Second North American Sea Duck Conference - Patuxent Wildlife ...

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SECOND NORTH AMERICAN SEA DUCK CONFERENCE DISTRIBUTION OF MICROBIAL PATHOGENS IN FIVE SPECIES OF SEA DUCKS: LOCAL OR GLOBAL IMPLICATIONS FOR DECLINING POPULATIONS? Tuula Hollmen¹, J. Christian Franson², and Paul L. Flint³ ¹University of Alaska Fairbanks and Alaska SeaLife Center, Seward, AK 99664; tuula_hollmen @alaskasealife.org ²U.S. Geological Survey, National Wildlife Health Center, Madison, WI 53711 ³U.S. Geological Survey, Alaska Science Center, Anchorage, AK 99503 We have conducted disease surveys in the Baltic, Beaufort, and Bering Sea regions since 1996 to investigate prevalences and potential effects of infectious diseases on declining populations within the Tribe Mergini. We examined the occurrence of viruses, bacteria, and fungi by screening blood samples and cloacal swabs for previously known avian pathogens and novel infectious agents among breeding, molting, or wintering populations of sea ducks. We summarize findings on host ranges, prevalences, and patterns of occurrence for potentially pathogenic agents identified in common eiders ((Somateria mollissima), spectacled eiders (Somateria fischeri), Steller’s eiders (Polysticta stelleri), long-tailed ducks (Clangula hyemalis), and harlequin ducks (Histrionicus histrionicus). To date, we have found evidence of exposure to at least 25 genera of micro-organisms, including reoviruses, adenoviruses, influenza viruses, Newcastle disease viruses, infectious bursal disease virus, Chlamydophila sp., and Aspergillus sp. We evaluated potential effects of selected organisms using three general approaches: 1) comparisons of prevalences among sea ducks in areas where mortality events occurred with reference populations; 2) correlations between disease exposure and reproductive success; and 3) controlled experimental challenges. Some microbes were found to have wide geographic and species distributions, with potential links to sea duck declines among several populations. We found evidence linking adenovirus exposure to mortality events in molting long-tailed ducks and breeding common eiders in the Beaufort and Baltic Seas, respectively, and to reproductive problems in spectacled eiders on the Yukon-Kuskokwim Delta. Reoviruses were associated with common eider duckling mortality in the Baltic and Beaufort Seas. Findings to date suggest a more limited distribution for other potential pathogens, however, populations with declining numbers and shrinking ranges may show increased vulnerability to localized impacts. Sources of outbreaks and, therefore, potential management implications may differ between localized and widely spread diseases. For newly discovered host-microbe relationships, the mechanism and magnitude of impact on populations are unknown and often challenging to characterize - especially in remote marine environments, where most sea ducks exist. However, we found evidence of exposure to infectious agents across all geographic locations and species studied, linked infectious agents with mortality events, and documented pathogenicity in experimental studies. We conclude that diseases may be contributing to declines or hindering recovery of some sea duck populations. 70 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005
SECOND NORTH AMERICAN SEA DUCK CONFERENCE EFFECTS OF DIETARY SELENIUM EXPOSURE IN CAPTIVE AMERICAN COMMON EIDERS J. Christian Franson¹, David J. Hoffman², Alicia M. Wells-Berlin 2 , Matthew C. Perry², Valerie S. Bochsler 1 , Daniel L. Finley1, Paul L. Flint 3 , andTuula Hollmén 4 ¹USGS National Wildlife Health Center, Madison, Wisconsin, USA; chris_franson@usgs.gov ²USGS Patuxent Wildlife Research Center, Laurel, Maryland, USA; ³USGS Alaska Science Center, Anchorage, Alaska, USA; 4 Alaska Sealife Center and School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, Seward, Alaska, USA We conducted two studies of Se exposure in captive common eiders (Somateria mollissima). In Study 1, eiders were fed diets with added Se (as L-selenomethionine) in concentrations increasing from 10 ppm to 80 ppm. In Study 2, eiders received control, low exposure (20 ppm Se), and high exposure (60 ppm Se) diets. One duck in the high exposure group in Study 2 died after 36 days. Remaining high exposure ducks in Study 2 and ducks in Study 1 were euthanized after losing 25- 30% of their body weight, which occurred after 41 days and 60-78 days, respectively. Body weights did not differ between control and low exposure ducks in Study 2. At the end of Study 1, the mean Se concentration in blood was 32 ppm wet weight (ww). In Study 2, mean blood Se reached 14 ppm ww in the low exposure group and 17 ppm ww in high exposure ducks. Mean Se concentrations in liver were 1252 ppm dry weight (dw) in Study 1, and 351 and 735 ppm dw, respectively, in the low and high exposure groups of Study 2. Oxidative stress was evidenced by Se-associated effects on glutathione metabolism, but not entirely in the same manner as with previous laboratory studies in mallards. In plasma, activities of total and Se-dependent glutathione peroxidase increased with time. As Se concentrations in liver increased, Se-dependent glutathione peroxidase, glutathione reductase, oxidized glutathione, and the ratio of hepatic oxidized to reduced glutathione increased. Total and protein bound sulfhydryl concentrations, reduced glutathione, glutathione-S-transferase, and glucose- 6-phosphate dehydrogenase in liver were negatively correlated with Se concentrations in the liver. In Study 2, spleen weights were significantly lower in ducks receiving 60 ppm Se than in those receiving 20 ppm. Gross lesions associated with high Se exposure included emaciation, absence of thymus, loss of nails from digits, and alopecia. Microscopic lesions included severe depletion of lymphoid organs, hepatopathy, and necrosis of feather pulp and feather epithelium. Common eiders fed high levels of Se lost weight and developed lesions similar to findings in experimental mallards, but they accumulated greater Se concentrations in tissues, particularly liver. Field studies have shown that apparently healthy seaducks generally have higher levels of Se in liver than healthy fresh water birds, but lower than the concentrations we found in our study. We conclude common eiders and probably other seaducks have a higher threshold, or adverse effect level, of Se in tissues than fresh water species. NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA 71
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Allard, Karel 5, 62 Anderson, Eric
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