Evaluating Potential Infectious Disease Threats for Southern Resident Killer Whales (Orcinus orca)
The southern resident killer whale (Orcinus orca) population, found within the inland waters of Washington (USA) and British Columbia (Canada), has declined 20 percent since 1996 and is listed as endangered by the Canadian Committee for the Status on Endangered Wildlife in Canada. As with many endangered and threatened wildlife populations, information about the role that infectious diseases may be playing in the decline of this small population is not available, nor is information regarding infectious diseases that may threaten its long-term viability. Using reference literature, we identified 15 infectious agents (bacteria, viruses, and fungi) reported in free-ranging and captive killer whales. We also identified 28 additional infectious agents reported in free-ranging and captive odontocete species that are sympatric to southern resident killer whales, specifically common dolphins (Delphinus delphis), Dall's porpoises (Phocoenoides dalli), false killer whales (Pseudorca crassidens), harbor porpoises (Phocoena phocoena), northern right whale dolphins (Lissodelphis borealis), bottlenose dolphins (Tursiops truncatus), white-sided dolphins (Lagenorhynchus obliquidens), Risso's dolphins (Grampus griseus), short-finned pilot whales (Globicephala macrorhynchus), and striped dolphins (Stenella coeruleoalba). Infectious agents were scored as having a high, medium, or low ability to affect fecundity or reproductive success, to cause disease in individual animals, and to cause epizootics. Marine Brucella sp., cetacean poxvirus, cetacean morbilliviruses, and herpes viruses were identified as high priority pathogens that warrant further study. To better understand the impacts of priority and non-priority infectious agents on southern resident killer whales, we intend to use identified pathogens to develop a standardized necropsy and disease testing protocol for southern resident killer whales and sympatric odontocetes.
We thank C. Soos, K. Gilardi, and S. Raverty for improving this project. This work was supported by the Marine Ecosystem Health Program, Wildlife Health Center, School of Veterinary Medicine, University of California, Davis.