Sick Sea Mammals: A Sign of Sick Seas? (13-Nov-2004)

Transcription

1 In: 55th Annual Meeting of the American College of Veterinary Pathologists (ACVP) & 39th Annual Meeting of the American Society of Clinical Pathology (ASVCP), ACVP and ASVCP (Eds.) Publisher: American College of Veterinary Pathologists & American Society for Veterinary Clinical Pathology, Middleton WI, USA Internet Publisher: Publisher: International Veterinary Information Service ( Ithaca, New York, USA. Sick Sea Mammals: A Sign of Sick Seas? (13-Nov-2004) L. J. Lowenstine Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, CA, USA. Introduction Marine mammals (cetaceans - the whales, porpoises, dolphins; pinnipeds - the seals, sea lions and walruses; sea and marine otters; polar bears; and the sirenians - manatees and dugongs) are obligate inhabitants of marine, coastal and, less frequently, fresh water environments [13,60]. With the exception of the herbivorous sirenians and the planktivorous cetaceans, marine mammals are "high on the food chain" predators feeding on invertebrates, fish, and, in the case of killer whales and polar bears, sea birds and other marine mammals. Many of the prey species, such as hake, pollock, salmon, anchovies, sardines, crabs, market squid, and mollusks are favored in human diets as well. The habitat and diet of marine mammals makes them ideal sentinels of aquatic ecosystem health [22,49,61,85]. Since about three quarters of the earth is covered by water, the role of marine mammals can be extended to that of sentinels of global health. Thus, the mass strandings of seals in Europe and small cetaceans throughout the Atlantic due to phocine distemper virus, dolphins and manatees on the eastern sea board of the US and sea lions seizuring in California due to toxins from harmful algal blooms, the high prevalence of neoplasia in beluga whales and California sea lions, and other such events give cause for alarm about the health of our oceans [19,69]. Notable threats to marine mammals, and to their ecosystems include: direct (e.g. entanglement in gear, gun shot) and indirect (e.g. competition for food resources) fisheries interactions; boat strikes; anthropogenic chemical pollution (including petroleum products and other industrial chemicals); pathogen pollution; biotoxins from harmful algal blooms; sound pollution (from naval exercises and general ship traffic), and global warming with reduction of polar ice [69]. Increased human populations in costal areas and human activity on the open seas are responsible for many of these threats. This paper will highlight some of the causes of marine mammal morbidity and mortality that may be related to environmental degradation and will summarize current studies, to address some of these problems, at the University of California School of Veterinary Medicine. Studying Marine Mammal Health Many different tools are used to assess the health of marine mammals as individuals and as populations. These include: census monitoring of marine mammal "stocks" in open waters and in breeding areas or rookeries; and investigations into causes of marine mammal morbidity and mortality. In the United States, in accordance with the Marine Mammal Protection Act (MMPA) of 1972, access to marine mammals for health investigations is limited to catch and release of free-living individuals and studies conducted on animals that strand either dead or alive or are held in rehabilitation facilities ( Invasive research and prospective studies of toxins or pathogens are not allowed. Protection and study of marine mammals falls under the purview of two separate government agencies. Cetaceans (whales, porpoises and dolphins) and pinnipeds (seals and sea lions) are guarded by The Office of Protected Resources, National Marine Fisheries Service, National Oceanographic and Atmospheric Authority, Department of Commerce ( while walruses, sea and marine otters, manatees, dugongs and polar bears are the jurisdiction of the US Fish and Wildlife Service, Department of the Interior ( Permits or letters or authorization are required for marine mammal salvage, rehabilitation, and research. The MMPA also dictated the formation of The Marine Mammal Commission ( to review national and international laws, assess the condition of marine mammal populations and to recommend means of protection of these species, as well as the Marine Mammal Stranding and Health Assessment Program and the Working Group on Unusual Marine Mammal Mortality Events

2 ( These later two programs address investigation of both dead and live strandings, provide for rehabilitation of individual animals and provide for assessment and study of unusual mortality events. Rehabilitators are encouraged to include scientific inquiry into the rehabilitation process. Large rehabilitation centers, such as The Marine Mammal Center (TMMC) in Sausalito, California, have contributed enormously to our understanding of causes of stranding and diseases affecting marine mammals, as well as normal clinical data and natural history, safe methods of chemical restraint, surgical interventions, and use of telemetry to track treated and released individuals ( Funding for emergency response and for research on stranding is provided by legislature, though sometimes unmatched by actual appropriations. The University of California Davis, School of Veterinary Medicine, has been collaborating with The Marine Mammal Center for 25 years, to investigate causes of stranding in pinnipeds and cetaceans along the California Coast. There is also an 8- year study, in collaboration with the California Department of Fish and Game (CDFG) and the US Fish and Wildlife Service (USFWS), on causes of sea otter mortality. In addition, a major program for oil spill response and research, a collaborative effort with CDFG, is based in the Wildlife Health Center at UC Davis ( ACVP diplomate veterinary pathologists, working with marine mammal biologists and clinical veterinarians, have been vital to the investigations at UC Davis, and at other organizations studying marine mammal diseases in the US, Canada, Europe and New Zealand. Examples of Marine Mammal Strandings and Possible Implications for Ocean Health Marine Morbilliviruses harbor seals (Phoca vitulina) in 1988, and over 20,000 in 2002, died during epizootics of phocine distemper virus (PDV) in the waters of the UK and northern European countries [31,35,62,65]. 10,000 Baikal seals (Pusa siberica) died of canine distemper virus (CDV) in 1987 and 10,000 Caspian seals (Pusa caspica) in 2000 [41,51,54]. In 1997 there was a mass mortality in the population of critically endangered Mediterranean monk seals (Monachus monachus) along the coast of north Africa; more than half of the estimated total population of 340 seals died [16]. Morbilliviruses closely related to dolphin morbillivirus were detected [84]. 20,000 Striped dolphins (Stenella coerueoalba) in the Mediterranean Sea in , uncounted Common dolphins (Delphinus delphinus) in the Black Sea in 1994, and about 750 Atlantic bottlenose dolphins (Tursiops truncatus) on the east coast of the USA died with evidence of dolphin morbillivirus infection (DMV) [6,81]. Why have morbilliviruses suddenly emerged as major pathogens in marine mammals? In the case of the small cetaceans, it may be that histopathology was not historically performed to look for signs of disease in mass strandings. The seals epizootics, however, have only one reported precedent - a mass mortality of crabeater seals (Lobodon carconiphagus) in 1957 in the Antarctic (which some suspect may have been due to CDV from sled dogs used by polar explorers) [47]. Contaminant induced immune suppression has been a suggested predisposing factor [86]. Investigations after the 1988 epizootic demonstrated that harbor seals from the North Sea carried high body burdens of anthropogenic chemicals [28,29]. Feeding North Sea fish to harbor seals depressed markers of immune function [10-12]. However, a PDV challenge study in seal fed diets high in PCBs failed to recreate this scenario [29] (Unlike the US, several European countries and Canada allow prospective research on marine mammals). Striped dolphins from the Mediterranean epizootic also had high contaminant burdens [2]. For the Baikal and Caspian outbreaks, surface water runoff was suspected to have carried CDV into these two inland seas from infected domestic dogs, and, possibly, wild canids, living in the area. In addition, Caspian seals have been shown to carry high body burdens of chemical contaminants [4,27,57]. Marine biotoxins from harmful algal blooms may have also contributed to some the deaths of the US Atlantic bottlenose dolphins and the Mediterranean monk seals [32]. There is controversy as to the relative importance of the two agents (virus vs biotoxin), as minimal histopathology was performed [66]. It is now suspected that marine morbilliviruses are endemic in some species and become epizootic in others due to changes in the ocean environment [26,40]. Global warming, and dynamic alterations in marine currents can cause interactions between species that are usually geographically separated. The situation is complex, however. Concurrent disease processes may also set off epizootics along with immune suppression from land-based anthropogenic chemicals and marine biotoxins [9,30,36,61].Since the morbiliviruses are themselves immunosuppressive, this will be a hard knot to untangle. Marine Biotoxins - Harmful algal blooms (HABs, "red tides") are increasing in number, intensity and duration along the coasts of North America and elsewhere throughout the world ( The cause of this increase is unknown, but is likely related to increased nutrient load from runoff, which carries silica and

3 nitrogen-rich agricultural products, such as fertilizers and animal manure, into the oceans (eutrafication) [87]. Global transport of algae in ballast water of ships, and altered ocean temperature patterns, due to global warming, have also been evoked [75]. The increase seems to be a real phenomenon and not just a result of increased reporting. There are several algal species and algal toxins that have been found in HABs causing marine mammal morbidity and mortality (see above web sites). These include: Karenia brevis producing brevetoxin; Gymnodydium sp, Alexandrium sp, and Pyrodinium sp dinoflagellates and cyanobacteria producing saxitoxins (21 different compounds) and Pseudo-nitzchia species diatoms producing domoic acid. Outbreaks of brevetoxicosis ("neurotoxic shell fish poisoning") have occurred in the endangered Florida Manatee (Trichechus manatus latirostris) in 1982, 1996, 2002 and 2003 resulting in deaths of between 47 and 150 animals in each epizootic (out of an estimated population of about 2,200) [7]. The route of exposure was both by inhalation and ingestion. Brevetoxicosis was also thought to be involved in the 1988 die- off of bottle-nosed dolphins on the Atlantic seaboard of the US, however, as mentioned above morbillivirus was also identified, and the exact contribution of each factor is still in debate. Saxitoxicosis ("paralytic shell fish poisoning") is the suspected cause of a bottle-nosed dolphin mortality event in the Indian River area of Florida in 2001, and in 14 Humpback whales (Megaptera novaeangliae) that stranded in Cape Cod Bay in 1987 [5,55]. Saxitoxicosis is listed as one of the major threats to the critically endangered Mediterranean Monk Seal (Monachus monachus) [16,70]. As mentioned above, both Saxitoxin and morbillivirus were identified in monk seal tissues, but histopathology was not performed. Saxitoxicosis occurs through ingestion of prey items that have ingested or filtered out the toxin-producing organisms. Along the coast of California, domoic acid intoxication (amnestic shell-fish poisoning) due to blooms of Pseudonitzchia australis was associated with the deaths or stranding of at least 81 California sea lions (Zalophus californianus) in 1998, 184 in 2000, and 71 in 2001 [33,77]. In 2002, DA was implicated in the deaths or stranding of 672 sea lions, 95 cetaceans (whales and dolphins) and 32 threatened southern sea otters (Enhydra lutrans neris) [33]. And in 2003, 1000s of individuals of multiple species were affected (NMFS national stranding data base). Domoic acid in found in all levels of the food web.[50] Prey items acting as vectors for DA intoxication included sardines and anchovies in the case of the sea lions and cetaceans, and benthic invertebrates, especially crabs, in the case of the sea otters. Domoic acid intoxication in sea lions and marine birds has been a focus of investigation at UC Davis. Domoic acid is an excitatory neurotoxin that is a glutamate analog. Affected sea lions have acute neuronal necrosis in the dentate gyrus and hippocampus. If a sea lion survives the acute episode, it may suffer repeated seizures culminating in hippocampal atrophy [77,78]. Long-term effects of hippocampal atrophy are under investigation using MRI imaging and post release telemetry. In addition to the neurologic effects DA has been associated with late term abortions and stillbirths in California sea lions [23]. DA is also associated with acute myocardial necrosis in sea lions and is statistically a risk factor for cardiomyopathy in southern sea otters [43,78]. Domoic acid producing blooms of varying magnitudes have become a frequent occurrence on the California coast only during the last decade and a half [46]. The presence of blooms causing marine mammal unusual mortality events (as well mortality in fish and sea birds) signals an alteration in coastal and marine ecosystem homeostasis [87]. Pathogen Pollution - Land-based pathogen pollution is an area of increased research interest. Toxoplasma gondii and Sarcocystis neurona have been associated with deaths in the threatened southern sea otter and in harbor seals along the coast of central and northern California. First recognized as a cause of sea otter mortality by colleagues at the National Wildlife Health Center (USBRS, USGS, DOI) in Madison Wisconsin, protozoal encephalitis is now recognized to be responsible for 16% of sea otter deaths and contributory to death in many others [44,82]. Analysis of distribution of sea otter cases have led to the conclusion that these parasites reach the marine coastal environment from storm water run-off [59]. The contribution of human sewage effluent to the problem is under investigation. With increasing population density in coastal communities comes increased populations of feral cats and peridomestic wildlife such as opossums and raccoons. As in the case of morbiliviruses, protozoal infections may become more florid in the face of heavy contaminant burdens in sea otters [39]. Bacterial pathogens, such as Plesiomonas shigelloides, an inhabitant of human sewage effluent, has been responsible for diarrhea and deaths in neonatal harbor seals from rookeries at the mouth of the Russian River in California (which receives treated waste water from several communities)(tmmc/ucdavis case archives). Other fecal pathogens (e.g. Salmonella and

4 Campylobacter) found in marine mammals are being studied in a collaborative study between TMMC, UCD and Northwest Fisheries Science Center, Seattle, WA. Antibiotic resistance in many isolates may suggest a land-based source [79]. Leptospira interogans serovar pomona (aka Leptospira pomona kenniwickii) is now endemic in California sea lions, with periodic outbreaks that may be related to population immunity and El Nino climatic events [8,24,58]. However the first outbreak recognized in 1970 may have had its origin along the Point Reyes National Seashore, an area of dairy farm runoff. In addition to severe renal disease, leptospirosis has also been implicated in abortions and reproductive failure in California sea lions [21]. Molecular strain differentiation may help sort out whether the origins of marine mammal leptospires is terrestrial or marine. Anthropogenic Contaminants - Chemical hazards to which marine mammals are exposed include: petrochemicals from oil spills, runoff or natural seeps; heavy metals; and persistent organic pollutants that bioaccumulate in the food web. Reported or suspected effects include direct toxicity, immune modulation, endocrine disruption, genotoxicity (possibly leading to cancer or fetal losses) [17,21,53,73,74]. Petroleum Chemicals - Although the most numerous victims of oil spills are marine birds, coastal and open ocean marine mammals including seals, otters and whales, have suffered morbidity and mortality from oil spills [14,20]. Large oil spills, such as the Exxon Valdez in Alaska, the Treasure spill off the Cape of South Africa, and the Jessica spill in the Galapagos, are spectacular and a not infrequent occurrence due to the transportation of oil by tanker and through pipelines. In addition petroleum products enter the oceans from discharge of ballast water, illegal dumping, and even storm water runoff of automotive oils and gasoline. Direct effects of petroleum products include burns on skin and in respiratory track, gastrointestinal and renal toxicity, loss of insulating quality of pelage is important in sea otters and fur seals [52,66,76]. In addition to the direct effects of oil contamination, long-term reproductive effects on sea otters have been hypothesized. Decreased post implantation reproductive success was shown in exposed mink and decreased reproductive success also carried over to the female offspring of treated mink [57]. Population effects have been noted in sea otters, harbor seals and killer whales following the Exxon Valdez spill [15,60]. Persistent Organic Pollutants - Numerous other chemicals also enter the marine and costal ecosystems due to accidental contamination of waste and storm water run-off or airborne fall out, and intentional illegal dumping (either directly into the ocean or into wastewater). Of greatest concern are the persistent organic pollutants (POPs) including PCBs, DDTs, dioxins, and other halogenated hydrocarbons that are bioaccumulated and end up in high concentrations in the blubber of marine mammals [3,45,48,83]. Concentrations of these pollutants increase with increasing tropic levels, so that killer whales have extremely high blubber burdens. Recent concern has been raised about the high levels of butyltin (from boat anti-fouling paint) and the fire retardant polybrominated diphenyl ethers [39,48]. The effect of POPs on marine mammals, and other wildlife, is a subject of intense investigation [45,73]. Effects attributed to these chemicals include immune suppression, poor survivability of first born offspring, genotoxicity and carcinogenesis. A large portion of the contaminants are transferred from mother to offspring in utero, and to a greater extent via nursing. Thus the first offspring receives the greatest burden [80]. The exact suite of contaminants is related to the feeding location of the animals or the origins of their prey [3,80]. One example is that the high level of contaminants found in the blubber of killer whales (Orcinus orca) resident off the coast of British Columbia have the signature of eastern Europe and Asia [71]. Their main prey species, salmon, carry North American contaminants when they leave their natal streams, but return from the open ocean with the Eurasian contaminants. Resident (fish eating) pods of killer whales in the US-Canadian boundary waters are experiencing a population decline, though their body burdens are less than those of the migratory (mammal eating) killer whales [89]. Harbor seals in the boundary waters of the Pacific Northwest also carry both atmospheric and runoff contaminants [72]. The subpopulation of beluga whales (Delphinapterus leucas) in the Saint Lawerence Estuary of Canada has been intensely studied due to the heavily contaminated nature of their environment and the heavy contaminant burden in their blubber [18,34]. This population has an 18% prevalence of cancers in stranded animals and 27% in adults [56]. Reported cancers are of a variety of types including: gastrointestinal intestinal (8/21), mammary gland (3/21), ovary (3/21) and bladder (1/21). Interestingly, in spite of high levels of PHAs, no primary hepatobillliary tumors were found. Another highly contaminated species, the California sea lion, is being intensely studied at UC Davis. Most of the US population of California sea lions are born on the Channel Islands off shore from Los Angeles and Santa Barbara, California.

5 The area between the rookery islands and the mainland is called the Southern California Bight. In the late 1960s and early 1970s there was direct chemical dumping of organic chemicals including PCBs and DDTs into the bight [64]. Although slow degradation of these environmental compounds with time has lead to declining blubber concentrations, all California sea lions still carry very large burdens of anthropogenic chemicals [38]. These chemicals have been linked to pre-term parturition [21]. In addition, about 20% of stranded subadult and adult California sea lions, of both sexes, have cancers, the majority of which (85%) are highly aggressive carcinomas arising from the lower genitourinary tract [25]. Sea lions with these cancers have a higher levels of contaminants, especially PCB s on a lipid weight basis, than do age and condition matched controls dying of trauma or acute DA intoxication [90]. One hundred percent of sea lions with these cancers are also infected with a gammaherpesvirus (OtHV-1) [42]. In the population at large, only 45% of free ranging males and about 20% of free-ranging or acutely stranded females are infected (unpublished). In addition, sea lions with cancer are relatively more related than those dying of trauma [1], and cancer is statistically associated with a specific MHC locus (unpublished). Thus, although contaminants likely play a role in sea lion carcinogenesis, the relative contribution to initiation and promotion of POPs and herpesvirus needs further investigation. Conclusions The title of this presentation was posed as a question: Are sick sea mammals a sign of sick seas? The answer is "Yes". Through the study of marine mammal epizootics and long-term stranding databases, we are learning that there are complex interactions between contaminants, biotoxins, climate and pathogens. The evidence is mounting that marine mammal epizootics indicate imbalances in marine and coastal environments, rather than being isolated events. We are finding out that "the solution to pollution is not dilution", and that the oceans cannot serve as a dumping ground. Fortunately, with awareness comes the opportunity for action. Acknowledgements: Thanks to Dr. Frances Gulland for helpful comments. References 1. Acevedo-Whitehouse K, Gulland F, Greig D, Amos W Inbreeding: Disease susceptibility in California sea lions. Nature 2003; 422(6927): Aguilar A, Borrell A. Abnormally high polychlorinated biphenyl levels in striped dolphins (Stenella coeruleoalba) affected by the Mediterranean epizootic. Sci Total Environ 1994; 154(2-3): Aguilar A, Borrell A, Reijnders PJ. Geographical and temporal variation in levels of organochlorine contaminants in marine mammals. Mar Environ Res 2002; 53(5): Anan Y, Kunito T, Ikemoto T, et al. Elevated concentrations of trace elements in Caspian seals (Phoca caspica) found stranded during the mass mortality events in Arch Environ Contam Toxicol 2002; 42(3): Baker CS, Weinrich MT, Early G, et al. Genetic impact of an unusual group mortality among humpback whales. J Hered 1994; 85(1): Birkun A, Kuiken T, Krivokhizhin S, et al. Epizootic of morbilliviral disease in common dolphins (Delphinus delphis ponticus) from the Black sea. Vet Rec 1999; 144(4): Bossart GD, Baden DG, Ewing RY, et al. Brevetoxicosis in manatees (Trichechus manatus latirostris) from the 1996 epizootic: gross, histologic, and immunohistochemical features. Toxicol Pathol 1998; 26(2): Colagross-Schouten AM, Mazet JA, Gulland FM, et al. Diagnosis and seroprevalence of leptospirosis in California sea lions from coastal California. J Wildl Dis 2002; 38(1): Daszak P, Cunningham AA, Hyatt AD.Anthropogenic environmental change and the emergence of infectious diseases in wildlife. Acta Trop 2001; 78(2): de Swart RL, Ross PS, Vos JG, et al. Impaired immunity in harbour seals [Phoca vitulina] fed environmentally contaminated herring. Vet Q 1996; 18 Suppl 3:S de Swart RL, Ross PS, Vos JG, et al. Impaired immunity in harbour seals (Phoca vitulina) exposed to bioaccumulated environmental contaminants: review of a long-term feeding study. Environ Health Perspect Aug;104 Suppl 4: de Swart RL, Ross PS, Vedder EJ, et al. Impairment of immunological functions in harbor seals (Phoca vitulina) feeding on fish from polluted coastal waters. Ambio 1994; 23: Dierauf L, Gulland FMD, eds. CRC Handbook of Marine Mammal Medicine, 2nd edition. Boca Raton: CRC Press, Draffen G, List of major oil spills [online], Available from: State of Alaska, Exxon Valdez Oil Spill Council [online]. Available from: Foley E, The end of the Mediterranean monk seal? [online] World Wildlife Fund website, Available from: Gauthier JM, Dubeau H, Rassart E, et al Biomarkers of DNA damage in marine mammals. Mutat Res 1999; 444 (2):

6 18. Gouteux B, Lebeuf M, Muir DC, et al. Levels and temporal trends of toxaphene congeners in beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, Canada. Environ Sci Technol 2003; 37(20): Geraci JR, Harwood J, Lounsbury VJ. Marine mammal die-offs. Causes, investigations and issues. In: Twiss JR, Reeves RR, eds. Conservation and Management of Marine Mammals. Washington, DC: Smithsonian Institution Press, 1999; Geraci JR, St.Aubins DJ, eds. Sea Mammals and Oil. Confronting the Risks. San Diego: Academic Press, Gilmartin WG, Delong RL, Smith AW, et al. Premature parturition in the California sea lion. J Wildl Dis 1976; 12 (1): Gulland FM. Stranded seals: important sentinels. J Am Vet Med Assoc 1999; 214(8): Gulland FM, Haulena M, Fauquier D, et al. Domoic acid toxicity in Californian sea lions (Zalophus californianus): clinical signs, treatment and survival. Vet Rec 2002; 150(15): Gulland FMD, Koski M, Lowenstine LJ, et al. Leptospirosis in California sea lions (Zalophus californianus) stranded along the central California coast, J Wildl Dis 1996; 32(4): Gulland F, Trupkiewicz J, Spraker TR, et al. Metastatic carcinoma of probable transitional cell origin in 66 free-living California sea lions (Zalophus californianus), 1979 to J Wildl Dis 1996; 32(2): Erratum in: J Wildl Dis 1996; 32 (3): Hall AJ. Morbilliviruses in marine mammals. Trends Microbiol 1995; 3(1): Hall AJ, Duck CD, Law RJ, et al. Organochlorine contaminants in Caspian and harbour seal blubber. Environ Pollut 1999; 106(2): Hall AJ, Law RJ, Wells DE, et al. Organochlorine levels in common seals (Phoca vitulina) which were victims and survivors of the 1988 phocine distemper epizootic. Sci Total Environ 1992; 115(1-2): Harder TC, Willhaus T, Leibold W, et al. Investigations on course and outcome of phocine distemper virus infection in harbour seals (Phoca vitulina) exposed to polychlorinated biphenyls. Virological and serological investigations. Zentralbl Veterinarmed B 1992; 39(1): Harvell CD, Kim K, Burkholder JM, et al. Emerging marine diseases -- climate links and anthropogenic factors. Science 1999; 285(5433): Heide-Jorgensen MP, Harkonen T, Dietz R, et al. Retrospective of the 1988 European seal epizootic. Dis Aquat Org 1992; 13: Hernandez M, Robinson I, Aguilar A, et al. Did algal toxins cause monk seal mortality? Nature 1998; 393(6680): Heyning JE Final Report on the multi-species marine mammal unusual mortality event along the Southern California Coast. National Marine Fisheries Service, Tech. Memorandum, Hobbs KE, Muir DC, Michaud R, et al. PCBs and organochlorine pesticides in blubber biopsies from free-ranging St. Lawrence River Estuary beluga whales (Delphinapterus leucas), Environ Pollut 2003; 122(2): Jensen T, van de Bildt M, Dietz HH, et al. Another phocine distemper outbreak in Europe. Science 2002; 297(5579): Jepson PD, Bennett PM, Allchin CR, et al. Investigating potential associations between chronic exposure to polychlorinated biphenyls and infectious disease mortality in harbour porpoises from England and Wales. Sci Total Environ 1999; : Kajiwara N, Niimi S, Watanabe M, et al. Organochlorine and organotin compounds in Caspian seals (Phoca caspica) collected during an unusual mortality event in the Caspian Sea in Environ Pollut 2002;117(3): Kannan K, Kajiwara N, Le Boeuf BJ, et al. Organochlorine pesticides and polychlorinated biphenyls in California sea lions. Environ Pollut 2004; 131(3): Kannan K, Kajiwara N, Watanabe M, et al. Profiles of polychlorinated biphenyl congeners, organochlorine pesticides, and butyltins in southern sea otters and their prey. Environ Toxicol Chem 2004; 23(1): Kennedy S. Morbillivirus infections in aquatic mammals. J Comp Pathol 1998; 119(3): Kennedy S, Kuiken T, Jepson PD, et al. Mass die-off of Caspian seals caused by canine distemper virus. Emerg Infect Dis 2000; 6(6): King DP, Hure MC, Goldstein T, et al. Otarine herpesvirus-1: a novel gammaherpesvirus associated with urogenital carcinoma in California sea lions (Zalophus californianus). Vet Microbiol 2002; 86(1-2): Kreuder C, Miller MA, Lowenstine LJ, et al. Domoic acid-associated myocarditis and cardiomyopathy in southern sea otters (Enhydra lutris nereis). Am Jour Vet Res 2004; In Press. 44. Kreuder C, Miller MA, Jessup DA, et al. Patterns of mortality in southern sea otters (Enhydra lutris nereis) from J Wildl Dis 2003; 39(3): Kuiken T, Bennett PM, Allchin CR, et al. PCB's, cause of death and body condition in harbor porpoises (Phocoena phocoena) from British waters. Aquat Tox 1994; 28: Langlois GW, Marine Biotoxin Monitoring Program, Annual Reports [online], California Department of Health Services, Division of Drinking Water and Environmental Management, Available from: Laws RM, Taylor RFJ. A mass mortality of crabeater seals Lobodon carconiphagus (Gray). Proceedings of the Zoological Society of London 1957; 129: Lebeuf M, Gouteux B, Measures L, et al. Levels and temporal trends ( ) of polybrominated diphenyl ethers in

7 beluga whales (Delphinapterus leucas) from the St. Lawrence Estuary, Canada. Environ Sci Technol 2004; 38(11): LeBlanc GA, Bain LJ. Chronic toxicity of environmental contaminants: sentinels and biomarkers. Environ Health Perspect 1997; 105 Suppl 1: Lefebvre KA, Bargu S, Kieckhefer T, et al. From sanddabs to blue whales: the pervasiveness of domoic acid. Toxicon 2002; 40(7): Likhoshway YeV, Grachev MA, Kumarev VP, et al Baikal seal virus. Nature 1989; 339(6222): Lipscomb TP, Harris RK, Moeller RB, et al. Histopathologic lesions in sea otters exposed to crude oil. Vet Pathol 1993; 30(1): Luebke RW, Hodson PV, Faisal M, et al. Aquatic pollution-induced immunotoxicity in wildlife species. Fundam Appl Toxicol 1997; 37(1): Mamaev LV, Denikina NN, Belikov SI, et al. Characterisation of morbilliviruses isolated from Lake Baikal seals (Phoca sibirica). Vet Microbiol 1995; 44(2-4): Marine Mammal Commission (USA), Annual report: Species of special concern. Chapter III Bottlenosed dolphins (Tursiops truncates) of the Atlantic and Gulf of Mexico [online], pp.73-78, Available from: Martineau D, Lemberger K, Dallaire A, et al. Cancer in wildlife, a case study: beluga from the St. Lawrence estuary, Quebec, Canada. Environ Health Perspect 2002; 110(3): Mazet JAK, Gardner IA, Jessup DA, et al. Effects of petroleum on mink applied as a model for reproductive success in sea otters. J Wildl Dis 2001; 37(4): McIlhattan TJ, Martin JW, Wagner RJ, et al. Isolation of Leptospira pomona from a naturally infected California sea lion, Sonoma County, California. J Wildl Dis 1971; 7(3): Miller MA, Gardner IA, Kreuder C, et al Coastal freshwater runoff is a risk factor for Toxoplasma gondii infection of southern sea otters (Enhydra lutris nereis). Int J Parasitol 2002; 32(8): Monson DH, Doak DF, Ballachey BE, et al. Long-term impacts of the Exxon Valdez oil spill on sea otters, assessed through age-dependent mortality patterns. Proc Natl Acad Sci USA 2000; 97(12): Mossner S, Ballschmiter K. Marine mammals as global pollution indicators for organochlorines. Chemosphere 1997; 34 (5-7): Muller G, Wohlsein P, Beineke A, et al. Phocine distemper in German seals, Emerg Infect Dis 2004; 10(4): Olsson M, Karlsson B, Ahnland E. Diseases and environmental contaminants in seals from the Baltic and the Swedish west coast. Sci Total Environ 1994; 154(2-3): O Shea T, Brownell RL. California sea lion (Zalophus californianus) populations and DDT contamination. Mar Pollut Bull 1998; 36: Osterhaus A. A morbillivirus causing mass mortality in seals. Vaccine 1989; 7(6): Osterhaus A, van de Bildt M, Vedder L, et al. Monk seal mortality: virus or toxin? Vaccine 1998; 16(9-10): Rebar AH, Lipscomb TP, Harris RK, et al. Clinical and clinical laboratory correlates in sea otters dying unexpectedly in rehabilitation centers following the Exxon Valdez oil spill. Vet Pathol 1995; 32(4): Reeves RR, Stewart BS, Clapham PJ, et al. National Audubon Society Guide to Marine Mammals of the World. New York: Alfred A. Knopf, Reeves RR, Rangen TJ. Report of the Consultation on Future Directions in Marine Mammal Research. Bethesda MD: Marine Mammal Commission, Reyero M, Cacho E, Martinez A, et al. Evidence of saxitoxin derivatives as causative agents in the 1997 mass mortality of monk seals in the Cape Blanc Peninsula. Nat Toxins 1999; 7(6): Ross PS, Ellis GM, Ikonomou MG, et al. High PCB concentrations in free-ranging Pacific killer whales, Orcinus orca: Effects of age, sex and dietary preference. Mar Pollut Bull 2000; 40(6): Ross PS, Jeffries SJ, Yunker MB, et al. Harbor seals (Phoca vitulina) in British Columbia, Canada, and Washington State, USA, reveal a combination of local and global polychlorinated biphenyl, dioxin, and furan signals. Environ Toxicol Chem 2004; 23(1): Ross PS, Vos JG, Birnbaum LS, et al. PCBs are a health risk for humans and wildlife. Science 2000; 289(5486): Ruby S, Mendoza LT, Fournier M, et al. Reproductive system impairment of mice fed diets containing beluga whale blubber from the St Lawrence estuary and arctic populations. J Toxicol Environ Health A 2003; 66(11): Ruiz GM, Rawlings TK, Dobbs FC, et al. Global spread of microorganisms by ships. Nature 2000; 408(6808): Salazar S. Impacts of the Jessica oil spill on sea lion (Zalophus wollebaeki) populations. Mar Pollut Bull 2003; 47(7-8): Scholin CA, Gulland F, Doucette GJ, et al. Mortality of sea lions along the central California coast linked to a toxic diatom bloom. Nature 2000; 403(6765): Silvagni PA, Lowenstine LJ, Spraker T, et al. Pathology of domoic acid toxicity in California sea lions (Zalophus californianus). Vet Pathol In Press. 79. Smith WA, Mazet JA, Hirsh DC. Salmonella in California wildlife species: prevalence in rehabilitation centers and characterization of isolates. J Zoo Wildl Med 2002; 33(3): Storr-Hansen E, Spliid H. Coplanar polychlorinated biphenyl congener levels and patterns and the identification of separate populations of harbor seals (Phoca vitulina) in Denmark. Arch Environ Contam Toxicol 1993; 24(1):44-58.

8 81. Taubenberger JK, Tsai M, Krafft AE, et al. Two morbilliviruses implicated in bottlenose dolphin epizootics. Emerg Infect Dis 1996; 2(3): Thomas NJ, Cole RA. The risk of disease and threats to the wild population. Endang Spec Update 1996; 13(12): Tittlemier S, Borrell A, Duffe J, et al. Global distribution of halogenated dimethyl bipyrroles in marine mammal blubber. Arch Environ Contam Toxicol 2002; 43(2): van de Bildt MW, Martina BE, Vedder EJ, et al. Identification of morbilliviruses of probable cetacean origin in carcases of Mediterranean monk seals (Monachus monachus). Vet Rec 2000; 146(24): van der Schalie WH, Gardner HS Jr, Bantle JA, et al. Animals as sentinels of human health hazards of environmental chemicals. Environ Health Perspect 1999; 107(4): Van Loveren H, Ross PS, Osterhaus AD, et al. Contaminant-induced immunosuppression and mass mortalities among harbor seals. Toxicol Lett 2000; : Viviani R. Eutrophication, marine biotoxins, human health. Sci Total Environ 1992; Suppl: Wolkers H, Burkow IC, Hammill MO, et al. Transfer of polychlorinated biphenyls and chlorinated pesticides from mother to pup in relation to cytochrome P450 enzyme activities in harp seals (Phoca groenlandica) from the gulf of St. Lawrence, Canada. Environ Toxicol Chem 2002; 21(1): Ylitalo GM, Matkin CO, Buzitis J, et al. Influence of life-history parameters on organochlorine concentrations in freeranging killer whales (Orcinus orca) from Prince William Sound, AK. Sci Total Environ 2001; 281(1-3): Ylitalo GM, Stein JE, Hom T, et al. The role of organochlorines in cancer-associated morality in California sea lions (Zalophus californianus). Mar Pollut Bull In Press. All rights reserved. This document is available on-line at Document No. P This manuscript is reproduced in the IVIS website with the permission of the ACVP & ASVCP