Between 1998 and 2010, 1,860 marine mammal cases were recovered and necropsied along the British Columbia and Pacific Northwest region of the United States, including 1,200 seals (65%), 380 whales (20%), dolphins and porpoises, 150 sea lions (8%), and 130 (7%) otters. These studies revealed a number of surprising findings:
- Some harbor and Dall’s porpoises were carrying Cryptococcus gatti, a fungus typically associated with dead and decomposing eucalyptus trees in subtropic and tropical regions of the globe. These are the first documented cases of a multispecies outbreak of this pathogen. This pathogen was initially recognized in 1998 on Vancouver Island (1) and has since spread to the mainland of British Columbia and southward, along the western seaboard of the continental United States (2, 3). Infections and fatalities have been documented in humans, companion animals, including cats, dogs, ferrets and horses as well as wildlife (4, 5).
- Similarly, since 2002, increasing numbers of subadult and adult harbour seals, particularly along the outer coast of Washington State, have had antemortem neurologic clinical signs and varying degrees of meningoencephalitis.
- Through collaborations with the National Institutes of Health, detections of novel genotypes of Toxoplasma gondii and the subsequent emergence of Sarcocystis neurona and Neospora caninum have been documented (8-13). These protozoal agents are recognized pathogens of terrestrial wildlife, domestic and livestock species. Efforts are ongoing to define their mode of transfer to the near-shore marine environment and their potential impact on harbour seal, other marine mammal populations, and people.
- Systematic post mortem examinations and ancillary diagnostic studies have been undertaken at the Animal Health Center, Abbotsford, BC, which has established baseline information in population health and facilitated comparison of laboratory findings between terrestrial and marine mammal species.
- The iconic nature and intimate association of killer whales to the northeastern Pacific and decline of the southern resident population by 20% through the 1990’s prompted an investigation into worldwide strandings of this species. This is among the first studies into the epidemiology of global strandings of a marine mammal species and an initial effort to characterize pathological findings with infectious disease on a broad scale.
- Review of published cases and laboratory reports of post mortem findings of wild stranded killer whales has disclosed respiratory illness as a prime cause of morbidity and morbidity. To better define the microbial flora of the upper respiratory tract of these animals, a field study was performed to identify bacterial and fungal growth from exhaled blowhole air and compare this to microbial isolates recovered from the surface microlayer of water. Many commonly recognized pathogens from marine mammals were recovered in large numbers, particularly in more urban or densely populated regions and suggests a potential source of environmental exposure and infection for these animals. This study was done in collaboration with the National Oceanic and Atmospheric Administration (NOAA), Department of Fisheries and Oceans (DFO) and a non-governmental organization
- Harbor seal pups abound along the British Columbia coastline. From late July through November increased numbers of stranded or abandoned neonates and pups have been documented. Through the efforts of the Vancouver Aquarium Marine Mammal Rescue Program, Marine Mammal Incident Reporting Hotline with Department of Fisheries and Oceans, and the Marine Mammal Research Unit, at the University of British Columbia a better understanding of pathogen exposure in the field, improved husbandry in rehabilitation and understanding of nutrition and physiology have been garnered. This information is shared with local communities through media releases and blogging and disseminated via scientific meetings and peer reviewed articles.
Some specific questions being explored are:
- What criteria should be used to best determine population health of marine wildlife?
- How does foraging ecology relate to the health of marine wildlife populations?
- What are the most important environmental variables driving the occurrence of disease in marine ecosystems?
- Where do pathogens occur in marine ecosystems?
- What are the potential implications for human exposure to pathogens via consumption of invertebrates, fish, or coming into physical contact with marine mammals?
- Stephen C, Lester S, Black W, Fyfe M, Raverty S. Multispecies outbreak of cryptococcosis on southern Vancouver Island, British Columbia. Can Vet J. 2002;43:792–4.
2) MacDougall L, Kidd SE, Galanis E, Mak S, Leslie MJ, Cieslak PR,et al. Spread of Cryptococcus gattii in British Columbia, Canada, and detection in the Pacific Northwest, USA. Emerg Infect Dis.2007;13:42–50.
3) Kidd SE, Hagen F, Tscharke RL, Huynh M, Bartlett KH, Fyfe M,et al. A rare genotype of Cryptococcus gattii caused the cryptococcosis outbreak on Vancouver Island (British Columbia, Canada).Proc Natl Acad Sci U S A. 2004;101:17258–63. DOI: 10.1073/pnas.0402981101
4) Duncan C, Stephen C, Lester S, Bartlett KH. Follow-up study of dogs and cats with asymptomatic Cryptococcus gattii infection or nasal colonization. Med Mycol. 2005;43:663–6. DOI10.1080/13693780500220076
5) Duncan C, Schwantje H, Stephen C, Campbell J, Bartlett K. Cryptococcus gattii in wildlife of Vancouver Island, British Columbia, Canada. J Wildlife Dis 2006;42:175–178.
6) Miller, W, Padhye, A, van Bonn, W, Jensen, E, Brandt, M, Ridgeway, S. Cryptococcosis in a bottlenose dolphin (Tursiops truncatus) caused by Cryptococcus neoformans var. gattii. J of Clin Micro. 2002:40(2):721-724. DOI: 10.1128/JCM.40.2.721-724.2002
7) Raverty, S. Harbour and Dall’s porpoises: early indicators of cryptococcosis in people and pets, American Association for the Advancement of Science, Annual Conference, San Diego, California, February, 2010
8) Colegrove, K.M., M.E. Grigg, D. Carlson-Bremer, R.H. Miller, F.M.D. Gulland, D.J.P. Ferguson, D. Rejmanek, B.C. Barr, R. Nordhausen, A. Melli, P.A. Conrad. 2011. Discovery of three novel coccidian parasites infecting California sea lions (Zalophus californianus) with evidence of sexual replication and interspecies pathogenicity. J. Parasitol 97:868-77.
9) Wendte J.M., A.K. Gibson, M.E. Grigg. 2011. Toxoplasma in wildlife: population genetic perspectives on parasite genotypes. Vet. Parasitol. 182:96-111.
10) Gibson, A.K., S. Raverty, D.M. Lambourn, J. Huggins, S.L. Magargal, M.E. Grigg. 2011. Polyparasitism is associated with disease severity in Toxoplasma gondii infected marine sentinel species. PLoS Neg Trop Dis 5(5): e1142.
11) Wendte J.M., Miller M.A., Lambourn D.M., Magargal S.L., Jessup D.A., M.E. Grigg. 2010. Self-mating in the definitive host potentiates clonal outbreaks of the Apicomplexan parasites Sarcocystis neurona and Toxoplasma gondii. PLoS Genetics 6(12):1-13.
12) Miller, M.A., P.A. Conrad, M. Harris, B. Hatfield, G. Langlois, D. Jessup, S. Magargal, A.E. Packham, S. Toy-Choutka, A.C. Mellis, M.A. Murray, F.M. Gulland, M.E. Grigg. 2010. Protozoal-associated epizootic impacting marine wildlife: Mass mortality of southern sea otters due to Sarcocystis neurona infection. Vet Parasitol. 172:183-94.
13) Miller, M.A., W.A. Miller, P.A. Conrad, E.R. James, A.C. Melli, C.M. Leutenegger, H.A. Dabritz, A.E. Packham, D. Paradies, M. Harris, J. Ames, D.A. Jessup, K. Worcester, and M.E. Grigg. 2008. Type X Toxoplasma gondii in a wild mussel and terrestrial carnivores from coastal California: new linkages between terrestrial mammals, runoff and toxoplasmosis of sea otters. Int J Parasitol 38:1319-1328.