in opossums. Further molecular characterization allowed us to determine the relatedness of S. neurona parasites being shed by opossums with those infecting horses and sea otters. Together these techniques allowed us to draw significant conclusions about the transmission of S. neurona in California. Throughout the course of this study we have managed to share and disseminate our findings on a regular basis. Information relevant to sea otter scientists was presented at two annual sea otter research conferences in Santa Cruz, CA. In order to help spur the scientific interest of grade school children we also presented our research at a science camp in Cambria, CA. Other conferences at which we shared our research findings included the Northern California Parasitologists meeting as well as the European Wildlife Disease Association conference. Finally, the summary of all our findings will be described in two upcoming publications. PARTICIPANTS: Individuals: PI- Patricia Conrad; Graduate Student- Daniel Rejmanek. Partner Organizations/Collaborators: Fish & Game, Marine Wildlife Care Research Center, Elkhorn Slough Reserve, Moss Landing Reasearch Center. Training/development: training provided for one graduate student. TARGET AUDIENCES: Equine communities and practitioners, sea otter biologists/scientists and those communities or individuals interested in marine wildlife conservation and care. PROJECT MODIFICATIONS: Not relevant to this project.

Impacts
Over the past 3 years we have sampled 270 opossums from the Monterey Bay area and 29 opossums at the Percheron farm in the central valley. Our aims have been to determine the S. neurona infection prevalence in these opossums, identify factors associated with positive infections such as when and where opossums are most likely to shed S. neurona, and finally to determine whether the S. neurona parasites shed by these opossums are genetically identical to those infecting sea otters and horses. Knowing when, where, and how many opossums are shedding S. neurona in these high-risk sites is important for developing appropriate prevention and control strategies. Molecular characterization of the S. neurona parasites is needed to firmly establish the link between the source of these parasites (opossums) and their unfortunate victims (horses and marine mammals). The S. neurona infection prevalence among opossums at all sites was found to be 5.7%. However there was a significant difference between the two study sites. In the Monterey Bay area we found that only 4.4% of opossums were infected with S. neurona while 17.2% of opossums were infected with S. neurona at the Percheron farm. At both sites we found that adult opossums were significantly more likely to shed S. neurona parasites during the spring than any other time of year. Interestingly, this is also the time of year when the majority of sea otters become acutely infected with S. neurona. We found that S. neurona infections in horses at the Percheron farm were also consistently highest during the springtime. Finally, we have genetically characterized over 20 S. neurona parasites obtained from opossums, sea otters, and horses. By comparing 4 different DNA sequences we were able to show that the S. neurona parasites infecting several sea otters and a harbor porpoise in Monterey Bay, and 3 different horses from central California were all genetically identical to the S. neurona parasites being shed by opossums at both of our study sites. While it has been known for some time that opossums are the definitive hosts for S. neurona and that they are the likely source of S. neurona for horses and sea otters, this is the first study to show a direct seasonal and molecular link between shedding of S. neurona by opossums and S. neurona infection in horses, sea otters and other marine mammals. This study helps confirm the fact that protozoal pathogens originating on land are negatively impacting sea otters and marine mammals in coastal California. This study is also important for horse owners and farm managers in that it gives them a specific season in which to focus opossum trapping and removal efforts. More importantly, our findings highlight the most appropriate time to protect horses from becoming infected and developing EPM by protecting their feed and water sources from fecal contamination by opossums.

Publications

• No publications reported this period